OR/15/047 The IGB groundwater system - Revision history

Ajhil: /* Sediment characteristics */

2019-12-03T11:54:56Z

Sediment characteristics

← Older revision		Revision as of 12:54, 3 December 2019
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	The different distribution of Pleistocene and Holocene sediment across the basin, and their distinct depositional systems and environments, has led to important differences in terms of the IGB aquifer properties and the groundwater resource. Holocene sediments are composed predominantly of channel (medium sand‐dominated) deposits within the stratigraphy, and the sediments are generally unoxidised and overall slightly finer than Pleistocene channel deposits since they are in the more distal part of the basin (Singh 1996)<ref name="Singh 1996"></ref>.		The different distribution of Pleistocene and Holocene sediment across the basin, and their distinct depositional systems and environments, has led to important differences in terms of the IGB aquifer properties and the groundwater resource. Holocene sediments are composed predominantly of channel (medium sand‐dominated) deposits within the stratigraphy, and the sediments are generally unoxidised and overall slightly finer than Pleistocene channel deposits since they are in the more distal part of the basin (Singh 1996)<ref name="Singh 1996"></ref>.

	— Figure 3. In contrast, the Pleistocene sediment is comprised predominantly of inter‐ channel deposits (sand and silt dominated), with clustered (laterally and vertically) coarser channel deposits (Singh 1999<ref name="Singh 1999"></ref>; Sinha 2005<ref name="Sinha 2005"></ref>). The Pleistocene sediment in the upper Ganges and Indus basins is proximal to the Himalaya source and contains mainly oxidised coarse sands and silt components (Saha et al. 2011<ref name="Saha 2001">Saha D, Sahu S and Chandra PC. 2011. As‐safe alternate aquifers and their hydraulic characteristics in contaminated areas of Middle Ganga Plain, Eastern India. ''Environ Monit Assess'', 175; 331–348.</ref>). Both the Pleistocene and Holocene sediments are in essence a continuum of the same complex, heterogeneous alluvium aquifer, deposited by fluvial systems, and composed of stacked channel and inter‐channel deposits of a great range of permeability, and which are discontinuous over 10s of kilometres and individual units less than 50 m thick (Sinha 2005<ref name="Sinha 2005"></ref>; Samadder et al. 2011<ref name="Samadder 2011">Samadder R K, Kumar S and Gupta R P. 2011. Paleochannels and their potential for artificial recharge in the western Ganga plains. ''Journal of Hydrology'', 400; 154–164.</ref>).		— Figure 3. In contrast, the Pleistocene sediment is comprised predominantly of inter‐ channel deposits (sand and silt dominated), with clustered (laterally and vertically) coarser channel deposits (Singh 1999<ref name="Singh 1999"></ref>; Sinha 2005<ref name="Sinha 2005">Sinha R, Gibling M R, Tandon S K, Jain V & Dasgupta A S. 2005. Quaternary stratigraphy and sedimentology of the Kotra Section on the Betwa River, Southern Gangetic Plains, Uttar Pradesh, J of Geological Society India, 65; 441–450.</ref>). The Pleistocene sediment in the upper Ganges and Indus basins is proximal to the Himalaya source and contains mainly oxidised coarse sands and silt components (Saha et al. 2011<ref name="Saha 2001">Saha D, Sahu S and Chandra PC. 2011. As‐safe alternate aquifers and their hydraulic characteristics in contaminated areas of Middle Ganga Plain, Eastern India. ''Environ Monit Assess'', 175; 331–348.</ref>). Both the Pleistocene and Holocene sediments are in essence a continuum of the same complex, heterogeneous alluvium aquifer, deposited by fluvial systems, and composed of stacked channel and inter‐channel deposits of a great range of permeability, and which are discontinuous over 10s of kilometres and individual units less than 50 m thick (Sinha 2005<ref name="Sinha 2005"></ref>; Samadder et al. 2011<ref name="Samadder 2011">Samadder R K, Kumar S and Gupta R P. 2011. Paleochannels and their potential for artificial recharge in the western Ganga plains. ''Journal of Hydrology'', 400; 154–164.</ref>).

	[[Image:15047_fig3.jpg\|thumb\|center\| 500px\| '''Figure 3''' Schematic cross‐sections of the IGB within the Indus (A) and upper Ganges basin (B), illustrating the systematic variations in alluvium sedimentology.]]		[[Image:15047_fig3.jpg\|thumb\|center\| 500px\| '''Figure 3''' Schematic cross‐sections of the IGB within the Indus (A) and upper Ganges basin (B), illustrating the systematic variations in alluvium sedimentology.]]

Ajhil: /* Sediment characteristics */

2019-12-03T11:53:47Z

Sediment characteristics

← Older revision		Revision as of 12:53, 3 December 2019
Line 20:		Line 20:
	The different distribution of Pleistocene and Holocene sediment across the basin, and their distinct depositional systems and environments, has led to important differences in terms of the IGB aquifer properties and the groundwater resource. Holocene sediments are composed predominantly of channel (medium sand‐dominated) deposits within the stratigraphy, and the sediments are generally unoxidised and overall slightly finer than Pleistocene channel deposits since they are in the more distal part of the basin (Singh 1996)<ref name="Singh 1996"></ref>.		The different distribution of Pleistocene and Holocene sediment across the basin, and their distinct depositional systems and environments, has led to important differences in terms of the IGB aquifer properties and the groundwater resource. Holocene sediments are composed predominantly of channel (medium sand‐dominated) deposits within the stratigraphy, and the sediments are generally unoxidised and overall slightly finer than Pleistocene channel deposits since they are in the more distal part of the basin (Singh 1996)<ref name="Singh 1996"></ref>.

	— Figure 3. In contrast, the Pleistocene sediment is comprised predominantly of inter‐ channel deposits (sand and silt dominated), with clustered (laterally and vertically) coarser channel deposits (Singh 1999<ref name="Singh 1999"></ref>; Sinha 2005<ref name="Sinha 2005"></ref>). The Pleistocene sediment in the upper Ganges and Indus basins is proximal to the Himalaya source and contains mainly oxidised coarse sands and silt components (Saha et al. 2011<ref name="Saha 2001">Saha D, Sahu S and Chandra PC. 2011. As‐safe alternate aquifers and their hydraulic characteristics in contaminated areas of Middle Ganga Plain, Eastern India. ''Environ Monit Assess'', 175; 331–348.</ref>). Both the Pleistocene and Holocene sediments are in essence a continuum of the same complex, heterogeneous alluvium aquifer, deposited by fluvial systems, and composed of stacked channel and inter‐channel deposits of a great range of permeability, and which are discontinuous over 10s of kilometres and individual units less than 50 m thick (Sinha 2005<ref name"Sinha 2005"></ref>; Samadder et al. 2011<ref name="Samadder 2011">Samadder R K, Kumar S and Gupta R P. 2011. Paleochannels and their potential for artificial recharge in the western Ganga plains. ''Journal of Hydrology'', 400; 154–164.</ref>).		— Figure 3. In contrast, the Pleistocene sediment is comprised predominantly of inter‐ channel deposits (sand and silt dominated), with clustered (laterally and vertically) coarser channel deposits (Singh 1999<ref name="Singh 1999"></ref>; Sinha 2005<ref name="Sinha 2005"></ref>). The Pleistocene sediment in the upper Ganges and Indus basins is proximal to the Himalaya source and contains mainly oxidised coarse sands and silt components (Saha et al. 2011<ref name="Saha 2001">Saha D, Sahu S and Chandra PC. 2011. As‐safe alternate aquifers and their hydraulic characteristics in contaminated areas of Middle Ganga Plain, Eastern India. ''Environ Monit Assess'', 175; 331–348.</ref>). Both the Pleistocene and Holocene sediments are in essence a continuum of the same complex, heterogeneous alluvium aquifer, deposited by fluvial systems, and composed of stacked channel and inter‐channel deposits of a great range of permeability, and which are discontinuous over 10s of kilometres and individual units less than 50 m thick (Sinha 2005<ref name="Sinha 2005"></ref>; Samadder et al. 2011<ref name="Samadder 2011">Samadder R K, Kumar S and Gupta R P. 2011. Paleochannels and their potential for artificial recharge in the western Ganga plains. ''Journal of Hydrology'', 400; 154–164.</ref>).

	[[Image:15047_fig3.jpg\|thumb\|center\| 500px\| '''Figure 3''' Schematic cross‐sections of the IGB within the Indus (A) and upper Ganges basin (B), illustrating the systematic variations in alluvium sedimentology.]]		[[Image:15047_fig3.jpg\|thumb\|center\| 500px\| '''Figure 3''' Schematic cross‐sections of the IGB within the Indus (A) and upper Ganges basin (B), illustrating the systematic variations in alluvium sedimentology.]]

