OR/15/047 Resilience to future climate and abstraction - Revision history

Dbk at 09:52, 24 November 2015

2015-11-24T09:52:40Z

← Older revision		Revision as of 10:52, 24 November 2015
Line 18:		Line 18:
	Across the entire basin, the annual change in groundwater storage is estimated at approximately 10 km<sup>3</sup>. As discussed above, this integrates much complexity and variability within the IGB alluvial aquifer system, with some areas depleting and others accumulating. This compares well with the estimate of groundwater depletion using GRACE from Rodell et al. (2009)<ref name="Rodell 2009">Rodell M, Velicogna I and Famiglietti J S. 2009. Satellite‐based estimates of groundwater depletion in India, Nature, 460; 999–1002.</ref> who estimated 18 km<sup>3</sup> depletion per year for the states of Rajasthan, Punjab and Haryana, with the majority of the depletion occurring in Rajasthan. Interpretation of GRACE data by Tiwari et al. (2009)<ref name="Tiwari 2009">Tiwari V M, Whar J and Swenson S. 2009. Dwindling groundwater resources in northern India, from satellite gravity observations, Geophysical research Letters, 36; L18401, doi: 10.1029/2009GL039401.</ref> inferred a much higher rate of depletion (approximately 50 km<sup>3</sup> per annum); however this work again had much of the depletion occurring outside the IGB alluvial aquifer system (e.g. within the poorer aquifer systems of Rajasthan) where recharge is negligible, and also indicated significant depletion in Bangladesh which was difficult to reconcile with observations (Shamsudduha et al. 2012<ref name="Shamsuddha 2012">Shamsudduha M, Taylor R G & Longuevergne L. 2012. Monitoring groundwater storage changes in the highly seasonal humid tropics: validation of GRACE measurements in the Bengal Basin. Water Resources Research, 48; WO2508, doi: 10.1029/WR010993</ref>). More recent work on the GRACE data by Chen et al (2014)<ref name="Chen 2014">Chen J, Li J, Zhang Z and Ni S. 2014. Long‐term variations in Northwest India from Satellite gravity measurements, Global and Planetary Change, 116; 130–138.</ref> suggests average depletion of 20 km<sup>3</sup> per year across the region (again with significant depletion outside of the IGB alluvial aquifer system), with several years actually showing net accumulation. Using GRACE within this region to infer groundwater storage change is challenging: for example accounting for the significant changes in mass balance from ongoing tectonic activity, erosion and sedimentation; the large surface water flows within the river systems, the changes in moisture in the atmosphere, and the change in mass from snow and ice melt. Constraining and disaggregating the bulk estimates of mass change from GRACE to give groundwater storage changes required additional information and data. It is hoped that the groundwater storage changes developed here from analysis of the best available regional observational groundwater level data and specific yield information will be a useful tool to the further development and interpretation of GRACE data in the region.		Across the entire basin, the annual change in groundwater storage is estimated at approximately 10 km<sup>3</sup>. As discussed above, this integrates much complexity and variability within the IGB alluvial aquifer system, with some areas depleting and others accumulating. This compares well with the estimate of groundwater depletion using GRACE from Rodell et al. (2009)<ref name="Rodell 2009">Rodell M, Velicogna I and Famiglietti J S. 2009. Satellite‐based estimates of groundwater depletion in India, Nature, 460; 999–1002.</ref> who estimated 18 km<sup>3</sup> depletion per year for the states of Rajasthan, Punjab and Haryana, with the majority of the depletion occurring in Rajasthan. Interpretation of GRACE data by Tiwari et al. (2009)<ref name="Tiwari 2009">Tiwari V M, Whar J and Swenson S. 2009. Dwindling groundwater resources in northern India, from satellite gravity observations, Geophysical research Letters, 36; L18401, doi: 10.1029/2009GL039401.</ref> inferred a much higher rate of depletion (approximately 50 km<sup>3</sup> per annum); however this work again had much of the depletion occurring outside the IGB alluvial aquifer system (e.g. within the poorer aquifer systems of Rajasthan) where recharge is negligible, and also indicated significant depletion in Bangladesh which was difficult to reconcile with observations (Shamsudduha et al. 2012<ref name="Shamsuddha 2012">Shamsudduha M, Taylor R G & Longuevergne L. 2012. Monitoring groundwater storage changes in the highly seasonal humid tropics: validation of GRACE measurements in the Bengal Basin. Water Resources Research, 48; WO2508, doi: 10.1029/WR010993</ref>). More recent work on the GRACE data by Chen et al (2014)<ref name="Chen 2014">Chen J, Li J, Zhang Z and Ni S. 2014. Long‐term variations in Northwest India from Satellite gravity measurements, Global and Planetary Change, 116; 130–138.</ref> suggests average depletion of 20 km<sup>3</sup> per year across the region (again with significant depletion outside of the IGB alluvial aquifer system), with several years actually showing net accumulation. Using GRACE within this region to infer groundwater storage change is challenging: for example accounting for the significant changes in mass balance from ongoing tectonic activity, erosion and sedimentation; the large surface water flows within the river systems, the changes in moisture in the atmosphere, and the change in mass from snow and ice melt. Constraining and disaggregating the bulk estimates of mass change from GRACE to give groundwater storage changes required additional information and data. It is hoped that the groundwater storage changes developed here from analysis of the best available regional observational groundwater level data and specific yield information will be a useful tool to the further development and interpretation of GRACE data in the region.

	[[Image:15047_fig18.jpg\|center\|thumb\|500px\|Figure 18 The estimated annual change in groundwater storage estimated from the average annual measured change in annual water levels.]]		[[Image:15047_fig18.jpg\|center\|thumb\|500px\|'''Figure 18''' The estimated annual change in groundwater storage estimated from the average annual measured change in annual water levels.]]

	==Groundwater recharge==		==Groundwater recharge==
Line 27:		Line 27:
	A caveat must be added to the above discussion, in that it is reliant on the quality of the existing groundwater level data for the basin. Although every effort has been made to QA and check the datasets used, there is still an absence of reliable representative groundwater level data across the IGB alluvial aquifer system. Only with improved groundwater level monitoring networks can more confident analysis be undertaken; as discussed above, it is unwise to rely on unconstrained large scale remotely sensed gravity data.		A caveat must be added to the above discussion, in that it is reliant on the quality of the existing groundwater level data for the basin. Although every effort has been made to QA and check the datasets used, there is still an absence of reliable representative groundwater level data across the IGB alluvial aquifer system. Only with improved groundwater level monitoring networks can more confident analysis be undertaken; as discussed above, it is unwise to rely on unconstrained large scale remotely sensed gravity data.

	[[Image:15047_fig19.jpg\|center\|thumb\|500px\|Figure 19 Net recharge, calculated by subtracting the calculated annual water storage change from the abstraction. Net recharge will be equivalent to the groundwater recharge minus natural discharge to rivers.]]		[[Image:15047_fig19.jpg\|center\|thumb\|500px\|'''Figure 19''' Net recharge, calculated by subtracting the calculated annual water storage change from the abstraction. Net recharge will be equivalent to the groundwater recharge minus natural discharge to rivers.]]

	{\| class="wikitable"		{\| class="wikitable"
Line 53:		Line 53:
	Irrigation and abstraction has led to considerable salinization of groundwater in the Mid Indus, Upper Ganges typology, and the Lower Indus groundwater typology — Figure 20. Canal leakage and irrigation returns, although useful for groundwater recharge, have also degraded the quality of the groundwater through water‐logging and subsequent phreatic salinization. It is possible that increased groundwater abstraction has been reducing this trend by lowering groundwater levels, however, high abstraction has also mobilised older, deeper saline water into shallow depths. This is evident in Mid Indus/Upper Ganges typology where high abstraction is being accompanied by increasingly saline water. In the Indus, the reduction of outflow of water at the Kotri Barrage means that there is little or no natural outflow from the basin. Therefore, the salts generated from weathering of the rocks in the Himalaya are all retained within the basin, leading inevitably to an increase in salt concentration in the groundwater. Within the lower Indus, much of the groundwater is already saline, and the shallow freshwater lenses are highly vulnerable to abstraction.		Irrigation and abstraction has led to considerable salinization of groundwater in the Mid Indus, Upper Ganges typology, and the Lower Indus groundwater typology — Figure 20. Canal leakage and irrigation returns, although useful for groundwater recharge, have also degraded the quality of the groundwater through water‐logging and subsequent phreatic salinization. It is possible that increased groundwater abstraction has been reducing this trend by lowering groundwater levels, however, high abstraction has also mobilised older, deeper saline water into shallow depths. This is evident in Mid Indus/Upper Ganges typology where high abstraction is being accompanied by increasingly saline water. In the Indus, the reduction of outflow of water at the Kotri Barrage means that there is little or no natural outflow from the basin. Therefore, the salts generated from weathering of the rocks in the Himalaya are all retained within the basin, leading inevitably to an increase in salt concentration in the groundwater. Within the lower Indus, much of the groundwater is already saline, and the shallow freshwater lenses are highly vulnerable to abstraction.

	[[Image:15047_fig20.jpg\|center\|thumb\|400px\|Figure 20 intensive agriculture within the Upper Ganges typology.]]		[[Image:15047_fig20.jpg\|center\|thumb\|400px\|'''Figure 20''' intensive agriculture within the Upper Ganges typology.]]

