| The middle route of the South-North Water Diversion Project is an important strategic infrastructure for alleviating the severe shortage of water resources,optimizing the allocation of water resources and improving the ecological environment in North China.There is a difference of 7 degrees between the north and south latitudes of the project channel,and the water flow flows from warm temperate zone to semi-cold area.During the water transportation in winter,there may be ice jam,ice dam and other dangerous situations under certain water transportation flow and cold climate conditions.Water temperature is one of the main indexes of winter water transport in ice period forecast,so how to accurately forecast water temperature and ice condition,and on the basis of ensuring the safety of water transport in ice period,improve the water transport capacity of the main trunk channel in ice period is the key problem of winter water transport research in the middle route project.In this paper,the measured data of flow rate,water temperature and ice condition after the whole line was put into operation in 2014 were analyzed.Then,the temperature characteristics of the main areas along the main canal over the past years are studied from the aspects of M-K mutation test,typical year division and stable turning negative date.Then,a one-dimensional mathematical model of water temperature was established to simulate the water temperature change process along the main canal under different meteorological cold and warm winter conditions and different water flow schemes.Finally,aiming at the water temperature regulation measures of the online storage reservoir,the water temperature mathematical model is used to simulate and analyze the water temperature regulation effect of the Xiongan storage reservoir on the main channel.The main research results are as follows.(1)The data of typical gate stations along the main channel in winter since 2014 show that the water temperature process can be roughly divided into three stages:descending,stabilizing and rising.The lowest water temperature has a great relationship with the geographical location,and the water temperature of the gate station in the north is lower.The lowest water temperature of the Beiguma River control gate in the past years is only 0-0.82℃.There was a strong cooling process in 2015-2016,and the temperature of typical control sluice was 0-0.8℃,which was the lowest over the years,indicating that the change of water temperature was closely related to the change of air temperature.(2)The interannual variation of temperature in the main regions along the main canal in winter is consistent and synchronized to a certain extent.The lowest average temperature in winter at the typical meteorological stations north of Anyang occurred in1957,which were-2.369℃,-3.747℃,-4.044℃ and-4.917℃,respectively.From 1950 to 2020,the overall winter temperature of the main channel presents a significant upward trend,and the 1990 s can be regarded as the time node of abrupt warming of temperature.According to the classification standard of winter temperature,1969,2013,2006 and2017 were divided into typical strong cold winter,weak cold winter,normal winter and warm winter,respectively.(3)The typical winter forecast results show that: Under the same meteorological conditions,the greater the water flow,the less the water temperature along the main canal decreases.For example,in 2013,when the water flow at the head of Taocha canal increases from 150 m3/s to 350 m3/s,the cooling rate along the canal decreases from0.37 ℃/100 km to 0.16 ℃/100 km.Under the same water flow condition,although the increase of air temperature has a certain effect on the increase of water temperature,there is no significant correlation between the cooling rate of different typical winter years.(4)Xiongan storage depot has a certain regulating effect on the water temperature regulation of the main channel.The water flow of the main channel is 280m3/s,and the minimum water temperature and maximum temperature increase of the Beijuma River Sluice reach 0.32℃ under the two water distribution point design schemes.When other conditions are similar,the minimum water temperature and maximum temperature increase of the Beiguma River Sluice are 0.32℃ when the water distribution point is in the upstream and downstream of Xiheishan Sluice,indicating that the water temperature regulation effect of the storage depot on the main channel is basically the same.(5)It is suggested that a large flow and low water level water transport scheme can be adopted in winter to reduce the drop of water temperature,aiming at improving the feasibility of non-ice cover water transport across the whole line. |
