| Niulan River—Dianchi Lake water supplement project is one of the 172 major water conservancy projects for water saving and water supply under the State Council.It is a strategic project for optimal allocation of water resources in Yunnan province in the near and medium term,as well as a key measure for comprehensive treatment of water pollution in Dianchi Lake.Based on comprehensive treatment measures such as sewage interception around the lake and river regulation into the lake,it can effectively improve the water environmental capacity,accelerate the water circulation,and reduce the replacement cycle of lake water by the introduction of Niulan River high-quality water source,which is of great significance to the water pollution control and water environment improvement of Dianchi Lake.The main task of the project in the near future(2020)is to replenish water,cooperate with other measures for water pollution prevention and control,promote the water quality of Dianchi Lake to reach the standard as soon as possible,as well as provide emergency water supply for Kunming.At a specified future date(2030),the main task is to supply water to Qujing city,and to replenish water to Dianchi Lake together with the central Yunnan water diversion project,and at the same time to serve as a backup water source for Kunming city.The project mainly consists of water source project,water lifting project and water conveyance project,of which the water source project is Deze reservoir hub,located on the main stream of Niulan River in Deze township,Zhanyi district,Qujing city,Yunnan province.Deze reservoir,as the water source of Niulan River-Dianchi Lake water supplement project,it has played an important role in optimizing the allocation of water resources since its completion,but it also inevitably affects the downstream hydrological situation and ecosystem.Reasonable and scientific reservoir operation can effectively reduce the impact of hydrological situation changes on the downstream of the reservoir while meeting the project operation tasks.According to the operation data of Deze reservoir and the hydrological measured data of upstream and downstream hydrological stations,the change law and trend of downstream hydrological situation after the construction of the reservoir are studied to provide relevant reference for the water regulation of Deze reservoir and the sustainable utilization of water resources in the basin.Based on the hydrological data of Deze hydrological station and Huanglishu hydrological station in the lower reaches of Deze reservoir from 2015 to 2019,it is concluded that there is a significant positive correlation between the monthly average discharge and the monthly average water level at Deze hydrological station by Pearson correlation analysis,wavelet analysis and M-K catastrophe analysis,which has an obvious quadratic function relationship,and there are 17-month and 18-month change cycles.There has been a sudden change between 2015 and 2019,in which the monthly average discharge has a sudden change in March/May/November 2015 and September 2016,and the monthly average water level has a sudden change in May/November 2015 and August/October 2016.There is a significant positive correlation between the monthly average discharge and the monthly average water level at Huanglishu Hydrological Station,which has an obvious quadratic functional relationship,and there are 17-month and 18-month change cycles,which have undergone sudden changes between 2015 and 2019,Among them,the monthly average discharge has sudden changes in July/November 2015,June/November 2017,October 2018 and July/September 2019,and the monthly average water level has sudden changes in July 2015,January/May 2016,2018/November and November 2019.According to the analysis results,based on the hydrological data of Deze reservoir and its upstream and downstream hydrological stations in the same period,the influence of upstream flow on water storage and discharge from 2015 to 2019 is further analyzed.Using Sen slope estimation method,MK trend test method and R/S analysis method to predict the future hydrological situation in the lower reaches of the reservoir,it is concluded that the historical trend of Deze Hydrological Station is that the monthly average discharge is declining and the monthly average water level is rising.The historical trend of Huanglishu Hydrological Station is that both monthly average discharge and monthly average water level are rising;The monthly average discharge and monthly average water level Hurst values of the two hydrological stations are both greater than 0.5,which indicates that the future trend is consistent with the historical trend.At the same time,the data of hydrological station discharge in the upper reaches and inflow and outflow of Deze Reservoir are statistically analyzed,and it is concluded that after the completion of Deze reservoir,it has played an important role in flood regulation and storage by cutting peaks and shifting peaks.The research shows that,firstly,the monthly average discharge and monthly average water level of hydrological stations in the lower reaches of Deze reservoir have obvious periodic fluctuation laws.Second,Deze hydrological station and Huanglishu hydrological station have periodic changes of 15-20 months in monthly average discharge and monthly average water level.There is an obvious "dry-abundant" change law in the change cycle,which can provide a reference basis for the future hydrological situation prediction of the hydrological station,and the monthly average discharge and monthly average water level of the Huanglishu hydrological station are consistent with the change cycle of the Deze Hydrological Station.Thirdly,through the hydrological data in recent 5 years,the trend change law of hydrological elements in the hydrological station downstream of the reservoir is analyzed,and the future trend change is predicted.Fourthly,according to the daily flow of upstream and reservoir in recent five years,the regulation and storage function of Deze reservoir to downstream is analyzed.Therefore,it is suggested that Deze reservoir should strengthen short-term weather forecast and upstream hydrological monitoring,and conduct in-depth research on the correlation between Deze reservoir and upstream and downstream hydrological stations,so as to provide technical support for Deze reservoir to formulate scientific and reasonable dispatching plans and rules. |
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