Darling, George

Gooddy, Daren

Krishan, G

Lapworth, Dan

MacDonald, Alan

Rao, M S

NERC Open Research Archive

© NERC All rights reservedIAH Congress Marrakech September 2014USING ENVIRONMENTAL TRACERS TO UNDERSTAND THE RESPONSE OF GROUNDWATER RESOURCES IN NW INDIA TO SUSTAINED ABSTRACTION Groundwater Resilience to Climate Change and Abstraction in the Indo-Gangetic BasinD.J. LAPWORTH (1), G. KRISHAN (2), A.M. MACDONALD (1), M.S. RAO (2), D.C. GOODDY (1), W.G. DARLING (1) 1: British Geological Survey, UK, e-mail: djla@bgs.ac.uk 2: National Institute of Hydrology, Roorkee, Uttrakhand, India www.bgs.ac.uk/gwresilienceasia© NERC All rights reserved• 20 million boreholes access groundwater resources for drinking water, irrigation, industry across the IGB• 1 billion people are highly dependant on this resource• Increased pressure on groundwater resources in this region due to population growth, rising incomes, food security, high levels of abstraction and climate change• The resilience of groundwater resources will play a large role in determining the future availability of water in this regionBackground:© NERC All rights reservedThe Indo-Gangetic basinFigure 1.  The location of the Indo-Gangetic basin (left) and estimated groundwater depletion (mm.a-1) for year 2000: ■300-1000, ■100-300Data Source: Wada et al., 2010. Global depletion of groundwater resources. Geophysical Research Letters, 37, L20402, 1-5.Plains aquifer system of NW India© NERC All rights reservedSome major groundwater issues in the region1. Increased Groundwater Abstraction• Falling groundwater levels• Tension between agricultural and growing ‘high value’ urban and industrial users• Public vs private interests and allocation© NERC All rights reservedSome major groundwater issues in the region2. Water Quality• Arsenic, fluoride, salinity, microbial contamination from flooding• Contamination from agriculture and waste water• Rising salinity levels • Salinisation problems in irrigated soils© NERC All rights reservedRegional settingHighly abstracted unconsolidated layered alluvial aquifer systemDraft typology map of the Indo-Gangetic Basin Criteria:Multi-layered, extensive, thick unconsolidated alluvium aquifer – coarse sedimentFalling groundwater levelsGroundwater salinity at depthExtensive irrigationSurface water groundwater interactionResilience:+High productivity/storage aquifer+moderate potential meteoric recharge- High abstraction including some cities- Significant long-term trends in fallingwater table- Saline groundwater at depth© NERC All rights reservedLong-term trends in groundwater levels© NERC All rights reservedObjective of this study• O1: To collate new evidence on recharge processes, groundwater quality, groundwater residence times, to understand the connectivity of the layered aquifer system and the impact of high levels of pumping in the alluvial plains aquifer on natural flow regimes• Q1: What are the major sources of GW recharge across the aquifer?• Q2: Is there evidence of vertical leakage to depth within the layered alluvial system?• How?: repeated sampling of shallow and deep piezometers using a suite of environmental tracers© NERC All rights reservedStudy area – Bist Doab, Punjab, India• Sampling from paired shallow (<50 mbgl) and deep (>100 mbgl) tube wells at 19 locations across the catchment• Pre and post monsoon samplingBread basket for India© NERC All rights reservedTracers used in this study• CFCs, SF6 – groundwater residence time tracers• Inorganic chemistry: e.g. Cl, NO3 and trace elements• Stable isotopes – recharge sourcesAtmosphere Groundwater© NERC All rights reservedGroundwater residence time tracer resultsZone 1 Zone 2 Zone 3Z1: Higher rainfall (900 mm/a) and areal/surface rechargeZ2: 700 mm/a rainfall, recharge from irrigation and canalsZ3: 600 mm/a rainfall, shallow gw limited recharge potentialTraditional conceptual model of GW flow© NERC All rights reservedGroundwater residence time tracer results – anthropogenic and naturalDeep-PostM. Shallow-PreM.010203040506070PFM-Mean Residence Time [Years]Deep-PreM. Shallow-PostM.CFC-12 data Trace elements (e.g. Sr, Mo, As, U)© NERC All rights reservedGroundwater nitrate* variations*See the same trends for Cl and SEC – conservative behaviour, aerobic© NERC All rights reservedStable isotope resultsEvaporative effects in some shallow GWSurface water- GWinteraction• Large overlap between shallow and deep GW isotope signatures, • No significant difference between pre-post monsoon conditions in deep or shallow sites (most sites)• A few shallow sites show evidence of surface water recharge – R. Beas alluvial aquifer• Evaporative enrichment in some shallow sites• No evidence of significant recharge from R. Satluj and related canal system in the south of the catchment© NERC All rights reservedInitial findings • Long term GWL data shows evidence of enhanced recharge potential• But there are significant parts of the catchment where abstraction is outstripping recharge potential leading to long term loss of shallow groundwater security – cost implications for access to shallow GW• Clear evidence, from a range of independent groundwater tracers, that there is significant vertical leakage and recharge from shallow sources to depth (>150) mbgl induced by pumping• The natural regional groundwater flow regime is highly perturbed due to pumping and the system can be considered highly isotropic under pumped conditions• This has implication for long term groundwater vulnerability of deeper aquifers and water resource management• Reduced shallow groundwater levels in some regions is good news: lower salinity build up, soil waterlogging and of course flooding© NERC All rights reservedThanks for listeninge-mail: djla@bgs.ac.ukwww.bgs.ac.uk/gwresilienceasia

Using environmental tracers to understand the response of groundwater resources in NW India to sustained abstraction

http://nora.nerc.ac.uk/510609/1/Using%20environmental%20tracers%20to%20understand%20the%20response%20of%20gw%20resources%20in%20NW%20India%20to%20sustained%20abstraction.pdf

Using environmental tracers to understand the response of groundwater resources in NW India to sustained abstraction

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