Abstract: The construction of eco-system in the loess hilly-gully region which was based on de-farming and afforestation policy has made remarkable improvement in the past decade. To probe into the relationship between precipitation and surface water and groundwater since the de-farming and afforestation policy was implemented, taking the Kanggou watershed in Yanan as an example, based on the daily meteorology data from Yan'an station during 1997-2006, and the actual measured data of runoff, spring flow, well level, landforms and land-use, this study was conducted by correlation analysis and GIS spatial analysis. This paper analysed the spatio-temporal variation of precipitation, surface water and groundwater in Kanggou watershed, explored the relationship between precipitation and surface runoff, and groundwater runoff, and revealed different responses to the precipitation of the surface water and the groundwater. Results are as follows: (1) There is a close connection between runoff and precipitation. The largest surface runoff occurs in the wet season with the peak precipitation. The distribution of precipitation and the surface water is basically consistent all the year. The runoff concentrates in May to September, accounting for 66.83% of the total annual runoff. The surface runoff forms a curve with peak and valley in turns, having a single peak with limited precipitation and double peaks with abundant precipitation. (2) There is a clear difference of surface runoff between morning and afternoon in the same day, and the difference between noon and afternoon is small. The average difference of surface runoff is 21.16 m³/d. The annual surface runoff varies significantly. One of the possible reasons is the difference of the wet year, normal year and dry year caused by the recharge of precipitation, and the other reason is the effects of eco-environment management in recent years. (3) The amount and the seasonal distribution of the precipitation directly affect the springs and wells, and wells are more sensible than springs under the same conditions. The response time of the wells to rainfall recharge is as long as 22 to 30 days, and the response time of springs is only 7 to 10 days. The reason is that groundwater runoff flow in rock gaps and soils is very slow. Also, the groundwater system contains giant storage vacuum, which makes permeation and discharge become limited. So the system relies on the concentrated or discontinuous recharge by precipitation as the only source of the storage, and then recharges to the other aquifers when seasons change.

Key words: Kanggou watershed, loess hilly region, precipitation, spring flow, surface runoff, well