In most arid regions, where fresh water scarcity is a major threat to sustainability of agriculturalproduction irrigation consumes a major part of the fresh water resources. Therefore,determining the agricultural water demand is a prerequisite for developing fundamentalinfrastructure, and effi ciently managing the allocation of water as well. Accurate estimation ofevapotranspiration (ET) or crop water requirements is one of the main challenges in agriculturalwater management. In the recent years, by development of global and regional climatemodels, long-term predictions of weather parameters affecting evapotranpiration have beendone more easily. In this study, the ability of RegCM3 regional climate model in modelling thepotential evapotranspiration (ETo) in Kashafrud basin, northeast of Iran, has been evaluatedduring the base period of 1961 to 1985 and future period 2021-2035. Due to lack of measuredamount of ET, the Penman–Monteith (P-M) equation was chosen to estimate actual valuesof ET in base period. There are two synoptic stations in study area, namely Mashhad andGolmakan. Since Golmakan station has been established in 1984, it has limited historicaldata in base period; therefore it was excluded from the study. For initialization of the RegCM3model, boundary condition data from EH5OM General Circulation Model (GCM) was used asinitial and boundary conditions data to feed the RegCM3 regional model. Future predictions ofevapotranspiration were done under A1B emission scenario. Spatial resolution of 50 km wasconsidered for the model. Based on the assumed conditions in running the model, the resultsshowed that the non-post-processed RegCM model outputs cannot be used for estimation ofpotential evapotranspiration, but after the post processing using multivariate regression, resultswere more close to those calculated by P-M equation. Temperature and radiation parametershave been considered as independent variables in the multiple regression models to performpost-processing. The results showed that the mean annual evapotranspiration in the futureperiod (787.54 mm) will be increased by 2.34% comparing to the base period (769.59mm). Inoverall, the average potential evapotranspiration will be increased in the months of January,March, April, May, July, September, October, December, and decreased in months February,June, August and November compared to the base period. The fi ndings of this study revealedthat the maximum evapotranspiration in the future period will be in July while in the baseperiod the maximum amount of evapotranspiration occur in June.
展开▼
