Characteristics and yield mechanisms of stream runoffs in the Northern Shaanxi Energy and Chemical Base

There are entirely different runoff characteristics, yield mechanisms and transformation relations of three waters (precipitation, surface water and underground water) of rivers in the east and west part of the Northern Shaanxi Energy and Chemical Base. Revealing spatial-temporal characteristics and yield mechanisms of runoffs is the key to rational development and efficient use of water resources. Based on the runoff data from 1956 to 2005, this paper analyses the characteristics of the space composition, inter-annual variation and intra-annual change of runoffs by using such methods as hydrological calculation, base flow separation, Mann-Kendall statistic test and characteristic index analysis. Meanwhile, the yield mechanisms of runoffs and the development pattern of water resources are also discussed. The underlying surface of the loess gully area consists of silty loess, which is unfavorable for precipitation infiltration but favorable for runoff formation. The surface runoffs fluctuate rapidly and are mainly recharged from precipitation. On that basis, it is advisable to adopt the pattern of development mainly of surface water with subordinate underground water in this area. By contrast, the underlying surface of the blown-sand area consists predominantly of eolian silt and fine sand, which is favorable for precipitation infiltration but unfavorable for runoff formation; thus the surface runoff fluctuates gently and is mainly recharged from groundwater. It is advisable to adopt the pattern of combined development of surface water and subsurface water in this area.