	Intense groundwater abstraction is also accompanied by increases in the use of fertilizer, pesticide and herbicides. Elevated nitrate concentrations are found within the Punjab (Lapworth et al. 2014<ref name="Lapworth 2014"> Lapworth D J, Gopal K, Rao M S, MacDonald A M. 2014. Intensive Groundwater Exploitation in the Punjab – an evaluation of resource and quality trends, British Geological Survey Open Report, ''Groundwater Science Programme'', OR/14/068. </ref>), and have been drawn down to >100 m depth by deep pumping. Elevated nitrate concentrations are also likely to be associated with the presence of other agriculturally derived contaminants. Recycling of groundwater through abstraction, irrigation and irrigation returns has also been shown to intensify this process (Ó Dochartaigh et al, 2010<ref name="ODoch 2010">O Dochartaigh B E, MacDonald A M, Darling W G, Hughes A G, Li J X and Shi L A. 2010. Determining groundwater degradation from irrigation in desert‐marginal northern China, Hydrogeology Journal, 18; 1939–1952.</ref>), with increasing concentrations of solutes and contaminants within irrigation returns derived from groundwater. Routinely monitoring groundwater quality enables trends in degrading quality to be identified and strategies developed to try to mitigate the problem.		Intense groundwater abstraction is also accompanied by increases in the use of fertilizer, pesticide and herbicides. Elevated nitrate concentrations are found within the Punjab (Lapworth et al. 2014<ref name="Lapworth 2014"> Lapworth D J, Gopal K, Rao M S, MacDonald A M. 2014. Intensive Groundwater Exploitation in the Punjab – an evaluation of resource and quality trends, British Geological Survey Open Report, ''Groundwater Science Programme'', OR/14/068. </ref>), and have been drawn down to >100 m depth by deep pumping. Elevated nitrate concentrations are also likely to be associated with the presence of other agriculturally derived contaminants. Recycling of groundwater through abstraction, irrigation and irrigation returns has also been shown to intensify this process (Ó Dochartaigh et al, 2010<ref name="ODoch 2010">O Dochartaigh B E, MacDonald A M, Darling W G, Hughes A G, Li J X and Shi L A. 2010. Determining groundwater degradation from irrigation in desert‐marginal northern China, Hydrogeology Journal, 18; 1939–1952.</ref>), with increasing concentrations of solutes and contaminants within irrigation returns derived from groundwater. Routinely monitoring groundwater quality enables trends in degrading quality to be identified and strategies developed to try to mitigate the problem.
Line 67:		Line 67:
	Groundwater from the IGB alluvial aquifer system sustains many of the region’s cities, notably, New Delhi, Dhaka and Lahore. Although urban groundwater has not been a focus of this study, given that the total volumes abstracted are small compared to irrigation, and urban groundwater is a highly complex issue, the resilience of the water supplies to these cities is of major concern. The high density of the abstraction (e.g. for Dhaka an estimated 0.8 km<sup>3</sup> within 300 km<sup>2</sup> DWASA 2012) and the mixture of private and public water supplies, means groundwater is locally becoming highly depleted in these cities with groundwater levels falling rapidly (>100 m depth in some locations) and bringing with it a set of issues, such as subsidence, declining yields, increased costs (Morris et al. 2003<ref name="Morris 2003">Morris, B L, Lawrence, A R, Chilton, P J, Adams, B, Calow, R and Klinck, B A. 2003). Groundwater and its Susceptibility to Degradation: A Global Assessment of the Problems and Options for Management. Early Warning and Assessment Report Series, RS, 03‐3. ''United Nations Environment Programme'', Nairobi. </ref>) — Figure 21. In tandem with the high abstraction is pervasive, and widespread, contamination of groundwater from both domestic water (sewerage) and industrial waste (Foster and Choudhary 2009<ref name="Foster 2009">Foster S and Chaudhary NK. 2009. Lucknow City — India: Groundwater Resource Use and Strategic Planning Needs, GW‐MATE Case Profile Collection, in Sustainable Groundwater Management: Lessons from Practice, World Bank, pp 8.</ref>). The stratification of the aquifers protects some of the deeper groundwater from contamination, but shallow groundwater, often used for private water supply, can by highly contaminated. Therefore, continued good quality groundwater supply in the largest cities will be difficult to sustain in the long term, without developing large protected wells fields outside of the urban areas and building groundwater protection into land use planning. A systematic assessment of the scale and significance of existing groundwater pollution in city regions is also required, together with a robust evaluations of private water well use and the role of institutions in relation to urban groundwater use and protection (Foster and Choudhary 2009<ref name="Foster 2009"></ref>; Foster et al. 2010<ref name="Foster 2010">Foster S, van Steenbergen F, Zuleta J and Garduno H. 2010. Conjuctive use of groundwater and surface water — from spontaneous coping strategy to adaptive resource management. GW‐MATE Strategic Overview Series 2: World Bank, Washington DC, pp 26.</ref>).		Groundwater from the IGB alluvial aquifer system sustains many of the region’s cities, notably, New Delhi, Dhaka and Lahore. Although urban groundwater has not been a focus of this study, given that the total volumes abstracted are small compared to irrigation, and urban groundwater is a highly complex issue, the resilience of the water supplies to these cities is of major concern. The high density of the abstraction (e.g. for Dhaka an estimated 0.8 km<sup>3</sup> within 300 km<sup>2</sup> DWASA 2012) and the mixture of private and public water supplies, means groundwater is locally becoming highly depleted in these cities with groundwater levels falling rapidly (>100 m depth in some locations) and bringing with it a set of issues, such as subsidence, declining yields, increased costs (Morris et al. 2003<ref name="Morris 2003">Morris, B L, Lawrence, A R, Chilton, P J, Adams, B, Calow, R and Klinck, B A. 2003). Groundwater and its Susceptibility to Degradation: A Global Assessment of the Problems and Options for Management. Early Warning and Assessment Report Series, RS, 03‐3. ''United Nations Environment Programme'', Nairobi. </ref>) — Figure 21. In tandem with the high abstraction is pervasive, and widespread, contamination of groundwater from both domestic water (sewerage) and industrial waste (Foster and Choudhary 2009<ref name="Foster 2009">Foster S and Chaudhary NK. 2009. Lucknow City — India: Groundwater Resource Use and Strategic Planning Needs, GW‐MATE Case Profile Collection, in Sustainable Groundwater Management: Lessons from Practice, World Bank, pp 8.</ref>). The stratification of the aquifers protects some of the deeper groundwater from contamination, but shallow groundwater, often used for private water supply, can by highly contaminated. Therefore, continued good quality groundwater supply in the largest cities will be difficult to sustain in the long term, without developing large protected wells fields outside of the urban areas and building groundwater protection into land use planning. A systematic assessment of the scale and significance of existing groundwater pollution in city regions is also required, together with a robust evaluations of private water well use and the role of institutions in relation to urban groundwater use and protection (Foster and Choudhary 2009<ref name="Foster 2009"></ref>; Foster et al. 2010<ref name="Foster 2010">Foster S, van Steenbergen F, Zuleta J and Garduno H. 2010. Conjuctive use of groundwater and surface water — from spontaneous coping strategy to adaptive resource management. GW‐MATE Strategic Overview Series 2: World Bank, Washington DC, pp 26.</ref>).

	[[Image:15047_fig21.jpg\|center\|thumb\|400px\|Figure 21 Competing high abstraction rates from public and private water supply in Dhaka Mega City (Source: UN 2015).]]		[[Image:15047_fig21.jpg\|center\|thumb\|400px\|'''Figure 21''' Competing high abstraction rates from public and private water supply in Dhaka Mega City (Source: UN 2015).]]

	==References==		==References==

Dbk at 09:51, 24 November 2015

2015-11-24T09:51:56Z

← Older revision		Revision as of 10:51, 24 November 2015
Line 18:		Line 18:
	Across the entire basin, the annual change in groundwater storage is estimated at approximately 10 km<sup>3</sup>. As discussed above, this integrates much complexity and variability within the IGB alluvial aquifer system, with some areas depleting and others accumulating. This compares well with the estimate of groundwater depletion using GRACE from Rodell et al. (2009)<ref name="Rodell 2009">Rodell M, Velicogna I and Famiglietti J S. 2009. Satellite‐based estimates of groundwater depletion in India, Nature, 460; 999–1002.</ref> who estimated 18 km<sup>3</sup> depletion per year for the states of Rajasthan, Punjab and Haryana, with the majority of the depletion occurring in Rajasthan. Interpretation of GRACE data by Tiwari et al. (2009)<ref name="Tiwari 2009">Tiwari V M, Whar J and Swenson S. 2009. Dwindling groundwater resources in northern India, from satellite gravity observations, Geophysical research Letters, 36; L18401, doi: 10.1029/2009GL039401.</ref> inferred a much higher rate of depletion (approximately 50 km<sup>3</sup> per annum); however this work again had much of the depletion occurring outside the IGB alluvial aquifer system (e.g. within the poorer aquifer systems of Rajasthan) where recharge is negligible, and also indicated significant depletion in Bangladesh which was difficult to reconcile with observations (Shamsudduha et al. 2012<ref name="Shamsuddha 2012">Shamsudduha M, Taylor R G & Longuevergne L. 2012. Monitoring groundwater storage changes in the highly seasonal humid tropics: validation of GRACE measurements in the Bengal Basin. Water Resources Research, 48; WO2508, doi: 10.1029/WR010993</ref>). More recent work on the GRACE data by Chen et al (2014)<ref name="Chen 2014">Chen J, Li J, Zhang Z and Ni S. 2014. Long‐term variations in Northwest India from Satellite gravity measurements, Global and Planetary Change, 116; 130–138.</ref> suggests average depletion of 20 km<sup>3</sup> per year across the region (again with significant depletion outside of the IGB alluvial aquifer system), with several years actually showing net accumulation. Using GRACE within this region to infer groundwater storage change is challenging: for example accounting for the significant changes in mass balance from ongoing tectonic activity, erosion and sedimentation; the large surface water flows within the river systems, the changes in moisture in the atmosphere, and the change in mass from snow and ice melt. Constraining and disaggregating the bulk estimates of mass change from GRACE to give groundwater storage changes required additional information and data. It is hoped that the groundwater storage changes developed here from analysis of the best available regional observational groundwater level data and specific yield information will be a useful tool to the further development and interpretation of GRACE data in the region.		Across the entire basin, the annual change in groundwater storage is estimated at approximately 10 km<sup>3</sup>. As discussed above, this integrates much complexity and variability within the IGB alluvial aquifer system, with some areas depleting and others accumulating. This compares well with the estimate of groundwater depletion using GRACE from Rodell et al. (2009)<ref name="Rodell 2009">Rodell M, Velicogna I and Famiglietti J S. 2009. Satellite‐based estimates of groundwater depletion in India, Nature, 460; 999–1002.</ref> who estimated 18 km<sup>3</sup> depletion per year for the states of Rajasthan, Punjab and Haryana, with the majority of the depletion occurring in Rajasthan. Interpretation of GRACE data by Tiwari et al. (2009)<ref name="Tiwari 2009">Tiwari V M, Whar J and Swenson S. 2009. Dwindling groundwater resources in northern India, from satellite gravity observations, Geophysical research Letters, 36; L18401, doi: 10.1029/2009GL039401.</ref> inferred a much higher rate of depletion (approximately 50 km<sup>3</sup> per annum); however this work again had much of the depletion occurring outside the IGB alluvial aquifer system (e.g. within the poorer aquifer systems of Rajasthan) where recharge is negligible, and also indicated significant depletion in Bangladesh which was difficult to reconcile with observations (Shamsudduha et al. 2012<ref name="Shamsuddha 2012">Shamsudduha M, Taylor R G & Longuevergne L. 2012. Monitoring groundwater storage changes in the highly seasonal humid tropics: validation of GRACE measurements in the Bengal Basin. Water Resources Research, 48; WO2508, doi: 10.1029/WR010993</ref>). More recent work on the GRACE data by Chen et al (2014)<ref name="Chen 2014">Chen J, Li J, Zhang Z and Ni S. 2014. Long‐term variations in Northwest India from Satellite gravity measurements, Global and Planetary Change, 116; 130–138.</ref> suggests average depletion of 20 km<sup>3</sup> per year across the region (again with significant depletion outside of the IGB alluvial aquifer system), with several years actually showing net accumulation. Using GRACE within this region to infer groundwater storage change is challenging: for example accounting for the significant changes in mass balance from ongoing tectonic activity, erosion and sedimentation; the large surface water flows within the river systems, the changes in moisture in the atmosphere, and the change in mass from snow and ice melt. Constraining and disaggregating the bulk estimates of mass change from GRACE to give groundwater storage changes required additional information and data. It is hoped that the groundwater storage changes developed here from analysis of the best available regional observational groundwater level data and specific yield information will be a useful tool to the further development and interpretation of GRACE data in the region.

