In thermally stratified reservoirs, inflows form density currents according to the interplay between inflow temperature and reservoir stratification. The temperature of inflowing water is affected by catchment properties, including shading by riparian vegetation. We hypothesize that the degree of shading in the catchment can affect the inflow dynamics in downstream reservoirs by changing inflow temperature and consequently the nature of the density current. We test it for a subtropical drinking water reservoir by combining catchment-scale hydrological and stream temperature modeling with observations of reservoir stratification. We analyze the formation of density currents, defined as under, inter and overflow, for scenarios with contrasting shading conditions in the catchment. Inflow temperatures were simulated with the distributed water-balance model LARSIM-WT, which integrates heat-balance and water temperature. River temperature measurements and simulations are in good agreement with a RMSE of 0.58°C. In simulations using the present state of shading, underflows are the most frequent flow path, 63% of the annual period. During the remaining time, river intrusion form interflows. In a scenario without stream shading, average inflow temperature increased by 2.2°C. Thus, interflows were the most frequent flow path (51%), followed by underflows (34%) and overflows (15%). With this change, we would expect a degradation of reservoir water quality, as overflows promote longer periods of anoxia and nutrient loads would be delivered to the photic zone, a potential trigger for algae blooms. This study revealed a potentially important, yet unexplored aspect of catchment management for controlling reservoir water quality.

中文翻译：

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河流遮蔽对下游水库入流特性的影响

在热分层储层中，根据流入温度和储层分层之间的相互作用，流入形成密度流。流入水的温度受集水区特性的影响，包括河岸植被的遮荫。我们假设集水区的阴影程度可以通过改变流入温度和密度流的性质来影响下游水库的流入动态。我们通过将流域尺度水文和溪流温度建模与水库分层观察相结合，对亚热带饮用水水库进行了测试。我们分析了密度电流的形成，定义为下、间和溢流，用于集水区阴影条件对比鲜明的场景。入流温度采用分布式水平衡模型 LARSIM-WT 进行模拟，该模型集成了热平衡和水温。河流温度测量和模拟与 0.58°C 的 RMSE 非常吻合。在使用当前阴影状态的模拟中，下溢是最常见的流动路径，占全年的 63%。在剩下的时间里，河流入侵形成互流。在没有河流遮蔽的情况下，平均流入温度增加了 2.2°C。因此，互流是最常见的流动路径 (51%)，其次是下溢 (34%) 和溢出 (15%)。随着这种变化，我们预计水库水质会下降，因为溢流会促进更长时间的缺氧，营养负荷将被输送到透光区，这是藻类大量繁殖的潜在触发因素。