OR/15/047 Typologies - Revision history

Ajhil: /* Minor Typologies */

2019-12-03T12:01:04Z

Minor Typologies

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	''The Sylhet Basin''<br>		''The Sylhet Basin''<br>
	The Sylhet Basin occupies a distinctive region in east Bangladesh of tectonic subsidence, and forms a discrete typology in the IGB aquifer system of significantly lower aquifer permeability <10 m/d and specific yield <5%. The typology is composed of a high proportion of silts, muds and clays (>60%) deposited in low energy fluvial and wetland settings in the basin (Johnson and Alam 1991<ref name="Johnson 1991">Johnson, Y J, Alam, A M N. 1991. Sedimentation and tectonics of the Sylhet Trough, Bangladesh. Geological Society of America Bulletin, 103; 1513–1527.</ref>). Channel deposits are often separated by significant thicknesses (tens of metres) of muds, and individual channel deposits have to be targeted in groundwater development (Johnson and Alam 1991<ref name="Johnson 1991">~~Johnson, Y J, Alam, A M N. 1991. Sedimentation and tectonics of the Sylhet Trough, Bangladesh. Geological Society of America Bulletin, 103; 1513–1527.~~ </ref>). Depth to groundwater is very shallow (<3 m bgl), with water logging characteristic of the typology. Lower aquifer units are semi‐confined or confined and typically have a piezometric head which is above the water‐level in the upper aquifer units (Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>).		The Sylhet Basin occupies a distinctive region in east Bangladesh of tectonic subsidence, and forms a discrete typology in the IGB aquifer system of significantly lower aquifer permeability <10 m/d and specific yield <5%. The typology is composed of a high proportion of silts, muds and clays (>60%) deposited in low energy fluvial and wetland settings in the basin (Johnson and Alam 1991<ref name="Johnson 1991">Johnson, Y J, Alam, A M N. 1991. Sedimentation and tectonics of the Sylhet Trough, Bangladesh. Geological Society of America Bulletin, 103; 1513–1527.</ref>). Channel deposits are often separated by significant thicknesses (tens of metres) of muds, and individual channel deposits have to be targeted in groundwater development (Johnson and Alam 1991<ref name="Johnson 1991"></ref>). Depth to groundwater is very shallow (<3 m bgl), with water logging characteristic of the typology. Lower aquifer units are semi‐confined or confined and typically have a piezometric head which is above the water‐level in the upper aquifer units (Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>).

	Groundwater abstraction is limited within the typology, probably as a result of the abundant rainfall. Actual groundwater recharge can be low, due to the lack of spare capacity within the aquifer to receive the recharge. There are locally elevated concentrations of arsenic within shallow groundwater and methane concentrations can also be elevated (Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>).		Groundwater abstraction is limited within the typology, probably as a result of the abundant rainfall. Actual groundwater recharge can be low, due to the lack of spare capacity within the aquifer to receive the recharge. There are locally elevated concentrations of arsenic within shallow groundwater and methane concentrations can also be elevated (Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>).

Ajhil: /* Typology 7 The marine influenced deltaic areas */

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Typology 7 The marine influenced deltaic areas

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	A marine groundwater typology exists within the coastal margins of both the Indus and Ganges‐ Brahmaputra river systems. Permeability of these aquifers tends to be low <10 m/d, specific yield <5% and anisotopy very high, 20 000, as a result of the aquifer being composed of highly stratified silt and clay sediments which were deposited in deltaic or marine‐influenced settings (Mott MacDonald and Partners 1986<ref name="MacDonald 1986"></ref>; Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>; Michael and Voss 2009<ref name="Michael 2009"></ref>). Shallow groundwater is not used in the coastal regions; here, deep groundwater, below the occurrence of excessive salinity, is a vital resource, especially in the large coastal towns (Taylor et al. 2014<ref name="Taylor 2014">Taylor R G, Burgess W G, Shamsudduha M, Zahid A, Lapworth D J, Ahmed K, Mukherjee A and Nowreen S. 2014. Deep groundwater in the Bengal Mega‐Delta: new evidence of aquifer hydraulics and the influence of intensive abstraction. British Geological Survey Open Report, OR/14/070. 24pp. </ref>).		A marine groundwater typology exists within the coastal margins of both the Indus and Ganges‐ Brahmaputra river systems. Permeability of these aquifers tends to be low <10 m/d, specific yield <5% and anisotopy very high, 20 000, as a result of the aquifer being composed of highly stratified silt and clay sediments which were deposited in deltaic or marine‐influenced settings (Mott MacDonald and Partners 1986<ref name="MacDonald 1986"></ref>; Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>; Michael and Voss 2009<ref name="Michael 2009"></ref>). Shallow groundwater is not used in the coastal regions; here, deep groundwater, below the occurrence of excessive salinity, is a vital resource, especially in the large coastal towns (Taylor et al. 2014<ref name="Taylor 2014">Taylor R G, Burgess W G, Shamsudduha M, Zahid A, Lapworth D J, Ahmed K, Mukherjee A and Nowreen S. 2014. Deep groundwater in the Bengal Mega‐Delta: new evidence of aquifer hydraulics and the influence of intensive abstraction. British Geological Survey Open Report, OR/14/070. 24pp. </ref>).

	In Bangladesh, rainfall is high and there is much river water, allowing for recharge in the shallow groundwater both from rainfall and river infiltration (Shamsudduha et al. 2009). Deeper groundwater in this typology receives little modern recharge due to the low vertical permeability (Michael and Voss 2009<ref name="Michael 2009"></ref>). In Pakistan, rainfall is negligible and river flow significantly diminished leading to a rapid decline in the availability of freshwater, with a corresponding imapct on the mangrove ecosystems (Basharat et al. 2014<ref name="Basharat 2014"></ref>). Therefore in Pakistan the groundwater is extensively saline in this typology, both from the influence of sea water intrusion through the creeks and also from terrigenous impact described in [[#Typology 6 The Lower Indus \| Typology 6]]. The saline water in the coastal areas of Bangladesh is more complex (Allison et al. 2003<ref name="Allison 2003">~~Allison M A, Khan S R, Goodbred Jr S L and Kuehl SA. 2003. Stratigraphic evolution of the late Holocene Ganges‐ Brahmaputra lower delta plain, Sedimentary Geology, 155; 317–342~~ </ref>; Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>). Shallow groundwater can be saline far inland from the impact of storm surges, and deeper groundwater (>100 m depth) can have much lower salinity due to its partially isolation from the modern influence of the sea due to the presence of clay and silt and the high anisotropy.		In Bangladesh, rainfall is high and there is much river water, allowing for recharge in the shallow groundwater both from rainfall and river infiltration (Shamsudduha et al. 2009). Deeper groundwater in this typology receives little modern recharge due to the low vertical permeability (Michael and Voss 2009<ref name="Michael 2009"></ref>). In Pakistan, rainfall is negligible and river flow significantly diminished leading to a rapid decline in the availability of freshwater, with a corresponding imapct on the mangrove ecosystems (Basharat et al. 2014<ref name="Basharat 2014"></ref>). Therefore in Pakistan the groundwater is extensively saline in this typology, both from the influence of sea water intrusion through the creeks and also from terrigenous impact described in [[#Typology 6 The Lower Indus \| Typology 6]]. The saline water in the coastal areas of Bangladesh is more complex (Allison et al. 2003<ref name="Allison 2003"></ref>; Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>). Shallow groundwater can be saline far inland from the impact of storm surges, and deeper groundwater (>100 m depth) can have much lower salinity due to its partially isolation from the modern influence of the sea due to the presence of clay and silt and the high anisotropy.

