Kua Zi Xun, Davis Cassandra M, Townley Lauren A, Stella John C, Shaw Stephen B
Department of Sustainable Resources Management, State University of New York College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, NY, 13210, USA.
Division of Water, Bureau of Water Resource Management, 625 Broadway, 4th Floor, Albany, NY, 12233-3508, USA.
J Environ Manage. 2023 Jun 1;335:117521. doi: 10.1016/j.jenvman.2023.117521. Epub 2023 Mar 2.
Despite the widespread use of agricultural best management practices (BMPs) to reduce watershed scale nutrient loads, there remain few studies that use directly observed data - instead of models - to evaluate BMP effectiveness at the watershed scale. In this study, we make use of extensive ambient water quality data, stream biotic health data, and BMP implementation data within the New York State portion of the Chesapeake Bay watershed to assess the role of BMPs on reducing nutrient loads and modifying biotic health in major rivers. The specific BMPs considered were riparian buffers and nutrient management planning. A simple mass balance approach was used to evaluate the role of wastewater treatment plant nutrient reductions, agricultural land use changes, and these two agricultural BMPs in matching observed downward trends in nutrient load. In the Eastern nontidal network (NTN) catchment - where BMPs have been more widely reported - the mass balance model suggested a small but discernible contribution of BMPs in matching the observed downward trend in total phosphorus. Contrastingly, BMP implementations did not show clear contributions towards total nitrogen reductions in the Eastern NTN catchment nor for the total nitrogen and phosphorus in the Western NTN catchment, where BMP implementation data are more limited. Assessment of the relationship between stream biotic health and BMP implementation using regression models found limited connection between extent of BMP implementation and biotic health. In this case, however, spatiotemporal mismatches between the datasets and the relatively stable biotic health, typically of moderate to good quality even before BMP implementation, may reflect the need for better monitoring design to assess BMP effects at the subwatershed scale. Additional studies, perhaps using citizen scientists, may be able to provide more suitable data within the existing frameworks of the long-term surveys. Given the preponderance of studies that rely only on modeling to understand nutrient loading reductions achieved by implementation of BMPs, it is essential to continue to collect empirical data to meaningfully evaluate whether there are actual measurable changes due to BMPs.
尽管农业最佳管理实践（BMPs）被广泛用于减少流域尺度的养分负荷，但很少有研究使用直接观测数据而非模型来评估BMPs在流域尺度上的有效性。在本研究中，我们利用切萨皮克湾流域纽约州部分广泛的环境水质数据、河流生物健康数据和BMP实施数据，来评估BMPs在减少主要河流养分负荷和改善生物健康方面的作用。所考虑的具体BMPs是河岸缓冲带和养分管理规划。采用简单的质量平衡方法来评估污水处理厂养分削减、农业土地利用变化以及这两种农业BMPs在匹配观测到的养分负荷下降趋势中的作用。在东部非潮汐网络（NTN）集水区——BMPs报告更为广泛的地区——质量平衡模型表明，BMPs在匹配观测到的总磷下降趋势方面有微小但可察觉的贡献。相比之下，在东部NTN集水区，BMP实施对总氮削减没有明显贡献，在西部NTN集水区（BMP实施数据更有限），对总氮和总磷也没有明显贡献。使用回归模型评估河流生物健康与BMP实施之间的关系发现，BMP实施程度与生物健康之间的联系有限。然而，在这种情况下，数据集之间的时空不匹配以及相对稳定的生物健康状况（即使在BMP实施之前通常质量也为中等至良好）可能反映出需要更好的监测设计来评估次流域尺度上的BMP效果。也许利用公民科学家进行的更多研究能够在长期调查的现有框架内提供更合适的数据。鉴于大量研究仅依靠建模来理解实施BMPs所实现的养分负荷减少情况，继续收集实证数据以有意义地评估BMPs是否带来实际可测量的变化至关重要。
