The U.S. Environmental Protection Agency National Stormwater Calculator (NSWC) simplifies the task of estimating runoff through a straightforward simulation process based on the EPA Stormwater Management Model. The NSWC accesses localized climate and soil hydrology data, and options to experiment with low‐impact development (LID) features for parcels up to 5 ha in size. We discuss how the NSWC treats the urban hydrologic cycle and focus on the estimation uncertainty in soil hydrology and its impact on runoff simulation by comparing field‐measured soil hydrologic data from 12 cities to corresponding NSWC estimates in three case studies. The default NSWC hydraulic conductivity is 10.1 mm/h, which underestimates conductivity measurements for New Orleans, Louisiana (95 ± 27 mm/h) and overestimates that for Omaha, Nebraska (3.0 ± 1.0 mm/h). Across all cities, the NSWC prediction, on average, underestimated hydraulic conductivity by 10.5 mm/h compared to corresponding measured values. In evaluating how LID interact with soil hydrology and runoff response, we found direct hydrologic interaction with pre‐existing soil shows high sensitivity in runoff prediction, whereas LID isolated from soils show less impact. Simulations with LID on higher permeability soils indicate that nearly all of pre‐LID runoff is treated; while features interacting with less‐permeable soils treat only 50%. We highlight the NSWC as a screening‐level tool for site runoff dynamics and its suitability in stormwater management.

中文翻译：

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使用美国环境保护署国家雨水计算器管理径流估算的不确定性。

美国环境保护署国家雨水计算器 (NSWC) 通过基于 EPA 雨水管理模型的简单模拟过程简化了估算径流的任务。NSWC 获取本地气候和土壤水文数据，以及对面积不超过 5 公顷的地块进行低影响开发 (LID) 功能试验的选项。我们通过比较 12 个城市的实地测量土壤水文数据与三个案例研究中相应的 NSWC 估计值，讨论了 NSWC 如何处理城市水文循环，并重点关注土壤水文的估计不确定性及其对径流模拟的影响。默认的 NSWC 水力传导率为 10.1 毫米/小时，低估了路易斯安那州新奥尔良的传导率测量值 (95 ± 27 毫米/小时)，高估了内布拉斯加州奥马哈的传导率测量值 (3.0 ± 1.0 毫米/小时)。在所有城市中，与相应的测量值相比，NSWC 的预测平均将水力传导率低估了 10.5 毫米/小时。在评估 LID 如何与土壤水文和径流响应相互作用时，我们发现与现有土壤的直接水文相互作用在径流预测中表现出较高的敏感性，而与土壤分离的 LID 显示出较小的影响。在高渗透性土壤上进行的 LID 模拟表明，几乎所有 LID 前的径流都得到了处理；而与渗透性较差的土壤相互作用的特征只能处理 50%。我们强调 NSWC 作为场地径流动态及其在雨水管理中的适用性的筛选级工具。