Variation Of Precipitation And Its Impacts On Water Resources In Haihe River Basin

Under the influence of climate change and human activities,the precipitation in Haihe River Basin has changed significantly.In recent years,with the increase of population and urbanization,the development and utilization of water resources in Haihe River Basin have become more and more severe and excessive,and water resources has decreased more and more badly.Precipitation is the most direct source of water resources,and its changing situation is crucial to the safety and security of water resources in Haihe River Basin.Based on the daily precipitation data of 289 stations in Haihe River Basin and its surrounding areas from 1956 to 2016,this thesis used statistical methods to study the variation of precipitation,the causes of precipitation variation and the impacts of precipitation changes on water resources.The study can provide a basis for water resources planning and management,prevention and control of water disasters,and analysis of attribution of water resources attenuation in Haihe River Basin.The main research contents and conclusions are as follows:(1)Interannual variation and annual distribution of precipitation in Haihe River Basin were analyzed.The average annual precipitation of Haihe River Basin decreases from southeast to northwest in space,the average annual precipitation days of Haihe River Basin increases from southeast to northwest in space,the average annual precipitation during the flood season decreases from southeast to northwest in space,and the average annual precipitation during the non-flood season decreases from south to north in space.The annual precipitation in Haihe River Basin has decreased,but the downward trend is not significant,and the annual precipitation days in Haihe River Basin has decreased significantly.The precipitation during the flood season has a significant downward trend,and the precipitation in the non-flood season has an insignificant upward trend.The precipitation is unevenly distributed in one year,and the monthly changes of precipitation are not consistent.The precipitation concentration index decreases significantly,thus the precipitation is becoming more and more even in one year.The variation of precipitation concentration period is not significant,so the precipitation period has advanced slightly.(2)Variation of daily precipitation structure in Haihe River Basin was analyzed.The light rain,moderate rain,heavy rainfall and rainstorm in Haihe River Basin all show a downward trend.For the proportion of precipitation in different grades,the light rain and moderate rainfall are on the rise,the heavy rainfall has almost no trend change,and the heavy rainfall shows a downward trend.The number of small rainy days accounts for the most of annual precipitation days,and the number of precipitation days of each grade all show a downward trend,and small rainfall days decrease mostly.The daily precipitation concentration index of Haihe River Basin decreases in space from southeast to northwest,and shows a very significant downward trend,indicating that the proportion of high-intensity precipitation is decreasing.(3)Ten extreme precipitation indexes in Haihe River Basin were studied.For spatial distribution,the extreme precipitation indexes mainly decrease from southeast to northwest,and continuous dry period(CDD)decreases from north to south,but continuous wet period(CWD)increases from southeast to northwest.For time variation,in addition to CDD,all other extreme precipitation indexes show a downward trend.Among them,extraordinary precipitation(R99p),CWD,maximum daily precipitation(RX1day),and maximum five days of precipitation(RX5day)have a significant downward trend.Except for the poor correlation between CDD and other extreme precipitation indexes,other extreme precipitation indexes have a significant correlation.For spatial variation,the extreme precipitation changes of most stations are not significant.(4)Several influencing factors of precipitation change were discussed.The external water vapor has a great impact on the precipitation in the eastern and western Haihe River Basin,and the influence of water vapor on heavy rainfall and rainstorm is more than the influence of light rain and moderate rain.The temperature in Haihe River Basin shows a very significant upward trend,and the temperature has a restraining effect on precipitation,but the correlation between them is not significant.The El Ni?o phenomenon is an important cause of extreme precipitation changes.(5)Based on the previous studies,the impacts of precipitation variation on water resources was evaluated.The surface water resources,groundwater resources and total water resources in Haihe River Basin all show a significant downward trend.By analyzing the impacts of precipitation of different grades on water resources,the impact of heavy rainfall and rainstorm on the total water resources is greater than the impact of small rainfall and moderate rainfall on the total water resources.The correlation between total water resources and precipitation has changed significantly at different time periods.Compared with the conditions of 1956-1980,the total water resources produced by the same precipitaition in most areas have decreased,and the ability to produce water resources has also decreased.