Liu Leyang, Dobson Barnaby, Mijic Ana
Department of Civil and Environmental Engineering, Imperial College London, London, United Kingdom.
Department of Civil and Environmental Engineering, Imperial College London, London, United Kingdom.
Sci Total Environ. 2022 Feb 1;806(Pt 2):150642. doi: 10.1016/j.scitotenv.2021.150642. Epub 2021 Sep 29.
Managing river quality is important for sustainable catchment development. In this study, we present how catchment management strategies benefit from a coordinated implementation of measures that are based on understanding key drivers of pollution. We develop a modelling approach that integrates environmental impacts, human activities, and management measures as three hierarchical levels. We present a catchment water management model (CatchWat) that achieves all three hierarchical levels and is applied to the Cherwell Catchment, UK. CatchWat simulations are evaluated against observed river flow and pollutant data including suspended solids, total nitrogen, and total phosphorus. We compare three competing hypotheses, or framings, of the catchment representation (integrated, urban-only, and rural-only framings) to test the impacts of model boundaries on river water quality modelling. Scenarios are formulated to simulate separate, combined and coordinated implementation of fertiliser application reduction and enhanced wastewater treatment. Results show that models must represent both urban and rural pollution emissions to accurately estimate river quality. Agricultural activities are found to drive river quality in wet periods because runoff is the main pathway for rural pollutants. Meanwhile, urban activities are the key source of pollution in dry periods because effluent constitutes a larger percentage of river flow during this time. Based on this understanding, we identify a coordinated management strategy that implements fertiliser reduction measures to improve river quality during wet periods and enhanced wastewater treatment to improve river quality during dry periods. The coordinated strategy performs comparably to the combined strategy but with higher overall efficiency. This study emphasises the importance of systems boundaries in integrated water quality modelling and simulating the mechanisms of seasonal water quality behaviour. Our key recommendation is that incorporating these mechanisms is required to develop coordinated strategies for river water quality management, that can ultimately lead to more efficient and sustainable catchment management.
管理河流水质对于流域的可持续发展至关重要。在本研究中，我们展示了流域管理策略如何受益于基于对污染关键驱动因素的理解而协调实施的措施。我们开发了一种建模方法，将环境影响、人类活动和管理措施整合为三个层次级别。我们提出了一种流域水管理模型（CatchWat），该模型实现了所有三个层次级别，并应用于英国的切尔韦尔流域。根据观测到的河流流量和污染物数据（包括悬浮固体、总氮和总磷）对CatchWat模拟进行评估。我们比较了流域表示的三种相互竞争的假设或框架（综合框架、仅城市框架和仅农村框架），以测试模型边界对河流水质建模的影响。制定了情景来模拟减少化肥施用和加强废水处理的单独、联合和协调实施。结果表明，模型必须同时考虑城市和农村的污染排放，才能准确估计河流水质。研究发现，农业活动在湿润期驱动河流水质，因为径流是农村污染物的主要排放途径。与此同时，城市活动是干旱期的关键污染源，因为在此期间污水在河流流量中所占比例更大。基于这一认识，我们确定了一种协调管理策略，即在湿润期实施减少化肥措施以改善河流水质，在干旱期加强废水处理以改善河流水质。协调策略的表现与联合策略相当，但总体效率更高。本研究强调了系统边界在综合水质建模和模拟季节性水质行为机制方面的重要性。我们的主要建议是，为了制定河流水质管理的协调策略，需要纳入这些机制，这最终可以实现更高效和可持续的流域管理。
