كليدواژه :
Rainfall intensity , Single storm erosivity , Universal soil loss equation , مدل كولي , كشاورزي , درياچه اروميه , Orumeie lake basin , رگبار منفرد , Rainfall duration , Rainfall erosion indices , فرسايش زايي , Coolyʹs model
چكيده لاتين :
Many researchers have been working on various models and equations to predict the severity of erosion. The universal soil loss equation (USLE) is one of them. Parameters used in this equation can be calculated or obtained for a particular area from the tables or charts that have been recorded in many scientific sources or handbooks by considering the regional conditions of that area. Rainfall erosion index (REI), one of the parameters of USLE, however, depends on rainfall nature and conditions; it must be calculated by analyzing the storm events of the area using longtime rainfall records. Efforts have been done and are being done all over the world to analyze storm events and to produce tabulated REI. Unfortunately, such information is not readily available for many watersheds in Iran. In this investigation the rainfall events from 19 continuous recording rainfall stations around the Orumeie lake, north-west of Iran, operated under Regional Water Organization of East and West Azarbaijan were analyzed. 15-minute rainfall intensities and energy, max. 30-minute intensities, and total energy for every event was tabulated and REI were computed. Finally Coolyʹs model, based on rain depth and duration of storm, for estimating of rainfall erosion index of single storm was evaluated. This model has good adaptation to the statistical condition of Orumeie lakeʹs watershed. Therefore, the coefficient of model was determined and tabulated for the region. The average of determination coefficient (R2), for all of the recording rainfall stations, were 0.99 and this model was significant at one- percent level of probabiliy for stations. Coolyʹs model showed good conformity with storm specification of the area, comparing to the other regions where already the model employed. The computed average for coefficients of a, (Beta) and y of the model were 0.15, 2.31 and 0.83, respectively. Thus, improved equation was presented by computing the applied coefficient of Coolyʹs model by using rainfall depth (mm), and duration (hr) for computing single storm erosion index (Mj.mm.ha^-1hf^-1) in Urmieh lake basin.
