Christchurch office of the National Institute of Water and Atmospheric Research, Hamilton, New Zealand.
Land Water People, Christchurch, New Zealand.
Environ Manage. 2020 Feb;65(2):272-285. doi: 10.1007/s00267-019-01235-x. Epub 2019 Dec 13.
A common land and water management task is to determine where and by how much source loadings need to change to meet water quality limits in receiving environments. This paper addresses the problem of quantifying changes in loading when limits are specified in many locations in a large and spatially heterogeneous catchment, accounting for cumulative downstream impacts. Current approaches to this problem tend to use either scenario analysis or optimization, which suffer from difficulties of generating scenarios that meet the limits, or high complexity of optimization approaches. In contrast, we present a novel method in which simple catchment models, load limits, upstream/downstream spatial relationships and spatial allocation rules are combined to arrive at source load changes. The process iteratively establishes the critical location (river segment or lake) where the limits are most constraining, and then adjusts sources upstream of the critical location to meet the limit at that location. The method is demonstrated with application to New Zealand (268,000 km) for nutrients and the microbial indicator E. coli, which was conducted to support policy development regarding water quality limits. The model provided useful insights, such as a source load excess (the need for source load reduction) even after mitigation measures are introduced in order to comply with E. coli limits. On the other hand, there was headroom (ability to increase source loading) for nutrients. The method enables assessment of the necessary source load reductions to achieve water quality limits over broad areas such as large catchments or whole regions.
土地和水资源综合管理的常见任务是确定污染源的位置和排放量应如何变化，才能使受纳环境水质达标。本文针对在大尺度空间异质性流域的众多位置指定水质限制的情况下，量化污染源变化的问题展开研究，同时考虑累积的下游影响。目前，该问题的解决方法倾向于采用情景分析或优化方法，但这些方法存在难以生成符合限制条件的情景，或优化方法过于复杂的问题。相比之下，我们提出了一种新颖的方法，该方法将简单的集水区模型、负荷限制、上下游空间关系和空间分配规则相结合，从而得出源负荷的变化。该过程通过迭代确定限制条件最严格的关键位置（河段或湖泊），然后调整关键位置上游的污染源，以满足该位置的限制条件。该方法应用于新西兰（268,000 平方公里）的营养物质和微生物指标大肠杆菌，以支持有关水质限制的政策制定。该模型提供了有用的见解，例如，即使在引入缓解措施以符合大肠杆菌限制的情况下，仍存在源负荷过剩（需要减少源负荷）的情况。另一方面，营养物质仍有一定的余量（增加源负荷的能力）。该方法可用于评估在大流域或整个地区等广泛区域内实现水质限制所需的源负荷减少量。