	[[Image:~~15047fig18~~.jpg\|center\|thumb\|500px\|Figure 18 The estimated annual change in groundwater storage estimated from the average annual measured change in annual water levels.]]		[[Image:15047_fig18.jpg\|center\|thumb\|500px\|Figure 18 The estimated annual change in groundwater storage estimated from the average annual measured change in annual water levels.]]

	==Groundwater recharge==		==Groundwater recharge==
Line 27:		Line 27:
	A caveat must be added to the above discussion, in that it is reliant on the quality of the existing groundwater level data for the basin. Although every effort has been made to QA and check the datasets used, there is still an absence of reliable representative groundwater level data across the IGB alluvial aquifer system. Only with improved groundwater level monitoring networks can more confident analysis be undertaken; as discussed above, it is unwise to rely on unconstrained large scale remotely sensed gravity data.		A caveat must be added to the above discussion, in that it is reliant on the quality of the existing groundwater level data for the basin. Although every effort has been made to QA and check the datasets used, there is still an absence of reliable representative groundwater level data across the IGB alluvial aquifer system. Only with improved groundwater level monitoring networks can more confident analysis be undertaken; as discussed above, it is unwise to rely on unconstrained large scale remotely sensed gravity data.

	[[Image:~~15047fig19~~.jpg\|center\|thumb\|500px\|Figure 19 Net recharge, calculated by subtracting the calculated annual water storage change from the abstraction. Net recharge will be equivalent to the groundwater recharge minus natural discharge to rivers.]]		[[Image:15047_fig19.jpg\|center\|thumb\|500px\|Figure 19 Net recharge, calculated by subtracting the calculated annual water storage change from the abstraction. Net recharge will be equivalent to the groundwater recharge minus natural discharge to rivers.]]

	{\| class="wikitable"		{\| class="wikitable"
Line 53:		Line 53:
	Irrigation and abstraction has led to considerable salinization of groundwater in the Mid Indus, Upper Ganges typology, and the Lower Indus groundwater typology — Figure 20. Canal leakage and irrigation returns, although useful for groundwater recharge, have also degraded the quality of the groundwater through water‐logging and subsequent phreatic salinization. It is possible that increased groundwater abstraction has been reducing this trend by lowering groundwater levels, however, high abstraction has also mobilised older, deeper saline water into shallow depths. This is evident in Mid Indus/Upper Ganges typology where high abstraction is being accompanied by increasingly saline water. In the Indus, the reduction of outflow of water at the Kotri Barrage means that there is little or no natural outflow from the basin. Therefore, the salts generated from weathering of the rocks in the Himalaya are all retained within the basin, leading inevitably to an increase in salt concentration in the groundwater. Within the lower Indus, much of the groundwater is already saline, and the shallow freshwater lenses are highly vulnerable to abstraction.		Irrigation and abstraction has led to considerable salinization of groundwater in the Mid Indus, Upper Ganges typology, and the Lower Indus groundwater typology — Figure 20. Canal leakage and irrigation returns, although useful for groundwater recharge, have also degraded the quality of the groundwater through water‐logging and subsequent phreatic salinization. It is possible that increased groundwater abstraction has been reducing this trend by lowering groundwater levels, however, high abstraction has also mobilised older, deeper saline water into shallow depths. This is evident in Mid Indus/Upper Ganges typology where high abstraction is being accompanied by increasingly saline water. In the Indus, the reduction of outflow of water at the Kotri Barrage means that there is little or no natural outflow from the basin. Therefore, the salts generated from weathering of the rocks in the Himalaya are all retained within the basin, leading inevitably to an increase in salt concentration in the groundwater. Within the lower Indus, much of the groundwater is already saline, and the shallow freshwater lenses are highly vulnerable to abstraction.

	[[Image:~~15047fig20~~.jpg\|center\|thumb\|400px\|Figure 20 intensive agriculture within the Upper Ganges typology.]]		[[Image:15047_fig20.jpg\|center\|thumb\|400px\|Figure 20 intensive agriculture within the Upper Ganges typology.]]

	Intense groundwater abstraction is also accompanied by increases in the use of fertilizer, pesticide and herbicides. Elevated nitrate concentrations are found within the Punjab (Lapworth et al. 2014<ref name="Lapworth 2014"> Lapworth D J, Gopal K, Rao M S, MacDonald A M. 2014. Intensive Groundwater Exploitation in the Punjab – an evaluation of resource and quality trends, British Geological Survey Open Report, ''Groundwater Science Programme'', OR/14/068. </ref>), and have been drawn down to >100 m depth by deep pumping. Elevated nitrate concentrations are also likely to be associated with the presence of other agriculturally derived contaminants. Recycling of groundwater through abstraction, irrigation and irrigation returns has also been shown to intensify this process (Ó Dochartaigh et al, 2010<ref name="ODoch 2010">O Dochartaigh B E, MacDonald A M, Darling W G, Hughes A G, Li J X and Shi L A. 2010. Determining groundwater degradation from irrigation in desert‐marginal northern China, Hydrogeology Journal, 18; 1939–1952.</ref>), with increasing concentrations of solutes and contaminants within irrigation returns derived from groundwater. Routinely monitoring groundwater quality enables trends in degrading quality to be identified and strategies developed to try to mitigate the problem.		Intense groundwater abstraction is also accompanied by increases in the use of fertilizer, pesticide and herbicides. Elevated nitrate concentrations are found within the Punjab (Lapworth et al. 2014<ref name="Lapworth 2014"> Lapworth D J, Gopal K, Rao M S, MacDonald A M. 2014. Intensive Groundwater Exploitation in the Punjab – an evaluation of resource and quality trends, British Geological Survey Open Report, ''Groundwater Science Programme'', OR/14/068. </ref>), and have been drawn down to >100 m depth by deep pumping. Elevated nitrate concentrations are also likely to be associated with the presence of other agriculturally derived contaminants. Recycling of groundwater through abstraction, irrigation and irrigation returns has also been shown to intensify this process (Ó Dochartaigh et al, 2010<ref name="ODoch 2010">O Dochartaigh B E, MacDonald A M, Darling W G, Hughes A G, Li J X and Shi L A. 2010. Determining groundwater degradation from irrigation in desert‐marginal northern China, Hydrogeology Journal, 18; 1939–1952.</ref>), with increasing concentrations of solutes and contaminants within irrigation returns derived from groundwater. Routinely monitoring groundwater quality enables trends in degrading quality to be identified and strategies developed to try to mitigate the problem.
Line 67:		Line 67:
	Groundwater from the IGB alluvial aquifer system sustains many of the region’s cities, notably, New Delhi, Dhaka and Lahore. Although urban groundwater has not been a focus of this study, given that the total volumes abstracted are small compared to irrigation, and urban groundwater is a highly complex issue, the resilience of the water supplies to these cities is of major concern. The high density of the abstraction (e.g. for Dhaka an estimated 0.8 km<sup>3</sup> within 300 km<sup>2</sup> DWASA 2012) and the mixture of private and public water supplies, means groundwater is locally becoming highly depleted in these cities with groundwater levels falling rapidly (>100 m depth in some locations) and bringing with it a set of issues, such as subsidence, declining yields, increased costs (Morris et al. 2003<ref name="Morris 2003">Morris, B L, Lawrence, A R, Chilton, P J, Adams, B, Calow, R and Klinck, B A. 2003). Groundwater and its Susceptibility to Degradation: A Global Assessment of the Problems and Options for Management. Early Warning and Assessment Report Series, RS, 03‐3. ''United Nations Environment Programme'', Nairobi. </ref>) — Figure 21. In tandem with the high abstraction is pervasive, and widespread, contamination of groundwater from both domestic water (sewerage) and industrial waste (Foster and Choudhary 2009<ref name="Foster 2009">Foster S and Chaudhary NK. 2009. Lucknow City — India: Groundwater Resource Use and Strategic Planning Needs, GW‐MATE Case Profile Collection, in Sustainable Groundwater Management: Lessons from Practice, World Bank, pp 8.</ref>). The stratification of the aquifers protects some of the deeper groundwater from contamination, but shallow groundwater, often used for private water supply, can by highly contaminated. Therefore, continued good quality groundwater supply in the largest cities will be difficult to sustain in the long term, without developing large protected wells fields outside of the urban areas and building groundwater protection into land use planning. A systematic assessment of the scale and significance of existing groundwater pollution in city regions is also required, together with a robust evaluations of private water well use and the role of institutions in relation to urban groundwater use and protection (Foster and Choudhary 2009<ref name="Foster 2009"></ref>; Foster et al. 2010<ref name="Foster 2010">Foster S, van Steenbergen F, Zuleta J and Garduno H. 2010. Conjuctive use of groundwater and surface water — from spontaneous coping strategy to adaptive resource management. GW‐MATE Strategic Overview Series 2: World Bank, Washington DC, pp 26.</ref>).		Groundwater from the IGB alluvial aquifer system sustains many of the region’s cities, notably, New Delhi, Dhaka and Lahore. Although urban groundwater has not been a focus of this study, given that the total volumes abstracted are small compared to irrigation, and urban groundwater is a highly complex issue, the resilience of the water supplies to these cities is of major concern. The high density of the abstraction (e.g. for Dhaka an estimated 0.8 km<sup>3</sup> within 300 km<sup>2</sup> DWASA 2012) and the mixture of private and public water supplies, means groundwater is locally becoming highly depleted in these cities with groundwater levels falling rapidly (>100 m depth in some locations) and bringing with it a set of issues, such as subsidence, declining yields, increased costs (Morris et al. 2003<ref name="Morris 2003">Morris, B L, Lawrence, A R, Chilton, P J, Adams, B, Calow, R and Klinck, B A. 2003). Groundwater and its Susceptibility to Degradation: A Global Assessment of the Problems and Options for Management. Early Warning and Assessment Report Series, RS, 03‐3. ''United Nations Environment Programme'', Nairobi. </ref>) — Figure 21. In tandem with the high abstraction is pervasive, and widespread, contamination of groundwater from both domestic water (sewerage) and industrial waste (Foster and Choudhary 2009<ref name="Foster 2009">Foster S and Chaudhary NK. 2009. Lucknow City — India: Groundwater Resource Use and Strategic Planning Needs, GW‐MATE Case Profile Collection, in Sustainable Groundwater Management: Lessons from Practice, World Bank, pp 8.</ref>). The stratification of the aquifers protects some of the deeper groundwater from contamination, but shallow groundwater, often used for private water supply, can by highly contaminated. Therefore, continued good quality groundwater supply in the largest cities will be difficult to sustain in the long term, without developing large protected wells fields outside of the urban areas and building groundwater protection into land use planning. A systematic assessment of the scale and significance of existing groundwater pollution in city regions is also required, together with a robust evaluations of private water well use and the role of institutions in relation to urban groundwater use and protection (Foster and Choudhary 2009<ref name="Foster 2009"></ref>; Foster et al. 2010<ref name="Foster 2010">Foster S, van Steenbergen F, Zuleta J and Garduno H. 2010. Conjuctive use of groundwater and surface water — from spontaneous coping strategy to adaptive resource management. GW‐MATE Strategic Overview Series 2: World Bank, Washington DC, pp 26.</ref>).

