EXTRACTING THE CURVE-NUMBER MAP OF WATERSHEDS OF LIGHVAN CHAY IN GIS ENVIRONMENT

One of the factors involved in the planning of water resources, is calculating the amount of runoff resulting from rainfall. Many of catchments in our country do not have hydrometric stations. Implementation water resource development projects, requires estimating these information. SCS method is one of the customary methods for solving this problem and as information required for this method, we can mention the runoff curve-number. This article has been performed about the Lighvan Chay catchment in East Azerbaijan and its purpose is the extraction of runoff curve number. To determine the curve-number, the land-use map and the soil map of the area have been prepared and then it is modulated in ArcGIS and the calculations have been performed. Using geographic information processing system, the weighted average value of the curve has been estimated under moisture condition and its amount is about 85.3. According to that the highest level of catchment obtained about 86. Comparing the results with curve numbers showed us that the obtained numbers are so close to each other and therefore the offered method is an easy and fast method for obtaining the curve number of catchments.