关键词: 枯水径流, 极值机理, 贮存系统

Abstract: This paper mainly expounds the hydrographical features of the river low water runoff and its extremum, including discharge variation, occurring time, water quality and water temperature of river low water runoff In the paper, discussion is emphsized on the mechanism of river low water runoff and its influencing factors such as: ① zonal elements, including climate, vegetation, etc.; ② non zonal elements, including hydrogeological condition, geomorphological element, etc.; ③ human made factors The above mentioned mechanism factors interact each other and synthetically affect the river low water runoff and its basic geo distribution The following conclusions could be drawn after a synthetic analysis procedure: (1) River low water runoff is heavily affected by the rainfall of its watershed. The statistic result from the minimum month's flow, shows that river low water runoff has almost the same geo zone as the year's rainfall distribution. In China, river low water flow decreases and presents zonal distribution from rainy area of south east foreland to drought area of north west backland. (2) Soil and vegetation affecting the rainfall's infiltration and speed, are the most important elements to river low water flow. For example, the rate between minimum month's flow and whole year's flow(%) would also increase while the vegetation's covering area in watershed increases. (3) Topography is another important element affecting low water's extremum. The minimum month's flow in highland area would be richer than that in plain area. It also changes proportionally with the size of water assemblage area. This geo referenced law is demonstrated in humid area and semi humid area, or drought area and semi drought area. (4) The rocks, with differential permeability function, would also play a role in low water flow. The minimum month's flow would increase with the rock with high lacuna, and decrease with the low. The research on mechanism or regularity of river low water runoff's formulation, motion and storage, and the geo analysis on relationship between low water's generation procedure and underlayer's hydrological storage system, are most important to estimate or predict low water hydrological parameters. It plays a positive role in rationally developing water resources.

Key words: low water runoff, mechanism of extremum, storage system