In this study

we analyze the spatial and temporal distribution of irrigation water requirements in the North China Plain using soil water balance

precipitation

and evapotranspiration.The soil parameters are taken from 76 sites

the precipitation data is taken from 14 meteorological stations

and evapotranspiration is estimated by using the ETWatch model for the period from 2002 to 2007.We further analyze the quantitative relationships among irrigation water requirement

precipitation and the cultivated crop-area by using multiple regression correlation analysis.The results show an increase in the irrigation water requirements from the coastal to the piedmont regions of the study area.The average annual irrigation water requirements are 172 mm

238 mm and 282 mm

respectively

in the Taihang Mountain piedmont

the middle plain

and the coastal region.The main driving factors of irrigation water requirements are precipitation and the cultivated areas of wheat and vegetables.In the study area

precipitation is inversely related to the irrigation water requirement.A high irrigation water requirement is found in counties with high cultivated areas of wheat and vegetables.Meanwhile

a low irrigation water requirement is found in counties with high cultivated areas of cotton and soybean.