Lapworth, D; (2018) Hydrogeological responses to deep groundwater pumping in the Indo-Gangetic Basin: Evidence from environmental tracers. Doctoral thesis (Ph.D), UCL (University College London).

Text Lapworth_eThesis_LapworthDJ.pdf - Accepted Version Access restricted to UCL open access staff Download (12MB)

Abstract

Deep, fresh groundwater (typically >150 m below ground) provides a vital source of drinking water across the Indo-Gangetic Basin, and is being increasingly developed. Current understanding of the sustainability and vulnerability of this resource is largely based on model estimates and there is a paucity of in-situ observations with which to inform current debate on their vulnerability and on-going exploitation. This thesis applies a suite of environmental tracers (CFCs, SF6, stable isotopes, hydrochemistry, micro-organics) to enable, for the first time, a detailed assessment of age-depth and water quality profiles in three case study areas across the Indo-Gangetic Basin. Specifically, the thesis assesses depth profiles (0 to 360 m) of: i) mean residence times (MRT), ii) sources of recharge/contaminants and iii) key water quality parameters (e.g. arsenic, fluoride, and salinity). These tracers are also used to explore evidence of local by-pass flow at borehole-scales and the vertical migration of younger groundwater. Tracers reveal the general resilience of the Bengal Aquifer System, and highlight the relative vulnerability of the upper Indus and mid Ganges aquifer systems to the vertical ingress of shallow groundwater as well as the ingress of anthropogenic contaminants to depth within these aquifer systems. MRT distributions at depth in the upper Indus and mid-Ganges are comparable, between 20 to 60 years, and contrast sharply with MRTs in the BAS that are found to be 5,000 to 10,000 years. Pumped wells in all three aquifer systems show evidence of rapid by-pass flow to deep boreholes. In the upper Indus and mid Ganges aquifer systems, evidence is presented of local, vertical, pumping-induced migration of shallow groundwater. In order to ensure the protection of deep groundwater supplies in the Indo-Gangetic Basin for future generations, it is argued that continued exploitation of deep groundwater requires long-term monitoring to enable early detection of water quality deterioration.

Download activity - last month

Export as XMLCSVJSON

Download activity - last 12 months

Export as XMLCSVJSON

Downloads by country - last 12 months

Export as CSVXMLJSON

Archive Staff Only

View Item