Ajhil at 11:52, 3 December 2019

2019-12-03T11:52:20Z

← Older revision		Revision as of 12:52, 3 December 2019
Line 16:		Line 16:
	The effective aquifer thickness exploited is generally represented by the upper 200 m of alluvium sediment across most of the basin. Within the Bengal Basin the effective thickness is greater and typically 350 m. The aquifer to these depths is composed of Pleistocene alluvium within the upper Ganges and Indus basins and of younger Holocene alluvium across the major part of the central and lower basin areas (Shroder 1993<ref name="Shroder">Schroder J F. 1993. Himalaya to the Sea: Geomorphology and the Quaternary of Pakistan in the Regional Context, in Schroder J F (ed) Himalaya to the Sea: Geology, ''Geomorhphology and the Quaternary'', Routledge New York, pp 1–28 </ref>; Singh et al. 2004)		The effective aquifer thickness exploited is generally represented by the upper 200 m of alluvium sediment across most of the basin. Within the Bengal Basin the effective thickness is greater and typically 350 m. The aquifer to these depths is composed of Pleistocene alluvium within the upper Ganges and Indus basins and of younger Holocene alluvium across the major part of the central and lower basin areas (Shroder 1993<ref name="Shroder">Schroder J F. 1993. Himalaya to the Sea: Geomorphology and the Quaternary of Pakistan in the Regional Context, in Schroder J F (ed) Himalaya to the Sea: Geology, ''Geomorhphology and the Quaternary'', Routledge New York, pp 1–28 </ref>; Singh et al. 2004)

	— Figures 2 and 3. This distribution of different aged sediment is the result of different fluvial depositional processes operating in the upper and lower basins: rivers in the upper basins are strongly incising, depositing modern alluvium only within narrow terraces (km wide) in the extensive Pleistocene alluvium cover (Clift and Giosan 2013<ref name="Clift">Clift P D and Giosan L. 2013. Sediment fluxes and buffering the post‐glacial Indus Basin, ''Basin Research'', 25; 1–18.</ref>); whilst in the central‐lower parts of the basin, there is a reduced gradient to sea‐level, rivers are less incising, and significant amounts of Holocene sediment have been deposited by the numerous lateral aggrading sinuous river channels (Sinha ~~et al~~ 2005<ref name"Sinha 2005">Sinha R, Gibling M R, Tandon S K, Jain V & Dasgupta A S. 2005. Quaternary stratigraphy and sedimentology of the Kotra Section on the Betwa River, Southern Gangetic Plains, Uttar Pradesh, J of Geological Society India, 65; 441–450.</ref>). The exact rates of sediment accumulation and geomorphology of these fluvial systems through time are highly sensitive to changes in climate and sediment input, as well as sea‐level changes (Valdiya 2002<ref name="Validya 2002">Valdiya K S. 2002. Emergence and Evolution of Himlaya: reconstructing history in the light of recent studies, Progress in Physcial Geography, 26; 3; 60. </ref>; Goodbred 2003<ref name="Goodbred">Goodbred S L. 2003. Response of the Ganges dispersal system to climate change: a source to sink view since the last interstade, Sedimnetary Geology, 162; 1–2, 83–104. *continuity of sed dep processes</ref>; Sinha ~~et al.~~ 2005<ref name="Sinha 2005"></ref>). Reduced rates of sediment input and river discharge in drier climatic periods in the last 14 000 years have led to areas of lacustrine (lake) deposition and evaporites with ponding of surface waters in the Indus and within the upper and central parts of the Ganges basin (Validya 2002<ref name="Validya 2002"></ref>).		— Figures 2 and 3. This distribution of different aged sediment is the result of different fluvial depositional processes operating in the upper and lower basins: rivers in the upper basins are strongly incising, depositing modern alluvium only within narrow terraces (km wide) in the extensive Pleistocene alluvium cover (Clift and Giosan 2013<ref name="Clift">Clift P D and Giosan L. 2013. Sediment fluxes and buffering the post‐glacial Indus Basin, ''Basin Research'', 25; 1–18.</ref>); whilst in the central‐lower parts of the basin, there is a reduced gradient to sea‐level, rivers are less incising, and significant amounts of Holocene sediment have been deposited by the numerous lateral aggrading sinuous river channels (Sinha 2005<ref name"Sinha 2005">Sinha R, Gibling M R, Tandon S K, Jain V & Dasgupta A S. 2005. Quaternary stratigraphy and sedimentology of the Kotra Section on the Betwa River, Southern Gangetic Plains, Uttar Pradesh, J of Geological Society India, 65; 441–450.</ref>). The exact rates of sediment accumulation and geomorphology of these fluvial systems through time are highly sensitive to changes in climate and sediment input, as well as sea‐level changes (Valdiya 2002<ref name="Validya 2002">Valdiya K S. 2002. Emergence and Evolution of Himlaya: reconstructing history in the light of recent studies, Progress in Physcial Geography, 26; 3; 60. </ref>; Goodbred 2003<ref name="Goodbred">Goodbred S L. 2003. Response of the Ganges dispersal system to climate change: a source to sink view since the last interstade, Sedimnetary Geology, 162; 1–2, 83–104. *continuity of sed dep processes</ref>; Sinha 2005<ref name="Sinha 2005"></ref>). Reduced rates of sediment input and river discharge in drier climatic periods in the last 14 000 years have led to areas of lacustrine (lake) deposition and evaporites with ponding of surface waters in the Indus and within the upper and central parts of the Ganges basin (Validya 2002<ref name="Validya 2002"></ref>).

	The different distribution of Pleistocene and Holocene sediment across the basin, and their distinct depositional systems and environments, has led to important differences in terms of the IGB aquifer properties and the groundwater resource. Holocene sediments are composed predominantly of channel (medium sand‐dominated) deposits within the stratigraphy, and the sediments are generally unoxidised and overall slightly finer than Pleistocene channel deposits since they are in the more distal part of the basin (Singh 1996)<ref name="Singh 1996"></ref>.		The different distribution of Pleistocene and Holocene sediment across the basin, and their distinct depositional systems and environments, has led to important differences in terms of the IGB aquifer properties and the groundwater resource. Holocene sediments are composed predominantly of channel (medium sand‐dominated) deposits within the stratigraphy, and the sediments are generally unoxidised and overall slightly finer than Pleistocene channel deposits since they are in the more distal part of the basin (Singh 1996)<ref name="Singh 1996"></ref>.

	— Figure 3. In contrast, the Pleistocene sediment is comprised predominantly of inter‐ channel deposits (sand and silt dominated), with clustered (laterally and vertically) coarser channel deposits (Singh 1999<ref name="Singh 1999"></ref>; Sinha ~~et al.~~ 2005<ref name=""></ref>). The Pleistocene sediment in the upper Ganges and Indus basins is proximal to the Himalaya source and contains mainly oxidised coarse sands and silt components (Saha et al. 2011<ref name="Saha 2001">Saha D, Sahu S and Chandra PC. 2011. As‐safe alternate aquifers and their hydraulic characteristics in contaminated areas of Middle Ganga Plain, Eastern India. ''Environ Monit Assess'', 175; 331–348.</ref>). Both the Pleistocene and Holocene sediments are in essence a continuum of the same complex, heterogeneous alluvium aquifer, deposited by fluvial systems, and composed of stacked channel and inter‐channel deposits of a great range of permeability, and which are discontinuous over 10s of kilometres and individual units less than 50 m thick (Sinha ~~et al.~~ 2005<ref name"Sinha 2005"></ref>; Samadder et al. 2011<ref name="Samadder 2011">Samadder R K, Kumar S and Gupta R P. 2011. Paleochannels and their potential for artificial recharge in the western Ganga plains. ''Journal of Hydrology'', 400; 154–164.</ref>).		— Figure 3. In contrast, the Pleistocene sediment is comprised predominantly of inter‐ channel deposits (sand and silt dominated), with clustered (laterally and vertically) coarser channel deposits (Singh 1999<ref name="Singh 1999"></ref>; Sinha 2005<ref name="Sinha 2005"></ref>). The Pleistocene sediment in the upper Ganges and Indus basins is proximal to the Himalaya source and contains mainly oxidised coarse sands and silt components (Saha et al. 2011<ref name="Saha 2001">Saha D, Sahu S and Chandra PC. 2011. As‐safe alternate aquifers and their hydraulic characteristics in contaminated areas of Middle Ganga Plain, Eastern India. ''Environ Monit Assess'', 175; 331–348.</ref>). Both the Pleistocene and Holocene sediments are in essence a continuum of the same complex, heterogeneous alluvium aquifer, deposited by fluvial systems, and composed of stacked channel and inter‐channel deposits of a great range of permeability, and which are discontinuous over 10s of kilometres and individual units less than 50 m thick (Sinha 2005<ref name"Sinha 2005"></ref>; Samadder et al. 2011<ref name="Samadder 2011">Samadder R K, Kumar S and Gupta R P. 2011. Paleochannels and their potential for artificial recharge in the western Ganga plains. ''Journal of Hydrology'', 400; 154–164.</ref>).

