| Summary: | 碩士 === 國立交通大學 === 環境工程所 === 87 === Non-point source pollution (NPSP) generated from the upstream watershed of a reservoir can be effectively controlled by Best Management Practices (BMPs). However, at the initial stage of implementing a BMP for a cropland may cause extra cost load and decreasing harvest. Therefore, the farmer may be reluctant to adopt the BMP. Subsidy is one of effective strategies to encourage the farmer to adopt a proper BMP. An appropriate subsidy policy, in addition to encourage the farmer to adopt a proper BMP, should be fair, effective in reducing NPSP, and not too complex. This study applied the Agricultural Non-point Source Pollution (AGNPS) model to simulate NPSP loading and BMP efficiencies. Four indexes for evaluating equity were established based on four subsidy rates of loss, BMP cost, total cost (loss+cost), and pollution reduction equivalence unit, respectively. Five subsidy policies of subsidy of loss (SL), uniform cost sharing rate (UCSR), uniform total cost sharing rate (UTCSR), fixed subsidy per pollution reduction equivalence unit (FSPREU), and fixed subsidy per unit area (FSUA), were proposed based on the equity indexes, loss, BMP cost, and BMP effectiveness in reducing NPSP. A mixed-integer programming model was developed for evaluating the effectiveness of each subsidy policy in terms of cost, phosphorus and sediment reduction, and equity. The watershed of the Derchi reservoir located in central Taiwan was the area studied. The proposed policies and model were applied to the watershed. The result shows that the SL policy has best water quality efficiency with a proper level of equity. When the budget is limited between 10 and 15 hundred millions, the pollution reduction rate achieves 70%. The UCSR and UTCSR policies perform slightly, but not significantly, worse than the SL policy. The UCSR policy with the budget limit of 15 hundred millions and cost sharing rate of 40% or 45% and the UTCSR policy with the budget limit between 15 and 20 hundred millions and cost sharing rate of 30% or 40% can also achieve 70% pollution reduction.
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