	====Minor Typologies====		====Minor Typologies====

Ajhil: /* Typology 4 The fluvial influenced deltaic area */

2019-12-03T12:00:10Z

Typology 4 The fluvial influenced deltaic area

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	The fluvial influenced deltaic area is dominated by extremely high concentrations of arsenic in shallow (generally <100 m deep) groundwater. The sediments comprise alluvium sediments deposited in fluvial to deltaic and tidally influenced setting, and therefore have a greater proportion of silts and fine sands then typologies further upstream (Jones 1985<ref name="Jones 1985">Jones P H. 1985. Geology and Groundwater Resources of Bangladesh, World Bank South Asian Region, 60 pp.</ref>; Allison et al 2003<ref name="Allison 2003">Allison M A, Khan S R, Goodbred Jr S L and Kuehl S A. 2003. Stratigraphic evolution of the late Holocene Ganges‐Brahmaputra lower delta plain, Sedimentary Geology, 155; 317–342</ref>; DPHE 2007<ref name="DPHE 2007"></ref>; Holly and Voss 2009). The geological setting gives a complex highly heterogeneous aquifer. Permeability can be low — typically 10–25 m/d and specific yield is <10% (Mott MacDonald and Partners 1982<ref name="McDonald 1982">MacDonald and Partners. 1982. Second Tubewell Project, Final report Vol III, Groundwater, 53 pp. </ref>, 1986<ref name="McDonald 1986">MacDonald and Partners. 1986. Phase One Completion Report, Annexure I: Project Well Data, Kishorganj & Dhaka Regions, Government of the Peoples Republic of Bangladesh, Bangladesh Agricultural Development Corporation, 134 pp. </ref>; Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>; Mukherjee et al. 2007<ref name="Mukherjee 2007">Mukherjee, A, Fryar, A E and Howell, P., 2007. Regional hydrostratigraphy and groundwater flow modeling of the arsenic contaminated aquifers of the western Bengal basin, West Bengal, India. Hydrogeology Journal, 15; 1397–1418</ref>). Low permeability units are continuous over 10s of kilometres and as a consequence the aquifer is highly anisotropic, with mean horizontal permeability 10 000 times greater than vertical permeability (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>).		The fluvial influenced deltaic area is dominated by extremely high concentrations of arsenic in shallow (generally <100 m deep) groundwater. The sediments comprise alluvium sediments deposited in fluvial to deltaic and tidally influenced setting, and therefore have a greater proportion of silts and fine sands then typologies further upstream (Jones 1985<ref name="Jones 1985">Jones P H. 1985. Geology and Groundwater Resources of Bangladesh, World Bank South Asian Region, 60 pp.</ref>; Allison et al 2003<ref name="Allison 2003">Allison M A, Khan S R, Goodbred Jr S L and Kuehl S A. 2003. Stratigraphic evolution of the late Holocene Ganges‐Brahmaputra lower delta plain, Sedimentary Geology, 155; 317–342</ref>; DPHE 2007<ref name="DPHE 2007"></ref>; Holly and Voss 2009). The geological setting gives a complex highly heterogeneous aquifer. Permeability can be low — typically 10–25 m/d and specific yield is <10% (Mott MacDonald and Partners 1982<ref name="McDonald 1982">MacDonald and Partners. 1982. Second Tubewell Project, Final report Vol III, Groundwater, 53 pp. </ref>, 1986<ref name="McDonald 1986">MacDonald and Partners. 1986. Phase One Completion Report, Annexure I: Project Well Data, Kishorganj & Dhaka Regions, Government of the Peoples Republic of Bangladesh, Bangladesh Agricultural Development Corporation, 134 pp. </ref>; Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>; Mukherjee et al. 2007<ref name="Mukherjee 2007">Mukherjee, A, Fryar, A E and Howell, P., 2007. Regional hydrostratigraphy and groundwater flow modeling of the arsenic contaminated aquifers of the western Bengal basin, West Bengal, India. Hydrogeology Journal, 15; 1397–1418</ref>). Low permeability units are continuous over 10s of kilometres and as a consequence the aquifer is highly anisotropic, with mean horizontal permeability 10 000 times greater than vertical permeability (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>).

	Rainfall across the typology is high, greater than 2000 mm and increasing from west to east — potential recharge is therefore dominated by rainfall recharge and actual recharge is limited by the space in the aquifer to receive the water and also by the presence of low permeability soils in some places (CGWB 2007<ref name="CGWB 2007"></ref>; Shamsudduha et al. 2009). Elevated arsenic concentrations in shallow groundwater are widespread, with very high concentrations (>200 µg/L) common (Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>; Acharyya 2005<ref name=">Acharyya S K. 2005. Arsenic levels in groundwater from Quaternary Alluvium in the Ganga Plain and Bengal Basin, Indian subcontinent: insights into influence of stratigraphy. Gondwana Research, 8; 1; 55–56. </ref>; Harvey 2006<ref name="Harvey 2006">Harvey C F et al. 2006. Groundwater dynamics and arsenic contamination in Bangladesh, Chemical Geology, 228; 112–136.</ref>; Mukherjee et al. 2011<ref name="Mukherjee 2001">Mukherjee, A, Fryar, A E, Scanlon, B R, Bhattacharya, P and Bhattacharya, A. 2011. Elevated arsenic in deeper groundwater of western Bengal basin, India: Extents and controls from regional to local‐scale. Applied Geochemistry, 26; 600–613.</ref>). At depth (>150 m) groundwater can have lower arsenic concentrations, due to the complex history of deposition, historic flushing, redox conditions and the presence of the pervasive low permeability layers which limit the downward movement of the shallow groundwater. The deeper groundwater, however, receives little modern groundwater recharge (Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>; Shah 2008<ref name="Shah 2008">~~Shah B A. 2008. Role of Qauternary stratigraphy on arsenic‐contaminated groundwater from parts of the Middle Ganga Plain, UP‐Bihar, India. Environ Geology, 53; 1553–1561.~~		Rainfall across the typology is high, greater than 2000 mm and increasing from west to east — potential recharge is therefore dominated by rainfall recharge and actual recharge is limited by the space in the aquifer to receive the water and also by the presence of low permeability soils in some places (CGWB 2007<ref name="CGWB 2007"></ref>; Shamsudduha et al. 2009). Elevated arsenic concentrations in shallow groundwater are widespread, with very high concentrations (>200 µg/L) common (Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>; Acharyya 2005<ref name=">Acharyya S K. 2005. Arsenic levels in groundwater from Quaternary Alluvium in the Ganga Plain and Bengal Basin, Indian subcontinent: insights into influence of stratigraphy. Gondwana Research, 8; 1; 55–56. </ref>; Harvey 2006<ref name="Harvey 2006">Harvey C F et al. 2006. Groundwater dynamics and arsenic contamination in Bangladesh, Chemical Geology, 228; 112–136.</ref>; Mukherjee et al. 2011<ref name="Mukherjee 2001">Mukherjee, A, Fryar, A E, Scanlon, B R, Bhattacharya, P and Bhattacharya, A. 2011. Elevated arsenic in deeper groundwater of western Bengal basin, India: Extents and controls from regional to local‐scale. Applied Geochemistry, 26; 600–613.</ref>). At depth (>150 m) groundwater can have lower arsenic concentrations, due to the complex history of deposition, historic flushing, redox conditions and the presence of the pervasive low permeability layers which limit the downward movement of the shallow groundwater. The deeper groundwater, however, receives little modern groundwater recharge (Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>; Shah 2008<ref name="Shah 2008"></ref>; Hoque and Burgess 2009<ref name="Hogue 2009">Hoque M A and Burgess W. 2009. Provenance and travel time of groundwater pumped from 'arsenic safe' depths in the aquifer of southern Bangladesh: aquifer representation to assess </ref>; Fendorf et al. 2010<ref name="Fendorf 2010">Fendorf S, Michael H A and van Geen A 2010. Spatial and temporal variations of groundwater arsenic in south and southeast Asia, Science 328 1123–1127 DOI: 10.1126/science.1172974 </ref>; Burgess et al 2010<ref name="Burgess 2010">Burgess W G, Hoque M A ,Michael H A, Voss C I, Breit G N and Ahmed KM. 2010. Vulnerability of deep groundwater in the Bengal Aquifer System to contamination by arsenic. Nature Geoscience 3: 83–87</ref>).
	</ref>; Hoque and Burgess 2009<ref name="Hogue 2009">Hoque M A and Burgess W. 2009. Provenance and travel time of groundwater pumped from 'arsenic safe' depths in the aquifer of southern Bangladesh: aquifer representation to assess </ref>; Fendorf et al. 2010<ref name="Fendorf 2010">Fendorf S, Michael H A and van Geen A 2010. Spatial and temporal variations of groundwater arsenic in south and southeast Asia, Science 328 1123–1127 DOI: 10.1126/science.1172974 </ref>; Burgess et al 2010<ref name="Burgess 2010">Burgess W G, Hoque M A ,Michael H A, Voss C I, Breit G N and Ahmed KM. 2010. Vulnerability of deep groundwater in the Bengal Aquifer System to contamination by arsenic. Nature Geoscience 3: 83–87</ref>).

