Global Science, The Nature Conservancy, 4245 North Fairfax Drive Suite 100, Arlington, VA 22203, USA.
Atlantic Forest and Central Savannas Program, The Nature Conservancy, Avenida das Pitangueiras 168, Daniela, CEP 88.053-050 Florianópolis, Santa Catarina, Brazil.
Sci Total Environ. 2019 Mar 20;657:1368-1381. doi: 10.1016/j.scitotenv.2018.12.116. Epub 2018 Dec 11.
Watershed management may have widespread potential to cost-effectively deliver hydrologic services. Mobilizing the needed investments requires credible assessments of how watershed conservation compares to conventional solutions on cost and effectiveness, utilizing an integrated analytical framework that links the bio-, litho-, hydro- and economic spheres and uses counterfactuals. We apply such a framework to a payment for watershed services (PWS) program in Camboriú, Santa Catarina State, Brazil. Using 1 m resolution satellite imagery, we assess recent land use and land cover (LULC) change and apply the Land Change Modeler tool to predict future LULC without the PWS program. We use current and predicted counterfactual LULC, site costs and a Soil and Water Assessment Tool model calibrated to the watershed to both target watershed interventions for sediment reduction and predict program impact on total suspended solids (TSS) concentrations at the municipal water intake-the principal program objective. Using local water treatment and PWS program costs, we estimate the return on investment (ROI; benefit/costs) of the program. Program ROI exceeds 1 for the municipal water utility in year 44, well within common drinking water infrastructure planning horizons. Because some program costs are borne by third parties, over that same period, for overall (social) program ROI to exceed 1 requires delivery of very modest flood and supply risk reduction and biodiversity co-benefits, making co-benefits crucial for social program justification. Transaction costs account for half of total program costs, a result of large investments in efficient targeting and program sustainability. Co-benefits justify increased cost sharing with other beneficiaries, which would increase ROI for the utility, demonstrating the sensitivity of the business case for watershed conservation to its broader social-economic case and the ability to forge institutional arrangements to internalize third-party benefits.
流域管理可能具有广泛的潜力，可以以具有成本效益的方式提供水文服务。调动所需投资需要对流域保护在成本和效益方面与传统解决方案进行可信评估，利用一个综合分析框架，将生物、岩石、水文和经济领域联系起来，并使用反事实。我们将这种框架应用于巴西圣卡塔琳娜州坎博里乌的一个流域服务支付（PWS）计划。我们使用 1 米分辨率的卫星图像评估最近的土地利用和土地覆盖（LULC）变化，并应用土地变化模型工具预测没有 PWS 计划的未来 LULC。我们使用当前和预测的反事实 LULC、场地成本以及针对流域校准的土壤和水评估工具模型，来针对流域干预措施以减少泥沙，并预测计划对市政供水入口处总悬浮固体（TSS）浓度的影响——这是计划的主要目标。我们使用当地的水疗和 PWS 计划成本来估计投资回报率（ROI；收益/成本）。在第 44 年，该计划的投资回报率超过了市政供水公司，远在常见的饮用水基础设施规划范围内。由于部分计划成本由第三方承担，在同一时期，为了使总体（社会）计划的投资回报率超过 1，需要实现非常适度的洪水和供应风险降低以及生物多样性共同效益，这使得共同效益对于社会计划的合理性至关重要。交易成本占总计划成本的一半，这是由于在高效目标定位和计划可持续性方面进行了大量投资。共同效益证明了与其他受益者分担成本的合理性，这将提高公用事业的投资回报率，表明流域保护的商业案例对其更广泛的社会经济案例的敏感性，以及建立机构安排内化第三方利益的能力。
