Computing Spatio - Temporal Water Demand of Wheat Crop Using GIS and Remote Sensing - A Case Study of Faisalabad Irrigation District, Pakistan

Water resources are considered to be finite and their management and judicious use is emerging as a big challenge in the 21st century due to high population growth rate and associated food security. For effective water management of water resources, the assessment of evapotranspiration is necessary. GIS and RS is a best tool to estimate crop evapotranspiration of agricultural crops. The aims and objectives of this study are to compute the real time spatially distributed crop coefficient (Kc) and water demand of wheat crop grown in Faisalabad Irrigation District, Pakistan. In this study monthly crop evapotranspiration for command area was computed using MODIS 13Q1 satellite imagery. The crop evapotranspiration (ETc) was computed by pixel wise multiplication of crop coefficient (Kc) maps and the reference evapotranspiration (ETo) in ERDAS Imagine Model Maker (EIMM). Kc maps were generated from MODIS 13Q1 satellite imagery while reference evapotranspiration (ET0) was estimation using CROPWAT model which compute ETO based FAO-24 modified Blaney-Criddle method using multi variables i.e., temperature, wind speed, sunshine, sun radiations and relative humidity. It was observed that ETc value varied from 0.30-0.89, 0.52-1.47, 0.68-1.64, and 0.61-2.49 mm/day for Dec, Jan, Feb and Mar respectively. Seasonal minimum and maximum value of ETc for wheat crop was 0.30 and 2.49 mm/day for whole command area. It was found that average ETc value for wheat was increased gradually from Dec to Feb as 0.59 to 1.16 mm/days and then decreased to 1.05 mm/days in March. Seasonal crop water requirement of wheat was varied from 265 mm to 665 mm with an average of 465 mm. Results of this study were very close to past studies therefore, it can be concluded that remote sensing based computation of Kc is capable of estimating crop water requirement of the command area satisfactorily for the wheat crop.