Evaluation Of Evapotranspiration And Submarine Fresh Groundwater Discharge In Liaodong Bay Catchment Area

Submarine groundwater discharge(SGD)is an important pathway of water and material exchange between ocean and land.Driven by both terrestrial and marine forcing components,SGD comprises submarine fresh groundwater discharge(SFGD)and re-circulated submarine groundwater discharge(RSGD).SGD increases the amount and variety of dissolved substances in seawater.SFGD,a net water input from land to ocean,increases the volume of seawater.Liaodong bay is one of the three bays of the Bohai Sea.It is the bay of the highest latitude in China.The bay mouth is the straightline between the Daqing River estuary in Qinhuangdao City and the west corner of Lao Tie Mountain in Dalian,extending in the direction of NNE,and its southwestern part is connected to the central basin in the middle of the Bohai Sea.The catchment area of Liaodong Bay is composed of large and small river basins that flow into Liaodong Bay and covers an area about 260000 km~2.There are only a few research about Liaodong Bay.This study takes the Liaodong Bay land catchment area as the research object,and estimates evapotranspiration in inland catchment area of Liaodong Bay and the SFGD in Liaodong Bay.The evapotranspiration and SFGD of Liaodong Bay are estimated by SEBS(Surface Energy Balance System)algorithm and Water balance principle,analyzing the temporal and spatial variation of evapotranspiration in the catchment area of Liaodong Bay and its influencing factors.The precipitation is a main replenishment sources in the study area,meanwhile the discharge is mainly evapotranspiration and the river runoff into the sea.Under the multi-year scale,groundwater keeps its balance of payments.Evapotranspiration is the most difficult term to calculate accurately,with the greatest uncertainty.So this study use ENVI software and AVHRR data in the Liaodong bay catchment area from 2008 to 2017 to get evapotranspiration.Then put evapotranspiration into Water balance principle,acquiring SFGD of Liaodong Bay.The main conclusion and results of this study are as follows:Evapotranspiration is influenced not only by meteorological factors like air pressure,air temperature,but also by rainfall and vegetation.Evapotranspiration is larger in coastal area than the inner land areas.Due to the large amount of farmland and vegetation covering,the seasonal variations in evapotranspiration is large.The annual evapotranspiration of Liaodong Bay catchment area is about 737.94×10~8m3(20.22×10~7m3/d).The annual SFGD of Liaodong Bay catchment area is about 10.77×10~7m3/d,which is about four times of the river runoff into the sea.