低水温条件下多泥沙河流水库群水沙调控

Given the low water temperature and large flow in high latitudes river after ice flood when the river completely break-up, sediment transporting capacity in low water temperature is more than several times higher than in normal temperature condition under the same flow in the river, and is more beneficial to coarse sediment transport. Therefore, the Ningxia-Inner Mongolia reach upper the Yellow River is selected as research object in this study, to study water and sediment regulation under low water temperature and flowing condition by controllable flood peak process formed by cascade reservoirs joint optimal operation. First, water and sediment relationship, sediment transport law in the river are studied under low water temperature, and water and sediment regulation threshold series and sediment transport process of flood event are obtained. Moreover, multi-objective, including flood control, ice prevention, water supply, power generation and water and sediment regulation, cascade reservoirs water and sediment regulation model is established and solved by improved Successive Approximation Methods of Dynamic Programming based on feasible search space optimization. Furthermore, four regulation modes are analyzed and long series adjustable flushing water of cascade reservoirs are proposed. Then four-dimensional coordinate system is chosen to represent the regulation objectives and parameters are selected to describe each objective quantitatively, to analysis the mutual transformation law among each objective. At last, response laws between water and sediment regulation effect and scouring and deposition processes of the channel under low water temperature condition are revealed by comparing pre and post change process of each section. The research outcomes have an important theoretical significance to enrich and improve the sediment theory and reservoirs operation theory, and can provide scientific basis for sediment transport and deposition reduction of Ningxia-Inner Mongolia reach.

高纬度地区河道凌汛开河后水温低、流量大，同一流量下，河道输沙能力是常温情况下的数倍，且更有利于粗泥沙的输移。因此，本项目以黄河宁蒙河段为研究对象，利用上游水库群联合调度塑造可控洪峰过程，在低水温畅流条件下研究河道水沙调控机理和方法。一是，分析低水温条件下水沙关系和泥沙输移规律，获得各断面水沙调控阈值系列和场次洪水输沙过程；二是，建立兼顾防凌、供水、发电、水沙调控的多目标梯级水库群水沙联合调控模型，采用可行搜索空间优化的改进逐次逼近算法求解模型；三是，分析调控模式，提出长系列梯级水库可调冲沙水量；四是，以四维坐标系代表各调控目标，选取各目标量化参数，分析各目标之间的相互转化规律；五是，比较水沙调控前后各断面的变化过程，揭示低水温条件下水沙调控效果与河道冲淤的响应规律。研究成果对于丰富和完善河道泥沙理论和库群水沙调度理论具有重要的理论意义，可为黄河宁蒙河道的输沙减淤提供科学依据。

针对黄河上游干支流的 “二级悬河”和凌洪灾害频发等问题，以“低水温条件对河道泥沙输移是有利的”为契机，选取黄河宁蒙河段为研究对象，利用黄河上游凌期开河后水温低、流量大的优势，通过上游水库群联合调度塑造人工可控洪峰过程，开展低水温畅流条件下河道水沙调控研究。本研究的主要内容包括：（1）低水温条件下水沙关系和泥沙输移规律的分析；（2）多目标梯级水库群水沙联合调控模型的建立与解算；（3）各调控目标之间相互转化规律的分析；（4）低水温条件下水沙调控效果的定量描述。.通过研究工作取得了以下成果：（1）获得了低水温条件下不同含沙量下不同区间河段的水沙阈值；（2）率定了基于场次洪水的输沙率计算模型的参数，得到了低水温条件下各站点的输沙率计算公式；（3）揭示了水温变化对河道输沙率的影响规律，即同一流量、含沙量下，水温降低24℃输沙率增加2.54倍；（4）建立与求解了黄河上游梯级水库群的多目标优化调度模型，选取四维坐标系代表各调控目标，揭示了常温条件下各调控目标之间的相互转化规律，即随着未来供水量的增加，水沙调控与供水的矛盾突出；（5）低温条件下进行水沙调控，一方面，显著增加了各断面的输沙量，更有利于河槽内的粗颗粒泥沙输移，达到维持河道的冲淤平衡的长远目标；另一方面，达到同样的输沙量所消耗的水量大幅度减少，解决了水沙调控与供水之间的矛盾。.研究成果对于丰富和完善河道泥沙理论和库群水沙调度理论具有重要的理论意义，可为黄河宁蒙河道在凌汛后的输沙减淤提供科学依据和技术支撑。