	====Typology 5 Middle Indus and Upper Ganges====		====Typology 5 Middle Indus and Upper Ganges====

Ajhil at 11:59, 3 December 2019

2019-12-03T11:59:17Z

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	The fluvial influenced deltaic area is dominated by extremely high concentrations of arsenic in shallow (generally <100 m deep) groundwater. The sediments comprise alluvium sediments deposited in fluvial to deltaic and tidally influenced setting, and therefore have a greater proportion of silts and fine sands then typologies further upstream (Jones 1985<ref name="Jones 1985">Jones P H. 1985. Geology and Groundwater Resources of Bangladesh, World Bank South Asian Region, 60 pp.</ref>; Allison et al 2003<ref name="Allison 2003">Allison M A, Khan S R, Goodbred Jr S L and Kuehl S A. 2003. Stratigraphic evolution of the late Holocene Ganges‐Brahmaputra lower delta plain, Sedimentary Geology, 155; 317–342</ref>; DPHE 2007<ref name="DPHE 2007"></ref>; Holly and Voss 2009). The geological setting gives a complex highly heterogeneous aquifer. Permeability can be low — typically 10–25 m/d and specific yield is <10% (Mott MacDonald and Partners 1982<ref name="McDonald 1982">MacDonald and Partners. 1982. Second Tubewell Project, Final report Vol III, Groundwater, 53 pp. </ref>, 1986<ref name="McDonald 1986">MacDonald and Partners. 1986. Phase One Completion Report, Annexure I: Project Well Data, Kishorganj & Dhaka Regions, Government of the Peoples Republic of Bangladesh, Bangladesh Agricultural Development Corporation, 134 pp. </ref>; Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>; Mukherjee et al. 2007<ref name="Mukherjee 2007">Mukherjee, A, Fryar, A E and Howell, P., 2007. Regional hydrostratigraphy and groundwater flow modeling of the arsenic contaminated aquifers of the western Bengal basin, West Bengal, India. Hydrogeology Journal, 15; 1397–1418</ref>). Low permeability units are continuous over 10s of kilometres and as a consequence the aquifer is highly anisotropic, with mean horizontal permeability 10 000 times greater than vertical permeability (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>).		The fluvial influenced deltaic area is dominated by extremely high concentrations of arsenic in shallow (generally <100 m deep) groundwater. The sediments comprise alluvium sediments deposited in fluvial to deltaic and tidally influenced setting, and therefore have a greater proportion of silts and fine sands then typologies further upstream (Jones 1985<ref name="Jones 1985">Jones P H. 1985. Geology and Groundwater Resources of Bangladesh, World Bank South Asian Region, 60 pp.</ref>; Allison et al 2003<ref name="Allison 2003">Allison M A, Khan S R, Goodbred Jr S L and Kuehl S A. 2003. Stratigraphic evolution of the late Holocene Ganges‐Brahmaputra lower delta plain, Sedimentary Geology, 155; 317–342</ref>; DPHE 2007<ref name="DPHE 2007"></ref>; Holly and Voss 2009). The geological setting gives a complex highly heterogeneous aquifer. Permeability can be low — typically 10–25 m/d and specific yield is <10% (Mott MacDonald and Partners 1982<ref name="McDonald 1982">MacDonald and Partners. 1982. Second Tubewell Project, Final report Vol III, Groundwater, 53 pp. </ref>, 1986<ref name="McDonald 1986">MacDonald and Partners. 1986. Phase One Completion Report, Annexure I: Project Well Data, Kishorganj & Dhaka Regions, Government of the Peoples Republic of Bangladesh, Bangladesh Agricultural Development Corporation, 134 pp. </ref>; Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>; Mukherjee et al. 2007<ref name="Mukherjee 2007">Mukherjee, A, Fryar, A E and Howell, P., 2007. Regional hydrostratigraphy and groundwater flow modeling of the arsenic contaminated aquifers of the western Bengal basin, West Bengal, India. Hydrogeology Journal, 15; 1397–1418</ref>). Low permeability units are continuous over 10s of kilometres and as a consequence the aquifer is highly anisotropic, with mean horizontal permeability 10 000 times greater than vertical permeability (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>).

