Abstract: Experiments were conducted on the grassland watershed at the Heshan Hill Region Experimental Station. Rainfall and runoff records were kept for four years, while evapotranspiration in the grassland watershed was studied in just one year, 1994. These studies indicate: 1) average annual precipitation was 1761mm,and there is significant seasonal variation. Dry season rain accounted for 12 % of the annual precipitation, while wet season rain made up 88 %. Moderate and light rain events were the most frequent though most precipitation was derived from by heavy rain and downpours. 62 % of rain fell in events sufficient to cause surface runoff. 2) The annual runoff and surface runoff coefficient were respectively 50% and 17%. Variation in surface runoff was closely related to variation in precipitation, though less with variation in rainfall intensity. 3) The water balance for 1994 included rainfall input of 1842mm and the output via runoff and evapotranspiration were 970mm and 852mm respectively. Annual moisture variation for the entire system was just 19.7mm, but monthly variation was significant, ranging from-68mm to 104mm. This adjusted water distribution over a single year ,and between years so that the water balance of the grassland was in a form of dynamic balance. 4) Unbalanced seasonal distribution of both water availability and heat, large rainfall events causing surface runoff and the large proportion of surface runoff are three important factors restricting vegetation improvement. Managing change in the way the system losses and reserves its water is a key element in the restoration mechanisms of damaged ecosystem.

Key words: Grassland ecosystem, Hydrological properties, Water balance, Rainfall causing surface runoff, Restor