近30年内蒙古入湖流域干旱特征时空变化分析

Spatio-temporal variability of drought characteristics in the entering lake watershed in Inner Mongolia during the past 30 years

黄河中上游地区入湖流域干旱特征时空变化对下游淡水湖泊水量调控及生态环境改善具有重要作用。基于乌梁素海东部流域23个水文气象站1986-2015年的逐日降水资料,经预白化处理后,选取基于标准化降水指数(SPI)的干旱历时和干旱严重度作为评价指标,应用Mann-Kendall法分析30 a来乌梁素海东部流域的干旱特征及变化趋势。研究结果表明:乌梁素海东部流域山区降水量多于平原地区降水量;干旱历时及干旱严重度随时间变化均不显著,流域北部和东南部地区干旱呈持续发展趋势;短时间尺度气象干旱集中发生在流域中部及东南部,中长时间尺度的农业和水文干旱共同发生在流域北部。在乌梁素海降水量微幅减少的趋势下,由于东部流域受水利工程建设等人类活动的影响,流域径流补给量呈明显降低趋势,而为改善湖泊水质、抑制黄藻,必然需相应增加凌汛期及灌溉间隙期引黄水量,二者关系的有效平衡及合理调控,可为区域从量质综合角度改善湖泊环境提供新思路。

Knowledge of the spatio -temporal variability of drought characteristics in the entering lake watershed is crucial for water regulation and ecological environment improvement of downstream freshwater lake in the upper and middle Yellow River. In this study, daily precipitation data collected at 23 stations in the eastern watersheds of Wuliangsuhai Lake from 1986 to 2015 were used to analyze the drought characteristics and its variation trends during past 30 years which were described by drought duration and drought severity in terms of Standardized Precipitation Index （ SPI ） after pre - whitening treatments using the Mann - Kendall test. The results showed that, the precipitation in the mountain area was larger than that in the plain area. The variations of drought duration and drought severity over time were both non - significant, but the drought in the northern and southeastern watershed increased continuously. The short time -scale meteorological drought mainly occured in the central and southeastern parts of water- shed, while the medium and the long time - scale hydrological droughts primarily occurred in the northern parts of watershed. Under the condition of slight decrease in precipitation of Wuliangsuhai Lake, the dis- charge from watershed to lake presented obvious decreasing trend with the influences of the human activi- ties such as hydraulic engineering construction in the eastern watershed. In order to improve lake water quality and control the yellow algae growth, the water supplement from the Yellow River during ice flood season and irrigation clearance period are required to increase in order. Therefore, the balance between the diversion water from Yellow River and the discharge from eastern watershed and reasonable regulation will provide new ideas for the regional lake environment improvement from both the quantitative and qualitalive respects.