Runoff Variation Characteristics And Attribution Analysis Of Min River Basin From 1956 To 2016

As an important component of ecology and environment,water resources are greatly affected by global change.At present,the direct and indirect impacts of climate change and human activities on water resources are one of the important contents of global change research.Water cycle system is an important part of climate system.Climate change will inevitably lead to spatial and temporal changes of water resources.However,human activities such as changing underlying surface,industrial and agricultural water intake and so on,have changed the natural mechanism of water production and concentration in different degrees,and have a direct impact on the spatial and temporal distribution of water resources in the basin.Climate change and human activities are the main driving factors of water resources evolution.It is of great significance to study the interaction and mutual feedback mechanism between climate change and human activities on surface water resources for the rational utilization of water resources.In this paper,the runoff of Min River Basin is taken as the research object.By collecting the meteorological and hydrological data of the Min River Basin from 1956 to 2016,the evolution characteristics of runoff and its response to climate change under regional environmental change are analyzed by using Mann Kendall nonparametric trend and mutation test,ensemble empirical mode decomposition(EEMD),correlation analysis and other statistical methods.Based on the Budyko hypothesis,the impacts of climate change and human activities on runoff change of Min River were quantitatively identified,and the attribution of runoff change was studied.At the same time,it also provides theoretical support and decision-making reference for rational and effective development and utilization of water resources and scientific formulation of water resources adaptive Countermeasures under climate change.The main conclusions are summarized as follows:(1)The runoff shows obvious change trend and mutation characteristicsThe average annual runoff of Min River decreased significantly in flood season,but increased slowly in non-flood season.The average annual runoff of Min River is 2658.9m~3/s,and the average annual decline rate is-1.9×10~8 m~3/a.The average annual runoff in flood season is 4629.7m~3/s,and the average annual decline rate is-4.6×108m~3/a;the average runoff in non-flood season is 1248.6m~3/s,with an average annual increase rate of 2.7×10~7 m~3/a.The annual runoff and flood season runoff are mainly affected by the interannual scale of 2 years and quasi 8 years and the interdecadal scale of 12years.The runoff cycle in non-flood season is mainly 4 years and quasi 8 years.In the abrupt year,the annual runoff and the flood season runoff had a sudden decrease in the mid-1990s.The non-flood season runoff showed an increase mutation in 1957 and a decrease mutation in 2010.The change trend,period and mutation time of flood season and non-flood season are more similar,and the impact of flood season runoff on annual runoff is greater.Affected by the upstream water and atmospheric precipitation,the runoff in the lower reaches of the basin is the largest.(2)Change characteristics of regional climate and human activity backgroundFrom 1956 to 2016,the annual average precipitation of Min River Basin was 1069.8mm,which decreased significantly at the rate of 2mm/a;the annual average temperature was 10.8?,increased significantly at the rate of 0.02?/a;the annual average potential evapotranspiration was 1018.7mm,showing a weak upward trend;the vegetation index(NDVI)showed a significant upward trend after1998.The annual precipitation is mainly affected by the interannual scale of 2-year,quasi-8-year and12-year interdecadal scale.The variation cycle of temperature is quasi-4-year and quasi-9-year.the change cycle of annual precipitation is highly consistent with the annual runoff,but the temperature change cycle is quite different from the runoff.In the abrupt year,the abrupt change of annual precipitation decrease was found in 1967,and the abrupt change of temperature appeared in 2001,both of which had a long time interval with the abrupt change of runoff.Due to the influence of atmospheric circulation and vegetation coverage,the maximum precipitation is concentrated in the Emeishan-Ya'an area.On the whole,the average temperature decreases from southeast to northwest,with Kangding-Xiaojin-Malkang as the boundary.The temperature in southeast is higher than that in Northwest.The maximum value of potential evapotranspiration is in the middle reaches of the basin,and the low value center is in the upper reaches.The vegetation coverage is higher in the whole area,and the vegetation index is low in some areas due to the influence of urbanization and snow cover.(3)Attribution of influencing factors of runoff variation in Min River BasinThe water balance method based on Budyko hypothesis shows that the contribution rate of precipitation to runoff reduction is 77.7%,that of potential evapotranspiration is 7.93%,and that of human activities is 14.37%.The elastic coefficient of precipitation is between 1.32 and 1.34,the elastic coefficient of potential evaporation is between-0.32 and-0.34,and the elastic coefficient of underlying surface coefficient is between-0.58 and-0.64.Runoff is the most sensitive to precipitation change.Among the meteorological factors,the impact of precipitation on Runoff in Min River Basin is much higher than the potential evapotranspiration;in terms of human activities,the impact of water conservancy project on runoff is higher than that of land use change.