Climate Change In The Head Regions Of The Yellow River And Its Effects On Water Resource

One of the most important consequences of global climate changes caused by increases in atmospheric trace gas concentrations is alterations in regional hydrologic cycles and subsequent effects on the quantity and quality of regional water resources. The issue of global warming more and more attracts the attention of people. The study on the response of hydrology to the climatic change has significance in developing and using water resources, in lessening the tension of water resource supply and demand and in promoting the regional economy.It is revealed from comparing the 5 GCMs outputs with the observation in the Head Regions of the Yellow River that temperature can be modeled well, and precipitation from the GCMs is a qualitative one only, which can express a long-term variation trend. In this paper, a single-direction coupling system is founded, including GCMs output data, down-scale model and distributed hydrologic model, and then the system is applied in the Head Regions of the Yellow River as a example to study the response of water resource to climate change.The digital analysis of catchments properties from DEM is studied, such as the extraction of river network, boundary of subwatershed and distributed catchments characters. Making use of three sources Xinanjiang model, the distributed hydrologic model is built based on unit grid combining with subwatershed. The calculation of the runoff concentration is done according to nature subwatershed applying with the runoff production of the grids, then the outflow of the whole watershed is calculated. Because the spatial resolution is too rough, the method of downscaling is made in the calculation. This model is applied for runoff from 1961 to 2000 of the Head Regions of the Yellow River, the results show that the calculation results are almost identical to the observed data.Changing trends and characters of water resource in the future are analyzed in this paper, under the condition of that the ranges of temperature change were assumed to be ± 0.5℃, 1℃, 1. 5℃, and the ranges of precipitation change were assumed to be ±5%, ±10 %, the sensitivity of runoff to climate change were studied. Results show that responses of runoff to changes in precipitation are much more obvious than that to changes in temperature. Indexes of unevenness, concentration and variation have been defined and calculatedaccording to gauge records of runoff from 1961 to 2000. The present situation, the cause and the harm of the absence of flow in the Head Regions of the Yellow River were briefly introduced.Finally, the problems that will be solved in the course of combining climatic change scenarios with hydrologic model are raised.