	[[Image:15047_fig3.jpg\|thumb\|center\| 500px\| '''Figure 3''' Schematic cross‐sections of the IGB within the Indus (A) and upper Ganges basin (B), illustrating the systematic variations in alluvium sedimentology.]]		[[Image:15047_fig3.jpg\|thumb\|center\| 500px\| '''Figure 3''' Schematic cross‐sections of the IGB within the Indus (A) and upper Ganges basin (B), illustrating the systematic variations in alluvium sedimentology.]]

Ajhil at 11:50, 3 December 2019

2019-12-03T11:50:46Z

← Older revision		Revision as of 12:50, 3 December 2019
Line 16:		Line 16:
	The effective aquifer thickness exploited is generally represented by the upper 200 m of alluvium sediment across most of the basin. Within the Bengal Basin the effective thickness is greater and typically 350 m. The aquifer to these depths is composed of Pleistocene alluvium within the upper Ganges and Indus basins and of younger Holocene alluvium across the major part of the central and lower basin areas (Shroder 1993<ref name="Shroder">Schroder J F. 1993. Himalaya to the Sea: Geomorphology and the Quaternary of Pakistan in the Regional Context, in Schroder J F (ed) Himalaya to the Sea: Geology, ''Geomorhphology and the Quaternary'', Routledge New York, pp 1–28 </ref>; Singh et al. 2004)		The effective aquifer thickness exploited is generally represented by the upper 200 m of alluvium sediment across most of the basin. Within the Bengal Basin the effective thickness is greater and typically 350 m. The aquifer to these depths is composed of Pleistocene alluvium within the upper Ganges and Indus basins and of younger Holocene alluvium across the major part of the central and lower basin areas (Shroder 1993<ref name="Shroder">Schroder J F. 1993. Himalaya to the Sea: Geomorphology and the Quaternary of Pakistan in the Regional Context, in Schroder J F (ed) Himalaya to the Sea: Geology, ''Geomorhphology and the Quaternary'', Routledge New York, pp 1–28 </ref>; Singh et al. 2004)

	— Figures 2 and 3. This distribution of different aged sediment is the result of different fluvial depositional processes operating in the upper and lower basins: rivers in the upper basins are strongly incising, depositing modern alluvium only within narrow terraces (km wide) in the extensive Pleistocene alluvium cover (Clift and Giosan 2013<ref name="Clift">Clift P D and Giosan L. 2013. Sediment fluxes and buffering the post‐glacial Indus Basin, ''Basin Research'', 25; 1–18.</ref>); whilst in the central‐lower parts of the basin, there is a reduced gradient to sea‐level, rivers are less incising, and significant amounts of Holocene sediment have been deposited by the numerous lateral aggrading sinuous river channels (Sinha et al 2005<ref name"Sinha 2005"></ref>). The exact rates of sediment accumulation and geomorphology of these fluvial systems through time are highly sensitive to changes in climate and sediment input, as well as sea‐level changes (Valdiya 2002<ref name="Validya 2002">Valdiya K S. 2002. Emergence and Evolution of Himlaya: reconstructing history in the light of recent studies, Progress in Physcial Geography, 26; 3; 60. </ref>; Goodbred 2003<ref name="Goodbred">Goodbred S L. 2003. Response of the Ganges dispersal system to climate change: a source to sink view since the last interstade, Sedimnetary Geology, 162; 1–2, 83–104. *continuity of sed dep processes</ref>; Sinha et al. 2005<ref name="Sinha 2005"></ref>). Reduced rates of sediment input and river discharge in drier climatic periods in the last 14 000 years have led to areas of lacustrine (lake) deposition and evaporites with ponding of surface waters in the Indus and within the upper and central parts of the Ganges basin (Validya 2002<ref name="Validya 2002"></ref>).		— Figures 2 and 3. This distribution of different aged sediment is the result of different fluvial depositional processes operating in the upper and lower basins: rivers in the upper basins are strongly incising, depositing modern alluvium only within narrow terraces (km wide) in the extensive Pleistocene alluvium cover (Clift and Giosan 2013<ref name="Clift">Clift P D and Giosan L. 2013. Sediment fluxes and buffering the post‐glacial Indus Basin, ''Basin Research'', 25; 1–18.</ref>); whilst in the central‐lower parts of the basin, there is a reduced gradient to sea‐level, rivers are less incising, and significant amounts of Holocene sediment have been deposited by the numerous lateral aggrading sinuous river channels (Sinha et al 2005<ref name"Sinha 2005">Sinha R, Gibling M R, Tandon S K, Jain V & Dasgupta A S. 2005. Quaternary stratigraphy and sedimentology of the Kotra Section on the Betwa River, Southern Gangetic Plains, Uttar Pradesh, J of Geological Society India, 65; 441–450.</ref>). The exact rates of sediment accumulation and geomorphology of these fluvial systems through time are highly sensitive to changes in climate and sediment input, as well as sea‐level changes (Valdiya 2002<ref name="Validya 2002">Valdiya K S. 2002. Emergence and Evolution of Himlaya: reconstructing history in the light of recent studies, Progress in Physcial Geography, 26; 3; 60. </ref>; Goodbred 2003<ref name="Goodbred">Goodbred S L. 2003. Response of the Ganges dispersal system to climate change: a source to sink view since the last interstade, Sedimnetary Geology, 162; 1–2, 83–104. *continuity of sed dep processes</ref>; Sinha et al. 2005<ref name="Sinha 2005"></ref>). Reduced rates of sediment input and river discharge in drier climatic periods in the last 14 000 years have led to areas of lacustrine (lake) deposition and evaporites with ponding of surface waters in the Indus and within the upper and central parts of the Ganges basin (Validya 2002<ref name="Validya 2002"></ref>).

	The different distribution of Pleistocene and Holocene sediment across the basin, and their distinct depositional systems and environments, has led to important differences in terms of the IGB aquifer properties and the groundwater resource. Holocene sediments are composed predominantly of channel (medium sand‐dominated) deposits within the stratigraphy, and the sediments are generally unoxidised and overall slightly finer than Pleistocene channel deposits since they are in the more distal part of the basin (Singh 1996)<ref name="Singh 1996"></ref>.		The different distribution of Pleistocene and Holocene sediment across the basin, and their distinct depositional systems and environments, has led to important differences in terms of the IGB aquifer properties and the groundwater resource. Holocene sediments are composed predominantly of channel (medium sand‐dominated) deposits within the stratigraphy, and the sediments are generally unoxidised and overall slightly finer than Pleistocene channel deposits since they are in the more distal part of the basin (Singh 1996)<ref name="Singh 1996"></ref>.