	Rainfall across the typology is high, greater than 2000 mm and increasing from west to east — potential recharge is therefore dominated by rainfall recharge and actual recharge is limited by the space in the aquifer to receive the water and also by the presence of low permeability soils in some places (CGWB 2007<ref name="CGWB 2007"></ref>; Shamsudduha et al. 2009). Elevated arsenic concentrations in shallow groundwater are widespread, with very high concentrations (>200 µg/L) common (Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000">~~Kinniburgh and Smedley. 2000. Arsenic contamination of groundwater in Bangladesh, BGS Technical Report WC/00/19 Vol 1, 656 pp~~ </ref>; Acharyya 2005<ref name=">Acharyya S K. 2005. Arsenic levels in groundwater from Quaternary Alluvium in the Ganga Plain and Bengal Basin, Indian subcontinent: insights into influence of stratigraphy. Gondwana Research, 8; 1; 55–56. </ref>; Harvey 2006<ref name="Harvey 2006">Harvey C F et al. 2006. Groundwater dynamics and arsenic contamination in Bangladesh, Chemical Geology, 228; 112–136.</ref>; Mukherjee et al. 2011<ref name="Mukherjee 2001">Mukherjee, A, Fryar, A E, Scanlon, B R, Bhattacharya, P and Bhattacharya, A. 2011. Elevated arsenic in deeper groundwater of western Bengal basin, India: Extents and controls from regional to local‐scale. Applied Geochemistry, 26; 600–613.</ref>). At depth (>150 m) groundwater can have lower arsenic concentrations, due to the complex history of deposition, historic flushing, redox conditions and the presence of the pervasive low permeability layers which limit the downward movement of the shallow groundwater. The deeper groundwater, however, receives little modern groundwater recharge (Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>; Shah 2008<ref name="Shah 2008">Shah B A. 2008. Role of Qauternary stratigraphy on arsenic‐contaminated groundwater from parts of the Middle Ganga Plain, UP‐Bihar, India. Environ Geology, 53; 1553–1561.		Rainfall across the typology is high, greater than 2000 mm and increasing from west to east — potential recharge is therefore dominated by rainfall recharge and actual recharge is limited by the space in the aquifer to receive the water and also by the presence of low permeability soils in some places (CGWB 2007<ref name="CGWB 2007"></ref>; Shamsudduha et al. 2009). Elevated arsenic concentrations in shallow groundwater are widespread, with very high concentrations (>200 µg/L) common (Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>; Acharyya 2005<ref name=">Acharyya S K. 2005. Arsenic levels in groundwater from Quaternary Alluvium in the Ganga Plain and Bengal Basin, Indian subcontinent: insights into influence of stratigraphy. Gondwana Research, 8; 1; 55–56. </ref>; Harvey 2006<ref name="Harvey 2006">Harvey C F et al. 2006. Groundwater dynamics and arsenic contamination in Bangladesh, Chemical Geology, 228; 112–136.</ref>; Mukherjee et al. 2011<ref name="Mukherjee 2001">Mukherjee, A, Fryar, A E, Scanlon, B R, Bhattacharya, P and Bhattacharya, A. 2011. Elevated arsenic in deeper groundwater of western Bengal basin, India: Extents and controls from regional to local‐scale. Applied Geochemistry, 26; 600–613.</ref>). At depth (>150 m) groundwater can have lower arsenic concentrations, due to the complex history of deposition, historic flushing, redox conditions and the presence of the pervasive low permeability layers which limit the downward movement of the shallow groundwater. The deeper groundwater, however, receives little modern groundwater recharge (Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>; Shah 2008<ref name="Shah 2008">Shah B A. 2008. Role of Qauternary stratigraphy on arsenic‐contaminated groundwater from parts of the Middle Ganga Plain, UP‐Bihar, India. Environ Geology, 53; 1553–1561.
	</ref>; Hoque and Burgess 2009<ref name="Hogue 2009">Hoque M A and Burgess W. 2009. Provenance and travel time of groundwater pumped from 'arsenic safe' depths in the aquifer of southern Bangladesh: aquifer representation to assess </ref>; Fendorf et al. 2010<ref name="Fendorf 2010">Fendorf S, Michael H A and van Geen A 2010. Spatial and temporal variations of groundwater arsenic in south and southeast Asia, Science 328 1123–1127 DOI: 10.1126/science.1172974 </ref>; Burgess et al 2010<ref name="Burgess 2010">Burgess W G, Hoque M A ,Michael H A, Voss C I, Breit G N and Ahmed KM. 2010. Vulnerability of deep groundwater in the Bengal Aquifer System to contamination by arsenic. Nature Geoscience 3: 83–87</ref>).		</ref>; Hoque and Burgess 2009<ref name="Hogue 2009">Hoque M A and Burgess W. 2009. Provenance and travel time of groundwater pumped from 'arsenic safe' depths in the aquifer of southern Bangladesh: aquifer representation to assess </ref>; Fendorf et al. 2010<ref name="Fendorf 2010">Fendorf S, Michael H A and van Geen A 2010. Spatial and temporal variations of groundwater arsenic in south and southeast Asia, Science 328 1123–1127 DOI: 10.1126/science.1172974 </ref>; Burgess et al 2010<ref name="Burgess 2010">Burgess W G, Hoque M A ,Michael H A, Voss C I, Breit G N and Ahmed KM. 2010. Vulnerability of deep groundwater in the Bengal Aquifer System to contamination by arsenic. Nature Geoscience 3: 83–87</ref>).

Ajhil: /* Typology 4 The fluvial influenced deltaic area */

2019-12-03T11:58:11Z

Typology 4 The fluvial influenced deltaic area

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	====Typology 4 The fluvial influenced deltaic area====		====Typology 4 The fluvial influenced deltaic area====
	The fluvial influenced deltaic area is dominated by extremely high concentrations of arsenic in shallow (generally <100 m deep) groundwater. The sediments comprise alluvium sediments deposited in fluvial to deltaic and tidally influenced setting, and therefore have a greater proportion of silts and fine sands then typologies further upstream (Jones 1985<ref name="Jones 1985">Jones P H. 1985. Geology and Groundwater Resources of Bangladesh, World Bank South Asian Region, 60 pp.</ref>; Allison et al 2003<ref name="Allison 2003">Allison M A, Khan S R, Goodbred Jr S L and Kuehl S A. 2003. Stratigraphic evolution of the late Holocene ~~Ganges‐ Brahmaputra~~ lower delta plain, Sedimentary Geology, 155; 317–342</ref>; DPHE 2007<ref name="DPHE 2007">~~DPHE. 2007. Final Report on Development of Deep Aquifer Database and Preliminary Deep Aquifer Map, DPHE, Government of the People’s Republic of Bangladesh, pp 173.~~</ref>; Holly and Voss 2009). The geological setting gives a complex highly heterogeneous aquifer. Permeability can be low — typically 10–25 m/d and specific yield is <10% (Mott MacDonald and Partners 1982<ref name="McDonald 1982">MacDonald and Partners. 1982. Second Tubewell Project, Final report Vol III, Groundwater, 53 pp. </ref>, 1986<ref name="McDonald 1986">MacDonald and Partners. 1986. Phase One Completion Report, Annexure I: Project Well Data, Kishorganj & Dhaka Regions, Government of the Peoples Republic of Bangladesh, Bangladesh Agricultural Development Corporation, 134 pp. </ref>; Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>; Mukherjee et al. 2007<ref name="Mukherjee 2007">Mukherjee, A, Fryar, A E and Howell, P., 2007. Regional hydrostratigraphy and groundwater flow modeling of the arsenic contaminated aquifers of the western Bengal basin, West Bengal, India. Hydrogeology Journal, 15; 1397–1418</ref>). Low permeability units are continuous over 10s of kilometres and as a consequence the aquifer is highly anisotropic, with mean horizontal permeability 10 000 times greater than vertical permeability (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>).		The fluvial influenced deltaic area is dominated by extremely high concentrations of arsenic in shallow (generally <100 m deep) groundwater. The sediments comprise alluvium sediments deposited in fluvial to deltaic and tidally influenced setting, and therefore have a greater proportion of silts and fine sands then typologies further upstream (Jones 1985<ref name="Jones 1985">Jones P H. 1985. Geology and Groundwater Resources of Bangladesh, World Bank South Asian Region, 60 pp.</ref>; Allison et al 2003<ref name="Allison 2003">Allison M A, Khan S R, Goodbred Jr S L and Kuehl S A. 2003. Stratigraphic evolution of the late Holocene Ganges‐Brahmaputra lower delta plain, Sedimentary Geology, 155; 317–342</ref>; DPHE 2007<ref name="DPHE 2007"></ref>; Holly and Voss 2009). The geological setting gives a complex highly heterogeneous aquifer. Permeability can be low — typically 10–25 m/d and specific yield is <10% (Mott MacDonald and Partners 1982<ref name="McDonald 1982">MacDonald and Partners. 1982. Second Tubewell Project, Final report Vol III, Groundwater, 53 pp. </ref>, 1986<ref name="McDonald 1986">MacDonald and Partners. 1986. Phase One Completion Report, Annexure I: Project Well Data, Kishorganj & Dhaka Regions, Government of the Peoples Republic of Bangladesh, Bangladesh Agricultural Development Corporation, 134 pp. </ref>; Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>; Mukherjee et al. 2007<ref name="Mukherjee 2007">Mukherjee, A, Fryar, A E and Howell, P., 2007. Regional hydrostratigraphy and groundwater flow modeling of the arsenic contaminated aquifers of the western Bengal basin, West Bengal, India. Hydrogeology Journal, 15; 1397–1418</ref>). Low permeability units are continuous over 10s of kilometres and as a consequence the aquifer is highly anisotropic, with mean horizontal permeability 10 000 times greater than vertical permeability (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>).

