Abstract Increased sediment loading to reservoirs and, ultimately, to Guánica Bay and reef areas is a significant concern in Puerto Rico. Sediment deposition has significantly reduced storage capacity of reservoirs, and sediment-attached contaminants can stress corals and negatively impact reef health. In this study, we examined sediment yield from an upper mountainous watershed, Yahuecas, contributing sediment to Lago Yahuecas reservoir and eventually Guánica Bay, Puerto Rico, to gain a better understanding on sediment loss. This watershed was chosen because it was the only watershed where runoff was monitored in Guánica Bay basin. The Soil and Water Assessment Tool was calibrated and validated using 4½ years of flow data (07/1980 to 01/1985) from the Yahuecas watershed. Five and a half years of suspended sediment concentration data (04/2000 to 09/2005) from the adjacent Adjuntas watershed were used to calibrate sediment simulation of the model because no sediment data were available for Yahuecas. After calibration and validation, Soil and Water Assessment Tool was used to evaluate temporal-spatial soil erosion and sediment yield and assess factors that impact sediment yield. From 1975 to 2011, approximately 80% of annual sediment yield occurred during the two rainy seasons (February to May and August to November). Heavy rainfall, erodible soils, and steep mountain slopes were the primary causes of sediment yield in the Yahuecas watershed. Land use that reduces the protective forest canopy (like sun-grown coffee farming) can exacerbate soil loss. More sediment per hectare was lost from areas producing coffee than forested or grass-covered areas. Conversion of coffee farming practices from sun-grown to shade-grown will reduce soil erosion and sediment yield.

中文翻译：

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使用土壤和水评估工具模型评估通往波多黎各瓜尼卡湾的山脊流域的土壤侵蚀和沉积物产量

摘要 水库以及最终到瓜尼卡湾和珊瑚礁区域的沉积物负荷增加是波多黎各的一个重要问题。沉积物沉积显着降低了水库的储存能力，沉积物附着的污染物会对珊瑚造成压力并对珊瑚礁健康产生负面影响。在这项研究中，我们检查了上游山区流域 Yahuecas 的沉积物产量，这些流域为 Lago Yahuecas 水库和最终波多黎各的 Guánica 湾贡献了沉积物，以更好地了解沉积物损失。之所以选择这个流域，是因为它是 Guánica 湾流域中唯一一个监测径流的流域。土壤和水评估工具使用来自 Yahuecas 流域的 4.5 年流量数据（07/1980 至 01/1985）进行校准和验证。由于没有 Yahuecas 的沉积物数据，使用来自相邻 Adjuntas 流域的五年半悬浮沉积物浓度数据（04/2000 至 09/2005）校准模型的沉积物模拟。经过校准和验证，土壤和水评估工具用于评估时空土壤侵蚀和产沙量，并评估影响产沙量的因素。1975年至2011年，约80%的年产沙量发生在两个雨季（2-5月和8-11月）。强降雨、易蚀土壤和陡峭的山坡是 Yahuecas 流域产生沉积物的主要原因。减少保护性森林树冠的土地使用（如阳光种植的咖啡种植）会加剧土壤流失。与森林或草地覆盖的地区相比，生产咖啡的地区每公顷损失的沉积物更多。将咖啡种植方式从阳光种植转变为遮荫种植将减少土壤侵蚀和沉积物产量。