Use of Geostatistics in Determining Average Maximum Daily Rainfall to Estimate the Flood Discharge Using WMS Model

Floods are of great importance in studies related to the use of water resources, flood management and the construction of dams, and the safety of structures related to dams is dependent on accurate hydrological studies. This study used geostatistical methods to determine the average maximum daily rainfall in the Amuqin catchment basin in Ardabil province as an input to the WMS model in order to estimate the maximum flood discharge. The Amuqin basin, which has an area of 78 km2 is located in the central part of Ardabil province, to determine the curve number of the basin, land use maps and soil hydrological groups (B, C, D) were integrated in the GIS environment. These maps were prepared using the Idrisi32 software and Landsat 8 satellite images. The basin curve number was estimated as 78.7. Different geostatistical kriging and global cokriging methods with circular, exponential, Gaussian, and normal models, weighted distance image method (IDW), Global Polynomial Interpolation (GPI), Local Polynomial Interpolation (LPI), and Radius Axis Relation Method (RBF) using geographic information system software were used to determine the average precipitation. The results showed that the normal Cokriging method has the lowest error for different return periods, then the average maximum daily rainfall for the basin was calculated using the normal Cokriging method for different return periods. Considering the rainfall-runoff events at the regional level in the calibration (RE=7.17, RMSE=0.44) and validation (RE=2.51, RMSE=0.0042) stages, was confirmed the accuracy and validity of the flood estimation by the model.