Hydrological Characteristics And Water Resources Of The Tuojiang River

The Tuojiang River is a first-class tributary on the left bank of the upper reaches of the Yangtze River,and it is also an important river flowing through the Sichuan Basin.As the heartland of ecological barrier construction in the upper reaches of the Yangtze River,the ecological security of the Tuojiang River Basin is of great significance to the Yangtze River Basin.Affected by climate change in recent years,the precipitation in the basin has declined;the concentration of cities and towns in the basin,the high population density,and the intensive development of water resources have resulted in an imbalance in the supply and demand of regional water resources and serious water pollution;the basin is also prone to sudden rainstorms.The typical place of occurrence is in the upstream Jintang and above areas;the terrain in the basin is relatively complex,the vegetation coverage is low,and the soil erosion is relatively typical.This paper quantitatively analyzes the hydrological characteristics of the Tuojiang River Basin and estimates the amount of water resources in the main and tributaries,in order to provide important parameters and theoretical basis for the establishment of the basin hydrological model and the optimization of water resources allocation in space and time.On the one hand,based on the DEM data(resolution 30m)of the Tuojiang River Basin,this paper uses Arc GIS to extract the river network,watershed and sub-basins,and calculates the density of the river network and the shape coefficient of the river basin based on the extracted basic characteristic values such as the area and length of the river.On the other hand,based on the raster precipitation data in the basin from1979 to 2017 and the measured runoff data of the main and tributaries,spatial interpolation and statistical analysis methods were used to analyze the spatial distribution differences and inter-annual variation trends of precipitation in the basin,and the runoff of the main and main tributaries.Interannual variation and seasonal distribution characteristics were analyzed.Secondly,the area comparison method and the runoff coefficient method are used to estimate the water resources of the main and tributaries of the Tuojiang River,and the runoff estimation results under the two methods are compared and analyzed.Since the runoff coefficient method considers the difference in precipitation,it is better than the area comparison method that only considers the area of the watershed.It can better reflect the spatial difference of precipitation and the surface characteristics of the basin.Finally,combined with the watershed runoff data and estimated values,the line fitting method is used to predict the runoff of the main and tributaries in wet and dry years.Research indicates:(1)The area of the watershed is 27,7006)8)~2,and the total length of the main stream is 569.11km.The river network in the basin is relatively sparse,and the river network density value is 0.18;The Tuojiang River Basin and its sub-basins are all narrow and elongated,and the minimum shape coefficient value is 1.95.Among the main and tributaries,the elevation of the source of the Jianjiang River is the highest at2824m;the longitudinal profile of the main and tributaries is mainly concave,and the upper tributaries and the main stream are typical;the average longitudinal ratio of the main stream of the Tuojiang River is 3.19‰;among the tributaries,the Shiting River longitudinal The maximum gradient is 19.99‰,the minimum vertical gradient of Qiuxi River is 0.66‰,and the vertical gradient of the upstream river is much larger than that of the middle and lower reaches.(2)The spatial difference of precipitation in the basin is as follows:it increases from the Longquan Mountains to the northwest and southeast;the precipitation in the basin generally shows a downward trend from 1979 to 2017,with a decline rate of19.57mm/10a.The annual runoff of Sanhuangmiao Station(1986-2017)and Dengyingyan Station(1954-2017)fluctuated and decreased,with a decline rate of 133million m3/10a and 378 million m3/10a,respectively;Lijiawan-Fushun Station(1973-1984,2007-2017),the annual runoff showed a fluctuating increase;the annual runoff in the basin changed slowly,and the inter-annual variation coefficient of the mainstream runoff was 0.2-0.25;the seasonal distribution of river runoff in the basin was extremely uneven,and the seasonal diameter in summer and autumn was extremely uneven.The flow accounts for 68-89%of the annual runoff.The upstream runoff coefficient value is larger than that of the midstream and downstream regions,and its water production capacity is stronger,and the runoff coefficient value of the tributaries is lower than that of the main stream.(3)The annual runoff variation coefficient under the runoff coefficient method is smaller than that under the area comparison method,and the inversion results of the former are better than those of the latter.Therefore,the runoff coefficient method was used as the estimation method for the water resources of the main and tributaries of the basin.Interpolate and extend the runoff of the main stream Sanhuangmiao Station from 1976 to 1985,Lijiawan-Fushun Station from 1985 to 2006,and Tuojiang Outlet from 1979 to 2017,and inversion estimate the runoff of 10 tributaries from 1979 to2017.Under the runoff coefficient method,the average inversion runoff of the Tuojiang River Basin from 1979 to 2017 was 12.751 billion m3;among the tributaries,the 39-year average historical annual runoff was the largest in the Qingbai River,accounting for 12.3%of the historical runoff in the entire basin.(4)The high water volume of the Tuojiang River Basin is 16.134 billion m3and14.755 billion m3once in 50 years and once in 10 years;The predicted values of the main stream in wet and dry years increase from upstream to downstream;among the main tributaries,the predicted values of the Qiuxi River in the wet and dry years are the largest,and the predicted value of the Fuxi River is the smallest.