Managing Irrigation Water by Yield and Water Productivity Assessment of a Rice-Wheat System Using Remote Sensing

Rice and wheat are very important grain crops and are heavily grown in lands between the Ravi and Chenab Rivers in Pakistan. Because rice is generally cultivated under standing water conditions, careful estimation of actual water consumption and crop water productivity (CWP) is key for proper water management. In the current study, an effort is made to estimate actual evapotranspiration (ETa ) by using the soil and energy balance algorithm (SEBAL), which used the moderate-resolution imaging spectroradiometer (MODIS) satellite with a spatial resolution of 1,000 m. Rice and wheat crop dominance areas were identified by using the ISODATA crop classification technique by utilizing MODIS normalized difference vegetation index (NDVI) 250 m resolution data. Crop-specific ETa was masked out both for rice and wheat, and this information was utilized with crop yield for estimation of CWP. Tehsil administrative-level crop-yield data were collected and extrapolated to model crop yield on a pixel basis by benefiting from crop yields and specific NDVI empirical relationships. Study results showed a variation of ETa(402–780 and 244–328 mm), yield (823–2,596 and1,287–3,646kg=ha), and CWP (0.14–0.56 and 0.54–1.44kg=m3 ) for rice and wheat, respectively. Best results were attained for rice in tehsil Hafizabad with a coefficient of variation in CWP of 7.94%. Most of the other tehsils showed higher variability of approximately 16%. The primary cause of lower CWP for rice crop in these tehsils is higher values of ET a (i.e., greater than 600 mm), which is ideal for maximizing CWP in the study region. For the wheat crop, because water consumption is almost similar in all parts and CWP is primarily variable owing to yield differences, this suggested minimum scope for CWP improvement by water management for wheat. Crop cultivation expenditures can be reduced both for rice and wheat by proper application and management of water and fertilizer.