Ajhil at 11:48, 3 December 2019

2019-12-03T11:48:24Z

← Older revision		Revision as of 12:48, 3 December 2019
Line 16:		Line 16:
	The effective aquifer thickness exploited is generally represented by the upper 200 m of alluvium sediment across most of the basin. Within the Bengal Basin the effective thickness is greater and typically 350 m. The aquifer to these depths is composed of Pleistocene alluvium within the upper Ganges and Indus basins and of younger Holocene alluvium across the major part of the central and lower basin areas (Shroder 1993<ref name="Shroder">Schroder J F. 1993. Himalaya to the Sea: Geomorphology and the Quaternary of Pakistan in the Regional Context, in Schroder J F (ed) Himalaya to the Sea: Geology, ''Geomorhphology and the Quaternary'', Routledge New York, pp 1–28 </ref>; Singh et al. 2004)		The effective aquifer thickness exploited is generally represented by the upper 200 m of alluvium sediment across most of the basin. Within the Bengal Basin the effective thickness is greater and typically 350 m. The aquifer to these depths is composed of Pleistocene alluvium within the upper Ganges and Indus basins and of younger Holocene alluvium across the major part of the central and lower basin areas (Shroder 1993<ref name="Shroder">Schroder J F. 1993. Himalaya to the Sea: Geomorphology and the Quaternary of Pakistan in the Regional Context, in Schroder J F (ed) Himalaya to the Sea: Geology, ''Geomorhphology and the Quaternary'', Routledge New York, pp 1–28 </ref>; Singh et al. 2004)

	— Figures 2 and 3. This distribution of different aged sediment is the result of different fluvial depositional processes operating in the upper and lower basins: rivers in the upper basins are strongly incising, depositing modern alluvium only within narrow terraces (km wide) in the extensive Pleistocene alluvium cover (Clift and Giosan 2013<ref name="Clift">Clift P D and Giosan L. 2013. Sediment fluxes and buffering the post‐glacial Indus Basin, ''Basin Research'', 25; 1–18.</ref>); whilst in the central‐lower parts of the basin, there is a reduced gradient to sea‐level, rivers are less incising, and significant amounts of Holocene sediment have been deposited by the numerous lateral aggrading sinuous river channels (Sinha et al 2005<ref name"Sinha 2005">Sinha R, Gibling M R, Tandon S K, Jain V and Dasgupta A S. 2005. Quaternary stratigraphy and sedimentology of the Kotra Section on the Betwa River, Southern Gangetic Plains, Uttar Pradesh, J of Geological Society India, 65; 441–450.</ref>). The exact rates of sediment accumulation and geomorphology of these fluvial systems through time are highly sensitive to changes in climate and sediment input, as well as sea‐level changes (Valdiya 2002<ref name="Validya 2002">Valdiya K S. 2002. Emergence and Evolution of Himlaya: reconstructing history in the light of recent studies, Progress in Physcial Geography, 26; 3; 60. </ref>; Goodbred 2003<ref name="Goodbred">Goodbred S L. 2003. Response of the Ganges dispersal system to climate change: a source to sink view since the last interstade, Sedimnetary Geology, 162; 1–2, 83–104. *continuity of sed dep processes</ref>; Sinha et al. 2005<ref name="Sinha 2005"></ref>). Reduced rates of sediment input and river discharge in drier climatic periods in the last 14 000 years have led to areas of lacustrine (lake) deposition and evaporites with ponding of surface waters in the Indus and within the upper and central parts of the Ganges basin (Validya 2002<ref name="Validya 2002"></ref>).		— Figures 2 and 3. This distribution of different aged sediment is the result of different fluvial depositional processes operating in the upper and lower basins: rivers in the upper basins are strongly incising, depositing modern alluvium only within narrow terraces (km wide) in the extensive Pleistocene alluvium cover (Clift and Giosan 2013<ref name="Clift">Clift P D and Giosan L. 2013. Sediment fluxes and buffering the post‐glacial Indus Basin, ''Basin Research'', 25; 1–18.</ref>); whilst in the central‐lower parts of the basin, there is a reduced gradient to sea‐level, rivers are less incising, and significant amounts of Holocene sediment have been deposited by the numerous lateral aggrading sinuous river channels (Sinha et al 2005<ref name"Sinha 2005"></ref>). The exact rates of sediment accumulation and geomorphology of these fluvial systems through time are highly sensitive to changes in climate and sediment input, as well as sea‐level changes (Valdiya 2002<ref name="Validya 2002">Valdiya K S. 2002. Emergence and Evolution of Himlaya: reconstructing history in the light of recent studies, Progress in Physcial Geography, 26; 3; 60. </ref>; Goodbred 2003<ref name="Goodbred">Goodbred S L. 2003. Response of the Ganges dispersal system to climate change: a source to sink view since the last interstade, Sedimnetary Geology, 162; 1–2, 83–104. *continuity of sed dep processes</ref>; Sinha et al. 2005<ref name="Sinha 2005"></ref>). Reduced rates of sediment input and river discharge in drier climatic periods in the last 14 000 years have led to areas of lacustrine (lake) deposition and evaporites with ponding of surface waters in the Indus and within the upper and central parts of the Ganges basin (Validya 2002<ref name="Validya 2002"></ref>).

	The different distribution of Pleistocene and Holocene sediment across the basin, and their distinct depositional systems and environments, has led to important differences in terms of the IGB aquifer properties and the groundwater resource. Holocene sediments are composed predominantly of channel (medium sand‐dominated) deposits within the stratigraphy, and the sediments are generally unoxidised and overall slightly finer than Pleistocene channel deposits since they are in the more distal part of the basin (Singh 1996)<ref name="Singh 1996"></ref>.		The different distribution of Pleistocene and Holocene sediment across the basin, and their distinct depositional systems and environments, has led to important differences in terms of the IGB aquifer properties and the groundwater resource. Holocene sediments are composed predominantly of channel (medium sand‐dominated) deposits within the stratigraphy, and the sediments are generally unoxidised and overall slightly finer than Pleistocene channel deposits since they are in the more distal part of the basin (Singh 1996)<ref name="Singh 1996"></ref>.

Ajhil at 11:47, 3 December 2019

2019-12-03T11:47:19Z

← Older revision		Revision as of 12:47, 3 December 2019
Line 16:		Line 16:
	The effective aquifer thickness exploited is generally represented by the upper 200 m of alluvium sediment across most of the basin. Within the Bengal Basin the effective thickness is greater and typically 350 m. The aquifer to these depths is composed of Pleistocene alluvium within the upper Ganges and Indus basins and of younger Holocene alluvium across the major part of the central and lower basin areas (Shroder 1993<ref name="Shroder">Schroder J F. 1993. Himalaya to the Sea: Geomorphology and the Quaternary of Pakistan in the Regional Context, in Schroder J F (ed) Himalaya to the Sea: Geology, ''Geomorhphology and the Quaternary'', Routledge New York, pp 1–28 </ref>; Singh et al. 2004)		The effective aquifer thickness exploited is generally represented by the upper 200 m of alluvium sediment across most of the basin. Within the Bengal Basin the effective thickness is greater and typically 350 m. The aquifer to these depths is composed of Pleistocene alluvium within the upper Ganges and Indus basins and of younger Holocene alluvium across the major part of the central and lower basin areas (Shroder 1993<ref name="Shroder">Schroder J F. 1993. Himalaya to the Sea: Geomorphology and the Quaternary of Pakistan in the Regional Context, in Schroder J F (ed) Himalaya to the Sea: Geology, ''Geomorhphology and the Quaternary'', Routledge New York, pp 1–28 </ref>; Singh et al. 2004)

	— Figures 2 and 3. This distribution of different aged sediment is the result of different fluvial depositional processes operating in the upper and lower basins: rivers in the upper basins are strongly incising, depositing modern alluvium only within narrow terraces (km wide) in the extensive Pleistocene alluvium cover (Clift and Giosan 2013<ref name="Clift">Clift P D and Giosan L. 2013. Sediment fluxes and buffering the post‐glacial Indus Basin, ''Basin Research'', 25; 1–18.</ref>); whilst in the central‐lower parts of the basin, there is a reduced gradient to sea‐level, rivers are less incising, and significant amounts of Holocene sediment have been deposited by the numerous lateral aggrading sinuous river channels (Sinha et al 2005<ref name"Sinha 2005"> Sinha R, Gibling M R, Tandon S K, Jain V and Dasgupta A S. 2005. Quaternary stratigraphy and sedimentology of the Kotra Section on the Betwa River, Southern Gangetic Plains, Uttar Pradesh, J of Geological Society India, 65; 441–450. </ref>). The exact rates of sediment accumulation and geomorphology of these fluvial systems through time are highly sensitive to changes in climate and sediment input, as well as sea‐level changes (Valdiya 2002<ref name="Validya 2002">Valdiya K S. 2002. Emergence and Evolution of Himlaya: reconstructing history in the light of recent studies, Progress in Physcial Geography, 26; 3; 60. </ref>; Goodbred 2003<ref name="Goodbred">Goodbred S L. 2003. Response of the Ganges dispersal system to climate change: a source to sink view since the last interstade, Sedimnetary Geology, 162; 1–2, 83–104. *continuity of sed dep processes</ref>; Sinha et al. 2005<ref name="Sinha 2005">Sinha R, Gibling M R, Tandon S K, Jain V and Dasgupta A S. 2005. Quaternary stratigraphy and sedimentology of the Kotra Section on the Betwa River, Southern Gangetic Plains, Uttar Pradesh, ''Journal of Geological Society India'', 65; 441–450.</ref>). Reduced rates of sediment input and river discharge in drier climatic periods in the last 14 000 years have led to areas of lacustrine (lake) deposition and evaporites with ponding of surface waters in the Indus and within the upper and central parts of the Ganges basin (Validya 2002<ref name="Validya 2002"></ref>).		— Figures 2 and 3. This distribution of different aged sediment is the result of different fluvial depositional processes operating in the upper and lower basins: rivers in the upper basins are strongly incising, depositing modern alluvium only within narrow terraces (km wide) in the extensive Pleistocene alluvium cover (Clift and Giosan 2013<ref name="Clift">Clift P D and Giosan L. 2013. Sediment fluxes and buffering the post‐glacial Indus Basin, ''Basin Research'', 25; 1–18.</ref>); whilst in the central‐lower parts of the basin, there is a reduced gradient to sea‐level, rivers are less incising, and significant amounts of Holocene sediment have been deposited by the numerous lateral aggrading sinuous river channels (Sinha et al 2005<ref name"Sinha 2005">Sinha R, Gibling M R, Tandon S K, Jain V and Dasgupta A S. 2005. Quaternary stratigraphy and sedimentology of the Kotra Section on the Betwa River, Southern Gangetic Plains, Uttar Pradesh, J of Geological Society India, 65; 441–450.</ref>). The exact rates of sediment accumulation and geomorphology of these fluvial systems through time are highly sensitive to changes in climate and sediment input, as well as sea‐level changes (Valdiya 2002<ref name="Validya 2002">Valdiya K S. 2002. Emergence and Evolution of Himlaya: reconstructing history in the light of recent studies, Progress in Physcial Geography, 26; 3; 60. </ref>; Goodbred 2003<ref name="Goodbred">Goodbred S L. 2003. Response of the Ganges dispersal system to climate change: a source to sink view since the last interstade, Sedimnetary Geology, 162; 1–2, 83–104. *continuity of sed dep processes</ref>; Sinha et al. 2005<ref name="Sinha 2005"></ref>). Reduced rates of sediment input and river discharge in drier climatic periods in the last 14 000 years have led to areas of lacustrine (lake) deposition and evaporites with ponding of surface waters in the Indus and within the upper and central parts of the Ganges basin (Validya 2002<ref name="Validya 2002"></ref>).

