Research On The Status And Improvement Of Water Conservation Of Reservoir Watershed Based On The InVEST Model

Water conservation is one of the most significant ecosystem services.It not only reflects the ability of ecosystem to keep the water,but also reflects the water that human can use.The evaluation and simulation of the water conservation have significant impact on the establishment of water source protection planning.This paper selects Shui Tao Zhuang reservoir watershed as research scope.In order to verify the feasibility and correctness of the InVEST(Integrated Valuation of Ecosystem Services and Trade offs)model,the water conservation of the research area was compared with the water balance method,the integrated water storage method and the InVEST model.According to the model results and in order to have better protection on the water environment of Shui Tao Zhuang reservoir watershed,this paper proposes various methods of the improvement of water conservation.Based on this,it calculates the water conservation of each method that combining the local situations,and then put forward the optimal solution of the water conservation.This paper provides optimal reference and promotion for the forest water conservation in Zhejiang and even subtropical areas.The main results are as follows:(1)The total research area was 5 756.04hm~2,forest area was 5 362.83 hm~2 in 2015.the research area can be divided into pecan forest,Pecan forest,Camellia forest,bamboo forest,high section of bamboo,pine,fir,pine,oak forest and so on,which cover eleven different types totally.According to the classification of slope can be divided into flat slope(0°-5°),slope(5°-15°),slope(15°-25°),slope(25°-35°),steep slope(35°-45°),dangerous slope(45°≤)a total of six grades.(2)Based on the monitoring data,the total water conservation of the research area in 2015 was2738.31×10~4m~3;as for the comprehensive water storage method,the total water conservation of the research area is 3498.86×10~4m~3;based on the InVEST model,the total water conservationof research area was 3193.90×10~4m~3,and the forest total water conservation of research area was3189.39×10~4m~3.Forest water conservation accounts for 99.87%of the total water conservation,indicating that the forest in the research area has a high water conservation function.(3)The average depth of water conservation was 594.82mm.Moreover,the water average retention of mixed conifer and broad-leaved forest shows the best performance,which was 902.79mm.The slope of the research area(15°-25°)on the amount of total water conservation was the largest,which was1498.54×10~4m~3.Water conservation capacity of different forest types at different slope grades decrease with the increasing of the slope,and reaching the maximum on the flat slope(0°-5°).With the increasing of the slope,the maximum change of water conservation capacity was the coniferous broad-leaved mixed forest.The largest forest area 2487.87hm~2 was on the 15°-25°slope.(4)Compared with the calculated value of the inflow water monitoring data,the accuracy of InVEST model is 83.36%;simulation of water conservation of InVEST model value regression test,R~2is 0.63,the accuracy of the model is 74.15%.Thus,it is reasonable to adopt InVEST model to calculate water conservation effectively,which based on the numerical solutions that have been presented.(5)Furthermore,underlying surface and climate factors are two greatest factors that influence the water conservation in research area,soil hydraulic conductivity is one of the most vital aspect.Therefore,it is rational to improve the water conservation capacity by enhancing the vegetation coverage of the underlying surface effectively.(6)Replacing forest vegetation with mixed conifer and broad-leaved forest to improve water conservation,which expect mixed conifer and broad-leaved forest.After comparing and analyzing different methods,this paper only reconstructs the 15°-35°gradien grade vegetation that based on the satisfaction of existing forest management of the residents in the research area.The result shows that the water conservation has been raised by 41.07%.At the same time,the economic benefits and forest water conservation advantages can be received promotion to a great degree.Through a variety of methods to evaluate the water conservation function of the research area,the result showed that the InVEST model was reasonable and feasible,and then,the environmental factors affecting regional water conservation function were analyzed.On this basis,the optimization model of regional water conservation function is put forward,which provides a theoretical reference and basis for the study of the current situation and optimization of water conservation function in Zhejiang and even subtropical areas.