	[[Image:~~15047fig21~~.jpg\|center\|thumb\|400px\|Figure 21 Competing high abstraction rates from public and private water supply in Dhaka Mega City (Source: UN 2015).]]		[[Image:15047_fig21.jpg\|center\|thumb\|400px\|Figure 21 Competing high abstraction rates from public and private water supply in Dhaka Mega City (Source: UN 2015).]]

	==References==		==References==

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	Groundwater recharge in the basin is controlled by: rainfall recharge (where the forecast increase in intensity of rainfall may lead to increased recharge, Taylor et al. 2013<ref name="Taylor 2013">Taylor R. et al. 2013. Groundwater and climate change, Nature Climate Change 3; 322–329, doi: 10.1038/nclimate1744</ref>); and leakage from canals and rivers. Future estimates of river flow are only as reliable as the future estimates of precipitation, which as discussed above are highly uncertain. For the Ganges, glacier melt comprises less than 10% of flow (Immerzeel et al. 2010<ref name="Immerzeel">Immerzeel W W, Pellicciotti F and Bierkens M F P. 2013. Rising river flows throughout the twenty‐first centrury in two Himalayan glacierized watersheds, ''Nature Geoscience'', Letters, doi: 10.1038/NGEO1896</ref>), much of which occurs during the monsoon period; therefore it is likely that future changes in glacier melt will not be a controlling influence on groundwater recharge. The situation in the Indus is different, with a much higher proportion of flow related to glacier melt. In the medium term this is likely to lead to higher river flows as the rate of melting of the glaciers increases (Jiménez‐Cisneros et al. 2014<ref name="Jim"></ref>). In the long term, when the contribution from glacial melt will reduce, it is postulated that increases in precipitation and snowmelt will compensate (Immerzeel et al. 2010<ref name="Immerzeel"></ref>), although the uncertainty in future precipitation forecasting reduces the reliability of such predictions. A greater and more tangible risk to groundwater recharge are programmes to line tertiary canals and limit localised leakage and therefore limit recharge.		Groundwater recharge in the basin is controlled by: rainfall recharge (where the forecast increase in intensity of rainfall may lead to increased recharge, Taylor et al. 2013<ref name="Taylor 2013">Taylor R. et al. 2013. Groundwater and climate change, Nature Climate Change 3; 322–329, doi: 10.1038/nclimate1744</ref>); and leakage from canals and rivers. Future estimates of river flow are only as reliable as the future estimates of precipitation, which as discussed above are highly uncertain. For the Ganges, glacier melt comprises less than 10% of flow (Immerzeel et al. 2010<ref name="Immerzeel">Immerzeel W W, Pellicciotti F and Bierkens M F P. 2013. Rising river flows throughout the twenty‐first centrury in two Himalayan glacierized watersheds, ''Nature Geoscience'', Letters, doi: 10.1038/NGEO1896</ref>), much of which occurs during the monsoon period; therefore it is likely that future changes in glacier melt will not be a controlling influence on groundwater recharge. The situation in the Indus is different, with a much higher proportion of flow related to glacier melt. In the medium term this is likely to lead to higher river flows as the rate of melting of the glaciers increases (Jiménez‐Cisneros et al. 2014<ref name="Jim"></ref>). In the long term, when the contribution from glacial melt will reduce, it is postulated that increases in precipitation and snowmelt will compensate (Immerzeel et al. 2010<ref name="Immerzeel"></ref>), although the uncertainty in future precipitation forecasting reduces the reliability of such predictions. A greater and more tangible risk to groundwater recharge are programmes to line tertiary canals and limit localised leakage and therefore limit recharge.

	With such uncertainty about future precipitation and a likelihood of continued annual increases in abstraction (given the continuation of the drivers and incentives, such as energy subsidies, leading to groundwater abstraction) the ''resilience ''of the groundwater systems to change is a useful lens through which to examine the groundwater resource. Groundwater resilience to change is governed by the volumes of freshwater, the permeability of the aquifer system and the likely long term recharge (Foster and MacDonald 2014<ref name="Foster">Foster S and MacDonald A M. 2014. The 'water security' dialogue: why it needs to be better informed about groundwater. ''Hydrogeology Journal'', 22; 7, 1489–1492.</ref>.		With such uncertainty about future precipitation and a likelihood of continued annual increases in abstraction (given the continuation of the drivers and incentives, such as energy subsidies, leading to groundwater abstraction) the ''resilience ''of the groundwater systems to change is a useful lens through which to examine the groundwater resource. Groundwater resilience to change is governed by the volumes of freshwater, the permeability of the aquifer system and the likely long term recharge (Foster and MacDonald 2014<ref name="Foster">Foster S and MacDonald A M. 2014. The 'water security' dialogue: why it needs to be better informed about groundwater. ''Hydrogeology Journal'', 22; 7, 1489–1492.</ref>).

	==Groundwater storage volumes and trends==		==Groundwater storage volumes and trends==

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Degradation

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	[[Image:15047fig20.jpg\|center\|thumb\|400px\|Figure 20 intensive agriculture within the Upper Ganges typology.]]		[[Image:15047fig20.jpg\|center\|thumb\|400px\|Figure 20 intensive agriculture within the Upper Ganges typology.]]

	Intense groundwater abstraction is also accompanied by increases in the use of fertilizer, pesticide and herbicides. Elevated nitrate concentrations are found within the Punjab (Lapworth et al. 2014<ref name="Lapworth 2014"></ref>), and have been drawn down to >100 m depth by deep pumping. Elevated nitrate concentrations are also likely to be associated with the presence of other agriculturally derived contaminants. Recycling of groundwater through abstraction, irrigation and irrigation returns has also been shown to intensify this process (Ó Dochartaigh et al, 2010<ref name="ODoch 2010">O Dochartaigh B E, MacDonald A M, Darling W G, Hughes A G, Li J X and Shi L A. 2010. Determining groundwater degradation from irrigation in desert‐marginal northern China, Hydrogeology Journal, 18; 1939–1952.</ref>), with increasing concentrations of solutes and contaminants within irrigation returns derived from groundwater. Routinely monitoring groundwater quality enables trends in degrading quality to be identified and strategies developed to try to mitigate the problem.		Intense groundwater abstraction is also accompanied by increases in the use of fertilizer, pesticide and herbicides. Elevated nitrate concentrations are found within the Punjab (Lapworth et al. 2014<ref name="Lapworth 2014"> Lapworth D J, Gopal K, Rao M S, MacDonald A M. 2014. Intensive Groundwater Exploitation in the Punjab – an evaluation of resource and quality trends, British Geological Survey Open Report, ''Groundwater Science Programme'', OR/14/068. </ref>), and have been drawn down to >100 m depth by deep pumping. Elevated nitrate concentrations are also likely to be associated with the presence of other agriculturally derived contaminants. Recycling of groundwater through abstraction, irrigation and irrigation returns has also been shown to intensify this process (Ó Dochartaigh et al, 2010<ref name="ODoch 2010">O Dochartaigh B E, MacDonald A M, Darling W G, Hughes A G, Li J X and Shi L A. 2010. Determining groundwater degradation from irrigation in desert‐marginal northern China, Hydrogeology Journal, 18; 1939–1952.</ref>), with increasing concentrations of solutes and contaminants within irrigation returns derived from groundwater. Routinely monitoring groundwater quality enables trends in degrading quality to be identified and strategies developed to try to mitigate the problem.

	==Resilience of deep groundwater abstraction (in the Bengal Basin) against contamination by arsenic and salinity==		==Resilience of deep groundwater abstraction (in the Bengal Basin) against contamination by arsenic and salinity==

Dbk at 08:57, 23 October 2015

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	The degradation of water quality is arguably the greatest threat to the IGB aquifer. Within the Indus Basin and parts of the Ganges, water management practices have led to significant degradation in groundwater quality, and continue to do so. Three of the most pressing issues are: increased salinization of the groundwater resources, contamination from agriculture and urban centres, and the mobilisation of arsenic and other naturally occurring contaminants. In this section we discuss salinization and agricultural contamination, arsenic and urban issues are considered separately below.		The degradation of water quality is arguably the greatest threat to the IGB aquifer. Within the Indus Basin and parts of the Ganges, water management practices have led to significant degradation in groundwater quality, and continue to do so. Three of the most pressing issues are: increased salinization of the groundwater resources, contamination from agriculture and urban centres, and the mobilisation of arsenic and other naturally occurring contaminants. In this section we discuss salinization and agricultural contamination, arsenic and urban issues are considered separately below.

	Irrigation and abstraction has led to considerable salinization of groundwater in the Mid Indus, Upper Ganges typology, and the Lower Indus groundwater typology — Figure 20. Canal leakage and irrigation returns, although useful for groundwater recharge, have also degraded the quality of the groundwater through water‐logging and subsequent phreatic salinization. It is possible that increased groundwater abstraction has been reducing this trend by lowering groundwater levels, however, high abstraction has also mobilised older, deeper saline water into shallow depths. This is evident in Mid Indus /Upper Ganges typology where high abstraction is being accompanied by increasingly saline water. In the Indus, the reduction of outflow of water at the Kotri Barrage means that there is little or no natural outflow from the basin. Therefore, the salts generated from weathering of the rocks in the Himalaya are all retained within the basin, leading inevitably to an increase in salt concentration in the groundwater. Within the lower Indus, much of the groundwater is already saline, and the shallow freshwater lenses are highly vulnerable to abstraction.		Irrigation and abstraction has led to considerable salinization of groundwater in the Mid Indus, Upper Ganges typology, and the Lower Indus groundwater typology — Figure 20. Canal leakage and irrigation returns, although useful for groundwater recharge, have also degraded the quality of the groundwater through water‐logging and subsequent phreatic salinization. It is possible that increased groundwater abstraction has been reducing this trend by lowering groundwater levels, however, high abstraction has also mobilised older, deeper saline water into shallow depths. This is evident in Mid Indus/Upper Ganges typology where high abstraction is being accompanied by increasingly saline water. In the Indus, the reduction of outflow of water at the Kotri Barrage means that there is little or no natural outflow from the basin. Therefore, the salts generated from weathering of the rocks in the Himalaya are all retained within the basin, leading inevitably to an increase in salt concentration in the groundwater. Within the lower Indus, much of the groundwater is already saline, and the shallow freshwater lenses are highly vulnerable to abstraction.

