A new technique to map groundwater recharge in irrigated areas using a SWAT model under changing climate

The Lower Chenab canal irrigation scheme, the largest irrigation scheme of the Indus Basin irrigation system was selected for an estimate of groundwater recharge using the soil and water assessment tool (SWAT) at high spatial and temporal resolution under changing climate. Groundwater recharge was simulated using the SWAT model for representative concentration pathways (RCP) 4.5 and 8.5 climate change scenarios for the period 2012–2020. Actual evapotranspiration (ETa) was estimated using the SWAT model for the period 2010–2011. This was compared with the ETa determined using the surface energy balance algorithm (SEBAL) calibrated using data for the period 2005–2009. We concluded that the SWAT ETa estimates showed good agreement with those of SEBAL (coefficient of determination = 0.85 ± 0.05, Nash–Sutcliffe efficiency = 0.83 ± 0.07). The total average annual groundwater recharge to the aquifer was 537 mm (±55 mm) with the maximum occurring during July (151 mm). The results showed that groundwater recharge would increase by 40%, as compared to the reference period, by the end of 2020 under RCP 4.5 and by 37% under RCP 8.5. The SWAT can thus be a handy tool for not only estimating the recharge at high spatial and temporal resolution, but also under changing climate.