水文干旱多变量联合设计及水库影响评估

Multivariate joint design of hydrological drought and impact of water reservoirs

基于东江流域博罗站月径流数据,采用游程理论提取水文干旱事件.选用Meta-Gaussian Copula函数,统计模拟水文干旱指标的多变量联合分布.采用Kendall联合重现期和最大可能权函数,设计给定联合超越重现期的水文干旱指标组合值,并定量评估水库径流调节作用对水文干旱多变量联合特征的影响.结果表明:东江流域水文干旱历时、强度和峰值的统计优选分布均为韦布尔分布.干旱指标之间具有较高的正相关性,Meta-Gaussian Copula能够很好地模拟水文干旱指标两变量和三变量联合分布.基于任意两个变量联合设计和三变量联合设计,干旱指标设计组合值位于同频位置附近,且同一个干旱指标设计值在不同变量组合之间差别较小.水库径流调节作用对于缓解东江流域水文干旱效果明显,同一组干旱指标的多变量联合超越重现期在水库影响下明显变大.联合超越重现期越小,水库对联合设计值的影响程度越大.根据目前水库运行模式,若要满足河道内最小管理流量目标,联合超越重现期10 a一遇的干旱历时、强度和峰值依然达到了约3.89~4.04月、7.20~7.97亿m3和2.99~3.12亿m3.

Using monthly streamflow data in Dongjiang Basin,South China,hydrological drought events were truncated on the basis of the run theory. The multivariate joint distributions of droughts were determined by using the function of Meta-Gaussian Copula. An improved method for multivariate design,the most-likely weight function,was applied to select design values of drought properties for the given Kendall joint return periods. Besides,impacts of water reservoirs in the joint design values of drought properties were quantified. Results demonstrate that the Weibull distribution fit the marginals of drought properties well. The dependences of drought properties were highly positive and the Meta-Gaussian Copula effectively modelled their bivariate and trivariate joint distributions. Despite of the bivariate or trivariate design,a set of design values of drought properties almost occurred in the identical cumulative frequencies with slight difference. The remarkable decrease in drought properties of the Dongjiang Basin was attributed to the regulation of water reservoirs. The exceeding joint return periods significantly increase for a set of drought properties under the impacts of water reservoirs. The shorter the joint return period was,the larger the change of the design values was. However,the duration,severity and peak of drought for the joint return period by 10 years still accounted for 3. 89-4. 04 months,7.20-7. 97 and 2. 99-3. 12 hundred-million m3,respectively,provided that minimum instream flow was satisfied for water demand in the Dongjiang Basin.