	[[Image:15047fig20.jpg\|center\|thumb\|400px\|Figure 20 intensive agriculture within the Upper Ganges typology.]]		[[Image:15047fig20.jpg\|center\|thumb\|400px\|Figure 20 intensive agriculture within the Upper Ganges typology.]]
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	==Resilience of deep groundwater abstraction (in the Bengal Basin) against contamination by arsenic and salinity==		==Resilience of deep groundwater abstraction (in the Bengal Basin) against contamination by arsenic and salinity==
	The potential vulnerability of deep wells to contamination by arsenic and salinity drawn down over time from shallow and intermediate levels is critical to the security of water supply in Bangladesh (Burgess et al. 2010<ref name="Burgess">Burgess W G, Hoque M A ,Michael H A, Voss C I, Breit G N and Ahmed K M 2010 Vulnerability of deep groundwater in the Bengal Aquifer System to contamination by arsenic. Nature Geoscience 3: 83–87</ref>). Michael and Voss (2008) have concluded from a regional modelling study of the Bengal basin that deep groundwater “could provide arsenic‐safe drinking water to >90% of the arsenic‐impacted region over a 1000‐year timescale, if its utilization is limited to domestic supply”. In a similar region a modelling study of SE Bangladesh, UCL (2013) have concluded that “deep groundwater abstraction for public water supply in southern Bangladesh is in general secure against ingress of arsenic for at least 100 years”.		The potential vulnerability of deep wells to contamination by arsenic and salinity drawn down over time from shallow and intermediate levels is critical to the security of water supply in Bangladesh (Burgess et al. 2010<ref name="Burgess">Burgess W G, Hoque M A ,Michael H A, Voss C I, Breit G N and Ahmed K M 2010 Vulnerability of deep groundwater in the Bengal Aquifer System to contamination by arsenic. Nature Geoscience 3: 83–87</ref>). Michael and Voss (2008)<ref name="Michael 2008">Michael H A and Voss C I 2008. Evaluation of the sustainability of deep groundwater as an arsenic — safe resource in the Bengal Basin. PNAS 105 (25) 8531‐8536 </ref> have concluded from a regional modelling study of the Bengal basin that deep groundwater “could provide arsenic‐safe drinking water to >90% of the arsenic‐impacted region over a 1000‐year timescale, if its utilization is limited to domestic supply”. In a similar region a modelling study of SE Bangladesh, UCL (2013) have concluded that “deep groundwater abstraction for public water supply in southern Bangladesh is in general secure against ingress of arsenic for at least 100 years”.

			Locally, deep groundwater is vulnerable to arsenic or salinity even under present pumping patterns, but these impacts are manageable through a programme of monitoring that could provide many years advance warning of impending problems. Despite concern for sustainability of the deep groundwater resource, there is little empirical evidence for an adverse impact on quality or water levels that can be attributed to deep groundwater pumping. In the Pakistan Punjab, there is evidence of upconing of deeper saline groundwater from abstraction. Across the basin, arsenic exceeds 10 μg/L in 18% of deep wells (Burgess et al. 2010<ref name="Burgess"></ref>), but whether this is a result of breached well casings or hydrological response to pumping remains uncertain. Empirical re‐appraisal of 46 deep wells in south‐central Bangladesh (Ravenscroft et al., 2013<ref name="Ravenscroft 2013"> Ravenscroft P, McArthur J M and Hoque M A. 2013. Stable groundwater quality in deep aquifers of Southern Bangladesh: the case against sustainable abstraction, Science of the Total Environment 454‐456: 627–638 </ref>) shows groundwater composition at >150 m depth has remained largely unchanged for the 13 years between 1998 and 2011 and with no deterioration inferred over the operating lifetimes of the deep tubewells concerned, between 20 and 43 years.

	Locally, deep groundwater is vulnerable to arsenic or salinity even under present pumping patterns, but these impacts are manageable through a programme of monitoring that could provide many years advance warning of impending problems. Despite concern for sustainability of the deep groundwater resource, there is little empirical evidence for an adverse impact on quality or water levels that can be attributed to deep groundwater pumping. In the Pakistan Punjab, there is evidence of upconing of deeper saline groundwater from abstraction. Across the basin, arsenic exceeds 10 μg/L in 18% of deep wells (Burgess et al. 2010), but whether this is a result of breached well casings or hydrological response to pumping remains uncertain. Empirical re‐appraisal of 46 deep wells in south‐central Bangladesh (Ravenscroft et al., 2013) shows groundwater composition at >150 m depth has remained largely unchanged for the 13 years between 1998 and 2011 and with no deterioration inferred over the operating lifetimes of the deep tubewells concerned, between 20 and 43 years.

	Therefore, the deeper groundwater resources in the Bengal basin have a high general resilience to change induced by climate or pumping: they are largely divorced from the modern climate, with negligible modern recharge, and at a regional level there appears little evidence of widespread changes in arsenic concentrations. However, at a highly localised level, around individual wells, the heads induced by pumping, and disruption to the aquifer system during drilling can lead to localised contamination at depth/localised contamination pathways. Therefore routine monitoring both of the regional aquifer system and individual pumping wells is paramount.		Therefore, the deeper groundwater resources in the Bengal basin have a high general resilience to change induced by climate or pumping: they are largely divorced from the modern climate, with negligible modern recharge, and at a regional level there appears little evidence of widespread changes in arsenic concentrations. However, at a highly localised level, around individual wells, the heads induced by pumping, and disruption to the aquifer system during drilling can lead to localised contamination at depth/localised contamination pathways. Therefore routine monitoring both of the regional aquifer system and individual pumping wells is paramount.

	==High abstraction from cities==		==High abstraction from cities==
	Groundwater from the IGB alluvial aquifer system sustains many of the region’s cities, notably, New Delhi, Dhaka and Lahore. Although urban groundwater has not been a focus of this study, given that the total volumes abstracted are small compared to irrigation, and urban groundwater is a highly complex issue, the resilience of the water supplies to these cities is of major concern. The high density of the abstraction (e.g. for Dhaka an estimated 0.8 km<sup>3</sup> within 300 km<sup>2</sup> DWASA 2012) and the mixture of private and public water supplies, means groundwater is locally becoming highly depleted in these cities with groundwater levels falling rapidly (>100 m depth in some locations) and bringing with it a set of issues, such as subsidence, declining yields, increased costs (Morris et al. 2003) — Figure 21. In tandem with the high abstraction is pervasive, and widespread, contamination of groundwater from both domestic water (sewerage) and industrial waste (Foster and Choudhary 2009). The stratification of the aquifers protects some of the deeper groundwater from contamination, but shallow groundwater, often used for private water supply, can by highly contaminated. Therefore, continued good quality groundwater supply in the largest cities will be difficult to sustain in the long term, without developing large protected wells fields outside of the urban areas and building groundwater protection into land use planning. A systematic assessment of the scale and significance of existing groundwater pollution in city regions is also required, together with a robust evaluations of private water well use and the role of institutions in relation to urban groundwater use and protection (Foster and Choudhary 2009; Foster et al. 2010).		Groundwater from the IGB alluvial aquifer system sustains many of the region’s cities, notably, New Delhi, Dhaka and Lahore. Although urban groundwater has not been a focus of this study, given that the total volumes abstracted are small compared to irrigation, and urban groundwater is a highly complex issue, the resilience of the water supplies to these cities is of major concern. The high density of the abstraction (e.g. for Dhaka an estimated 0.8 km<sup>3</sup> within 300 km<sup>2</sup> DWASA 2012) and the mixture of private and public water supplies, means groundwater is locally becoming highly depleted in these cities with groundwater levels falling rapidly (>100 m depth in some locations) and bringing with it a set of issues, such as subsidence, declining yields, increased costs (Morris et al. 2003<ref name="Morris 2003">Morris, B L, Lawrence, A R, Chilton, P J, Adams, B, Calow, R and Klinck, B A. 2003). Groundwater and its Susceptibility to Degradation: A Global Assessment of the Problems and Options for Management. Early Warning and Assessment Report Series, RS, 03‐3. ''United Nations Environment Programme'', Nairobi. </ref>) — Figure 21. In tandem with the high abstraction is pervasive, and widespread, contamination of groundwater from both domestic water (sewerage) and industrial waste (Foster and Choudhary 2009<ref name="Foster 2009">Foster S and Chaudhary NK. 2009. Lucknow City — India: Groundwater Resource Use and Strategic Planning Needs, GW‐MATE Case Profile Collection, in Sustainable Groundwater Management: Lessons from Practice, World Bank, pp 8.</ref>). The stratification of the aquifers protects some of the deeper groundwater from contamination, but shallow groundwater, often used for private water supply, can by highly contaminated. Therefore, continued good quality groundwater supply in the largest cities will be difficult to sustain in the long term, without developing large protected wells fields outside of the urban areas and building groundwater protection into land use planning. A systematic assessment of the scale and significance of existing groundwater pollution in city regions is also required, together with a robust evaluations of private water well use and the role of institutions in relation to urban groundwater use and protection (Foster and Choudhary 2009<ref name="Foster 2009"></ref>; Foster et al. 2010<ref name="Foster 2010">Foster S, van Steenbergen F, Zuleta J and Garduno H. 2010. Conjuctive use of groundwater and surface water — from spontaneous coping strategy to adaptive resource management. GW‐MATE Strategic Overview Series 2: World Bank, Washington DC, pp 26.</ref>).

	[[Image:15047fig21.jpg\|center\|thumb\|400px\|Figure 21 Competing high abstraction rates from public and private water supply in Dhaka Mega City (Source: UN 2015).]]		[[Image:15047fig21.jpg\|center\|thumb\|400px\|Figure 21 Competing high abstraction rates from public and private water supply in Dhaka Mega City (Source: UN 2015).]]

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	With such uncertainty about future precipitation and a likelihood of continued annual increases in abstraction (given the continuation of the drivers and incentives, such as energy subsidies, leading to groundwater abstraction) the ''resilience ''of the groundwater systems to change is a useful lens through which to examine the groundwater resource. Groundwater resilience to change is governed by the volumes of freshwater, the permeability of the aquifer system and the likely long term recharge (Foster and MacDonald 2014<ref name="Foster">Foster S and MacDonald A M. 2014. The 'water security' dialogue: why it needs to be better informed about groundwater. ''Hydrogeology Journal'', 22; 7, 1489–1492.</ref>.		With such uncertainty about future precipitation and a likelihood of continued annual increases in abstraction (given the continuation of the drivers and incentives, such as energy subsidies, leading to groundwater abstraction) the ''resilience ''of the groundwater systems to change is a useful lens through which to examine the groundwater resource. Groundwater resilience to change is governed by the volumes of freshwater, the permeability of the aquifer system and the likely long term recharge (Foster and MacDonald 2014<ref name="Foster">Foster S and MacDonald A M. 2014. The 'water security' dialogue: why it needs to be better informed about groundwater. ''Hydrogeology Journal'', 22; 7, 1489–1492.</ref>.


