Rainfall-Runoff Modeling Using the eWater Source in the Chel-Chay Watershed, the Province of Golestan

It is very complex and difficult to fully understand the relationships in watersheds due to the heterogeneity and non-linear nature of hydrological and erosive behaviors. Therefore, the evaluation of watersheds requires a modeling process. After introducing the features of the eWater Source software as a management modeling environment for watersheds, two rainfall-runoff models of the GR4J and the IHACRES were compared to simulate the runoff of the Chel-Chay Watershed in the eWater Source environment. Chel-Chay Watershed, with an area of 256 square kilometers is located in Province of Golestan. In order to simulate the rainfall -runoff, the position of the watershed, sub-watersheds, stations, watershed outlet, operational units (based on land use map) and the watershed waterway network was simulated using the digital height model (DEM) in the Source environment. The GR4J and the IHACRES models were used. In this rainfall -runoff models, the continuous time series data were considered in the daily time steps. The time series of the daily precipitation of the years (2001 to 2010), and the daily evaporation and transpiration (during the same period) were used to implement the models. The models were implemented in the eWater Source environment. The discharge data for the period (2001-2010) were used to calibrate the models. The accuracy of the flow simulation based on the Nash-Sutcliffe criterion for the GR4J and the IHACRES models in the calibration period (2001-2010) were 0.79 and 0.73, and in the validation period (2011-2015) were 0.76 and 0.68, respectively. Therefore, it may be concluded that these models performed well in the simulation. The evaluation of results indicates that the GR4J model performs better than the IHACRES model for simulating the daily flow. Due to the high capabilities of the eWater Source software, this environment is recommended as a management model for the discharge of watersheds.