Evaluating the impact of projected CO2, temperature, and rainfall change on groundwater resources in a rice–wheat dominated cropping region of northwestern India

Increasing CO2 concentration, temperature rise, and changes in rainfall due to climate change are expected to influence groundwater resources in irrigated agricultural regions. A simulation study using AquaCrop and MODFLOW models was undertaken to assess the combined effects of increasing CO2 concentrations, temperature, and rainfall changes on groundwater behavior in a rice–wheat cropping region of northwest India. Simulations were carried out for the 2016–2099 period under two scenarios: increasing CO2 concentrations corresponding to different RCPs (Scenario-I) and at a constant CO2 concentration of 369.4 ppm (Scenario-II). The results indicate that elevated CO2 negates the effect of rising temperature on evapotranspiration (ET) and water demand, and thus, lower ET is simulated under Scenario-I than Scenario-II for different RCPs during the future periods. The lower projected ET resulted in lower rice (2.3%–6.3%) and wheat (1.4%–16.1%) irrigation demand under Scenario-I than under Scenario-II. Of all RCPs, the lowest groundwater level (GWL) decline of 9.2, 20.5, and 24.4 m from the reference GWL (18.85 m) at the end of the early, mid-, and end-century periods, respectively, is projected under RCP8.5 and Scenario-I. Simulation results indicate that CO2 concentration plays an important role while assessing climate change effects on groundwater in irrigated agricultural systems.