	==Groundwater storage volumes and trends==		==Groundwater storage volumes and trends==
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	*SEC (Specific Electrical Conductivity)		*SEC (Specific Electrical Conductivity)
			\|}

	\|}
	So what of recharge to the IGB alluvial aquifer in the future? The climate forecasts do not suggest widespread and rapid reduction in precipitation volumes across the basin. Given the evidence that rainfall recharge can occur even where precipitation is low (<350 mm) and may be linked to intensity of rainfall events, significant rainfall recharge is likely to carry on within the bounds forecast for future climate variability. River flow is also not forecast to be severely impacted by climate change, or even glacier melting. However, river flow, particularly in the Indus, has been significantly impacted by diversions for irrigation, with severe impacts for the quality of water particularly in the Sindh. Canal leakage forms an important component of groundwater recharge, particularly in drier areas. Programmes to line tertiary canals, if not accompanied by a reduction in groundwater abstraction could have a much greater impact on groundwater recharge than any direct influence from climate change. Another area to focus on is returns from irrigation to the groundwater. Using more efficient irrigation methods may reduce this loss, and therefore reduce net groundwater recharge.		So what of recharge to the IGB alluvial aquifer in the future? The climate forecasts do not suggest widespread and rapid reduction in precipitation volumes across the basin. Given the evidence that rainfall recharge can occur even where precipitation is low (<350 mm) and may be linked to intensity of rainfall events, significant rainfall recharge is likely to carry on within the bounds forecast for future climate variability. River flow is also not forecast to be severely impacted by climate change, or even glacier melting. However, river flow, particularly in the Indus, has been significantly impacted by diversions for irrigation, with severe impacts for the quality of water particularly in the Sindh. Canal leakage forms an important component of groundwater recharge, particularly in drier areas. Programmes to line tertiary canals, if not accompanied by a reduction in groundwater abstraction could have a much greater impact on groundwater recharge than any direct influence from climate change. Another area to focus on is returns from irrigation to the groundwater. Using more efficient irrigation methods may reduce this loss, and therefore reduce net groundwater recharge.

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Dbk at 08:33, 23 October 2015

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Dbk at 14:49, 21 October 2015

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	Reliably forecasting the future nature of the Indian monsoon is proving difficult, with many Global Climate Models disagreeing on the impact of future emissions scenarios on both the timing and magnitude of rainfall (Gosht et al. 2012). However, progress is being made by the climate modelling community, and some of the key processes driving climate variability are being identified, uncovered and modelled (Turner et al. 2012<ref name="Turner 2012">Turner, A G Annamalai H. 2012. Climate change and the South Asian summer monsoon. Nature Climate Change 2 587–595.</ref>). From the perspective of groundwater, we need to understand how changes in the climate will impact on both abstraction and recharge. Looking at the issue from this perspective, there are some common elements of forecasts that could impact groundwater. There is a likelihood of increased storminess, with higher intensity rainfall as the energy in the climate system increases (IPCC 2013<ref name="IPCC 2013">IPCC. 2013. Climate Change 2013: The Physical Science Basis, pp 1535.</ref>; Jiménez‐Cisneros et al. 2014<ref name="Jim">Jiménez‐Cisneros, B E, Oki, T, Arnell, N W, Benito, G, Cogley, J G, Döll, P, Jiang, T and Mwakalila, S S. 2014. Freshwater resources. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Field, C B, Barros, V R, Dokken, D J, Mach, K J, Mastrandrea, M D, Bilir, T E, Chatterjee, M, Ebi, K L, Estrada, Y O, Genova, R C, Girma, B, Kissel, E S, Levy, A N, MacCracken, S, Mastrandrea, P R and White, L L. (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 229–269.</ref>). The timing of the start of the monsoon may also change. Temperature is highly likely to increase markedly, although this will be moderated in the basin by local effects of irrigation and evapotranspiration (Harding et al. 2013<ref name="Harding">Harding R J, Blyth E M, Tuinenburg O A and Wiltshire A. 2013. Land atmosphere feedbacks and their role in the water resources of the Ganges basin, ''Science of the Total Environment'', 468–469, S85‐92.</ref>). The increasing unreliability of rainfall and higher temperature are likely to exacerbate the demand for groundwater helping to sustain the rapid expansion of groundwater use (currently estimated at 2–5 km<sup>3</sup> per year).		Reliably forecasting the future nature of the Indian monsoon is proving difficult, with many Global Climate Models disagreeing on the impact of future emissions scenarios on both the timing and magnitude of rainfall (Gosht et al. 2012). However, progress is being made by the climate modelling community, and some of the key processes driving climate variability are being identified, uncovered and modelled (Turner et al. 2012<ref name="Turner 2012">Turner, A G Annamalai H. 2012. Climate change and the South Asian summer monsoon. Nature Climate Change 2 587–595.</ref>). From the perspective of groundwater, we need to understand how changes in the climate will impact on both abstraction and recharge. Looking at the issue from this perspective, there are some common elements of forecasts that could impact groundwater. There is a likelihood of increased storminess, with higher intensity rainfall as the energy in the climate system increases (IPCC 2013<ref name="IPCC 2013">IPCC. 2013. Climate Change 2013: The Physical Science Basis, pp 1535.</ref>; Jiménez‐Cisneros et al. 2014<ref name="Jim">Jiménez‐Cisneros, B E, Oki, T, Arnell, N W, Benito, G, Cogley, J G, Döll, P, Jiang, T and Mwakalila, S S. 2014. Freshwater resources. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Field, C B, Barros, V R, Dokken, D J, Mach, K J, Mastrandrea, M D, Bilir, T E, Chatterjee, M, Ebi, K L, Estrada, Y O, Genova, R C, Girma, B, Kissel, E S, Levy, A N, MacCracken, S, Mastrandrea, P R and White, L L. (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 229–269.</ref>). The timing of the start of the monsoon may also change. Temperature is highly likely to increase markedly, although this will be moderated in the basin by local effects of irrigation and evapotranspiration (Harding et al. 2013<ref name="Harding">Harding R J, Blyth E M, Tuinenburg O A and Wiltshire A. 2013. Land atmosphere feedbacks and their role in the water resources of the Ganges basin, ''Science of the Total Environment'', 468–469, S85‐92.</ref>). The increasing unreliability of rainfall and higher temperature are likely to exacerbate the demand for groundwater helping to sustain the rapid expansion of groundwater use (currently estimated at 2–5 km<sup>3</sup> per year).

	Groundwater recharge in the basin is controlled by: rainfall recharge (where the forecast increase in intensity of rainfall may lead to increased recharge, Taylor et al. 2013); and leakage from canals and rivers. Future estimates of river flow are only as reliable as the future estimates of precipitation, which as discussed above are highly uncertain. For the Ganges, glacier melt comprises less than 10% of flow (Immerzeel et al. 2010), much of which occurs during the monsoon period; therefore it is likely that future changes in glacier melt will not be a controlling influence on groundwater recharge. The situation in the Indus is different, with a much higher proportion of flow related to glacier melt. In the medium term this is likely to lead to higher river flows as the rate of melting of the glaciers increases (Jiménez‐Cisneros et al. 2014). In the long term, when the contribution from glacial melt will reduce, it is postulated that increases in precipitation and snowmelt will compensate (Immerzeel et al. 2010), although the uncertainty in future precipitation forecasting reduces the reliability of such predictions. A greater and more tangible risk to groundwater recharge are programmes to line tertiary canals and limit localised leakage and therefore limit recharge.		Groundwater recharge in the basin is controlled by: rainfall recharge (where the forecast increase in intensity of rainfall may lead to increased recharge, Taylor et al. 2013<ref name="Taylor 2013">Taylor R. et al. 2013. Groundwater and climate change, Nature Climate Change 3; 322–329, doi: 10.1038/nclimate1744</ref>); and leakage from canals and rivers. Future estimates of river flow are only as reliable as the future estimates of precipitation, which as discussed above are highly uncertain. For the Ganges, glacier melt comprises less than 10% of flow (Immerzeel et al. 2010<ref name="Immerzeel">Immerzeel W W, Pellicciotti F and Bierkens M F P. 2013. Rising river flows throughout the twenty‐first centrury in two Himalayan glacierized watersheds, ''Nature Geoscience'', Letters, doi: 10.1038/NGEO1896</ref>), much of which occurs during the monsoon period; therefore it is likely that future changes in glacier melt will not be a controlling influence on groundwater recharge. The situation in the Indus is different, with a much higher proportion of flow related to glacier melt. In the medium term this is likely to lead to higher river flows as the rate of melting of the glaciers increases (Jiménez‐Cisneros et al. 2014<ref name="Jim"></ref>). In the long term, when the contribution from glacial melt will reduce, it is postulated that increases in precipitation and snowmelt will compensate (Immerzeel et al. 2010<ref name="Immerzeel"></ref>), although the uncertainty in future precipitation forecasting reduces the reliability of such predictions. A greater and more tangible risk to groundwater recharge are programmes to line tertiary canals and limit localised leakage and therefore limit recharge.

			With such uncertainty about future precipitation and a likelihood of continued annual increases in abstraction (given the continuation of the drivers and incentives, such as energy subsidies, leading to groundwater abstraction) the ''resilience ''of the groundwater systems to change is a useful lens through which to examine the groundwater resource. Groundwater resilience to change is governed by the volumes of freshwater, the permeability of the aquifer system and the likely long term recharge (Foster and MacDonald 2014<ref name="Foster">Foster S and MacDonald A M. 2014. The 'water security' dialogue: why it needs to be better informed about groundwater. ''Hydrogeology Journal'', 22; 7, 1489–1492.</ref>.

	With such uncertainty about future precipitation and a likelihood of continued annual increases in abstraction (given the continuation of the drivers and incentives, such as energy subsidies, leading to groundwater abstraction) the ''resilience ''of the groundwater systems to change is a useful lens through which to examine the groundwater resource. Groundwater resilience to change is governed by the volumes of freshwater, the permeability of the aquifer system and the likely long term recharge (Foster and MacDonald 2014).

