The use of medium resolution remote sensing data to compare spatio-temporal variation of irrigation performances and water consumption (original) (raw)

Precise information on irrigation performance and water consumption at field or canal command level is important to irrigation managers and policymakers to make appropriate decisions on water management. Use of irrigation performance indices cum water consumption are the tools make such decisions. Calculate those figures are a challenging task for the past cropping years, that essential to make correct decisions especially in data-scarce regions of Asia and Africa. Similarly, calculation of these above at field or canal command level over large irrigation schemes are laborious, costly, timely inefficient and less accurate. The necessity for these figures is rapidly increasing due to the need to make the correct decisions with the continually rising population and food demand cum declining water availability parallel to climatic change issues. Accordingly, well established surface energy balance algorithm (SEBAL) technique has been employed in large irrigated areas in Punjab, Pakistan, as a tool to estimate actual evapotranspiration (ET a ), i.e., water consumption for the cropping years of 2004/05 and 2006/07. Freely available medium resolute daily MODIS images and hydrometeorological data were used as inputs for the ET a calculation. Under this study irrigation performance indices of equity and adequacy were calculated using actual evapotranspiration and evaporative fraction. Results show that annual ET a varies from less than 100 mm/year in desert/barren areas to 1,650 mm/year over large water bodies. For cropped areas, the variation ranges from 400 to 1,200 mm per year for both cropping years. In rice-wheat area of Punjab, average ET a of the cropping year 2004/05 is 896 mm, and 971 mm for cropping year 2006/07. In lower and southern Punjab, ET a is low and varies from 805 to 870 mm during 2004/05 and 2006/07, respectively. ET a was further analyzed in depth on a seasonal and canal command basis for a better understanding and shows that an average of 9% more water has been consumed by crops during the Kharif 2007 season while 10% higher consumption was observed for the Rabi 2006/07 season than in the previous 2004/05 cropping year. ET a of the Thal Canal has increased by 44% in the Kharif 2007 season followed by Lower Jhelum Canal with 28%. ET a of Upper Jhelum Canal has also increased by about 20% while that of Panjnad Canal has increased by 22% in the Rabi 2006/07 season. Equity of water consumption in 2006/07 has improved considerably compared to 2004/05 in many canals, especially Central Bari Doab, Bahawal, Thal, Chashma Right Bank, Muzaffargarh and Panjnad, which figured as 2, 12, 11, 7, 8 and 8%, respectively. Similarly, adequacy has also improved in many canal commands in the 2006/07 cropping year when compared to 2004/05. This study demonstrates how a remote sensing based estimation of water consumption and water stress can be combined to provide a better estimation of system and irrigation performance at a variety of spatial and temporal scales that would assist water managers and policymakers.