Temporal-spatial variations of reference crop evapotranspiration in Anhui Province in recent 35 years supported by GIS

The reference crop evapotranspiration is an important component of water resources. For studying its variation under the condition of climate change in Anhui Province, based on the meteorological data observed by 79 meteorological stations of Anhui Province during the period from 1971 to 2005, the values of evapotranspiration were calculated using the Penman-Monteith method recommended by the FAO in 1998. On this basis, a map of reference crop evapotranspiration distribution in Anhui Province was charted using the Kriging interpolation method. The results show that the spatial distribution of annual reference crop evapotranspiration in Anhui Province is strongly affected by many factors, such as the climatic and topographical factors, and the difference of annual reference crop evapotranspiration between the different localities is significant. Generally, it decreases from the northeast to the southwest, which is higher in plain, and lower in mountain. Temporally, it has been in a trend of “fluctuate-decrease” since 1971, and it was the highest at end of 1970s. Seasonal reference crop evapotranspiration is in a sequence of summer>spring>autumn>winter. Monthly reference crop evapotranspiration is the highest during the period from May to August and lowest during the period from November to next February, while the highest value appears in July, and the difference between the different localilities is also significant.