丹江口水库蓄水后汉江中下游水文时空变化的#br# 定量评估及其生态影响

采用变化范围法（RVA）定量研究了丹江口水库蓄水后汉江中下游水文情势的时空变化，评估出汉江干流变化度最大的江段和水文特征指标类别，分析了其对应的生态影响，并针对汉江流域的四大家鱼和水华问题进行了敏感水文指标的变化度分析。结果显示:丹江口大坝蓄水后，汉江下游河道流量是中变化度占主导，比例范围为47～63%；水位是高变化度占主导，襄阳站和皇庄站高变化度的水文指标所占比例远大于其它站点，依次为53% 和75%，各站水位较蓄水前下降了1～2 m。黄家港站高/低流量脉冲出现的频率减少（变化度为-0.49和 -0.62），且持续的时间变短（变化度为-0.87和 -0.74）。皇庄站和襄阳站流量和水位的月均值和极值较蓄水前减少，逆转次数在高RVA范围内较蓄水前增加（变化度为1.82）。四大家鱼产卵的敏感水文指标出现频率较蓄水前减少，且为中高变化度。下游河道枯水期流量和水位减小，增加了水华发生几率。

QUANTIFYING THE SPATIO-TEMPORAL VARIATION OF FLOW AND ITS ECOLOGICAL IMPACTS IN THE MIDDLE-SECTION OF HANJIANG RIVER FOLLOWING THE DANJIANGKOU RESERVOIR IMPOUNDMENT

The Range of Variability Approach is used to quantitatively estimate the temporal and spatial variation of the hydrologic regime in the middle-section of the Hanjiang River after the impoundment of the Danjiangkou Reservoir.The results show the highest Indicators of Hydrology Alteration (IHA) in different stations and IHA groups,as well as the corresponding ecological impacts.It is demonstrated that the degree of discharge alteration in the lower reaches of Hanjiang River is rather moderate (range from 47％ to 63％),the degree of water surface elevation alteration is rather high,XiangYang and HuangZhuang have highest alteration of water surface elevation (proportion is 53％ and 75％).More specifically,the water surface elevation decreased significantly at all stations (decreased 1 ～2 m).The frequency and duration of high/low flow pulses in Huangjiagang station of decreased (IHA is-0.49/-0.62 and-0.87/-0.74).The monthly mean and extreme values of discharge and water surface elevation at Huangzhuang and Xiangyang stations decreased,the frequency of discharge reversal magnitude increased (IHA is 1.82 in high RVA range).The occurrence of those Indicators that captured the effects of IHA on the four major Chinese carps was less frequent during the post-dam construction period compared to that before the impoundment.The discharge and water surface elevation of the lower reaches decreased during the dry season,thus increasing the possibility of water bloom occurrence.