	Rainfall across the typology is high, greater than 2000 mm and increasing from west to east — potential recharge is therefore dominated by rainfall recharge and actual recharge is limited by the space in the aquifer to receive the water and also by the presence of low permeability soils in some places (CGWB 2007<ref name="CGWB 2007"></ref>; Shamsudduha et al. 2009). Elevated arsenic concentrations in shallow groundwater are widespread, with very high concentrations (>200 µg/L) common (Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000">Kinniburgh and Smedley. 2000. Arsenic contamination of groundwater in Bangladesh, BGS Technical Report WC/00/19 Vol 1, 656 pp </ref>; Acharyya 2005<ref name=">Acharyya S K. 2005. Arsenic levels in groundwater from Quaternary Alluvium in the Ganga Plain and Bengal Basin, Indian subcontinent: insights into influence of stratigraphy. Gondwana Research, 8; 1; 55–56. </ref>; Harvey 2006<ref name="Harvey 2006">Harvey C F et al. 2006. Groundwater dynamics and arsenic contamination in Bangladesh, Chemical Geology, 228; 112–136.</ref>; Mukherjee et al. 2011<ref name="Mukherjee 2001">Mukherjee, A, Fryar, A E, Scanlon, B R, Bhattacharya, P and Bhattacharya, A. 2011. Elevated arsenic in deeper groundwater of western Bengal basin, India: Extents and controls from regional to local‐scale. Applied Geochemistry, 26; 600–613.</ref>). At depth (>150 m) groundwater can have lower arsenic concentrations, due to the complex history of deposition, historic flushing, redox conditions and the presence of the pervasive low permeability layers which limit the downward movement of the shallow groundwater. The deeper groundwater, however, receives little modern groundwater recharge (Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>; Shah 2008<ref name="Shah 2008">Shah B A. 2008. Role of Qauternary stratigraphy on arsenic‐contaminated groundwater from parts of the Middle Ganga Plain, UP‐Bihar, India. Environ Geology, 53; 1553–1561.		Rainfall across the typology is high, greater than 2000 mm and increasing from west to east — potential recharge is therefore dominated by rainfall recharge and actual recharge is limited by the space in the aquifer to receive the water and also by the presence of low permeability soils in some places (CGWB 2007<ref name="CGWB 2007"></ref>; Shamsudduha et al. 2009). Elevated arsenic concentrations in shallow groundwater are widespread, with very high concentrations (>200 µg/L) common (Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000">Kinniburgh and Smedley. 2000. Arsenic contamination of groundwater in Bangladesh, BGS Technical Report WC/00/19 Vol 1, 656 pp </ref>; Acharyya 2005<ref name=">Acharyya S K. 2005. Arsenic levels in groundwater from Quaternary Alluvium in the Ganga Plain and Bengal Basin, Indian subcontinent: insights into influence of stratigraphy. Gondwana Research, 8; 1; 55–56. </ref>; Harvey 2006<ref name="Harvey 2006">Harvey C F et al. 2006. Groundwater dynamics and arsenic contamination in Bangladesh, Chemical Geology, 228; 112–136.</ref>; Mukherjee et al. 2011<ref name="Mukherjee 2001">Mukherjee, A, Fryar, A E, Scanlon, B R, Bhattacharya, P and Bhattacharya, A. 2011. Elevated arsenic in deeper groundwater of western Bengal basin, India: Extents and controls from regional to local‐scale. Applied Geochemistry, 26; 600–613.</ref>). At depth (>150 m) groundwater can have lower arsenic concentrations, due to the complex history of deposition, historic flushing, redox conditions and the presence of the pervasive low permeability layers which limit the downward movement of the shallow groundwater. The deeper groundwater, however, receives little modern groundwater recharge (Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>; Shah 2008<ref name="Shah 2008">Shah B A. 2008. Role of Qauternary stratigraphy on arsenic‐contaminated groundwater from parts of the Middle Ganga Plain, UP‐Bihar, India. Environ Geology, 53; 1553–1561.

Ajhil at 11:57, 3 December 2019

2019-12-03T11:57:24Z

← Older revision		Revision as of 12:57, 3 December 2019
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	====Typology 5 Middle Indus and Upper Ganges====		====Typology 5 Middle Indus and Upper Ganges====
	The Middle Indus and Upper Ganges typology comprises a highly permeable aquifer stretching across the drier area of the middle Indus basin and into the Upper Ganges basin. The aquifer comprises a thick sequence of stacked channel and interchannel alluvial sediments (Singh 1996<ref name="Singh 1996">~~Singh I B. 1996. Geological evolution of Ganga Plain ‐ an overview, Journal of The Palaeontological Society of India , 41; 99–137.~~ </ref>; ISWARI 2005<ref name="ISWARI 2005">IWASRI 2005. Drainage Atlas of Pakistan, International Water Logging and Salinity Research Institute, Lahore.</ref>). The permeability of the aquifer is generally high, often 30–50 m/d, locally up to 50–60 m/d, with high specific yield, 10–20% and regional anisotropy, 25–100, although much lower in the recent deposits next to modern river channels (Bennett 1969<ref name="Bennett 1969"></ref>; Mott MacDonald and Partners 1982<ref name="MacDonald 1982">MacDonald and Partners. 1982. Second Tubewell Project, Final report Vol III, Groundwater, 53 pp.</ref>). Evaporite deposits are common within the alluvial stratigraphy at depth leading to areas with saline groundwater.		The Middle Indus and Upper Ganges typology comprises a highly permeable aquifer stretching across the drier area of the middle Indus basin and into the Upper Ganges basin. The aquifer comprises a thick sequence of stacked channel and interchannel alluvial sediments (Singh 1996<ref name="Singh 1996"></ref>; ISWARI 2005<ref name="ISWARI 2005">IWASRI 2005. Drainage Atlas of Pakistan, International Water Logging and Salinity Research Institute, Lahore.</ref>). The permeability of the aquifer is generally high, often 30–50 m/d, locally up to 50–60 m/d, with high specific yield, 10–20% and regional anisotropy, 25–100, although much lower in the recent deposits next to modern river channels (Bennett 1969<ref name="Bennett 1969"></ref>; Mott MacDonald and Partners 1982<ref name="MacDonald 1982">MacDonald and Partners. 1982. Second Tubewell Project, Final report Vol III, Groundwater, 53 pp.</ref>). Evaporite deposits are common within the alluvial stratigraphy at depth leading to areas with saline groundwater.

