Analysis On The Changes Of Water Resources Of The Mainstreams And Tributary In The Upper Reaches Of Lijiang River Basin

The ecological environment of the Lijiang River has been paid attention for a long time.With the development of society and economy,the issue of water resources in the Lijiang River Basin has gradually caused concern.Studying the changing characteristics of water resources in the upper reaches of the Lijiang River Basin and its influencing factors can provide a reference for flood control,tourism,water environmental protection,and rational development and utilization of water resources in the Lijiang River.Based on the actual runoff sequence of the mainstreams and tributary in the upper reaches of the Lijiang River Basin and the monitoring data of water quality indicators,this paper has used a variety of mathematical and statistical methods to comprehensively analyze the water resources changes rule of the runoff and water quality in the upper reaches of the Lijiang River.The specific findings are as follows:(1)Statistical analysis was used to analyze the intra-annual and inter-annual variations of runoff in the upper reaches of the Lijiang River basin.The Mann-Kendall trend analysis,five-year sliding average method,and linear trend analysis were used to analyze the inter-annual trend of runoff.The Mann-Kendall mutation test and orderly cluster were used to analyze the sudden change features of runoff variety.The minimum annual runoff at the Guilin hydrological station and the Darongjiang hydrological station appear in the same year.However,the maximum annual runoff at the main stream Darongjiang hydrological station and the tributary Lingqu hydrological station appear at the same year.The runoff variety at the Guilin hydrometric station show an upward trend,and the runoff variety at the Darongjiang hydrological station and Lingqu hydrological station show a downward trend,but the changes are not obvious.The runoff series at the Guilin hydrological station and Lingqu hydrological station respectively mutated in 2014 and 1963,and there was no significant mutation in the runoff series at the Darongjiang hydrological station.(2)The trend of p H,dissolved oxygen,permanganate index,ammonia nitrogen,total phosphorus index,and comprehensive pollution index in the upstream section of Lijiang River's upstream and downstream tributaries were analyzed.The results showed that the water quality in the upper reaches of the Lijiang River was in good condition,and the water quality categories were controlled in Classes II~III from 2006 to 2015,which meets the target requirements of the water functional area in the upper reach of the Lijiang River,and the water quality qualification rate is 100%.The water quality of the Guilin hydrological station located downstream of the mainstream is inferior to the upstream and tributaries.Seasonal Kendall test and Daniel trend test were used to analyze the water quality-changing trend and the results showed that the pollution of the river sections of the Guilin urban area was gradually controlled,but pollution in the upstream counties and townships increased.The box plot of water quality indicator shows that there are spatial differences and time differences in the water quality indicators of the mainstreams and tributary in the upper reaches of Lijiang River basin.(3)The relationship between runoff and water quality was analyzed comprehensively through Pearson correlation analysis,Kendall test for water quality control of runoff,and the diagram of relationship between runoff and water pollutant concentration.The analysis found that there was no significant correlation between runoff and water quality indicators of the mainstreams and tributary in the upper reaches of the Lijiang River basin.The changes in concentrations of permanganate index,ammonia nitrogen and total phosphorus are mainly affected by the pollution source factors,andthe change in dissolved oxygen concentration comes from the combined effect of runoff and pollution source factors.The water quality of mainstreams and tributary in the upper reaches of Lijiang River Basin is mainly affected by the discharge of pollutants.The water quality pollution comes from the combined effects of point sources and surface sources,and the water quality is less affected by the changes in runoff.