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Golden Algae Control: Efficacy of Hydraulic Manipulations in Coves of Lake Granbury

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Final rept.

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Bloom mitigation approaches employing deepwater flushing show great promise when targeting coves of Lake Granbury, USA. They may be limited, however, based on the natural water exchange rate between targeted coves and the surface waters of the open lake. This potential limitation was investigated by conducting dye-tracer studies that enabled direct measurement of water exchange rates. Historical data were also analyzed to explore the dissimilarity between coves and the open lake. Finally, a numerical model was built to estimate P. parvum bloom reduction levels under various deepwater flushing scenarios. Dye tracer studies involved time-series, high-resolution spatial mapping of Rhodamine WT in three target coves. To complement spatial mapping, vertical profiling was performed at fixed-location stations throughout these coves. These combined processes allowed researchers to calculate the total amount of Rhodamine WT over time in these coves. From this information, natural water exchange rates between coves and surface waters of the open lake could be determined, and were typically found to be in the range of 0.25-0.30 d-1. Analysis of historical data utilized an extensive data set comprised of biotic and abiotic parameters from 10 coves and 10 open lake stations. The data record spanned multiple years with a once-per-month sampling frequency. Dissimilarity relationships estimated from Euclidean distance measures between coves and the open lake with changes in winds and inflows to the lake were examined. It was found that water exchanges with coves located lower in the lake were linked to winds and inflows. Mechanisms driving water exchanges with coves higher in the lake, however, are still not clear. Proposed management scenarios were depicted with deepwaters being pumped from the open lake to the upper regions of coves.

Subject Categories:

  • Biology
  • Hydrology, Limnology and Potamology
  • Fluid Mechanics

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