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UBC Theses and Dissertations

A multi-method approach for determining a phosphorous budget for the Shuswap and Salmon Rivers in southern interior British Colombia Ludwig, Megan


Phosphorous (P) is a limiting nutrient in most freshwater systems, meaning growth rates of organisms are directly related to the amount available, and when in surplus, it can lead to excess plant and algae growth known as eutrophication (Dupas et al. 2015). Eutrophication can reduce oxygen levels in water and can potentially be harmful to human and animal health (Wolf and Klaiber 2017). Excess algae growth was reported in Shuswap and Mara Lakes in Southern Interior British Columbia and was said to be due to excess P from two rivers of concern; the Shuswap and Salmon Rivers (TriStar 2014). The aim of this study was to quantify the amount of total P (TP) and total dissolved P (TDP) entering these lakes from the Shuswap and Salmon Rivers. I sampled surface water and groundwater and used three hydrologic modeling techniques to quantify the TP and TDP flux from three individual sources; incremental flow sub-watersheds (IFSW, ungauged portions of the watersheds), tributary watersheds, and upper reaches. The techniques used included extrapolation, run-off coefficients, and geochemical methods. The fluxes of P calculated for all sub-watersheds were regressed with land uses in sub-watersheds to determine TP and TDP export coefficients for forested, urban, and agriculture land uses. The TP and TDP fluxes were greatest from IFSW in both the Shuswap and Salmon River watersheds, which is where the majority of the anthropogenic activities take place. Within the two river watersheds, the anthropogenic land uses (urban and agriculture) were estimated to contribute 7-66 times more TP and TDP than the undisturbed forest, depending on the technique used to estimate discharge. Knowledge of these inputs can be used to inform management practices to decrease future P loadings into the lakes system, thus reducing eutrophication risk.

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