The Lishui River Basin Runoff Evolution Law Analysis And Study On The Key Technology For Runoff Forcasting

Runoff in nonlinear dynamical systems subject to a variety of complex factors of theatmospheric environment, the climate, the status of basin cascade development and humanactivities, and fully understand the runoff variation, and study their spatial and temporaldistribution, contribute to understanding of the water cycle regularity, understanding of thecharacteristics of basin water resources, and provide an important basis for the rationaldevelopment and utilization of water resources and the optimized configuration. Theresearch of River runoff forecasting is a hot and difficult work of the hydrological study,most of the work in the past is focused on the research and improvement on the method offorecasting model, and lack of regularity of runoff time series analysis and evaluation,These make the management department lack of relevant evidence on runoff forecastingaccuracy requirements. This paper based on the years of history runoff data of LiShuiRiver’s three typical hydrological station in Hunan Province, which are located in theLiShui River’s upstream, midstream and downstream. We analyze runoff sequenceregularity and forecast error on the basis of summarizing the river runoff characteristicsand evolution of the Li River, and proposed the assessment methods of the upper limit ofthe runoff forecast accuracy, and then evaluated the upper limit of Runoff forecast passrate to the Jiangya station which is the typical hydrological plant of the Lishui River. Workand conclusions of the thesis is as follows:1）The research analyze the basic hydrological characteristics including variationduring the year, the inter-annual variation, Flood characteristics, frequency characteristicsand typical year choice according to the characteristics of temporal and spatial variation ofhydrological elements on the basis of the years measured historical hydrological data ofLishui River three typical station. we can conclude that the runoff proportion of wet anddry seasons is very close, and the basin has strong hydrological synchronization in theinter-annual variation. We can also conclude from the emergence time of the minimumrunoff and the main flood season that Jiangya in the upstream has a month delay comparedwith ChaLinHe and Sanjiangkou in the midstream and downstream. The results ofinter-annual variation analysis show that the value of Cv and the ratio of extreme values isvery close which suggests the inter-annual variability of the Lishui River stations runoffis relatively smooth, the hydrology synchrony of Chalinhe and Sanjiangkou is more evident and the hydrological characteristics is more closer. Then we study the typical yearof Jiangya’s wet year, normal year and dry year, and concluded that the typical wet year isfrom1958.4to1959.3, the typical normal year is from2010.4to2011.3and the typicaldry year is from1978.4to1979.3.2) The research analyze the runoff evolution of Lishui River’s typical station withmulti-angle evaluation using non-linear and non-stationary analysis methods. We analyzethe trend item of runoff time series using the method of the trend factor stepwiseregression. The analysis shows that there exist the obvious decreasing trends in March andApril runoff of Jiangya, and other months have no obvious trend item. We analyze thecycle entry of runoff time series using the method of the cycle factor stepwise regressionand cycle analysis based FFT spectrum. The analysis shows that there exist the obviouscycle entry in monthly runoff series and annual runoff series, and it can be drawn thatthere are amplitude comparison main cycle frequency by FFT-based frequency domainperiodogram, and the primary cycle of each month is not the same. It reflects thedifferences between the cyclical characteristics of each month.3) The research establish the self-regression equation for the Remaining stationarytime series to extract the regularity ingredients after separation of the trend and cycle itemsusing the method of AR(p), and comprehensively analyze the relation between theregularity of the runoff series and the error, and then proposed the method of theassessment for the upper limit of runoff forecast. Estimating the upper limit of thequalified rate for the runoff forecasting results before the runoff forecast with this methodcan effectively reveal the main factors lead to the error of the forecast results, which canprovide a basis for reasonable improve the forecasting accuracy. The case study show thatThe evaluation method is practical and effective in the evaluation for the upper limit oflong-term runoff forecast accuracy.