بررسي و تعميم روابط بارش - رواناب ماهانه و سالانه به حوضه هاي فاقد آمار ، مطالعه موردي : حوضه هاي نهرين و كريت واقع در منطقه طبس استان يزد

Estimation and Extension of Monthly and Annual Rainfall-runoff Relationships to Un-gauged Watersheds in a Dry Region: A Case Study in Nahrain and Korit Watersheds in Tabas

Complications in hydrological systems, lack and insufficient data cause difficulties in hydrological forecasting. Systematic approach is common lor hydrological surveys. Such analyses lead to better estimation of water balance components. Extending rainfall-runoff relationships from gauged watershed to un-gauged ones arc viewed in this category. A case study is done in this research for two neigbhboring watersheds of Nahrain and Korit located in Tabas city. Yazd province. Nahrain has some hydrological and meteorological stations while Korit is an uri-gauged watershed. Based on topographic and geological features. the two watersheds are hydrologically similar. Therefore. the process of rainfallrunoff is considered the same 1(11ʹ the two watersheds. After constructing rainfall time series for the t\VO watersheds. runoff coefficient for Nahrain was used for Korit. Rainfallrunoff relationships at monthly and annual scales surveyed. yet there were no acceptable results. We analyzed the effect of monthly and annual rainfall for the previous year in a multi-variable model to predict the Nahrain runoff Runoff coefficients determined by these models were compared and onc with the greatest R" was determined. This shows the effect of rainfall history on watershed yield. Five commonly used empirical models for annual runoff predications were examined. We found Justin equation and that of Irrigation Department ofUtrapradish ofTndian more convenient for the region.