Evaluation of a distributed monthly water balance model to ‎determine catchment runoff in arid region using RS and GIS ‎‎(A case study in Yazd-Ardakan basin)‎

Document Type : Research

Authors

1 Scientific Board, Agricultural and Natural Resources Research and Education Center, Yazd, Iran

2 Associate of Prof., Geography and Geology department, Yerevan State Unversity, Armania

Abstract

Fresh water is becoming a scarce resource of the arid region. The only option left to ‎manage with this situation is to conserve water resources. Since the amount of rainfall and ‎evapotranspiration rate vary within a watershed, available water for surface and ‎groundwater recharge also varies both on spatial and temporal scales. Moreover, ‎groundwater recharge (and ultimately the total water yield) is directly influenced by the ‎soil texture and land cover in the watershed.‎
In this study, the distributed Thornthwaite-Mather water balance model for the Yazd-‎Ardakan catchment in Iran was developed based on monthly precipitation, potential ‎evapotranspiration maps and water holding capacity map. The amount of annual runoff ‎from the catchment predicted by the model is 66.7 mm‏,‏‎ which is accumulated in the plain ‎and then salt desert. Half of discharge is contributed by the direct runoff and the ‎groundwater contribution is significant.‎
A statistical comparison of the estimated and the measured stream flow of Pishkouh show ‎the mean monthly and mean annual estimated and measured stream flows, the correlation ‎coefficient between measured and estimated stream flows, the mean monthly and annual ‎percentage error of estimation and the 90% confidence interval for the mean stream flow. ‎Since the study of water balance using the TM method with the help of remote sensing ‎and GIS was found to be very helpful in determining the amount of monthly runoff in an ‎arid region like the Yazd-Ardakan catchment.‎

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