With the aid of the rainfall erosivity model using daily rainfall and geographic information system ( GIS) software

ArcGIS 9.0

daily rainfall data from 21 weather stations in Da’ ning River watershed and its adjacent area

the Three Gorges Reservoir Region

were used to analyze the temporal2spatial variations of rainfall erosivity(R factor) for the watershed.R factor varied consistently with watershed elevation.R factor decreased rapidly in the upper reaches of the watershed from Gaolou station to Wuxi station

trended towards gentleness in the middle reaches from Wuxi station to Dachang station

and increased gradually in the down reaches from Dachang station to Wushang station(watershed outlet) .There was a great variation in year-toyear R factor with the maximum being three times greater than the minimum.The distribution of rainfall erosivity was highly seasonal with a single peak.Summer months from May to early September typically contributed 90.4 % of the yearly R factor.July and early August were the peak months with more than 38 % of the yearly R factor.