runoff regression models for small catchments

abstract this papare is resaults of analysing the data which reported from a harvesting project. the site for collecting data is buildings' roofs of azad islamic university of mashhad. a rain gauge and a small reservoir (capacity is 4 cubic meters) were set at this site. then the amount of precipitation and its runoff were measured during two years (from 1386, dey, 23 to 1388, tir, 3).the sample size is 35 observations. the relationship between runoff and rainfall was estimated by regression methods. the best model was chosen by analyzing residuals and testing the models. then the runoff were estimated through this model. the 55-year annual rainfalls of mashhad synoptic station (1951-2005) were selected and frequency analysis was done on them. then the roofs' runoff was estimated by this frequency analysis for both wet and dry years. the total area of roofs and their mean annual runoff in ordered are 18680 square meters and 8428 cubic meters.