Abstract Identifying sources of terrestrial sediment to the ocean is important for watershed managers because of the harmful impacts of sediment on nearshore marine ecosystems. The Rio Loco watershed (RLW) in southwest Puerto Rico has been extensively modified, currently comprised of small mountainous rivers connected by reservoirs and irrigation canals to the Lajas Valley Agricultural Reserve (LVAR). The RLW has regularly supplied sediment to Guanica Bay; however, the total annual yield and subbasins most responsible have remained unknown. We estimated sediment yield for the lower RLW using the Soil and Water Assessment Tool (SWAT) in separate scenarios to assess a range of conditions; a dry season scenario that modeled flow through the irrigation system and a wet season scenario that modeled flow through the natural river channel. Precipitation was similarly correlated with sediment yield in both seasons, with 1.5× more sediment per month predicted during the wet than dry season. The distribution of sediment yield among subbasins was the same in both seasons. The foothills north of the cement lined irrigation canal and subbasin north of Lago Loco were the largest source of sediment, both combined to produce nearly 40% of the total sediment reaching Guanica Bay. The next largest source was from subbasins that comprised a combination of agricultural and suburban land uses. Relative basin-scale model outputs for both the irrigation system and natural channel agree with empirical measurements from 2015. The SWAT model output provided some guidance and justification for sediment management strategies in the foothills, upstream of Lago Loco, and within the LVAR.

中文翻译：

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干湿季沉积物产量的空间分布模拟：波多黎各里约热内卢下游流域的案例研究

摘要 由于沉积物对近岸海洋生态系统的有害影响，确定海洋陆地沉积物的来源对于流域管理者来说很重要。波多黎各西南部的 Rio Loco 流域 (RLW) 已经过大规模改造，目前由小型山区河流组成，这些河流通过水库和灌溉渠与拉哈斯河谷农业保护区 (LVAR) 相连。RLW 定期向瓜尼卡湾提供沉积物；然而，年总产量和负最大责任的子流域仍然未知。我们在不同的情景中使用土壤和水评估工具 (SWAT) 估算了较低 RLW 的沉积物产量，以评估一系列条件；模拟通过灌溉系统的流量的旱季情景和模拟通过天然河道的流量的雨季情景。降水量与两个季节的沉积物产量相似，预计雨季每月的沉积物比旱季多 1.5 倍。两季流域产沙量分布基本一致。水泥衬砌灌溉渠以北的山麓和 Lago Loco 以北的子盆地是最大的沉积物来源，两者结合产生了到达瓜尼卡湾的沉积物总量的近 40%。下一个最大的来源来自子流域，包括农业和郊区土地用途的组合。灌溉系统和自然渠道的相对流域尺度模型输出与 2015 年的经验测量结果一致。 SWAT 模型输出为山麓、Lago Loco 上游和 LVAR 内的沉积物管理策略提供了一些指导和理由。