Determination of sugar beet water requirement in Tehran province using geostatistics methods

For the purposed water resources management, irrigation scheduling, water usage optimization and gaining maximum yield two step FAO method was applied to determine the water requirement (evapotranspiration) of sugar beet. In this paper reference evapotranspiration were computed from recorded meteorological data at 38 weather stations using the hargreaves-samani method; and then through applying proper crop coefficient the amount of sugar beet potential evapotranspiration were calculated. Sugar beet potential evapotranspiration at 3045 points (3300*5200 m) distancing from weather stations were estimated Using three interpolation methods (cokriging, kriging and inverse distance weighted) and based on derived data the spatial distribution maps for sugar beet potential evapotranspiration in Tehran province were developed through geographic information system (GIS). Evaluation of developed maps based on mean square error (MSE) which was computed by cross-validation showed that the map of cokriging interpolation method was the best. In Tehran, the minimum and maximum sugar beet evapotranspiration during July were 5.5 and 10 mm/day respectively, which equals 0.64 and 1.2 lit/sec/hectare. The acquired minimum and maximum sugar beet evapotranspiration at growth period in Tehran province were 600 and 1200 mm, respectively.