Background information and methodology to support estimation of sustainable groundwater abstraction using GEFIS

Sood, A.; Villholth, Karen G. 2021. Background information and methodology to support estimation of sustainable groundwater abstraction using GEFIS. Colombo, Sri Lanka: CGIAR Research Program on Water, Land and Ecosystems (WLE). 7p. (Appendix)

When assessing environmental flow requirements (EFR) of rivers, and adapting appropriate management strategies to comply with EFR, it is critical to understand the changes that may impact river flows. These could be river abstractions and discharges, land use changes, river diversion and impoundment, as well as groundwater abstraction in the catchment or river basin. The link between groundwater and surface water flow can be significant, implying that if groundwater is pumped near a river, it may significantly influence and reduce river flow (Barlow and Leake, 2012) (Figure A1). This is because in many, especially perennial rivers, groundwater provides part of the flow in the river, a flow component called base flow (BF) (Figure A1). By implication, management of rivers and EFR is closely linked to groundwater management, and to ensure sustainable outcomes, in most cases, management of both water resources are required. This is referred to as conjunctive water management (Barlow and Leake, 2012).