Theme 5-5-Rainfall-runoff relationship model for Amameh watershed in Iran.

Abstract

The Amameh catchment in Iran that covers 3712 ha in area is one of the mountainous sub basins of Jajroud River over which the Latian dam has been constructed. There the mean annual precipitation is 848.4 mm. The mean annual runoff of the river is about 18.735 million m3, with an average discharge of 0.55 m3/s.

Since the rainfall-runoff relationship is one of the fundamental investigations in the field of hydrometeorology studies, therefore an applicable model has to be defined for each of the case study area. While in some of the studies the equations, which have been developed under different conditions of the case study area, are being directly used and show large differences in between the predicted and the real data. To develop and select the appropriate model for the study watershed, 15 storms have been selected for which all of the characteristics of the storm viz., duration, intensity, amount, related runoff volume and peak, and time of incident are available for the analysis.

An attempt has been made in this paper to apply and observe the relative applicability of some of the available basic equations defining the relationship between rainfall and runoff. The SCS Curve Number method is being used for the development of the model.

Different types of statistical models, viz., bivariable and multivariable linear models as well as their polynomial, power, logarithmic and exponential are being checked. The best model will be selected based on the optimization approach and the statistical criteria. The result of the present study has shown that the models, which have been developed in other countries, are not reliable and their calibration for application on other watersheds are necessary for more accuracy.