Estimation of wheat yields and water savings with deficit irrigation in water-stressed NW India

Overextraction of groundwater for surface flood irrigation has been highlighted as the primary cause of severe groundwater depletion in the north-western Indian region. Adoption of water saving technologies and crop substitution has been inadequate despite governmental efforts. We evaluate the potential of efficient irrigation scheduling in managing irrigation water demand and quantify the amount of water that can be saved using a crop-growth model, AquaCrop-OSPy. We demonstrate this for spring wheat crop grown during rabi season in a water stressed district of Haryana which is a major wheat producing state. The crop model was calibrated using particle swarm optimization algorithm using 26 years district-scale weather and crop yield data. A total of 47 irrigation strategies were tested under three irrigation scenarios – soil moisture threshold based (SMT), historical rainfall based fixed interval (HRFI) and modified predefined calendar-based (MPC) irrigation for this study, which differ in their degree of sophistication. We found that 18.1–35 %, 12.3 – 38.1 % and 1.7 – 24.9 % water savings could be achieved using these scenarios, respectively, with yield loss under 5 %. Further, irrigation water productivity (IWP) could be improved by 0.18–0.35 kg/m 3 using SMT and HRFI strategies. SMT was best suited for wet years in terms of higher water savings and IWP, while HRFI performed better for dry years. The study highlights the potential of two novel low-tech scenarios, HRFI and MPC in aiding irrigation decision making, particularly by small and marginal farmers. It will help in checking depleting groundwater reserves as well as reduce the food-energy-water vulnerability. • Open-source Python-based AquaCrop model was auto-calibrated for spring wheat. • Particle Swarm Optimization algorithm was used to calibrate 9 model parameters. • Two technologically simpler alternatives to sensor-based irrigation were assessed. • Recommended strategies can achieve up to 38 % irrigation water savings. • Irrigation water productivity could be improved by up to 0.18–0.38 kg/m 3 .