	The different distribution of Pleistocene and Holocene sediment across the basin, and their distinct depositional systems and environments, has led to important differences in terms of the IGB aquifer properties and the groundwater resource. Holocene sediments are composed predominantly of channel (medium sand‐dominated) deposits within the stratigraphy, and the sediments are generally unoxidised and overall slightly finer than Pleistocene channel deposits since they are in the more distal part of the basin (Singh 1996)<ref name="Singh 1996"></ref>.		The different distribution of Pleistocene and Holocene sediment across the basin, and their distinct depositional systems and environments, has led to important differences in terms of the IGB aquifer properties and the groundwater resource. Holocene sediments are composed predominantly of channel (medium sand‐dominated) deposits within the stratigraphy, and the sediments are generally unoxidised and overall slightly finer than Pleistocene channel deposits since they are in the more distal part of the basin (Singh 1996)<ref name="Singh 1996"></ref>.

	— Figure 3. In contrast, the Pleistocene sediment is comprised predominantly of inter‐ channel deposits (sand and silt dominated), with clustered (laterally and vertically) coarser channel deposits (Singh 1999<ref name="Singh 1999"></ref>; Sinha et al. 2005<ref name=""></ref>). The Pleistocene sediment in the upper Ganges and Indus basins is proximal to the Himalaya source and contains mainly oxidised coarse sands and silt components (Saha et al. 2011<ref name="Saha 2001">Saha D, Sahu S and Chandra PC. 2011. As‐safe alternate aquifers and their hydraulic characteristics in contaminated areas of Middle Ganga Plain, Eastern India. ''Environ Monit Assess'', 175; 331–348.</ref>). Both the Pleistocene and Holocene sediments are in essence a continuum of the same complex, heterogeneous alluvium aquifer, deposited by fluvial systems, and composed of stacked channel and inter‐channel deposits of a great range of permeability, and which are discontinuous over 10s of kilometres and individual units less than 50 m thick (Sinha et al. 2005<ref name""></ref>; Samadder et al. 2011<ref name="Samadder 2011">Samadder R K, Kumar S and Gupta R P. 2011. Paleochannels and ~~thier~~ potential for artificial recharge in the western Ganga plains. ''Journal of Hydrology'', 400; 154–164.</ref>).		— Figure 3. In contrast, the Pleistocene sediment is comprised predominantly of inter‐ channel deposits (sand and silt dominated), with clustered (laterally and vertically) coarser channel deposits (Singh 1999<ref name="Singh 1999"></ref>; Sinha et al. 2005<ref name=""></ref>). The Pleistocene sediment in the upper Ganges and Indus basins is proximal to the Himalaya source and contains mainly oxidised coarse sands and silt components (Saha et al. 2011<ref name="Saha 2001">Saha D, Sahu S and Chandra PC. 2011. As‐safe alternate aquifers and their hydraulic characteristics in contaminated areas of Middle Ganga Plain, Eastern India. ''Environ Monit Assess'', 175; 331–348.</ref>). Both the Pleistocene and Holocene sediments are in essence a continuum of the same complex, heterogeneous alluvium aquifer, deposited by fluvial systems, and composed of stacked channel and inter‐channel deposits of a great range of permeability, and which are discontinuous over 10s of kilometres and individual units less than 50 m thick (Sinha et al. 2005<ref name"Sinha 2005"></ref>; Samadder et al. 2011<ref name="Samadder 2011">Samadder R K, Kumar S and Gupta R P. 2011. Paleochannels and their potential for artificial recharge in the western Ganga plains. ''Journal of Hydrology'', 400; 154–164.</ref>).

	[[Image:15047_fig3.jpg\|thumb\|center\| 500px\| '''Figure 3''' Schematic cross‐sections of the IGB within the Indus (A) and upper Ganges basin (B), illustrating the systematic variations in alluvium sedimentology.]]		[[Image:15047_fig3.jpg\|thumb\|center\| 500px\| '''Figure 3''' Schematic cross‐sections of the IGB within the Indus (A) and upper Ganges basin (B), illustrating the systematic variations in alluvium sedimentology.]]

Ajhil: /* Sediment characteristics */

2019-12-03T11:46:13Z

Sediment characteristics

← Older revision		Revision as of 12:46, 3 December 2019
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	The effective aquifer thickness exploited is generally represented by the upper 200 m of alluvium sediment across most of the basin. Within the Bengal Basin the effective thickness is greater and typically 350 m. The aquifer to these depths is composed of Pleistocene alluvium within the upper Ganges and Indus basins and of younger Holocene alluvium across the major part of the central and lower basin areas (Shroder 1993<ref name="Shroder">Schroder J F. 1993. Himalaya to the Sea: Geomorphology and the Quaternary of Pakistan in the Regional Context, in Schroder J F (ed) Himalaya to the Sea: Geology, ''Geomorhphology and the Quaternary'', Routledge New York, pp 1–28 </ref>; Singh et al. 2004)		The effective aquifer thickness exploited is generally represented by the upper 200 m of alluvium sediment across most of the basin. Within the Bengal Basin the effective thickness is greater and typically 350 m. The aquifer to these depths is composed of Pleistocene alluvium within the upper Ganges and Indus basins and of younger Holocene alluvium across the major part of the central and lower basin areas (Shroder 1993<ref name="Shroder">Schroder J F. 1993. Himalaya to the Sea: Geomorphology and the Quaternary of Pakistan in the Regional Context, in Schroder J F (ed) Himalaya to the Sea: Geology, ''Geomorhphology and the Quaternary'', Routledge New York, pp 1–28 </ref>; Singh et al. 2004)

