50 a来洮河流域降水径流变化趋势分析

Trend Analysis of the Precipitation and Runoff in the Taohe River Watershed during the Past 50 Years

洮河流域 40多年水文实测资料分析表明 ,由于受气候变化及人类活动影响 ,流域降水和径流特征发生了明显变化 ,降水与径流总体呈下降趋势 ,其下降的线性斜率分别为 - 0 .86～ - 1.34mm·a-1和 - 1.5 7～ - 3.36m3·s-1·a-1;而气温呈缓慢上升趋势 ,其上升的线性斜率为 0 0 2℃·a-1.降水的减少和温度的升高已经导致甘南草原荒漠化 ,使许多湿地和湖泊干涸 ;径流的减少和温度增加在近2 0a来有进一步加剧的趋势 .

Analyzing the past 50 a hydrological and meteorological data in the Taohe River basin, it is clear that precipitation and runoff decreases and temperature slowly rises. In the past 50 precipitation decreased 43～67 mm, runoff decreased 78^5～168 m 3 5s -15a -1, and temperature increased 1 ℃. This trend was significant in the 1980s and the 1990s. Precipitation decreased 10^2% from the 1980s to the 1990s, runoff decreased 33%～36% from the 1980s to the 1990s, the decreasing range of runoff was 3 times larger than that of precipitation. Since the 1960s temperature in the upper reach has slowly increased. Temperature increased 0^5 ℃ from the 1970s to the 1980s, and 0^6 ℃ from the 1980s to the 1990s.;Decrease in precipitation and runoff mainly occurs in May～October, and in November～April the decrease range is very small. However, temperature variation trend is opposite to precipitation and runoff.Increase in temperature mainly occurs in November～April, and in May～October, the increase range is very small.;In the basin, multi-annual average total surface ground water resources is 47^16×10 8 m 3 5a -1. In the 1950s the annual average total surface ground water resources was 46^25×10 8 m 35a -1, in the 1960s it was 59^05×10 8 m 35a -1, in the 1970s it was 47^51×10 8 m 35a -1, in the 1980s it was 49^42×10 8 m 35a -1, and in the 1990s it was 33^2×10 8 m 35a -1. Its decreasing amplitude was 32^8% from the 1980s to the 1990s. From 1996 to 2000 the decrease speeds up, resulting in the annual average total surface ground water resources equivalent to 36.6% of the multi-annual average.;The decrease of precipitation and runoff and the increase of temperature cause drought and desertification, together with disappearance of many wetlands or lakes in Gannan Grassland. This variation also worsens environment, and will spreads to the design of Taohe River Water Diversion Irrigations Project. Public will doubt the feasibility of the Taohe River Water Diversion Irrigations Project. So it is necessary to enhance the study of the impact of climate change on water resources, and to present scientific measures to the project.