Scenario Analysis Of Soil And Water Conservation Measures In Watershed Of The Red Soil Region,Fujian Provice

The red soil region of Fujian province has been suffering from serious soil erosion.Adapted to the characteristics of this region,a variety of soil and water conservation measures have been explored in practice,such as closing hillside for re-vegetation,grass-bush-tree mixed planting,barren forest transforming,and so on.Each measure has its own capability and suitability for specific parts of the basin,also with different cost.Different configurations(or,scenarios)of soil and water conservation measures have different benefits of soil and water conservation for a watershed.Detailed design and quantitative evaluation for a configuration plan of soil and water conversation measures in watershed is critical for the stakeholders.In this thesis I applied a fully-spatial-distributed watershed model to developing an approach to scenario analysis of soil and water conservation measures in watershed of the red soil region,Fujian province.Based on this appraoch,three methods of scenario design are provided to users.I applied the proposed approach to the Zhuxi watershed(about 43.93 kL2)in the red soil region,Fujian province.By comparing the results from three methods of scenario design,I evaluated the applicability of the proposed approach.The specific contents of this study are as follows:(1)During the preparation of the data set in the study area for the watershed simulation and scenario analysis,I conducted a digital soil mapping for detailed soil property maps in the study area because of the poor quality of the existing soil maps in this area.A fuzzy clustering method is applied to purposive soil sampling and predictive soil property mapping of sand content,silt content,clay content and organic matter content in the soil of the top 0-20 cm in the Zhuxi watershed at a resolution of 5 m.The evaluation results show that the predictive soil maps achieve good prediction accuracy and can well reflect the spatial variation of the soil in the study area.(2)I built a fully-spatial-distributed watershed model for evaluating the scenario of soil and water conservation measures in the study area.This model is based on a fully-spatial-distributed watershed modelling framework(SEIM)while the algorithm for each sub-process was select to match the application and the study area.The calibration results show that the SEIM model can reasonably simulate the hydrological process of the watershed under the situation of the data set.(3)The key in applying the watershed model to scenario analysis of soil and water conservation measures is to express each management measure in the watershed model.In this study,six conversation practices in the red soil region can be expressed in the SEIM model by adjusting specific parameters in the model according to the literatures on soil and water conservation measures in this region.I bulit a management-measure base,which is available for SEIM model,by storing the parameter-settings for the six conversation practices,i.e.closing hillside for re-vegetation,grass-bush-tree mixed planting,barren forest transforming,grass-bush planting along contour,seeding grass in pit,and changing the tea and fruittree farm to be terrace from slope.(4)Based on the SEIM model coupled with management-measure base,three methods of scenario design are provided for different ways of application,i.e.the scenario design based on the landuse type,the scenario design based on targeted placement for critical source zones,and the scenario design by automatical global optimization on the block level(the generic algorithm,?-NSGA-II,is used for optimization in this study).Then the approach to scenario analysis of soil and water conservation measures was used to conduct scenario analysis on the benefit from sediment reduction under different scenarios from three scenario design methods.Results of scenario analysis show that the automatical global optimization has the advantage of finding the best management practices,while the scenario design based on the landuse type and the scenario design based on targeted placement for critical source zones can provide good interactiveness with limit computation.The approach developed in this study can be provided as a decision support tool which is useful to plan benefical management practices of soil and water conservation measures in watershed of the red soil region,Fujian provice.