Abstract Water quality degradation from agricultural runoff remains a pressing problem worldwide. A major challenge for restoring water quality is the need for long-term evaluation of governance and management interventions. In agricultural contexts, the primary interventions are best management practices designed to minimize nutrient losses by reducing fertilizer application, soil erosion, and drainage. Most studies are undertaken over short time scales or a few farms, which makes it difficult to connect management to water quality outcomes at larger scales. This paper addresses these gaps by examining 22 years of water quality trends at monthly time scales across the entirety of the 166 small, artificial drainage basins in the Everglades Agricultural Area, the sugarcane-growing region of Florida, USA. The Everglades Forever Act mandated the adoption of best management practices to reduce phosphorus loads but devolved implementation to farms collectively rather than requiring individual compliance. We examined the effect of biophysical and management drivers on long-term trends for two outcomes: a ratio of pumping-to-rainfall, which measures drainage decisions, and total phosphorus load per acre. We analyzed the magnitude and consistency of observed trends using Theil-Sen and Mann-Kendall analysis respectively across wet and dry seasons. Statistically significant downward trends were more common for decreases in magnitude than in consistency for both variables, indicating important management shifts have occurred but that some have not been continually improved over time. However, we also found statistically significant upward trends in a small number of basins for both variables. These results suggest that devolving management to farms has led to a widespread shift in management but that incentives for ongoing improvement would be valuable. Findings on biophysical and management drivers were limited, indicating that more fine-grain data may be needed to better detect their effects.

中文翻译：

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佛罗里达大沼泽地的流域恢复：大沼泽地农业区的农业用水管理和养分结果的长期趋势

摘要 农业径流造成的水质退化仍然是世界范围内的一个紧迫问题。恢复水质的一个主要挑战是需要对治理和管理干预进行长期评估。在农业环境中，主要干预措施是最佳管理实践，旨在通过减少施肥、土壤侵蚀和排水来最大程度地减少养分损失。大多数研究是在短时间内或少数农场进行的，这使得很难将管理与更大规模的水质结果联系起来。本文通过检查美国佛罗里达州甘蔗种植区大沼泽地农业区 166 个小型人工流域整个 22 年每月时间尺度的水质趋势来解决这些差距。《永远的大沼泽地法案》要求采用最佳管理实践来减少磷负荷，但将实施下放给农场集体而不是要求个人遵守。我们研究了生物物理和管理驱动因素对两个结果的长期趋势的影响：抽水与降雨的比率，衡量排水决策，以及每英亩的总磷负荷。我们分别使用 Theil-Sen 和 Mann-Kendall 分析在雨季和旱季中分析了观察到的趋势的幅度和一致性。统计上显着的下降趋势在两个变量的幅度上比在一致性上更常见，这表明发生了重要的管理转变，但随着时间的推移，有些变化并未得到持续改进。然而，我们还发现，这两个变量在少数盆地中具有统计上显着的上升趋势。这些结果表明，将管理权下放给农场导致了管理的广泛转变，但持续改进的激励措施将是有价值的。关于生物物理和管理驱动因素的研究结果是有限的，这表明可能需要更多细粒度的数据来更好地检测它们的影响。