	Rainfall across this typology is highly seasonal with often less than 25 wet days within a year and average annual rainfall is less than 500 mm. Therefore, although rainfall recharge can occur, it does not dominate. Historically, the aquifer was recharged from the rivers, and large, thick (>100 m) fresh water lenses occur close to the rivers (Mott MacDonald and Partners 1986<ref name="MacDonald 1986">MacDonald and Partners. 1986. Phase One Completion Report, Annexure I: Project Well Data, Kishorganj & Dhaka Regions, Government of the Peoples Republic of Bangladesh, Bangladesh Agricultural Development Corporation, 134 pp.</ref>). At the present day, the aquifer is recharged both from the rivers, and the extensive canal network (Basharat 2012<ref name="Basharat 2012"></ref>). River flow has diminished due to the high volume diverted to the canal network. In general groundwater salinity is < 1000 mg/L close to the rivers, and >2500 mg/L away from the influence of the rivers (ISWARI 2005<ref name="ISWARI 2005"></ref>). Recharge from seepage from the canals can lead to a partial flushing of the shallow groundwater, but also to waterlogging and increased salinization in some areas. Elevated natural fluoride and arsenic concentrations and nitrate from agricultural practices are also common (Gupta et al. 2005<ref name="Gupta 2005">Gupta S K, Deshpande R D, Agarwal M and Raval BR. 2005. Origin of high flouride in groundwater in the North Gujurat‐Cambay region, India, Hydrogeology Journal, 13; 596–605 </ref>).		Rainfall across this typology is highly seasonal with often less than 25 wet days within a year and average annual rainfall is less than 500 mm. Therefore, although rainfall recharge can occur, it does not dominate. Historically, the aquifer was recharged from the rivers, and large, thick (>100 m) fresh water lenses occur close to the rivers (Mott MacDonald and Partners 1986<ref name="MacDonald 1986">MacDonald and Partners. 1986. Phase One Completion Report, Annexure I: Project Well Data, Kishorganj & Dhaka Regions, Government of the Peoples Republic of Bangladesh, Bangladesh Agricultural Development Corporation, 134 pp.</ref>). At the present day, the aquifer is recharged both from the rivers, and the extensive canal network (Basharat 2012<ref name="Basharat 2012"></ref>). River flow has diminished due to the high volume diverted to the canal network. In general groundwater salinity is < 1000 mg/L close to the rivers, and >2500 mg/L away from the influence of the rivers (ISWARI 2005<ref name="ISWARI 2005"></ref>). Recharge from seepage from the canals can lead to a partial flushing of the shallow groundwater, but also to waterlogging and increased salinization in some areas. Elevated natural fluoride and arsenic concentrations and nitrate from agricultural practices are also common (Gupta et al. 2005<ref name="Gupta 2005">Gupta S K, Deshpande R D, Agarwal M and Raval BR. 2005. Origin of high flouride in groundwater in the North Gujurat‐Cambay region, India, Hydrogeology Journal, 13; 596–605 </ref>).

Ajhil at 11:56, 3 December 2019

2019-12-03T11:56:36Z

← Older revision		Revision as of 12:56, 3 December 2019
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	The fluvial influenced deltaic area is dominated by extremely high concentrations of arsenic in shallow (generally <100 m deep) groundwater. The sediments comprise alluvium sediments deposited in fluvial to deltaic and tidally influenced setting, and therefore have a greater proportion of silts and fine sands then typologies further upstream (Jones 1985<ref name="Jones 1985">Jones P H. 1985. Geology and Groundwater Resources of Bangladesh, World Bank South Asian Region, 60 pp.</ref>; Allison et al 2003<ref name="Allison 2003">Allison M A, Khan S R, Goodbred Jr S L and Kuehl S A. 2003. Stratigraphic evolution of the late Holocene Ganges‐ Brahmaputra lower delta plain, Sedimentary Geology, 155; 317–342</ref>; DPHE 2007<ref name="DPHE 2007">DPHE. 2007. Final Report on Development of Deep Aquifer Database and Preliminary Deep Aquifer Map, DPHE, Government of the People’s Republic of Bangladesh, pp 173.</ref>; Holly and Voss 2009). The geological setting gives a complex highly heterogeneous aquifer. Permeability can be low — typically 10–25 m/d and specific yield is <10% (Mott MacDonald and Partners 1982<ref name="McDonald 1982">MacDonald and Partners. 1982. Second Tubewell Project, Final report Vol III, Groundwater, 53 pp. </ref>, 1986<ref name="McDonald 1986">MacDonald and Partners. 1986. Phase One Completion Report, Annexure I: Project Well Data, Kishorganj & Dhaka Regions, Government of the Peoples Republic of Bangladesh, Bangladesh Agricultural Development Corporation, 134 pp. </ref>; Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>; Mukherjee et al. 2007<ref name="Mukherjee 2007">Mukherjee, A, Fryar, A E and Howell, P., 2007. Regional hydrostratigraphy and groundwater flow modeling of the arsenic contaminated aquifers of the western Bengal basin, West Bengal, India. Hydrogeology Journal, 15; 1397–1418</ref>). Low permeability units are continuous over 10s of kilometres and as a consequence the aquifer is highly anisotropic, with mean horizontal permeability 10 000 times greater than vertical permeability (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>).		The fluvial influenced deltaic area is dominated by extremely high concentrations of arsenic in shallow (generally <100 m deep) groundwater. The sediments comprise alluvium sediments deposited in fluvial to deltaic and tidally influenced setting, and therefore have a greater proportion of silts and fine sands then typologies further upstream (Jones 1985<ref name="Jones 1985">Jones P H. 1985. Geology and Groundwater Resources of Bangladesh, World Bank South Asian Region, 60 pp.</ref>; Allison et al 2003<ref name="Allison 2003">Allison M A, Khan S R, Goodbred Jr S L and Kuehl S A. 2003. Stratigraphic evolution of the late Holocene Ganges‐ Brahmaputra lower delta plain, Sedimentary Geology, 155; 317–342</ref>; DPHE 2007<ref name="DPHE 2007">DPHE. 2007. Final Report on Development of Deep Aquifer Database and Preliminary Deep Aquifer Map, DPHE, Government of the People’s Republic of Bangladesh, pp 173.</ref>; Holly and Voss 2009). The geological setting gives a complex highly heterogeneous aquifer. Permeability can be low — typically 10–25 m/d and specific yield is <10% (Mott MacDonald and Partners 1982<ref name="McDonald 1982">MacDonald and Partners. 1982. Second Tubewell Project, Final report Vol III, Groundwater, 53 pp. </ref>, 1986<ref name="McDonald 1986">MacDonald and Partners. 1986. Phase One Completion Report, Annexure I: Project Well Data, Kishorganj & Dhaka Regions, Government of the Peoples Republic of Bangladesh, Bangladesh Agricultural Development Corporation, 134 pp. </ref>; Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>; Mukherjee et al. 2007<ref name="Mukherjee 2007">Mukherjee, A, Fryar, A E and Howell, P., 2007. Regional hydrostratigraphy and groundwater flow modeling of the arsenic contaminated aquifers of the western Bengal basin, West Bengal, India. Hydrogeology Journal, 15; 1397–1418</ref>). Low permeability units are continuous over 10s of kilometres and as a consequence the aquifer is highly anisotropic, with mean horizontal permeability 10 000 times greater than vertical permeability (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>).

