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Jason Fuller

Abstract

I measured the anthropogenic impacts from land use on nutrient concentrations along the Little Bear River in Cache Valley, Utah. Water samples from twelve stations along the Little Bear River were collected and analyzed using an auto analyzer in order to determine conductivity and concentrations of total nitrogen, total phosphorus, soluble reactive phosphorus (SRP), ammonia (NH3), and nitrate (NO3-). Samples were collected at stations thought to reveal anthropogenically influenced nutrient loading. Some of the anthropogenic land usages that potentially impact the nutrient concentrations include agricultural land use, urban land use, Hyrum Reservoir, the Trout of Paradise fishing reserve located near the town of Paradise, and the Wellsville Wastewater Treatment Plant. Specific conductivity measurements indicated a 172 percent increase in ions from the headwaters to the lowest site sampled, near the confluence with Cutler Reservoir. My study indicated that total nitrogen was significantly increased by anthropogenic land use, with nitrate increasing from 115 μg N L-1 in the headwaters to 1260 μg N L-1 in the lowland agricultural areas. Total phosphorus (TP) did not appear to be influenced by anthropogenic land use above Hyrum Reservoir: However, below the reservoir concentrations reached 60-75 μg P L-1, above Utah threshold criteria of 50 μg L-1. Total nitrogen : total phosphorus rations indicated that phosphorus was potentially the limiting nutrient at three of the twelve stations including the Trout of Paradise fishing reserve. The dissolved inorganic nitrogen (DIN): TP ratio indicated that phosphorus was the limiting nutrient at each of the stations except Station 8, which is located below Hyrum Reservoir. These findings highlight the influence of anthropogenic land use on the Little Bear River, within the framework of the Serial Discontinuity Hypothesis (Ward and Stanford, 1995).

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