渭干河流域“2002·7”特大洪水分析

Flash Flood Event of July,2002 in Weigan River Watershed,Xinjiang,China

渭干河是塔里木河流域第六大源流 ,位于天山西部南麓 ,渭干河干流起点有新疆最大的流域性控制工程———克孜尔水库 .2 0 0 2年 7月下旬天山中西部山区出现大暴雨 (雪 )过程 ,渭干河流域山区降水持续时间长达 30h以上 ,山区降水量 5 0mm左右 ,导致 5条支流和渭干河干流出现有水文记录以来的最大洪峰 ,流量超过警戒流量和危险流量的 2～ 3.5倍 ,暴雨 (雪 )过程结束之后 ,融雪型洪峰长时间居高不下 .洪水过程中 ,各支流以及暴雨与融雪等多种洪峰遭遇现象很明显 .克孜尔水库入库洪峰流量达 36 6 0m3 ·s-1,经水库调洪错峰 ,出库峰值流量为 10 0 0m3 ·s-1,削峰率 72 .7% .

As the global warming, water cycle accelerating, frequent and intensity of flood occurred tend to increasing and more damage in Xinjiang region. Floods are among the most frequent and costly natural disasters in terms of human hardship and economic loss. A flash flood is typically defined as flooding that occurs within short time of a heavy rain event. In Weigan River watershed on the southern slope of the Tianshan Mountains, Xinjiang, a heavy rain and snow weather process were spawned by an influx of moisture from the westerly in July 2002. During the more 30 hours period from 08 am July 22nd to 08 pm July 24th, 20～30 mm of rain were measured in the official recording rain gauge at lower and middle mountains and plain region of Weigan River, and more 50mm in high mountains of Tianshan. Heavy rain fell leaded to causing rapid rises of water in a short amount of time, 5 branch streams and main stream of the Weigan River caused the largest peak discharge of the historical recording data, and 2～3.5 times over the alerting and risking discharges. The storm weather process bring water to flooding in the Weigan River watershed, and the largest peak discharge source from the storm rain fell in the lower and middle mountains. The continues melting snow combined with storm precipitation rates in high mountains lead to large inflow to the reservoir, and a showery weather can tap continuous in prophase, low-level moisture inflow and outflow increasing from the ground were combined to contribute the flood. The storm peak flood simultaneous with melting snow peak flood, and simultaneous peak floods from four branch streams over Tokxun of the Muzart River, and simultaneous inflow flood from the two rivers to the reservoir are main the cause of the large flooding occurred in the watershed. The largest inflow peak discharge was up 3 660 m 3·s -1 in the Kezir Reservoir, and outflow peak discharge was only 1 000 m 3·s -1 , and reducing 72.7 % of peak discharge.