	— Figures 2 and 3. This distribution of different aged sediment is the result of different fluvial depositional processes operating in the upper and lower basins: rivers in the upper basins are strongly incising, depositing modern alluvium only within narrow terraces (km wide) in the extensive Pleistocene alluvium cover (Clift and Giosan 2013<ref name="Clift">Clift P D and Giosan L. 2013. Sediment fluxes and buffering the post‐glacial Indus Basin, ''Basin Research'', 25; 1–18.</ref>); whilst in the central‐lower parts of the basin, there is a reduced gradient to sea‐level, rivers are less incising, and significant amounts of Holocene sediment have been deposited by the numerous lateral aggrading sinuous river channels (Sinha et al 2005<ref name""> Sinha R, Gibling M R, Tandon S K, Jain V and Dasgupta A S. 2005. Quaternary stratigraphy and sedimentology of the Kotra Section on the Betwa River, Southern Gangetic Plains, Uttar Pradesh, J of Geological Society India, 65; 441–450. </ref>). The exact rates of sediment accumulation and geomorphology of these fluvial systems through time are highly sensitive to changes in climate and sediment input, as well as sea‐level changes (Valdiya 2002<ref name="Validya 2002">Valdiya K S. 2002. Emergence and Evolution of Himlaya: reconstructing history in the light of recent studies, Progress in Physcial Geography, 26; 3; 60. </ref>; Goodbred 2003<ref name="Goodbred">Goodbred S L. 2003. Response of the Ganges dispersal system to climate change: a source to sink view since the last interstade, Sedimnetary Geology, 162; 1–2, 83–104. *continuity of sed dep processes</ref>; Sinha et al. 2005<ref name="Sinha 2005">Sinha R, Gibling M R, Tandon S K, Jain V and Dasgupta A S. 2005. Quaternary stratigraphy and sedimentology of the Kotra Section on the Betwa River, Southern Gangetic Plains, Uttar Pradesh, ''Journal of Geological Society India'', 65; 441–450.</ref>). Reduced rates of sediment input and river discharge in drier climatic periods in the last 14 000 years have led to areas of lacustrine (lake) deposition and evaporites with ponding of surface waters in the Indus and within the upper and central parts of the Ganges basin (Validya 2002<ref name="Validya 2002"></ref>).		— Figures 2 and 3. This distribution of different aged sediment is the result of different fluvial depositional processes operating in the upper and lower basins: rivers in the upper basins are strongly incising, depositing modern alluvium only within narrow terraces (km wide) in the extensive Pleistocene alluvium cover (Clift and Giosan 2013<ref name="Clift">Clift P D and Giosan L. 2013. Sediment fluxes and buffering the post‐glacial Indus Basin, ''Basin Research'', 25; 1–18.</ref>); whilst in the central‐lower parts of the basin, there is a reduced gradient to sea‐level, rivers are less incising, and significant amounts of Holocene sediment have been deposited by the numerous lateral aggrading sinuous river channels (Sinha et al 2005<ref name"Sinha 2005"> Sinha R, Gibling M R, Tandon S K, Jain V and Dasgupta A S. 2005. Quaternary stratigraphy and sedimentology of the Kotra Section on the Betwa River, Southern Gangetic Plains, Uttar Pradesh, J of Geological Society India, 65; 441–450. </ref>). The exact rates of sediment accumulation and geomorphology of these fluvial systems through time are highly sensitive to changes in climate and sediment input, as well as sea‐level changes (Valdiya 2002<ref name="Validya 2002">Valdiya K S. 2002. Emergence and Evolution of Himlaya: reconstructing history in the light of recent studies, Progress in Physcial Geography, 26; 3; 60. </ref>; Goodbred 2003<ref name="Goodbred">Goodbred S L. 2003. Response of the Ganges dispersal system to climate change: a source to sink view since the last interstade, Sedimnetary Geology, 162; 1–2, 83–104. *continuity of sed dep processes</ref>; Sinha et al. 2005<ref name="Sinha 2005">Sinha R, Gibling M R, Tandon S K, Jain V and Dasgupta A S. 2005. Quaternary stratigraphy and sedimentology of the Kotra Section on the Betwa River, Southern Gangetic Plains, Uttar Pradesh, ''Journal of Geological Society India'', 65; 441–450.</ref>). Reduced rates of sediment input and river discharge in drier climatic periods in the last 14 000 years have led to areas of lacustrine (lake) deposition and evaporites with ponding of surface waters in the Indus and within the upper and central parts of the Ganges basin (Validya 2002<ref name="Validya 2002"></ref>).

	The different distribution of Pleistocene and Holocene sediment across the basin, and their distinct depositional systems and environments, has led to important differences in terms of the IGB aquifer properties and the groundwater resource. Holocene sediments are composed predominantly of channel (medium sand‐dominated) deposits within the stratigraphy, and the sediments are generally unoxidised and overall slightly finer than Pleistocene channel deposits since they are in the more distal part of the basin (Singh 1996)<ref name="Singh 1996"></ref>.		The different distribution of Pleistocene and Holocene sediment across the basin, and their distinct depositional systems and environments, has led to important differences in terms of the IGB aquifer properties and the groundwater resource. Holocene sediments are composed predominantly of channel (medium sand‐dominated) deposits within the stratigraphy, and the sediments are generally unoxidised and overall slightly finer than Pleistocene channel deposits since they are in the more distal part of the basin (Singh 1996)<ref name="Singh 1996"></ref>.

Ajhil at 11:45, 3 December 2019

2019-12-03T11:45:35Z

← Older revision		Revision as of 12:45, 3 December 2019
Line 84:		Line 84:

	''Rainfall recharge''<br>		''Rainfall recharge''<br>
	There is considerable evidence of high rates of groundwater recharge from seasonal rainfall within the basin. Studies of groundwater level variations and rainfall in India led to an empirical formula being developed relating rainfall to recharge (Chaturvedi 1973<ref name="Chaturvedi1973">Chaturvedi, R S. 1973. A note on the investigation of ground water resources in western districts of Uttar Pradesh. Annual Report, U. P. Irrigation Research Institute, 1973, pp 86–122.</ref>) which has been modified by others (e.g. Kumar and Seethapathi 2002<ref name="Kumar2002">Kumar C P and Seethapathi P V. 2002. Assessment of Natural Groundwater Recharge in Upper Ganges Canal Command area, Journal of Applied Hydrology, 15; 4, 13–20.</ref>) and tested using environmental tracers (e.g. Goel et al 1977<ref name="Goel1977">Goel P S, Datta P S, Tanwar B S. 1977. Measurement of vertical recharge to groundwater in Haryana State (India) using Tritium Tracer, Nordic Hydrology, 8; 211–224.</ref>, Datta and Goel 1977<ref name="Datta1977">Datta P S and Goel P S. 1977. Groundwater recharge in Panjab State (India) using Tritium Tracer, Nordic Hydrology, 8; 255–236. </ref>). Groundwater recharge is found by these studies to be negligible in areas with average annual rainfall below approximately 350 mm, less than 10% from 350–500mm and then increases to between 10 and 20 % of rainfall above 500 mm. These local studies give significantly higher values of recharge than those estimated by global hydrological models (e.g. Doll et al 2008), particularly where rainfall is less than 1000 mm. In areas with extensive clay soils (e.g. central Bangladesh), studies have indicated that groundwater recharge may be less than where the soil is less permeable (Goel et al 1977<ref name="Goel1977"></ref>, Shamsudduha et al. 2011<ref name="Shamsudduha 2011">~~Shamsudduha M, Taylor R, Ahmed K M and Zahid. 2011. The impact of intensive abstraction on recharge to a shallow regional aquifer system: evidence from Bangladesh, Hydrogeology Journal, 19; 901–916.~~</ref>).		There is considerable evidence of high rates of groundwater recharge from seasonal rainfall within the basin. Studies of groundwater level variations and rainfall in India led to an empirical formula being developed relating rainfall to recharge (Chaturvedi 1973<ref name="Chaturvedi1973">Chaturvedi, R S. 1973. A note on the investigation of ground water resources in western districts of Uttar Pradesh. Annual Report, U. P. Irrigation Research Institute, 1973, pp 86–122.</ref>) which has been modified by others (e.g. Kumar and Seethapathi 2002<ref name="Kumar2002">Kumar C P and Seethapathi P V. 2002. Assessment of Natural Groundwater Recharge in Upper Ganges Canal Command area, Journal of Applied Hydrology, 15; 4, 13–20.</ref>) and tested using environmental tracers (e.g. Goel et al 1977<ref name="Goel1977">Goel P S, Datta P S, Tanwar B S. 1977. Measurement of vertical recharge to groundwater in Haryana State (India) using Tritium Tracer, Nordic Hydrology, 8; 211–224.</ref>, Datta and Goel 1977<ref name="Datta1977">Datta P S and Goel P S. 1977. Groundwater recharge in Panjab State (India) using Tritium Tracer, Nordic Hydrology, 8; 255–236. </ref>). Groundwater recharge is found by these studies to be negligible in areas with average annual rainfall below approximately 350 mm, less than 10% from 350–500mm and then increases to between 10 and 20 % of rainfall above 500 mm. These local studies give significantly higher values of recharge than those estimated by global hydrological models (e.g. Doll et al 2008), particularly where rainfall is less than 1000 mm. In areas with extensive clay soils (e.g. central Bangladesh), studies have indicated that groundwater recharge may be less than where the soil is less permeable (Goel et al 1977<ref name="Goel1977"></ref>, Shamsudduha et al. 2011<ref name="Shamsudduha 2011"></ref>).

