كاربرد سنجش از دور دربرآورد سودمندي آب در شبكه هاي آبياري مطالعه موردي : شبكه سمت راست آبشار، اصفهان

Estimation of Water Productivity in an Irrigation Scheme by Remote Sensing (A Case Study in Abshar Right Bank Irrigation Scheme, Esfahan, Iran)

The irrigation management and water productivity of Abshar Right Bank irrigation district in Esfahan was evaluated by using remote sensing data and camputing various irrigation management indicators such as volume of water supply and demand, relative water supply, water productivity and economic water productivity. In order to obtain the required data, it was attempted to upscale the accuracy of NOAA satellite images by using Landsat images. From a time series of NOAA images during the one growing season, The relationship between actual irrigated area in each of the irrigation sub-districts with the Esfahan district was derived. Based on this relationship the actual irrigated area in the Abshar Right Bank irrigation district for each one of the ten growing seasons (1370-1380) were calculated. The irrigation water requirement of the Abshar sub-district was estimated by calculating the water use of nine major crops from the 40 different crops that are grown in the sub-district. The water requirement of one growing season, for each crop was calculated by Cropwat program during the ten years period of the study. The total water requirement of the sub-district was computed from the estimats of the crop water use by the Cropwat model and area under cultivation of each crop. Results indicated that most of the time the volume of water delivered exceeds the volume of water required by the sub-district. The relative water supply index was found to be greater than 1 for most of the growing seasons except during the dry years. The average of relative water supply during the ten-year period studied was 1.3. The average water productivity for all entire crops during the ten-years period, except for the two dry years was 0.8-1.4 and during the entire ten-years period was about 1.3kgIm3. The economic water productivity during the ten-years except for the two dry-years was 0.05-0.19 and during the whole ten-years period was 0.1 $/m3. The world average water productivity is however about 0.25$/m3.