	==Groundwater storage volumes and trends==		==Groundwater storage volumes and trends==
	The usable groundwater resource in the IGB is a function of the depth of the aquifer, the specific yield of the sediments (a measure of the drainable groundwater, related to the porosity) and the salinity of the groundwater. For this analysis we have limited the depth of the aquifer to 200 m, partly because so little information on aquifer properties or salinity is available below that depth, and also because so few boreholes currently abstract water from below 200 m except in the Bengal Basin.		The usable groundwater resource in the IGB is a function of the depth of the aquifer, the specific yield of the sediments (a measure of the drainable groundwater, related to the porosity) and the salinity of the groundwater. For this analysis we have limited the depth of the aquifer to 200 m, partly because so little information on aquifer properties or salinity is available below that depth, and also because so few boreholes currently abstract water from below 200 m except in the Bengal Basin.

	Overall groundwater storage in the top 200 m of the IGB alluvial aquifer system is estimated at approximately 30 000 km<sup>3</sup> ± 10 000 km<sup>3</sup>. For comparison, the estimated annual surface water flow from the Indus and Ganges‐Brahmaputra‐Meghna is approximately ~~1,100 km3~~ (FAO Aquastat 2014). The groundwater storage comprises 11 800 km<sup>3</sup> of high quality fresh water with TDS < 500 mg/L, 11 500 km<sup>3</sup> of water with TDS 500–1000 mg/L, 3000 km<sup>3</sup> with TDS 1000–2500 mg/L and 3300 km<sup>3</sup> with water of the poorest quality with TDS>2500 mg/L. Groundwater abstraction comprises 205 km<sup>3</sup> across the basin (in 2010), with much of it being abstracted from the freshwater areas: 159 km<sup>3</sup> from storage with TDS < 1000 mg/L, 32 km<sup>3</sup> from TDS 1000–2500 mg/L and 13 km<sup>3</sup> from TDS > 2500 mg/L. Therefore, this large store of groundwater offers a significant buffer against short term changes in climate, with several decades of abstraction within the aquifer, even if recharge were to cease. However, declining groundwater levels can have a devastating impact on ecosystems, river flows and users of shallow groundwater, many of whom will not be able to access deeper groundwater.		Overall groundwater storage in the top 200 m of the IGB alluvial aquifer system is estimated at approximately 30 000 km<sup>3</sup> ± 10 000 km<sup>3</sup>. For comparison, the estimated annual surface water flow from the Indus and Ganges‐Brahmaputra‐Meghna is approximately 1100 km<sup>3</sup> (FAO Aquastat 2014). The groundwater storage comprises 11 800 km<sup>3</sup> of high quality fresh water with TDS <500 mg/L, 11 500 km<sup>3</sup> of water with TDS 500–1000 mg/L, 3000 km<sup>3</sup> with TDS 1000–2500 mg/L and 3300 km<sup>3</sup> with water of the poorest quality with TDS >2500 mg/L. Groundwater abstraction comprises 205 km<sup>3</sup> across the basin (in 2010), with much of it being abstracted from the freshwater areas: 159 km<sup>3</sup> from storage with TDS <1000 mg/L, 32 km<sup>3</sup> from TDS 1000–2500 mg/L and 13 km<sup>3</sup> from TDS >2500 mg/L. Therefore, this large store of groundwater offers a significant buffer against short term changes in climate, with several decades of abstraction within the aquifer, even if recharge were to cease. However, declining groundwater levels can have a devastating impact on ecosystems, river flows and users of shallow groundwater, many of whom will not be able to access deeper groundwater.

	Figure 18 shows the estimated current annual change in groundwater storage across the basin, estimated from the groundwater level map developed for the basin as part of this study. A complex picture of groundwater storage changes emerges governed both by the abstraction and the recharge. Highest depletion of storage is occurring in parts of the Indian Punjab, Haryana and Punjab Region in Pakistan where annual mass change of > 100 mm equivalent of groundwater is occurring. If such trends of depletion continued, the groundwater resources in the upper 200 m in North West India and parts of the Punjab in Pakistan could be depleted to less than 50 % of their volume within 50 years. Similar trends are not observed in northern Bangladesh despite high abstraction, due to much greater natural recharge.		Figure 18 shows the estimated current annual change in groundwater storage across the basin, estimated from the groundwater level map developed for the basin as part of this study. A complex picture of groundwater storage changes emerges governed both by the abstraction and the recharge. Highest depletion of storage is occurring in parts of the Indian Punjab, Haryana and Punjab Region in Pakistan where annual mass change of > 100 mm equivalent of groundwater is occurring. If such trends of depletion continued, the groundwater resources in the upper 200 m in North West India and parts of the Punjab in Pakistan could be depleted to less than 50 % of their volume within 50 years. Similar trends are not observed in northern Bangladesh despite high abstraction, due to much greater natural recharge.

	Groundwater accumulation also occurs — most notably in the Sindh, where groundwater has been accumulating at a rate of > 10 mm per year. This is reflected in the water‐logging and corresponding salinity problems experienced in the Sindh. Groundwater accumulation also occurs across other parts of the basin — often close to where rapid depletion also occurs. This is a consequence of canal irrigation, where high leakage can cause rising groundwater levels and water‐logging within one part of the canal command, and rapid depletion further downstream.		Groundwater accumulation also occurs — most notably in the Sindh, where groundwater has been accumulating at a rate of >10 mm per year. This is reflected in the water‐logging and corresponding salinity problems experienced in the Sindh. Groundwater accumulation also occurs across other parts of the basin — often close to where rapid depletion also occurs. This is a consequence of canal irrigation, where high leakage can cause rising groundwater levels and water‐logging within one part of the canal command, and rapid depletion further downstream.

	Across the entire basin, the annual change in groundwater storage is estimated at approximately 10 km<sup>3</sup>. As discussed above, this integrates much complexity and variability within the IGB alluvial aquifer system, with some areas depleting and others accumulating. This compares well with the estimate of groundwater depletion using GRACE from Rodell et al. (2009) who estimated 18 km<sup>3</sup> depletion per year for the states of Rajasthan, Punjab and Haryana, with the majority of the depletion occurring in Rajasthan. Interpretation of GRACE data by Tiwari et al. (2009) inferred a much higher rate of depletion (approximately 50 km<sup>3</sup> per annum); however this work again had much of the depletion occurring outside the IGB alluvial aquifer system (e.g. within the poorer aquifer systems of Rajasthan) where recharge is negligible, and also indicated significant depletion in Bangladesh which was difficult to reconcile with observations (Shamsudduha et al. 2012). More recent work on the GRACE data by Chen et al (2014) suggests average depletion of 20 km<sup>3</sup> per year across the region (again with significant depletion outside of the IGB alluvial aquifer system), with several years actually showing net accumulation. Using GRACE within this region to infer groundwater storage change is challenging: for example accounting for the significant changes in mass balance from ongoing tectonic activity, erosion and sedimentation; the large surface water flows within the river systems, the changes in moisture in the atmosphere, and the change in mass from snow and ice melt. Constraining and disaggregating the bulk estimates of mass change from GRACE to give groundwater storage changes required additional information and data. It is hoped that the groundwater storage changes developed here from analysis of the best available regional observational groundwater level data and specific yield information will be a useful tool to the further development and interpretation of GRACE data in the region.		Across the entire basin, the annual change in groundwater storage is estimated at approximately 10 km<sup>3</sup>. As discussed above, this integrates much complexity and variability within the IGB alluvial aquifer system, with some areas depleting and others accumulating. This compares well with the estimate of groundwater depletion using GRACE from Rodell et al. (2009) who estimated 18 km<sup>3</sup> depletion per year for the states of Rajasthan, Punjab and Haryana, with the majority of the depletion occurring in Rajasthan. Interpretation of GRACE data by Tiwari et al. (2009) inferred a much higher rate of depletion (approximately 50 km<sup>3</sup> per annum); however this work again had much of the depletion occurring outside the IGB alluvial aquifer system (e.g. within the poorer aquifer systems of Rajasthan) where recharge is negligible, and also indicated significant depletion in Bangladesh which was difficult to reconcile with observations (Shamsudduha et al. 2012). More recent work on the GRACE data by Chen et al (2014) suggests average depletion of 20 km<sup>3</sup> per year across the region (again with significant depletion outside of the IGB alluvial aquifer system), with several years actually showing net accumulation. Using GRACE within this region to infer groundwater storage change is challenging: for example accounting for the significant changes in mass balance from ongoing tectonic activity, erosion and sedimentation; the large surface water flows within the river systems, the changes in moisture in the atmosphere, and the change in mass from snow and ice melt. Constraining and disaggregating the bulk estimates of mass change from GRACE to give groundwater storage changes required additional information and data. It is hoped that the groundwater storage changes developed here from analysis of the best available regional observational groundwater level data and specific yield information will be a useful tool to the further development and interpretation of GRACE data in the region.

← Older revision		Revision as of 09:33, 23 October 2015
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	The usable groundwater resource in the IGB is a function of the depth of the aquifer, the specific yield of the sediments (a measure of the drainable groundwater, related to the porosity) and the salinity of the groundwater. For this analysis we have limited the depth of the aquifer to 200 m, partly because so little information on aquifer properties or salinity is available below that depth, and also because so few boreholes currently abstract water from below 200 m except in the Bengal Basin.		The usable groundwater resource in the IGB is a function of the depth of the aquifer, the specific yield of the sediments (a measure of the drainable groundwater, related to the porosity) and the salinity of the groundwater. For this analysis we have limited the depth of the aquifer to 200 m, partly because so little information on aquifer properties or salinity is available below that depth, and also because so few boreholes currently abstract water from below 200 m except in the Bengal Basin.

