不同强度降雨径流对水源水库热分层和水质的影响

基于西安金盆水库2012~2019年汛期多场不同强度的降雨径流水质数据，对水温、浊度、总氮、总磷及含砂率等指标进行分析，全面探究不同强度降雨径流潜入过程及其对水源水库热分层与水质的影响.结果发现，不同强度降雨潜入库区位置不同，径流量较小时（洪峰流量<500m³/s），径流为等温度层潜流，从温跃层上部进入库区；中径流（洪峰流量为500~1500m³/s）受温度和含沙量共同作用，潜入点下移，以中部层间流方式进入库区；大径流（洪峰流量>1500m³/s）受含沙量影响显著，潜流层厚度变大，径流以底部潜流方式进入库区.不同强度降雨径流对库区热分层影响也不同，小径流影响较小；中径流会破坏水体上部的温跃层，并在底部形成温度梯度较小的温跃层；大径流则会使中底部水体完全更新混合，导致中底部水体水温均匀一致，由温跃层直接过渡到恒温层.不同径流量、来水水质和潜流位置对主库区水质影响不同，TN主要以溶解态为主，占比在76%以上，TP则以颗粒态为主，占比达61%；径流量较低时，温跃层上部氮磷浓度较高，随径流量的增大，冲刷效果的增强，潜流层水体氮磷浓度变高，当热分层被打破时，整个断面浓度均明显升高.

Influence of rainfall runoff with different intensities on thermal stratification and water quality of water source reservoir

Based on the rainfall-runoff and water quality data of Jinpen Reservoir in Xi'an from 2012 to 2019, indicators such as water temperature, turbidity, total nitrogen, total phosphorus and sand content were analyzed to comprehensively explore the infiltration process of rainfall-runoff with different intensities and its impact on thermal stratification and water quality of the water source reservoir. Research results show that different intensities of rainfall dive into the reservoir area at different locations. When the peak flow was less than 500m³/s, the density undercurrent entered the reservoir area from the upper thermocline; with peak inflow of 500~1500m³/s, the middle runoff was affected by the temperature and sediment concentration, whose diving point moved downward, entering the reservoir area in the form of interlayer flow in the middle; while the peak flow of the flood was over 1500m³/s, where the runoff was significantly affected by the sand content, entering the reservoir area in the form of underflow at the bottom, and the thickness of the intruding layer became larger. The effects of rainfall-runoff with different intensities on thermal stratification in the reservoir area were also different:small flow runoff had little impact; medium flow runoff would destroy the thermocline on the upper part of the water body, forming a thermocline with small temperature gradient at the bottom; while large flow runoff would completely renew and mix the water body, resulting in uniform water temperature in the middle and at the bottom, as well as transition from thermocline to constant temperature layer directly. Different inflow runoff, incoming water quality and intruding layer locations had different impacts on water quality of the main reservoir area. TN was mainly in dissolved state, accounting for more than 76%, while TP was mainly in granular state, accounting for 61%. When the inflow was low, the concentration of nitrogen and phosphorus in the upper thermocline was higher. With the increase of inflow and the scouring effect, the concentration of nitrogen and phosphorus in the intruding layer became higher. When the thermal stratification was broken, the concentration of the whole section increased obviously.