	''Irrigation transport losses''<br>		''Irrigation transport losses''<br>
Line 98:		Line 98:

	''Induced recharge''<br>		''Induced recharge''<br>
	There is growing evidence that increased pumping in areas with shallow water‐tables and permeable soils can increase groundwater recharge by creating additional space to store rain or river water (Shamsudduha et al. 2011<ref name="Shamsudduha 2011">Shamsudduha M, Taylor R, Ahmed K M, and Zahid. 2011. The impact of intensive abstraction on recharge to a shallow regional aquifer system: evidence from Bangladesh, Hydrogeology Journal, 19; 901–916.</ref>). This behaviour has led some to investigate the possibility of deliberately lowering groundwater levels in the dry season to increase infiltration during the monsoon to help control flooding and increase the water available for irrigation. These ideas were first published in the 1970s within an idea called the ''Ganges Water Machine ''(Revelle and Lakshminarayana 1975<ref name="Revelle1975">Revelle R, Lakshminarayana V. 1975. The Ganges water machine. Science 188:611–616 </ref>, Chaturvedi and Srivastava 1979) and have recently been revisited (Khan et al 2014<ref name="Khan2014">Khan M R, Voss C I, Y u W and Michael H A. 2014. Water resources management in the Ganges Basin: A comparison of Three Strategies for Conjunctive use of groundwater and surface water, Water Resources Management, doi:10.1007/s11269‐014‐0537‐y</ref>).		There is growing evidence that increased pumping in areas with shallow water‐tables and permeable soils can increase groundwater recharge by creating additional space to store rain or river water (Shamsudduha et al. 2011<ref name="Shamsudduha 2011"></ref>). This behaviour has led some to investigate the possibility of deliberately lowering groundwater levels in the dry season to increase infiltration during the monsoon to help control flooding and increase the water available for irrigation. These ideas were first published in the 1970s within an idea called the ''Ganges Water Machine ''(Revelle and Lakshminarayana 1975<ref name="Revelle1975">Revelle R, Lakshminarayana V. 1975. The Ganges water machine. Science 188:611–616 </ref>, Chaturvedi and Srivastava 1979) and have recently been revisited (Khan et al 2014<ref name="Khan2014">Khan M R, Voss C I, Y u W and Michael H A. 2014. Water resources management in the Ganges Basin: A comparison of Three Strategies for Conjunctive use of groundwater and surface water, Water Resources Management, doi:10.1007/s11269‐014‐0537‐y</ref>).

	[[Image:15047_fig9.jpg\|thumb\|center\| 500px\| '''Figure 9''' A combination of factors provides a highly complex pattern of recharge across the IGB. In areas with a high density of irrigation canals, such as the Upper Indus and Upper Ganges basins, leakage from irrigation canals can give annual recharge of 400 mm; where average annual rainfall is greater than 1000 mm, rainfall recharge generally dominates. Rainfall recharge can occur even where annual rainfall is as low as 250–500 mm due to the high intensity of individual rainfall events and the permeable soils. Recharge directly from rivers is particularly important on the River Indus where rainfall decreases significantly downstream, but can also be important in the Ganges, particularly during flood events.]]		[[Image:15047_fig9.jpg\|thumb\|center\| 500px\| '''Figure 9''' A combination of factors provides a highly complex pattern of recharge across the IGB. In areas with a high density of irrigation canals, such as the Upper Indus and Upper Ganges basins, leakage from irrigation canals can give annual recharge of 400 mm; where average annual rainfall is greater than 1000 mm, rainfall recharge generally dominates. Rainfall recharge can occur even where annual rainfall is as low as 250–500 mm due to the high intensity of individual rainfall events and the permeable soils. Recharge directly from rivers is particularly important on the River Indus where rainfall decreases significantly downstream, but can also be important in the Ganges, particularly during flood events.]]

Ajhil at 11:44, 3 December 2019

2019-12-03T11:44:58Z

← Older revision		Revision as of 12:44, 3 December 2019
Line 84:		Line 84:

	''Rainfall recharge''<br>		''Rainfall recharge''<br>
	There is considerable evidence of high rates of groundwater recharge from seasonal rainfall within the basin. Studies of groundwater level variations and rainfall in India led to an empirical formula being developed relating rainfall to recharge (Chaturvedi 1973<ref name="Chaturvedi1973">Chaturvedi, R S. 1973. A note on the investigation of ground water resources in western districts of Uttar Pradesh. Annual Report, U. P. Irrigation Research Institute, 1973, pp 86–122.</ref>) which has been modified by others (e.g. Kumar and Seethapathi 2002<ref name="Kumar2002">Kumar C P and Seethapathi P V. 2002. Assessment of Natural Groundwater Recharge in Upper Ganges Canal Command area, Journal of Applied Hydrology, 15; 4, 13–20.</ref>) and tested using environmental tracers (e.g. Goel et al 1977<ref name="Goel1977">Goel P S, Datta P S, Tanwar B S. 1977. Measurement of vertical recharge to groundwater in Haryana State (India) using Tritium Tracer, Nordic Hydrology, 8; 211–224.</ref>, Datta and Goel 1977<ref name="Datta1977">Datta P S and Goel P S. 1977. Groundwater recharge in Panjab State (India) using Tritium Tracer, Nordic Hydrology, 8; 255–236. </ref>). Groundwater recharge is found by these studies to be negligible in areas with average annual rainfall below approximately 350 mm, less than 10% from 350–500mm and then increases to between 10 and 20 % of rainfall above 500 mm. These local studies give significantly higher values of recharge than those estimated by global hydrological models (e.g. Doll et al 2008), particularly where rainfall is less than 1000 mm. In areas with extensive clay soils (e.g. central Bangladesh), studies have indicated that groundwater recharge may be less than where the soil is less permeable (Goel et al 1977<ref name="Goel1977"></ref>, Shamsudduha et al. 2011<ref name="~~Shamsudduha2011~~">Shamsudduha M, Taylor R, Ahmed K M and Zahid. 2011. The impact of intensive abstraction on recharge to a shallow regional aquifer system: evidence from Bangladesh, Hydrogeology Journal, 19; 901–916.</ref>).		There is considerable evidence of high rates of groundwater recharge from seasonal rainfall within the basin. Studies of groundwater level variations and rainfall in India led to an empirical formula being developed relating rainfall to recharge (Chaturvedi 1973<ref name="Chaturvedi1973">Chaturvedi, R S. 1973. A note on the investigation of ground water resources in western districts of Uttar Pradesh. Annual Report, U. P. Irrigation Research Institute, 1973, pp 86–122.</ref>) which has been modified by others (e.g. Kumar and Seethapathi 2002<ref name="Kumar2002">Kumar C P and Seethapathi P V. 2002. Assessment of Natural Groundwater Recharge in Upper Ganges Canal Command area, Journal of Applied Hydrology, 15; 4, 13–20.</ref>) and tested using environmental tracers (e.g. Goel et al 1977<ref name="Goel1977">Goel P S, Datta P S, Tanwar B S. 1977. Measurement of vertical recharge to groundwater in Haryana State (India) using Tritium Tracer, Nordic Hydrology, 8; 211–224.</ref>, Datta and Goel 1977<ref name="Datta1977">Datta P S and Goel P S. 1977. Groundwater recharge in Panjab State (India) using Tritium Tracer, Nordic Hydrology, 8; 255–236. </ref>). Groundwater recharge is found by these studies to be negligible in areas with average annual rainfall below approximately 350 mm, less than 10% from 350–500mm and then increases to between 10 and 20 % of rainfall above 500 mm. These local studies give significantly higher values of recharge than those estimated by global hydrological models (e.g. Doll et al 2008), particularly where rainfall is less than 1000 mm. In areas with extensive clay soils (e.g. central Bangladesh), studies have indicated that groundwater recharge may be less than where the soil is less permeable (Goel et al 1977<ref name="Goel1977"></ref>, Shamsudduha et al. 2011<ref name="Shamsudduha 2011">Shamsudduha M, Taylor R, Ahmed K M and Zahid. 2011. The impact of intensive abstraction on recharge to a shallow regional aquifer system: evidence from Bangladesh, Hydrogeology Journal, 19; 901–916.</ref>).

