Abstract
Rice is most important agricultural crop of Guilan province sensibility to salinity and alkalinity of water and soil. In recent years, using of toxicants and fertilizers in farmlands, constructing several dams upstream, entering agricultural, homemade and industrial sewage in to a river, and drought have decreased gradually discharge of river and increased salinity of Sefidrud River as an irrigation source of Sefidrud irrigation network of Guilan province. This research tries to determine the optimal intermittent and depth of irrigating of rice in proportion to salinity of Sefidrud River using of optimization- simulation mechanisms as is the decrease in crop efficacy become minimum. To achieve this, an agro hydrological SWAP was used to simulate different stages of rice growing and an optimization model was used in a reasonable range of the intermittent rice irrigation period and depth with regard to different growth stages. Because some types of rice are affected by salinity, field experiments of Hashemi variety in Rasht in 1386 were used to calibrate the model. Optimal values of the intermittent irrigation regime in current salinity of the Sefidrud River (1.747 ds/m) included 8 days intermittent irrigation period and the depth of water for irrigating was 1, 3, 4 and 5 for vegetative, tiller, maturity and harvest stages respectively. The comparison of results of optimization- simulation model with field data in 1389 showed good efficiency of this model in irrigation optimization. In the field experiment 8 days intermittent period with irrigation 5 cm in depth was highest crop performance in 2 ds/m salinity.

Keywords: Rice, Intermittent irrigation management optimization, Sefidrud, Salinity, SWAP model