巴图湾水库风沙入库量的估算

风沙入库给干旱、半干旱地区的水库带来了严重的填淤危害。本文通过对内蒙古乌审旗南部巴图湾水库岸边流动沙丘不同部位风速与风沙流的同步观测,计算出库岸流动沙丘表面的平均输沙率。利用巴图湾水库1986~2005年9月份的5期TM遥感影像统计出水库两岸受不同风向影响的流动沙丘断面的平均长度,结合巴图湾水库附近乌审旗河南乡气象站1985~2004年的气象资料,统计出不同风向大于起沙风的风速年均持续时间,初步计算出巴图湾水库的年均入库风沙量。结果表明:(1)巴图湾水库的年均入库风沙量为3.65万t,其中西岸风沙入库量为3.55万t,东岸为0.10万t。西岸风沙危害最为严重,是治沙工作的重点。(2)巴图湾水库的风沙入库具有明显的时间性和方向性。受季风气候的影响,风沙入库的方向会随着风向的变化而改变。东南风与西北风是造成东西两岸风沙入库的主要风向。西北风对风沙入库量的贡献最大。(3)在大于起沙风的风速中,5~12 m/s风速段是风沙入库的主要风速。当风速中7 m/s以上的风速持续时间有一个较小的增加时,入库风沙量将会有一个巨大的增加。(4)库岸半固定沙丘的风沙入库,降尘和风水复合侵蚀引起的库岸坍塌也是入库风沙量的重要组成部分。因此,巴图湾水库的实际年入库风沙量应该大于3.65万t。

Evaluation on the Amount of Sand Transported into the Batuwan Reservoir

Sand flow has damaged the reservoirs greatly in arid and semiarid regions.In this study,Batuwan Reservoir,located at south of Wushenqi County,Inner Mongolia was selected as the study area.Through the observation of wind speed and sand flow in different positions of shifting sand dune along the bank of the Batuwan Reservoir,sand transport rate on the surface of shifting dune was calculated and empirical formula of sand transport rate was derived.By using five years (1986~2005) of TM remote sensing image of the Batuwan Reservoir in September,the average length of shifting sand dune along the bank of Batuwan Reservoir influenced by different wind direction was computed.According to the 1985~ 2004 meteorological data from the weather station at Henan village near the Batuwan Reservoir,the duration of wind speed larger than the threshold wind per year was counted.The amount of sand transported into the Batuwan Reservoir per year was estimated.Results suggested that:(1) Sand transported into the Batuwan Reservoir per year is about 3.65×104 t,of which transported from the east bank is 0.10×104 t,and an influx of 3.55×104 t from the west bank,approximately 97.3% of the total amount of sand flowing into the Batuwan Reservoir.West bank with the serious sand blown damage is the emphasis of desert control.(2) Sand blown damage to the Batuwan Reservoir is timeliness and directivity.The directions of sand flowing into the reservoir change with the seasons under the influence of monsoon.In the winter and spring,most of the sands flows into the reservoir from west bank,and in the summer and autumn from the east bank.The northwest wind contributes the most sand flowing into the reservoir.(3) Among the wind speed larger than the threshold wind,5~12 m/s is the main wind segment bringing sand into the reservoir.When the duration of wind speed is larger than 7 m/s increases in a narrow range,the sand transported into the reservoir will augment over wide ranges.(4) Sands flowing into reservoir from semi-fixed dunes,dust and sand collapse by wind and water erosion also contribute to the sand transported into the Batuwan Reservoir,so the natural sand transported into the Batuwan Reservoir is large than 3.65×104 t.