Paper Title
Empirical Model to Estimate Evaporation From Water Plan in Semi Arid Region Case of Fontaine De Gazelles and Foum El-Gherza Dams –Algeria-

Abstract
The objective of our paper is to present a new empirical model to estimate the evaporation of water plans located in semi-arid region. Two dams have been chosen: Fontaine des Gazelles dam with water storage capacity of 47 million m3 and Foum El-Gherza dam with water storage capacity of 55 million m3. The two dams located in Biskra (Algeria) characterized by a semi arid climate. The proposed model is the result of a combination of two classical models: Ivanov (1970) and Vikulina (1979). We used climate data that is available in the weather reports to estimate monthly evaporation for each dam. The model requires four climate data: The mean temperature of air and water surface (°C), relative humidity (%) and wind speed at 2 m (m/s). The comparison of the proposed model and the measurements by the evaporation pan showed a very good correlation, R² varies from 0, 97 to 1. To validate the proposed model, we calculated Nash-Sutcliffe criterion (NSEF. Gherza=1, NSEF. des gazelles=0,97), the Root Mean Square Error (RMSE F. Gherza=7,61, RMSE F. des gazelles=20,24), the Mean Bias Error (MBE F. Gherza=2,20, MBE F. des gazelles=5,84), the coefficient of determination (R² F. Gherza=1,00, R² F. des gazelles=1,00), and the Rank Sum Ratio (RSR F. Gherza=0,07, RSR F. des gazelles=0,17). These results confirm the reliability and the good performance of the proposed model. Keywords - Evaporation, Semi-arid Region, Foum El-Gherza Dam, Fontaine des Gazelles Dam, Algeria.