Abstract Regulatory watershed mitigation programs typically emphasize widespread adoption of best management practices (BMPs) to meet total maximum daily load (TMDL) goals. To comply with the Chesapeake Bay TMDL, jurisdictions must develop watershed implementation plans (WIPs) to determine the number and type of BMPs to implement. However, the spatial resolution of the bay‐level model used to determine these load reduction goals is so coarse that the regulatory plan cannot consider heterogeneity in local conditions, which affects BMP effectiveness. Using the Topo‐SWAT modification of the Soil and Water Assessment Tool (SWAT), we simulated two BMP adoption scenarios in the Spring Creek watershed in central Pennsylvania to determine if leveraging fine‐scale spatial heterogeneity to place BMPs could achieve the same (or better) nutrient and sediment reduction at a lower cost than the state‐level WIP BMP adoption recommendations. Topo‐SWAT was initialized with detailed land use and management practice information, systematically calibrated, and validated against 12 yr of observed data. After determining individual BMP cost effectiveness, results were ranked to design a cost‐effective BMP adoption scenario that achieved equal or greater load reduction as the WIP scenario for 74% of the cost using eight management‐based BMPs: no‐till, manure injection, cover cropping, riparian buffers, land retirement, manure application timing, wetland restoration, and nitrogen management (15% less N input). Because watersheds of this size typically represent the smallest modeling unit in the Chesapeake Bay Model, results demonstrate the potential to use watershed models with finer inference scales to improve recommendations for BMP implementation under the Chesapeake Bay TMDL.

中文翻译：

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解决国家规模最大每日总负荷与本地土地管理决策之间的空间脱节


摘要 监管流域缓解计划通常强调广泛采用最佳管理实践 (BMP)，以实现最大日总负荷 (TMDL) 目标。为了遵守切萨皮克湾 TMDL，辖区必须制定流域实施计划 (WIP) 以确定要实施的 BMP 的数量和类型。然而，用于确定这些减载目标的间隔模型的空间分辨率非常粗糙，以至于控制规划无法考虑当地条件的异质性，从而影响了BMP的有效性。使用土壤和水评估工具 (SWAT) 的 Topo-SWAT 修改，我们模拟了宾夕法尼亚州中部 Spring Creek 流域的两种 BMP 采用场景，以确定利用精细尺度空间异质性来放置 BMP 是否可以实现相同（或更好）的效果。 ）以低于州级 WIP BMP 采用建议的成本减少营养物和沉积物。 Topo-SWAT 使用详细的土地利用和管理实践信息进行初始化，并根据 12 年的观测数据进行系统校准和验证。在确定单个 BMP 成本效益后，对结果进行排序，以设计一个具有成本效益的 BMP 采用方案，该方案使用八种基于管理的 BMP：免耕、喷粪、覆盖种植、河岸缓冲区、土地退役、肥料施用时机、湿地恢复和氮管理（氮输入减少 15%）。由于这种规模的流域通常代表切萨皮克湾模型中的最小建模单元，因此结果表明，使用具有更精细推理尺度的流域模型可以改进切萨皮克湾 TMDL 下 BMP 实施的建议。