Study On Groundwater Discharge Fluxs And Nutrient Salt Fluxs Transported By Groundwater To Ocean From The Yellow River Delta Area

Excessive nutrient salt is the chief contamination which destroy ocean balance, Nutrient salt transported by groundwater can not be ignored. The physical geography, the regional geological conditions and hydrogeologic conditions of the Yellow River Delta Area are summarized through systematically analyzing the former study. Each hydrogeological parameters of this area is defined through hydrogeological experiment and continuous observation for groundwater, then mathematical model of groundwater of the Yellow River Farm Area which is the representative area of the Yellow River Delta is built The hydrological section method is first used to evalute the groundwater discharge flux from the Yellow River Delta to ocean. Secondly, based on the hydrological conceptual model, a three-dimensional flow model of groundwater from the Yellow River Area is built and calibrated with FEFLOW which is one of the advanced groundwater simulation software. Using the calibrated model, the groundwater discharge flux from the Yellow River Farm Area to ocean is evaluated, and the change rule of the groundwater discharge flux from this area are analyzed under the effect of rainfall, evaporation, surface runoff and tide. Based on the groundwater discharge flux from the Yellow River Farm Area to ocean, the groundwater discharge flux from the Yellow River Delta to ocean is estimated. Finally combined with the nutrient salt concentration, the nutrient salt total flux to ocean are got.The result shows geological conditions, rainfall, evaporation, river and tide are the main influencing factors to the groundwater discharge flux to ocean. The hydraulic conductivity of aquifer is the import influencing factor. The difference of hydraulic conductivity of aquifer among the Yellow River Delta is distinct The hydraulic gradient of layer which is controlled by the Yellow River Delta's terrain have not much difference in the entire Yellow River DeltaRainfall and evaporation directly influence the trend of groundwater discharge flux to ocean with time, and the change of groundwater discharge flux to ocean lag behind the change of rainfall and evaporatioa The trend of groundwater discharge flux to ocean with time in high tide is similar to the trend in low tide. The trend of groundwater discharge flux to ocean with time when the river have water is similar to the trend when the river have no water. The degree of the groundwater discharge flux to ocean influenced by surface runoff is higher than by tide, and the degree of the groundwater discharge flux to ocean influenced by rivers together is higher than the sum of degree influenced by rivers in singles.The calculation shows that the groundwater discharge fluxes to ocean is between 7.0*104m3/a~9.5*104m3/a in mean water year. The groundwater discharge flux from the Yellow River Delta to ocean in 2001 is 8.717*104m3. Multiplied with the nutrient salt concentration, NOf-N flux, NQT-N flux, NH4+-N flux, Si flux and PO^-P flux transported by groundwater to ocean is 254.810kg/a, 4.725kg/a, 131.816kg/a, 391.629kg/a, 1.996kg/a respectively. By contrast with the nutrient salt total fluxs transported by the Yellow River to ocean, NO3~-N flux, NC>2~-N flux, NH4+-N flux transported by groundwater is its 0.002%, 0.0005%, 0.01% respectively. It shows the nutrient salt total flux ofBohai is small from the nutrient transported by groundwater.