Lake Lowell Water Quality Assessment
Deer Flat National Wildlife Refuge
Planning Aid and Contaminant Study
Lake Lowell has persistent problems with water quality including extensive algal blooms, oxygen depletion, and fecal coliform bacteria counts which often exceed Idaho's water quality standards. The Lake is on the State's 1998 303(d) (of the Clean Water Act) list for nutrients as pollutant. Inflows to the reservoir are a combination of diverted Boise River water and irrigation return flows. Water is withdrawn from the reservoir during the irrigation season (April through August), but reservoir levels normally rise from September through April. Nutrient rich inflows from the New York Canal and irrigation return flows, combined with the shallow depth and high water exchange rate in the Lake have led to reports of dense blue-green algal blooms for over 60 years. Open drains that collect surface and irrigation runoff are common throughout the area. This runoff includes drainage from agricultural industrial and residential areas around the Lake area. In addition to water quality issues, fish contamination is also a primary concern. Aquatic organisms are likely exposed to a broad range of agricultural and industrial chemicals including dieldrin, DDT and analogs, dacthol, PCB's, hexachlorobenzene, and pentachlorophenol and heavy metals which can potentially affect the food chain. Sediment, water, and biological samples were collected and analyzed to evaluate alternatives to improve water quality in Lake Lowell at Deer Flat National Wildlife Refuge (NWR) by the U.S. Fish and Wildlife Service who are assisting the US Bureau of Reclamation in performing the study.
Methods: This reconnaissance investigation selected 15 locations for collection of water and sediment samples. Eight of these locations were irrigation return flows that enter the Lake. The New York Canal was also selected as a sample site because it is the main source of water to the Lake and has the potential to become contaminated as it passes through 40 miles of agricultural land and urban areas in the Boise-Nampa area. Six sampling sites were within the Lake. Surface water samples were collected to determine what contaminants were entering the lake at a given point in time while sediment samples are used to evaluate what constituents may have been in the water in the past. Fish tissue samples from three different locations were also collected. Whole body and fillets samples from each location were submitted to the laboratory for mercury analysis. The investigation focus was on pesticides and herbicides that have been used in the past and may be currently used in local agricultural practices. Water samples were also analyzed for common ions and nutrients to assess the effect of eutrophication along with toxic contamination. The main interest in the fish tissue sampling was mercury. Mercury had been found in the water column samples at concentrations that exceeded the chronic criteria and it was also detected in the sediment samples. Since mercury is known to bioaccumulate, it is likely that the fish are exposed and contaminated with mercury which, in turn may affect birds that feed on the fish in the lake.
Results: A total of 16 sediment, 32 water, 2 botanical, and 60 fish tissue samples were collected and submitted for laboratory analysis of inorganic and organic constituents. From the samples collected and analyzed from Lake Lowell in 1998 there may be three problems occurring within the Lake: elevated mercury concentrations within the water column, elevated levels of DDT and it metabolites, and algae blooms or eutrophication of the Lake. Mercury was detected during the first round of sampling in Lake water at concentrations above Idaho's chronic water quality criteria. The Mercury may have been in the algae bloom that was occurring during the first round of sampling. The actual source and frequency of elevated mercury concentrations should be determined. This study shows that the inflows to the Lake are likely contributing to the algae bloom problem. Reducing the amount of nutrients entering the Lake would likely reduce the amount and severity of the algae blooms.
Future Recommendations: The study recommends that water samples be obtained on a weekly basis and be analyzed for mercury. The extent of DDT contamination needs further review, and a round of sampling for pH and dissolved oxygen should be conducted for a 24-hour period. This would determine if large changes in these parameters are occurring during the time when algae are not photosynthesizing but are respiring. This can cause very large swings in the pH which can allow metals to become dissolved and enter the water column at night and precipitate out during the daylight hours.
Learn more by reading the following full report: Burch, Susan & Judson King, 1998 Lake Lowell Water Quality Assessment Deer Flat National Wildlife Refuge Planning Aid and Contaminant Study, USFWS Snake River Basin Office, Boise, Idaho. May 2000. ( Prepared for US Bureau of Reclamation Snake River Area Office, Boise, Idaho)
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