大通河降雨径流关系演变与水资源衰减初步研究

大通河位于祁连山区,开发利用程度低,实测径流基本为天然径流,1956—2000年平均径流量28.95亿m~3。在全球气候变暖的背景下,降雨-径流关系发生了明显的改变,以水文气象要素明显的分界点1997年进行分时段比较,汛前径流明显衰减,汛后上游径流明显增加,中下游径流有一定减少,年均水资源减少1.72亿m~3。选择受冰川融水和冻土释水影响较小的中下游区间来水分析,得到蒸发增加减少径流深38 mm。基于上中游分阶段径流比较认为,枯季径流的增加来自冻结层下水的稳定释水,春季径流的减少由季节性冻土释水疏干和陆面蒸发增加导致,夏秋季径流的增加主要是冰川融水和冻结层上水转化成冻结层下水减少沼泽消耗所致。综合分析认为,随着气温的继续升高,冰川融水消失,冻结层上水进一步转化,伴随着源头沼泽的消失,冻结层下水的增加对蒸发增加引起的水资源衰减有所缓减。

The relationship evolution of rainfall and runoff and preliminary study of water resource attenuation

Datong river basin is located in Qilian mountain area and has a low degree of development and utilization. The measured runoff is basically natural runoff, with an annual average runoff of 2.895 billion m 3. With the global climate change, the rainfall-runoff relationship has changed significantly. The evolution of hydrological elements took 1997 as an obvious dividing point. The analysis of the rainfall-runoff relationship shows that the pre-flood runoff decreases significantly. After the flood season, the upstream runoff increases significantly,the middle and downstream runoff decreases to some extent,and the annual total water resources decrease by 172 million m³. Based on the comparison of the inflow water between the sections in the middle and lower reaches, the runoff decrease dominated by evaporation is 38, 010 m³/km². Based on the comparison of runoff at different periods between the upper and middle reaches,the increase of runoff in the dry season comes from the steady release of water from the frozen soil.The decrease of spring runoff is caused by the release of water from the seasonal frozen soil and the increase of land surface evaporation. The increase of runoff in summer and autumn is mainly caused by glacial melt water and conversion of water above the frozen layer to water in the frozen layer. According to the comprehensive analysis, as the temperature continues to rise, the glacier melt water disappears, and the water above the frozen layer is further transformed. With the increase of the water in the frozen layer, the source swamp disappears, and the attenuation of water resources caused by the increase of evaporation is slowed down.