	Overall groundwater storage in the top 200 m of the IGB alluvial aquifer system is estimated at approximately 30 000 km<sup>3</sup> ± 10 000 km<sup>3</sup>. For comparison, the estimated annual surface water flow from the Indus and Ganges‐Brahmaputra‐Meghna is approximately 1100 km<sup>3</sup> (FAO Aquastat 2014). The groundwater storage comprises 11 800 km<sup>3</sup> of high quality fresh water with TDS <500 mg/L, 11 500 km<sup>3</sup> of water with TDS 500–1000 mg/L, 3000 km<sup>3</sup> with TDS 1000–2500 mg/L and 3300 km<sup>3</sup> with water of the poorest quality with TDS >2500 mg/L. Groundwater abstraction comprises 205 km<sup>3</sup> across the basin (in 2010), with much of it being abstracted from the freshwater areas: 159 km<sup>3</sup> from storage with TDS <1000 mg/L, 32 km<sup>3</sup> from TDS 1000–2500 mg/L and 13 km<sup>3</sup> from TDS >2500 mg/L. Therefore, this large store of groundwater offers a significant buffer against short term changes in climate, with several decades of abstraction within the aquifer, even if recharge were to cease. However, declining groundwater levels can have a devastating impact on ecosystems, river flows and users of shallow groundwater, many of whom will not be able to access deeper groundwater.		Overall groundwater storage in the top 200 m of the IGB alluvial aquifer system is estimated at approximately 30 000 km<sup>3</sup> ± 10 000 km<sup>3</sup>. For comparison, the estimated annual surface water flow from the Indus and Ganges‐Brahmaputra‐Meghna is approximately 1100 km<sup>3</sup> (FAO Aquastat 2014<ref name="FAO 2014">FAO AQUASTAT 2014. Food and agriculture organization of the United Nations (Accessed Feb 2015)</ref>). The groundwater storage comprises 11 800 km<sup>3</sup> of high quality fresh water with TDS <500 mg/L, 11 500 km<sup>3</sup> of water with TDS 500–1000 mg/L, 3000 km<sup>3</sup> with TDS 1000–2500 mg/L and 3300 km<sup>3</sup> with water of the poorest quality with TDS >2500 mg/L. Groundwater abstraction comprises 205 km<sup>3</sup> across the basin (in 2010), with much of it being abstracted from the freshwater areas: 159 km<sup>3</sup> from storage with TDS <1000 mg/L, 32 km<sup>3</sup> from TDS 1000–2500 mg/L and 13 km<sup>3</sup> from TDS >2500 mg/L. Therefore, this large store of groundwater offers a significant buffer against short term changes in climate, with several decades of abstraction within the aquifer, even if recharge were to cease. However, declining groundwater levels can have a devastating impact on ecosystems, river flows and users of shallow groundwater, many of whom will not be able to access deeper groundwater.

	Figure 18 shows the estimated current annual change in groundwater storage across the basin, estimated from the groundwater level map developed for the basin as part of this study. A complex picture of groundwater storage changes emerges governed both by the abstraction and the recharge. Highest depletion of storage is occurring in parts of the Indian Punjab, Haryana and Punjab Region in Pakistan where annual mass change of > 100 mm equivalent of groundwater is occurring. If such trends of depletion continued, the groundwater resources in the upper 200 m in North West India and parts of the Punjab in Pakistan could be depleted to less than 50 % of their volume within 50 years. Similar trends are not observed in northern Bangladesh despite high abstraction, due to much greater natural recharge.		Figure 18 shows the estimated current annual change in groundwater storage across the basin, estimated from the groundwater level map developed for the basin as part of this study. A complex picture of groundwater storage changes emerges governed both by the abstraction and the recharge. Highest depletion of storage is occurring in parts of the Indian Punjab, Haryana and Punjab Region in Pakistan where annual mass change of >100 mm equivalent of groundwater is occurring. If such trends of depletion continued, the groundwater resources in the upper 200 m in North West India and parts of the Punjab in Pakistan could be depleted to less than 50 % of their volume within 50 years. Similar trends are not observed in northern Bangladesh despite high abstraction, due to much greater natural recharge.

	Groundwater accumulation also occurs — most notably in the Sindh, where groundwater has been accumulating at a rate of >10 mm per year. This is reflected in the water‐logging and corresponding salinity problems experienced in the Sindh. Groundwater accumulation also occurs across other parts of the basin — often close to where rapid depletion also occurs. This is a consequence of canal irrigation, where high leakage can cause rising groundwater levels and water‐logging within one part of the canal command, and rapid depletion further downstream.		Groundwater accumulation also occurs — most notably in the Sindh, where groundwater has been accumulating at a rate of >10 mm per year. This is reflected in the water‐logging and corresponding salinity problems experienced in the Sindh. Groundwater accumulation also occurs across other parts of the basin — often close to where rapid depletion also occurs. This is a consequence of canal irrigation, where high leakage can cause rising groundwater levels and water‐logging within one part of the canal command, and rapid depletion further downstream.

	Across the entire basin, the annual change in groundwater storage is estimated at approximately 10 km<sup>3</sup>. As discussed above, this integrates much complexity and variability within the IGB alluvial aquifer system, with some areas depleting and others accumulating. This compares well with the estimate of groundwater depletion using GRACE from Rodell et al. (2009) who estimated 18 km<sup>3</sup> depletion per year for the states of Rajasthan, Punjab and Haryana, with the majority of the depletion occurring in Rajasthan. Interpretation of GRACE data by Tiwari et al. (2009) inferred a much higher rate of depletion (approximately 50 km<sup>3</sup> per annum); however this work again had much of the depletion occurring outside the IGB alluvial aquifer system (e.g. within the poorer aquifer systems of Rajasthan) where recharge is negligible, and also indicated significant depletion in Bangladesh which was difficult to reconcile with observations (Shamsudduha et al. 2012). More recent work on the GRACE data by Chen et al (2014) suggests average depletion of 20 km<sup>3</sup> per year across the region (again with significant depletion outside of the IGB alluvial aquifer system), with several years actually showing net accumulation. Using GRACE within this region to infer groundwater storage change is challenging: for example accounting for the significant changes in mass balance from ongoing tectonic activity, erosion and sedimentation; the large surface water flows within the river systems, the changes in moisture in the atmosphere, and the change in mass from snow and ice melt. Constraining and disaggregating the bulk estimates of mass change from GRACE to give groundwater storage changes required additional information and data. It is hoped that the groundwater storage changes developed here from analysis of the best available regional observational groundwater level data and specific yield information will be a useful tool to the further development and interpretation of GRACE data in the region.		Across the entire basin, the annual change in groundwater storage is estimated at approximately 10 km<sup>3</sup>. As discussed above, this integrates much complexity and variability within the IGB alluvial aquifer system, with some areas depleting and others accumulating. This compares well with the estimate of groundwater depletion using GRACE from Rodell et al. (2009)<ref>Rodell M, Velicogna I and Famiglietti J S. 2009. Satellite‐based estimates of groundwater depletion in India, Nature, 460; 999–1002.</ref> who estimated 18 km<sup>3</sup> depletion per year for the states of Rajasthan, Punjab and Haryana, with the majority of the depletion occurring in Rajasthan. Interpretation of GRACE data by Tiwari et al. (2009) inferred a much higher rate of depletion (approximately 50 km<sup>3</sup> per annum); however this work again had much of the depletion occurring outside the IGB alluvial aquifer system (e.g. within the poorer aquifer systems of Rajasthan) where recharge is negligible, and also indicated significant depletion in Bangladesh which was difficult to reconcile with observations (Shamsudduha et al. 2012). More recent work on the GRACE data by Chen et al (2014) suggests average depletion of 20 km<sup>3</sup> per year across the region (again with significant depletion outside of the IGB alluvial aquifer system), with several years actually showing net accumulation. Using GRACE within this region to infer groundwater storage change is challenging: for example accounting for the significant changes in mass balance from ongoing tectonic activity, erosion and sedimentation; the large surface water flows within the river systems, the changes in moisture in the atmosphere, and the change in mass from snow and ice melt. Constraining and disaggregating the bulk estimates of mass change from GRACE to give groundwater storage changes required additional information and data. It is hoped that the groundwater storage changes developed here from analysis of the best available regional observational groundwater level data and specific yield information will be a useful tool to the further development and interpretation of GRACE data in the region.



	[[Image:15047fig18.jpg\|center\|thumb\|500px\|Figure 18 The estimated annual change in groundwater storage estimated from the average annual measured change in annual water levels.]]		[[Image:15047fig18.jpg\|center\|thumb\|500px\|Figure 18 The estimated annual change in groundwater storage estimated from the average annual measured change in annual water levels.]]
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	==High abstraction from cities==		==High abstraction from cities==
	Groundwater from the IGB alluvial aquifer system sustains many of the region’s cities, notably, New Delhi, Dhaka and Lahore. Although urban groundwater has not been a focus of this study, given that the total volumes abstracted are small compared to irrigation, and urban groundwater is a highly complex issue, the resilience of the water supplies to these cities is of major concern. The high density of the abstraction (e.g. for Dhaka an estimated 0.8 km<sup>3</sup> within 300 km<sup>2</sup> DWASA 2012) and the mixture of private and public water supplies, means groundwater is locally becoming highly depleted in these cities with groundwater levels falling rapidly (>100 m depth in some locations) and bringing with it a set of issues, such as subsidence, declining yields, increased costs (Morris et al. 2003) — Figure 21. In tandem with the high abstraction is pervasive, and widespread, contamination of groundwater from both domestic water (sewerage) and industrial waste (Foster and Choudhary 2009). The stratification of the aquifers protects some of the deeper groundwater from contamination, but shallow groundwater, often used for private water supply, can by highly contaminated. Therefore, continued good quality groundwater supply in the largest cities will be difficult to sustain in the long term, without developing large protected wells fields outside of the urban areas and building groundwater protection into land use planning. A systematic assessment of the scale and significance of existing groundwater pollution in city regions is also required, together with a robust evaluations of private water well use and the role of institutions in relation to urban groundwater use and protection (Foster and Choudhary 2009; Foster et al. 2010).		Groundwater from the IGB alluvial aquifer system sustains many of the region’s cities, notably, New Delhi, Dhaka and Lahore. Although urban groundwater has not been a focus of this study, given that the total volumes abstracted are small compared to irrigation, and urban groundwater is a highly complex issue, the resilience of the water supplies to these cities is of major concern. The high density of the abstraction (e.g. for Dhaka an estimated 0.8 km<sup>3</sup> within 300 km<sup>2</sup> DWASA 2012) and the mixture of private and public water supplies, means groundwater is locally becoming highly depleted in these cities with groundwater levels falling rapidly (>100 m depth in some locations) and bringing with it a set of issues, such as subsidence, declining yields, increased costs (Morris et al. 2003) — Figure 21. In tandem with the high abstraction is pervasive, and widespread, contamination of groundwater from both domestic water (sewerage) and industrial waste (Foster and Choudhary 2009). The stratification of the aquifers protects some of the deeper groundwater from contamination, but shallow groundwater, often used for private water supply, can by highly contaminated. Therefore, continued good quality groundwater supply in the largest cities will be difficult to sustain in the long term, without developing large protected wells fields outside of the urban areas and building groundwater protection into land use planning. A systematic assessment of the scale and significance of existing groundwater pollution in city regions is also required, together with a robust evaluations of private water well use and the role of institutions in relation to urban groundwater use and protection (Foster and Choudhary 2009; Foster et al. 2010).

			[[Image:15047fig21.jpg\|center\|thumb\|400px\|Figure 21 Competing high abstraction rates from public and private water supply in Dhaka Mega City (Source: UN 2015).]]

	==References==		==References==


	~~[[Image:15047fig21.jpg\|center\|thumb\|400px\|Figure 21 Competing high abstraction rates from public and private water supply in Dhaka Mega City (Source: UN 2015).]]~~
	[[category: OR/15/047 Groundwater resources in the Indo‐Gangetic Basin: resilience to climate change and abstraction \| 07]]		[[category: OR/15/047 Groundwater resources in the Indo‐Gangetic Basin: resilience to climate change and abstraction \| 07]]