Evaluation of an Ecosystem Service for Avoided-Reservoir-Sedimentation and Its Economic Value

In China the current approaches to evaluating the efficacy of the ecosystem service for avoided-reservoir-sedimentation cannot identify the supplier and beneficiary. In addition, the use of the same whole-country coefficient of sediment delivery for different areas can lead to inaccurate results. Based on the integrated geographic information system (GIS) software package, ArcGIS9.2, a new model was established to simulate this ecosystem service and its economic value. The model included fabricating the watershed of the study reservoir. The sediment delivery ratio (SDR) and the universal soil loss equation (USLE) were used to simulate the spatial patterns of the annual sediment yield and sediment retention in watershed. The economic value in this model of the ecosystem service was determined for a fixed number of years. Taking the Ertan reservoir as an example, the results showed that the actual sediment yield was 629.3times10⁴ tldra^-1 in the watershed. It occupied 12.7% of the actual soil erosion volume. Farmland was the most important source of sediment yield. Its actual sediment yield occupied 62.9% of the total. The region with a higher quantity of sediment yield and sediment retention was around the reservoir. The contribution ratio of the forest to the avoided-reservoir-sedimentation service value was higher than those of the other contributors on a per unit area basis. For the reservoirpsilas designed operating life, the total value of this service in the watershed was 27529.2times10⁸ Yuan.