城市雨水径流是营养污染的重要来源,处理成本很高。水质交易(WQT)是一种基于市场的策略,可用于降低与满足雨水水质法规相关的成本。虽然许多WQT计划的参与度很低,由于纳入了土地开发商和其他受监管的雨水排放者,弗吉尼亚州的计划参与度很高。然而,受监管的雨水排放装置在多大程度上使用WQT作为合规选项还没有得到很好的理解,特别是与采用传统的合规选项相比。为了解决这个知识差距,我们整理了一个新的数据集,该数据集包含罗阿诺克市所有开发项目的场地特征和雨水合规性方法,弗吉尼亚州从2015年12月到2022年3月。我们分析了这个数据集,以描述营养补偿信用和其他合规方法的采用情况,包括最佳管理实践(BMP)和改善与减少养分出口相关的土地覆盖。结果表明,学分是罗阿诺克的首选依从性选择,并且被用作59%有治疗要求的项目的唯一治疗依从性方法。与其他合规方法相比,使用信用额的项目具有较低的中值受干扰面积(1.36英亩)和较低的中值养分负荷减少需求(每年0.69磅总磷)。此外,我们发现,使用信用额的项目中有58%使用除实施雨水控制装置外的其他方法实现了雨水量的合规性。通过映射信用的买家和卖家,我们发现所有信贷卖方都在开发项目的下游。我们讨论了这种下游交易如何引起人们的关注,作为跟踪雨水合规性方法的优势的更大讨论的一部分,以罗阿诺克为案例研究。
Urban stormwater runoff is a significant source of nutrient pollution that is very costly to treat. Water quality trading (WQT) is a market-based strategy that can be used to lower the costs associated with meeting stormwater quality regulations. While many WQT programs have experienced low participation, Virginia\'s program has seen high participation due to the inclusion of land developers and other regulated stormwater dischargers. However, the extent to which WQT is used as a compliance option by regulated stormwater dischargers is not well understood, particularly when compared with the adoption of traditional compliance options. To address this knowledge gap, we collated a novel dataset comprising site characteristics and stormwater compliance methods for all development projects in the City of Roanoke, Virginia from December 2015 to March 2022. We analyzed this dataset to characterize the adoption of nutrient offset credits and other compliance methods being used, including best management practices (
BMPs) and improved land covers associated with reduced nutrient export. Results show that credits are the preferred compliance option in Roanoke and were used as the only treatment compliance method for 59% of projects with treatment requirements. Projects using credits corresponded with a lower median disturbed area (1.36 acres) and lower median nutrient load reduction requirement (0.69 pounds of total phosphorus per year) compared with other compliance methods. Furthermore, we found that 58% of the projects that used credits achieved stormwater quantity compliance using methods other than implementing stormwater control devices. By mapping buyers and sellers of credits, we found that all credit sellers are downstream of the development projects. We discuss how this downstream trading could be a cause for concern, as part of a larger discussion of the advantages of tracking stormwater compliance methods, drawing on Roanoke as a
case study.