	Rainfall across the typology is high, greater than 2000 mm and increasing from west to east — potential recharge is therefore dominated by rainfall recharge and actual recharge is limited by the space in the aquifer to receive the water and also by the presence of low permeability soils in some places (CGWB 2007<ref name="CGWB 2007">~~CGWB. 2007. Ground Water Scenario, India. CGWB, Ministry of Water Resources, Government of India. Faridabad BM Jha (ed).~~</ref>; Shamsudduha et al. 2009). Elevated arsenic concentrations in shallow groundwater are widespread, with very high concentrations (>200 µg/L) common (Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000">Kinniburgh and Smedley. 2000. Arsenic contamination of groundwater in Bangladesh, BGS Technical Report WC/00/19 Vol 1, 656 pp </ref>; Acharyya 2005<ref name=">Acharyya S K. 2005. Arsenic levels in groundwater from Quaternary Alluvium in the Ganga Plain and Bengal Basin, Indian subcontinent: insights into influence of stratigraphy. Gondwana Research, 8; 1; 55–56. </ref>; Harvey 2006<ref name="Harvey 2006">Harvey C F et al. 2006. Groundwater dynamics and arsenic contamination in Bangladesh, Chemical Geology, 228; 112–136.</ref>; Mukherjee et al. 2011<ref name="Mukherjee 2001">Mukherjee, A, Fryar, A E, Scanlon, B R, Bhattacharya, P and Bhattacharya, A. 2011. Elevated arsenic in deeper groundwater of western Bengal basin, India: Extents and controls from regional to local‐scale. Applied Geochemistry, 26; 600–613.</ref>). At depth (>150 m) groundwater can have lower arsenic concentrations, due to the complex history of deposition, historic flushing, redox conditions and the presence of the pervasive low permeability layers which limit the downward movement of the shallow groundwater. The deeper groundwater, however, receives little modern groundwater recharge (Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>; Shah 2008<ref name="Shah 2008">Shah B A. 2008. Role of Qauternary stratigraphy on arsenic‐contaminated groundwater from parts of the Middle Ganga Plain, UP‐Bihar, India. Environ Geology, 53; 1553–1561.		Rainfall across the typology is high, greater than 2000 mm and increasing from west to east — potential recharge is therefore dominated by rainfall recharge and actual recharge is limited by the space in the aquifer to receive the water and also by the presence of low permeability soils in some places (CGWB 2007<ref name="CGWB 2007"></ref>; Shamsudduha et al. 2009). Elevated arsenic concentrations in shallow groundwater are widespread, with very high concentrations (>200 µg/L) common (Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000">Kinniburgh and Smedley. 2000. Arsenic contamination of groundwater in Bangladesh, BGS Technical Report WC/00/19 Vol 1, 656 pp </ref>; Acharyya 2005<ref name=">Acharyya S K. 2005. Arsenic levels in groundwater from Quaternary Alluvium in the Ganga Plain and Bengal Basin, Indian subcontinent: insights into influence of stratigraphy. Gondwana Research, 8; 1; 55–56. </ref>; Harvey 2006<ref name="Harvey 2006">Harvey C F et al. 2006. Groundwater dynamics and arsenic contamination in Bangladesh, Chemical Geology, 228; 112–136.</ref>; Mukherjee et al. 2011<ref name="Mukherjee 2001">Mukherjee, A, Fryar, A E, Scanlon, B R, Bhattacharya, P and Bhattacharya, A. 2011. Elevated arsenic in deeper groundwater of western Bengal basin, India: Extents and controls from regional to local‐scale. Applied Geochemistry, 26; 600–613.</ref>). At depth (>150 m) groundwater can have lower arsenic concentrations, due to the complex history of deposition, historic flushing, redox conditions and the presence of the pervasive low permeability layers which limit the downward movement of the shallow groundwater. The deeper groundwater, however, receives little modern groundwater recharge (Kinniburgh and Smedley 2000<ref name="Kinniburgh 2000"></ref>; Shah 2008<ref name="Shah 2008">Shah B A. 2008. Role of Qauternary stratigraphy on arsenic‐contaminated groundwater from parts of the Middle Ganga Plain, UP‐Bihar, India. Environ Geology, 53; 1553–1561.
	</ref>; Hoque and Burgess 2009<ref name="Hogue 2009">Hoque M A and Burgess W. 2009. Provenance and travel time of groundwater pumped from 'arsenic safe' depths in the aquifer of southern Bangladesh: aquifer representation to assess </ref>; Fendorf et al. 2010<ref name="Fendorf 2010">Fendorf S, Michael H A and van Geen A 2010. Spatial and temporal variations of groundwater arsenic in south and southeast Asia, Science 328 1123–1127 DOI: 10.1126/science.1172974 </ref>; Burgess et al 2010<ref name="Burgess 2010">Burgess W G, Hoque M A ,Michael H A, Voss C I, Breit G N and Ahmed KM. 2010. Vulnerability of deep groundwater in the Bengal Aquifer System to contamination by arsenic. Nature Geoscience 3: 83–87</ref>).		</ref>; Hoque and Burgess 2009<ref name="Hogue 2009">Hoque M A and Burgess W. 2009. Provenance and travel time of groundwater pumped from 'arsenic safe' depths in the aquifer of southern Bangladesh: aquifer representation to assess </ref>; Fendorf et al. 2010<ref name="Fendorf 2010">Fendorf S, Michael H A and van Geen A 2010. Spatial and temporal variations of groundwater arsenic in south and southeast Asia, Science 328 1123–1127 DOI: 10.1126/science.1172974 </ref>; Burgess et al 2010<ref name="Burgess 2010">Burgess W G, Hoque M A ,Michael H A, Voss C I, Breit G N and Ahmed KM. 2010. Vulnerability of deep groundwater in the Bengal Aquifer System to contamination by arsenic. Nature Geoscience 3: 83–87</ref>).

Dbk: /* Minor Typologies */

2015-11-25T14:44:43Z

Minor Typologies

← Older revision		Revision as of 15:44, 25 November 2015
Line 52:		Line 52:

	''The Southern Marginal Alluvium''<br>		''The Southern Marginal Alluvium''<br>
	Located south of the Yamuna River along the southern edge of the upper and central Ganges basin, the marginal alluvium represents a genetically distinct typology composed of sediment sourced from Precambrian and Basaltic trap rocks south of the IGB (Heroy et al. 2003<ref name="Heroy 2003">Heroy D, Kuehl S A, Goodbred Jr S L. 2003. Mineralogy of the Ganges and Brahmaputra Rivers: implications for river switching and Late Quaternary climate change. Sedimentary Geology, 155; 343–359 </ref>). The effective thickness of the aquifer typology is also substantially less — ranging from over 200 m in the north, to 100 m or less at the southern edge (Singh 1996<ref name="Singh 1996"></ref>). The permeability and specific yield of the marginal aquifer is, however, comparable to that within the upper and central Ganges basin ([[#Typology 2 The Upper Indus and Upper and Mid Ganges \| typology 2]]), as a result of similar processes of fluvial deposition, comparable sediment coarseness, and proportion of sand‐dominated to silt and mud‐dominated deposits (Saha et al. 2010<ref name="Saha 2010">Saha D, Dhar Y R and Vittala S S. 2010. Delineation of groundwater development potential zones in parts of marginal Ganga Alluvial Plain in South Bihar, Eastern India. Environ Monit Assess, 165; 179‐191.</ref>). The groundwater quality of the typology is generally good, with large freshwater potential. Shallow groundwater is locally saline >1000 mg/l at the western limit of the typology as a consequence of water logging, or in pockets at depth associated with evaporite sequences deposits under previous climates.		Located south of the Yamuna River along the southern edge of the upper and central Ganges basin, the marginal alluvium represents a genetically distinct typology composed of sediment sourced from Precambrian and Basaltic trap rocks south of the IGB (Heroy et al. 2003<ref name="Heroy 2003">Heroy D, Kuehl S A, Goodbred Jr S L. 2003. Mineralogy of the Ganges and Brahmaputra Rivers: implications for river switching and Late Quaternary climate change. Sedimentary Geology, 155; 343–359 </ref>). The effective thickness of the aquifer typology is also substantially less — ranging from over 200 m in the north, to 100 m or less at the southern edge (Singh 1996<ref name="Singh 1996"></ref>). The permeability and specific yield of the marginal aquifer is, however, comparable to that within the upper and central Ganges basin ([[#Typology 2 The Upper Indus and Upper and Mid Ganges \|typology 2]]), as a result of similar processes of fluvial deposition, comparable sediment coarseness, and proportion of sand‐dominated to silt and mud‐dominated deposits (Saha et al. 2010<ref name="Saha 2010">Saha D, Dhar Y R and Vittala S S. 2010. Delineation of groundwater development potential zones in parts of marginal Ganga Alluvial Plain in South Bihar, Eastern India. Environ Monit Assess, 165; 179‐191.</ref>). The groundwater quality of the typology is generally good, with large freshwater potential. Shallow groundwater is locally saline >1000 mg/l at the western limit of the typology as a consequence of water logging, or in pockets at depth associated with evaporite sequences deposits under previous climates.

