变异条件下淮河流域生态径流变化特征及驱动因子

基于淮河流域7个水文站点1956—2016年逐日径流量和72个雨量站点1960—2016的逐日降水量数据,利用Pettitt变异点检测、生态赤字和生态剩余等生态径流指标,定量分析淮河流域水文变异特征,根据生物多样性指标和水文变异指数间的关系,分析该流域水文变异的生态效应,利用位置、尺度、形状的广义可加模型(Generalized Additive Models for Location, Scale and Shape,GAMLSS)理论框架量化气候因子对生态径流变化的贡献。研究表明:(1)水文变异后生态剩余减少,生态赤字增多,干流流量历时曲线比支流下移更明显;年生态剩余/赤字与面降水距平变化一致,水利工程调蓄作用是夏季生态径流与降水距平相关性差的主要原因;(2)除冬季外,淮河流域年、季尺度生态赤字(生态剩余)逐年增加(减小),春季增加最为明显。尽管冬季生态剩余比其他季节高,但生态剩余整体减小,21世纪干流生态剩余达最低,香农指数表明淮河流域生物多样性逐年下降。生态径流指标与水文改变指标(Indicators of Hydrologic Alteration,IHA)指标相关达0.45,能体现IHA大部分参数信息;(3)淮河流域生态径流对北大西洋涛动(North Atlantic Oscillation,NAO)、太平洋年代际振荡(Pacific Decadal Oscillation,PDO)和Nino3.4气候因子影响最为敏感。干流生态径流对气候因子响应最敏感,而支流生态径流对气候因子响应不敏感,通过GAMLSS模型构建的生态径流对极端值和局部趋势拟合的效果更优。

Change characteristics and driving factors in nonstationary ecological flow condition across the Huai River Basin, China

Based on daily streamflow data at 7 stations during 1956-2016 and daily precipitation data at 72 stations during 1960-2016 in the Huai River Basin (HRB), the eco-surplus and eco-deficit under influences of abrupt streamflow behaviors were analyzed using Flow Duration Curve (FDC). Regarding the relations between ecological indicators and hydrological alteration indicators, we analyzed the ecological effects of the altered hydrological processes. Besides, we also quantified fractional contributions of climatic indices to ecological flow using Generalized Additive Models for Location, Scale and Shape (GAMLSS) framework. The results indicated that: (1) the FDC was subject to general decrease due to hydrological alterations, and most streamflow components were lower than 25% FDC. We found the decreased eco-surplus and the increased eco-deficit due to altered hydrological processes. The FDC of the streamflow along the mainstream of the HRB was lower than that along the tributaries of the HRB. The changes of eco-surplus (eco-deficit) matched well those of precipitation anomalies. The hydrological regulations of water reservoirs acted as the major factor behind mismatch between summer ecological flow and precipitation anomalies. (2) Eco-deficit (eco-surplus) was increasing (decreasing) at annual and seasonal scales with exception of winter season. In winter, the eco-surplus was higher than other seasons. However, the eco-surplus was decreasing persistently. The 21^st century witnessed the lowest eco-surplus along the main streamflow of the HRB and Shannon index indicated the decreased ecological diversity across the HRB. (3) The ecological flow was highly sensitive to Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO) and Nino3.4. Meanwhile, the ecological flow along the main stream of the HRB was highly sensitive to climate indices. While the ecological flow by GAMLSS model had better performance in the fitting of extreme value and local trend.