A combined watershed–water quality modeling analysis of the Lake Waco reservoir: II. Watershed and reservoir management options and outcomes
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Abstract:
In this study, calibrated watershed and reservoir models are used to explore a range of possible watershed conditions and potential management options to reduce available nutrients and algal growth in the Lake Waco reservoir. The management options are divided between watershed and reservoir options. The watershed management options include wetland construction, manure haul-off, agriculture conversion to pasture, absolute nutrient retention in the watershed and control of urban nutrient run-off. For the reservoir, management options of phosphorus inactivation and increased algal consumption by grazers were evaluated. For all individual management scenarios, only complete conversion of agricultural lands into rangeland decreased nutrient levels and algae growth significantly and achieved target levels for chlorophyll-a and total phosphorus. Combined management scenarios including wetland construction, manure haul-off from dairy operations and increased in-reservoir herbivory could further reduce chlorophyll-a and nutrient values, but with less efficiency than agricultural conversion alone. The management option study showed that decreasing nutrient inputs and water clarity were important factors for controlling algal growth in Lake Waco, and that substantial reduction in total phosphorus is needed to achieve target conditions.Keywords:
Nutrient Management
Abstract Eutrophication is an emerging global issue associated with increasing anthropogenic nutrient loading. The impacts and extent of eutrophication are often limited to regions with dedicated monitoring programmes. Here we introduce the first global and Google Earth Engine-based interactive assessment tool of coastal eutrophication potential (CEP). The tool evaluates trends in satellite-derived chlorophyll- a (CHL) to devise a global map of CEP. Our analyses suggest that, globally, coastal waters (depth ≤200 m) covering ∼1.15 million km 2 are eutrophic potential. Also, waters associated with CHL increasing trends—eutrophication potential—are twofold higher than those showing signs of recovery. The tool effectively identified areas of known eutrophication with severe symptoms, like dead zones, as well as those with limited to no information of the eutrophication. Our tool introduces the prospect for a consistent global assessment of eutrophication trends with major implications for monitoring Sustainable Development Goals (SDGs) and the application of Earth Observations in support of SDGs.
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