	''The Sylhet Basin''<br>		''The Sylhet Basin''<br>

Dbk: /* Typology 6 The Lower Indus */

2015-11-25T14:43:27Z

Typology 6 The Lower Indus

← Older revision		Revision as of 15:43, 25 November 2015
Line 34:		Line 34:

	====Typology 6 The Lower Indus====		====Typology 6 The Lower Indus====
	The Lower Indus Basin, found within the Sindh in Pakistan is dominated by the presence of saline groundwater (IWASRI 2005<ref name="IWASRI 2005">IWASRI 2005. Drainage Atlas of Pakistan, International Water Logging and Salinity Research Institute, Lahore. </ref>). Salinity is especially widespread at depth, and there is a greater probability of finding good quality groundwater at shallower depths. The aquifer comprises alluvial sediment with a high proportion of fine sands and silts (Mott MacDonald and Partners 1986<ref name="MacDonald 1986"></ref> ; Schroder 1993<ref name="Schroder 1993">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>). However, despite this, the average permeability remains generally in the range 1–20 m/d, and specific yield 5–15% (Bennett 1969<ref name="Bennett 1969"></ref>; Mott MacDonald and Partners 1990). The increased presence of laterally extensive silt layers does decrease the regional vertical permeability and anisotropy is in the region of 100–500. Evaporite sequences in the sediment are common.		The Lower Indus Basin, found within the Sindh in Pakistan is dominated by the presence of saline groundwater (IWASRI 2005<ref name="IWASRI 2005">IWASRI 2005. Drainage Atlas of Pakistan, International Water Logging and Salinity Research Institute, Lahore. </ref>). Salinity is especially widespread at depth, and there is a greater probability of finding good quality groundwater at shallower depths. The aquifer comprises alluvial sediment with a high proportion of fine sands and silts (Mott MacDonald and Partners 1986<ref name="MacDonald 1986"></ref>; Schroder 1993<ref name="Schroder 1993">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>). However, despite this, the average permeability remains generally in the range 1–20 m/d, and specific yield 5–15% (Bennett 1969<ref name="Bennett 1969"></ref>; Mott MacDonald and Partners 1990). The increased presence of laterally extensive silt layers does decrease the regional vertical permeability and anisotropy is in the region of 100–500. Evaporite sequences in the sediment are common.

	Rainfall in the Lower Indus is low, <250 mm, and evapotranspiration is high and, therefore, groundwater recharge from rainfall is negligible (IWASRI 2005<ref name="ISWARI 2005"></ref>). Historically, groundwater was recharged from flow from the Indus River and this led to thick lenses >50 km wide of fresh water around modern and paleo river channels (Basharat et al. 2014<ref name="Basharat 2014">Basharat M, Hassan D, Bajkani A A and Sultan S J. 2014. Surface water and groundwater Nexus: groundwater management options for Indus Basin Irrigation System, International Waterlogging and Salinity Research Institute (IWASRI), Lahore, Pakistan Water and Power Development Authority, Publication no. 299, pp 155.</ref>). However, river flow in the Lower Indus has significantly reduced in the last 40 years due to irrigation and diversions, and recharge from the river is restricted to a smaller area next to the main Indus channel. Groundwater is recharged from the canal network leading to exensive water logging (Mott MacDonald and Partners 1994). This has lead to the development of thin freshwater lenses in some locations, but also increased phreatic salinisation where the water table is very shallow. Groundwater salinity is mostly > 2500 mg/L. However, next to the Indus, and in localised area, freshwate lenses can exist and groundwater can be <1000 mg/L (Mott MacDonald and Partners 1986<ref name="MacDonald 1986"></ref>; IWASRI 2005<ref name="ISWARI 2005"></ref>).		Rainfall in the Lower Indus is low, <250 mm, and evapotranspiration is high and, therefore, groundwater recharge from rainfall is negligible (IWASRI 2005<ref name="ISWARI 2005"></ref>). Historically, groundwater was recharged from flow from the Indus River and this led to thick lenses >50 km wide of fresh water around modern and paleo river channels (Basharat et al. 2014<ref name="Basharat 2014">Basharat M, Hassan D, Bajkani A A and Sultan S J. 2014. Surface water and groundwater Nexus: groundwater management options for Indus Basin Irrigation System, International Waterlogging and Salinity Research Institute (IWASRI), Lahore, Pakistan Water and Power Development Authority, Publication no. 299, pp 155.</ref>). However, river flow in the Lower Indus has significantly reduced in the last 40 years due to irrigation and diversions, and recharge from the river is restricted to a smaller area next to the main Indus channel. Groundwater is recharged from the canal network leading to exensive water logging (Mott MacDonald and Partners 1994). This has lead to the development of thin freshwater lenses in some locations, but also increased phreatic salinisation where the water table is very shallow. Groundwater salinity is mostly > 2500 mg/L. However, next to the Indus, and in localised area, freshwate lenses can exist and groundwater can be <1000 mg/L (Mott MacDonald and Partners 1986<ref name="MacDonald 1986"></ref>; IWASRI 2005<ref name="ISWARI 2005"></ref>).

Dbk at 09:49, 24 November 2015

2015-11-24T09:49:05Z

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	Three minor typologies at the margin of the basin accompany these large over‐arching major typologies. Each typology is summarised below with a block diagram and the extent of the typology shown in Figure 11. Table 1 summarises the main differences and characteristics of the typologies.		Three minor typologies at the margin of the basin accompany these large over‐arching major typologies. Each typology is summarised below with a block diagram and the extent of the typology shown in Figure 11. Table 1 summarises the main differences and characteristics of the typologies.

	[[Image:~~15047fig11~~.jpg\|thumb\|500px\|'''Figure 11''' The main groundwater typologies of the Indo‐Gangetic basin.]]		[[Image:15047_fig11.jpg\|thumb\|500px\|'''Figure 11''' The main groundwater typologies of the Indo‐Gangetic basin.]]

	====Typology 1 The Piedmont====		====Typology 1 The Piedmont====
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	Deep groundwater (beyond 150 m depth) provides a strategic water supply for tens of millions of people in the Ganges‐Brahmaputra‐Meghna (GBM) delta region of Bangladesh and West Bengal as an alternative to shallow As contaminated groundwater. This case study generated new evidence of aquifer hydraulics in the GBM delta and the influences of both intensive deep groundwater abstraction (>150 m) and climate change.		Deep groundwater (beyond 150 m depth) provides a strategic water supply for tens of millions of people in the Ganges‐Brahmaputra‐Meghna (GBM) delta region of Bangladesh and West Bengal as an alternative to shallow As contaminated groundwater. This case study generated new evidence of aquifer hydraulics in the GBM delta and the influences of both intensive deep groundwater abstraction (>150 m) and climate change.

	'''''Case study objectives''''': The study instrumented a series of nested piezometers to monitor high frequency variations in groundwater head at different depths both close to the coast and further inland. Repeated groundwater sampling was undertaken in both pumping and non‐pumped tubewells (see Fig 1) for a suite of environmental tracers – including groundwater age tracers CFCs and SF6, stable isotopes and noble gases. Preliminary results from the study are given in Taylor et al (2014)<ref name="Taylor 2014"></ref>.		'''''Case study objectives''''': The study instrumented a series of nested piezometers to monitor high frequency variations in groundwater head at different depths both close to the coast and further inland. Repeated groundwater sampling was undertaken in both pumping and non‐pumped tubewells (see Fig 1) for a suite of environmental tracers — including groundwater age tracers CFCs and SF6, stable isotopes and noble gases. Preliminary results from the study are given in Taylor et al (2014)<ref name="Taylor 2014"></ref>.

	'''''Key results:'''''<br>		'''''Key results:'''''<br>