Evaluation Of Ecological Service Function Of Water Retention And Soil Conservation In Water Source Area For The South-to-North Water Transfer

Ecosystem services research is the core of ecosystem assessment. The quantitative evaluation of ecosystem service is the foundation of reasonable and effective use of natural resources, protection of the ecological environment, harmonious development between the human and the nature, and is also the important theoretical basis of ecological compensation and Ecosystem service comprehensive management. Water and Soil is the basic natural resources as well as strategic economic resources. Today the empirical evaluation of water conservation and soil conservation ecosystem services function and value is relatively mature, but in precise quantitative calculation and visualization space is relatively weak, and this is asymmetry with the practice requirements of water and soil resources management decision-making and regulation, need further discussed, thus effectively take maximum comprehensive benefit of water and soil resources.Traditional evaluation of water conservation in a single ecosystem angle, is difficult to implement water conservation function evaluation under the condition of land use, the soil conservation function calculation always based on universal soil loss equation theory, ignoring the important hydrological processes of upstream sediment plot withholding, the accuracy on the evaluation results is weak; On the discuss of microscopic mechanism, lack of spatial heterogeneity results expression under the differences of underlying surface as well as the poor driven factor influence research, make the allocation of small scale space resources application more difficult; Comprehensive evaluation on ecosystem services is given priority to static evaluation, lack of correction considerations of multi-dimensional contribution rate, quality, spatial and temporal disparities and individual aspiration. Aiming at these problems, in order to applied the evaluation results in the soil and water conservation management and decision-making system of small watershed unit more practical and effective, under this background, this paper carried out the related research, select shangluo(The important water source of the middle route of south-to-north water transfer project and the national soil and water conservation priority area of danjiangkou reservoir) as the research object typically, the main research content is as follows:(a)By using the evaluation methods of In VEST, strengthen the suitability and accuracy of model.Play the advantage of comprehensive assessment of ecosystem service function and count the cost model, water production module participate in operations with other factors and obtain water production capacity with the weighted average, soil conservation module increase land holding sediment ability breakthrough and take reservoir effect into account, reinforce the interpretation of the results; This article have localized parameters for field rate and to ensure the relative accuracy of input data layers; verify the model result with experimental and observational data, improve the credibility of model results. Results show that:the In VEST model better evaluated the water conservation and soil retention ecosystem service function, have a reliable results and consistent trend validation.(b)The study of water conservation and soil retention ecosystem servicesQuantitatively studied the water yield, water depth, water conservation quantity and function from three levels unit respectively. Research the Potential and actual soil erosion rates, amount of sediment and sediment discharge, soil retention rates, sediment retention rates and the soil-water conservation pracices of ensuring water quality and desiting in the region based on the condition of innovative land use classification and refinement underlying surface difference assignmen. further discusses its space differentiation characteristics. The main conclusions are as follows:(1) The whole water yield is 3.55 billion m3 per year,water retention is 2.748 billion m3 per year. The average amount of water yield in sub-watershed is 464.84mm, The function of water retention in sub-watershed is 324.85mm.The space distributes generally enhance from north to south. (2) the total potential and actual soil erosion rate of Shangluo City was 1.21 ×109 t and 3.4 ×107 t, respectively, implying that the region, on the whole, was rated " slight" and " moderate " in soil erosion and had no sign of severe erosion.(3) The total sediment output from the region was 1.61× 106 t, whereas the total soil retention rate of the region was approximately 1.17× 109 t, of which 2.9 ×107 t was of sediment.(4) Under the two scenarios, Soil conservation value in per unit area was averaged to be 313.57 yuan hm-2 a-1 and 824.13 yuan hm-2 a-1.(5) The space heterogeneity of watershed unit was significantly.(c) Analysis the correlation between model results influence factors and driving factors.Further discuss the influence of climate, land use change, underlying surface properties, nature and human driving factors to water conservation and soil conservation ecosystem service function, on this basis quantitative calculated the relationship between 384 small watershed model results and the driving factors. It turned out that:(1) Climate factors influence water yield mainly by changing the amount of precipitation and potential evapotranspiration.(2)The amount of evapotranspiration, soil saturated hydraulic conductivity and the forest coverage rate has the most significant affect for river basin water conservation ability. (3) Under ten years of land use change, water yield and water conservation quantity change is not big, but the sub-watershed spatial heterogeneity is strong. (4) The main influence factors to decide soil erosion and soil conservation capacity is vegetation coverage and slope direction, while the amount of sediment withholding was keep closely related with soil and water conservation measures and management factors.(d) Based on the latest equivalent value to build space-time dynamic evaluation method of ecosystem services function and value.To improve the value of equivalent factor static evaluation method, constructs the dynamic assessment method of ecosystem services value based on the value of the equivalent factor method, realized the dynamic comprehensive evaluation of ecosystem services value in time and space. The results show that:(1) Significant difference of ecosystem services function was found in space, extremely and height important are mainly distributed in the xun river, north qianyou river and downstream of danjiang. (2) the total value of ecosystem service are 4.16 x 1010yuan/km2, west zhongshan landform and the middle and lower reaches of danjiang has the highest value of ecosystem services.(e) For sub-watershed unit partition management and regulation based on the model evaluation results.Fully take into account the county location and sub-watershed unit inclusive, use the most explanatory Pixel Size of In VEST mode, based on the space results characteristics of mode and driving factors, by adjust measures to local conditions, put forward the five partitions like, forest water retention area, soil and water erosion preventing area, slope regulation project area, Sediment and water safety control area and sub-watershed soil and water conservation comprehensive control area. So as to gives the practical reference for adjust land use, soil and water loss control and governance and ecological compensation measures.