	''Irrigation transport losses''<br>		''Irrigation transport losses''<br>
Line 98:		Line 98:

	''Induced recharge''<br>		''Induced recharge''<br>
	There is growing evidence that increased pumping in areas with shallow water‐tables and permeable soils can increase groundwater recharge by creating additional space to store rain or river water (Shamsudduha et al. 2011<ref name="~~Shamsudduha2011~~">Shamsudduha M, Taylor R, Ahmed K M, and Zahid. 2011. The impact of intensive abstraction on recharge to a shallow regional aquifer system: evidence from Bangladesh, Hydrogeology Journal, 19; 901–916.</ref>). This behaviour has led some to investigate the possibility of deliberately lowering groundwater levels in the dry season to increase infiltration during the monsoon to help control flooding and increase the water available for irrigation. These ideas were first published in the 1970s within an idea called the ''Ganges Water Machine ''(Revelle and Lakshminarayana 1975<ref name="Revelle1975">Revelle R, Lakshminarayana V. 1975. The Ganges water machine. Science 188:611–616 </ref>, Chaturvedi and Srivastava 1979) and have recently been revisited (Khan et al 2014<ref name="Khan2014">Khan M R, Voss C I, Y u W and Michael H A. 2014. Water resources management in the Ganges Basin: A comparison of Three Strategies for Conjunctive use of groundwater and surface water, Water Resources Management, doi:10.1007/s11269‐014‐0537‐y</ref>).		There is growing evidence that increased pumping in areas with shallow water‐tables and permeable soils can increase groundwater recharge by creating additional space to store rain or river water (Shamsudduha et al. 2011<ref name="Shamsudduha 2011">Shamsudduha M, Taylor R, Ahmed K M, and Zahid. 2011. The impact of intensive abstraction on recharge to a shallow regional aquifer system: evidence from Bangladesh, Hydrogeology Journal, 19; 901–916.</ref>). This behaviour has led some to investigate the possibility of deliberately lowering groundwater levels in the dry season to increase infiltration during the monsoon to help control flooding and increase the water available for irrigation. These ideas were first published in the 1970s within an idea called the ''Ganges Water Machine ''(Revelle and Lakshminarayana 1975<ref name="Revelle1975">Revelle R, Lakshminarayana V. 1975. The Ganges water machine. Science 188:611–616 </ref>, Chaturvedi and Srivastava 1979) and have recently been revisited (Khan et al 2014<ref name="Khan2014">Khan M R, Voss C I, Y u W and Michael H A. 2014. Water resources management in the Ganges Basin: A comparison of Three Strategies for Conjunctive use of groundwater and surface water, Water Resources Management, doi:10.1007/s11269‐014‐0537‐y</ref>).

	[[Image:15047_fig9.jpg\|thumb\|center\| 500px\| '''Figure 9''' A combination of factors provides a highly complex pattern of recharge across the IGB. In areas with a high density of irrigation canals, such as the Upper Indus and Upper Ganges basins, leakage from irrigation canals can give annual recharge of 400 mm; where average annual rainfall is greater than 1000 mm, rainfall recharge generally dominates. Rainfall recharge can occur even where annual rainfall is as low as 250–500 mm due to the high intensity of individual rainfall events and the permeable soils. Recharge directly from rivers is particularly important on the River Indus where rainfall decreases significantly downstream, but can also be important in the Ganges, particularly during flood events.]]		[[Image:15047_fig9.jpg\|thumb\|center\| 500px\| '''Figure 9''' A combination of factors provides a highly complex pattern of recharge across the IGB. In areas with a high density of irrigation canals, such as the Upper Indus and Upper Ganges basins, leakage from irrigation canals can give annual recharge of 400 mm; where average annual rainfall is greater than 1000 mm, rainfall recharge generally dominates. Rainfall recharge can occur even where annual rainfall is as low as 250–500 mm due to the high intensity of individual rainfall events and the permeable soils. Recharge directly from rivers is particularly important on the River Indus where rainfall decreases significantly downstream, but can also be important in the Ganges, particularly during flood events.]]

Ajhil at 11:44, 3 December 2019

2019-12-03T11:44:01Z

← Older revision		Revision as of 12:44, 3 December 2019
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	As discussed in the previous section on geology, at the local level the aquifer system is highly complex with alternating coarse and fine sands, silts and occasionally clay. Since these sequences have largely been laid down by a sequence of prograding and anastomising rivers, the sediments tend to form discontinuous packages rarely more than a few kilometres across. The high rate of drilling success, particularly in the main basins away from the coastal areas, indicates that sand sediments are usually encountered in a 100 m deep tubewell. In the main Ganges basin and the Upper Indus, lower permeability layers locally‐acting as vertical barriers to flow are common and encountered in most tubewells; however, since they are laterally discontinuous, groundwater can still move vertically deeper within the sequence in response to vertical hydraulic gradients induced by pumping. Further down both the Indus and Ganges rivers, closer to the coast, the finer grained sediments predominate and are much more continuous, so vertical hydraulic continuity is more restricted.		As discussed in the previous section on geology, at the local level the aquifer system is highly complex with alternating coarse and fine sands, silts and occasionally clay. Since these sequences have largely been laid down by a sequence of prograding and anastomising rivers, the sediments tend to form discontinuous packages rarely more than a few kilometres across. The high rate of drilling success, particularly in the main basins away from the coastal areas, indicates that sand sediments are usually encountered in a 100 m deep tubewell. In the main Ganges basin and the Upper Indus, lower permeability layers locally‐acting as vertical barriers to flow are common and encountered in most tubewells; however, since they are laterally discontinuous, groundwater can still move vertically deeper within the sequence in response to vertical hydraulic gradients induced by pumping. Further down both the Indus and Ganges rivers, closer to the coast, the finer grained sediments predominate and are much more continuous, so vertical hydraulic continuity is more restricted.

	A useful way to reflect the potential horizontal rather than vertical groundwater flow across the basin is to estimate the anisotropy in permeability. Studies in the Upper Indus suggest a bulk ratio of horizontal to vertical permeability of approximately 25 (Bennett 1969<ref name="Bennett 1969">Bennett G D, Rehman A U, Sheikh J A and Ali S. 1969. Analysis of pumping tests in the Punjab region of west Pakistan, Geological Survey Water‐Supply Paper 1608‐G, prepared in cooperation with the W Pakistan Water & Power Dec Authority under US AID.</ref>), rising to 50–100 in the main Ganges basin (Sinha et al. 2009, Khan et al. 2014<ref name="Khan 2014"></ref>), and 200–500 in the Lower Indus (Chilton 1986<ref name="Chilton 1986"></ref>, Ahmad 1995<ref name="~~Ahmad1995~~">Ahmed, 1995. Groundwater Resources of Pakistan. 560 pp</ref>); 10 000 in the southern Bengal Basin and 20 000 in the coastal areas (Michael and Voss 2009<ref name="Michael 2009">Michael, H A and Voss, C I. 2009. Estimation of regional‐scale flow properties in Bengal Basin of India and Bangladesh. ''Hydrogeology Journal'', 17; 6; 1329–1346.</ref>). Limited data from modern sediments close to the major rivers show a much lower ratio of <10 (Ahmad 1995<ref name="Ahmad 1995"></ref>).		A useful way to reflect the potential horizontal rather than vertical groundwater flow across the basin is to estimate the anisotropy in permeability. Studies in the Upper Indus suggest a bulk ratio of horizontal to vertical permeability of approximately 25 (Bennett 1969<ref name="Bennett 1969">Bennett G D, Rehman A U, Sheikh J A and Ali S. 1969. Analysis of pumping tests in the Punjab region of west Pakistan, Geological Survey Water‐Supply Paper 1608‐G, prepared in cooperation with the W Pakistan Water & Power Dec Authority under US AID.</ref>), rising to 50–100 in the main Ganges basin (Sinha et al. 2009, Khan et al. 2014<ref name="Khan 2014"></ref>), and 200–500 in the Lower Indus (Chilton 1986<ref name="Chilton 1986"></ref>, Ahmad 1995<ref name="Ahmad 1995">Ahmed, 1995. Groundwater Resources of Pakistan. 560 pp</ref>); 10 000 in the southern Bengal Basin and 20 000 in the coastal areas (Michael and Voss 2009<ref name="Michael 2009">Michael, H A and Voss, C I. 2009. Estimation of regional‐scale flow properties in Bengal Basin of India and Bangladesh. ''Hydrogeology Journal'', 17; 6; 1329–1346.</ref>). Limited data from modern sediments close to the major rivers show a much lower ratio of <10 (Ahmad 1995<ref name="Ahmad 1995"></ref>).

	==Groundwater chemistry: salinity and arsenic==		==Groundwater chemistry: salinity and arsenic==