LAUSR

The present study employs a process-based DSSAT (Decision Support System for Agrotechnology Transfer) model for estimating agriculture water use and its evaluation for simulating groundwater fluctuations. A field experiment was performed during kharif season with PR 121 variety (rice) at Punjab Agricultural University, Ludhiana. There were six treatments with three dates of transplanting – June 5 (D1), June 20 (D2) and July 5 (D3), one cultivar – PR121 (V) and two irrigation regimes – 2-day drainage (I1) and tensiometer-based (I2). Both simulation and experimental results showed that paddy transplanted on June 20 (D2) and tensiometer-based irrigation treatment (I2) gave 23 and 32% higher yield in comparison to June 5 (D1) and July 5 (D3) with maximum water use efficiency of 1.69 kg/m . The validated DSSAT model was simulated for a historical time slice (1998–2014) and indicated that 66% of applied water in the form of rainfall or irrigation in paddy fields was lost as drainage component. The simulated change in storage (rainfall minus evapotranspiration) was able to explain groundwater level fluctuations in terms of trends/magnitude in most of the years.