Evaluation Of Area Water Balance Model (AWBM) Application In Estimating Surface Runoff For Designing Small Scale Rainwater Catchment Systems
2007
Tahmasbi, R., Institute of Technical and Vocational Higher Education of Ministry of Jihad-e-Agriculture. | Sharifi, F., Soil Conservation and Watershed Management Research Center., | Kaveh, F., Department of Irrigation Science and Research, Islamic Azad University., | Tavasolli, A.Gh., Soil Conservation and Watershed Management Research Center.
In area with miger amount of rainfall, collection and storage of rainwater into the soil profile using small scale rainwater catchment systems can tend to supply some amount of water needed for plant production. But the important point in regard to building such systems in determining size and / or catchment area in such a way that the needed or expected water could be collected and stored. As in many cases required knowledge on runoff coefficient in relation to soil type, slope steepness, vegetation cover density and amount of evaporation are lacking it therefore, seems that calculation of depth and volume of runoff can not be an easy task. The AWBM is a model with capability of runoff simulation that appears to be a proper model for estimation of runoff for small scale rainwater catchment design in arid and semi-arid regions. In order to evaluate applicability of the AWBM in estimating resultant runoff and rainfall through consideration of different land slope and vegetation cover density, 20 experimental plots constructed on three slope classes of land with three different vegetation cover density classes in Lasgarak region located in north of Tehran city, having semi-arid climatic condition. Depth of resultant runoff each rainfall event was measured into the constructed counter bank at the toe of each plot. Runoff depth also estimated by running Area Water Balance Model (AWBM) which is capable to simulate rainfall ' runoff, using 8 different catchment area size, 3 slope classes and 3 vegetation covery density classes on the 5 soil textures. Then, depth of runoff was estimated by considering the rate of infiltration for each plot. Finally, estimated depth and calculated amount of runoff were capered with the measured depth and amount of runoff by using variance analysis test. Result of the study is shown that there is not good fitness between estimated monthly runoff using AWBM in comparison to the measured one, While AWBM has a good capability for estimating annual runoff in small scale catchments in terms of rainwater catchment systems is called micro ' catchments. Thus, the use of AWBM can be recommened for calculation of micro ' catchment area and / or size and dimension.
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