Abstract: The paper chose Yanchi County which is located in the arid area of central Ningxia Province,China,as the research object.The connotation and classification of ecological water requirement are analyzed firstly.Then the regional vegetation potential evaporation and ecological water requirement were estimated from month to month using the Penman-Monteith model.The soil moisture correction coefficient was determined using the Jensen formula combined with the measured regional soil characteristics curve at last.Through the proportion analysis of different types of ecological water requirement from vegetation,it showed that the current existing grassland ecological water requirement was far higher than that of woodland.For the three kinds of forest ecological water requirement,shrub land proportion was the largest,and the descending order list of grassland ecological water requirement from large to small was as follows:natural grassland,perennial artificial grassland,and annual artificial grassland.Secondly the temporal variation of balance law between rainfall and ecological water requirement for vegetation was analyzed,and it showed that the ecological water requirement from each kind of existing vegetation was in serious deficit except in the months of July,August and September with the situation in April being the worst.It also showed that whether there is water deficit or water surplus in terms of meeting ecological water requirement from the woodland,the shrub land was outstanding,and from the grass land,the natural grass land was outstanding.The analysis of ecological water requirement characteristics based on ecological zoning indicated that the proportion of ecological water requirement from the windy and sandy area was much greater than that in loess hilly region in the primary ecological division.For the secondary ecological division,the list in descending order based on the proportion of ecological water requirement from big to small was as follows:Huamachi town,Wanglejing town,Dashuikeng town,Gaoshawo town,Hui'anpu town,Fengjigou town and Qingshan town.The minimum value of existing rainfall consumptive ecological water requirement accounted for 30.51% of total evaporation and the suitable value accounted for 72.91% of total evaporation.The proportion was high and the rest of the evaporation part may be consumed in non-forest land soil evaporation,which belongs to ineffective evaporation of water consumption yet occupies a large proportion.

Key words: Yanchi County of Ningxia, proportion of ecological water requirement of vegetation, balance between rainfall resource and ecological water requirement, ecological water requirement