Document Type : Research Article
PhD Candidate, Water Engineering, Department of Water Sciences and Engineering, Ferdowsi University of Mashhad
MA Student in Water Engineering, Department of Water Sciences and Engineering, University of Tehran
Professor, Department of Water Sciences and Engineering, Ferdowsi University of Mashhad
Professor, Department of Water Sciences and Engineering, University of Tehran
Given the vital importance of water in human life, recognizing the effective use of rainfall and crop water requirement and economic planning are very important. Identifying and applying appropriate method for estimating effective rainfall, especially in rainfed is highly important. The current study aims to determine the most suitable experimental method for estimating effective rainfall for sowing Wheat, Barley, Peas and Lentils in high rainfall zones (Rasht in Gilan) as compared to low rainfall zones (Daran in Isfahan). In this study, five different experimental methods are presented in order to determine the effective rainfall including: the Soil Conservation Service (SCS), reliable method, empirical method, United States Department of Agriculture (USDA), and percentage method. The results show that all methods used for determination of effective rainfall in Rasht are useful. However, these methods require to be pre-calibrated in order to determine the effective rainfall in Daran identified as a low rainfall area. Based on the obtained results, as regards prioritization of using the methods under study in these areas, SCS and USDA methods are proposed for Rasht, while the USDA and percentage methods are proposed for Daran. Since the amount and duration of rainfall is not controllable, effective strategies can be applied to increase precipitation efficiency and consequently effective precipitation; these strategies include: reduction of surface runoff, water storage for times of low rainfall, reduced water depth penetration, and planning for the cultivation of plants that are consistent with the precipitation regime.