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Analysis of the effects of land use and soils on the water quality of the Salmon River Watershed, Langley Beale, Roxanna Louise

Abstract

The primary objective of this study was to evaluate quantitatively the effects of a mixture of agricultural and non-agricultural land use practices on the chemical characteristics of the Salmon River, near Fort Langley, B.C. Present land use and geomorphic unit maps were used to determine appropriate stream sampling sites which would give an indication of the combined and separate effects of land use and geologic materials on water quality. Chemical characteristics of the Salmon River and its tributaries were monitored over a 10 month period from May 1974 until April 1975. Eighteen chemical variables were analyzed in the laboratory using Standard Methods and 5 were monitored in the field. The in situ parameters included pH, temperature, oxidation-reduction potential, specific conductance and dissolved oxygen levels. Also monitored were 7 trace metals, Cr, Cu, Fe, Mn, Ni, Pb and Zn. Atmospheric precipitation collectors were installed at the end of June 1974 and precipitation samples collected monthly from July 1974 until April 1975. Eighteen separate chemical variables were monitored at these sites using standard methods. Stream bed sediment grab samples were taken in May and again in July 1974. These_ samples were analyzed for total elemental composition as well as total nitrogen, total carbon, total sulfur, total cation exchange capacity, exchangeable cations (Ca, Mg, Na, K) and pH. The major geologic materials in the watershed were sampled in 6 sites located in undisturbed and cultivated areas on marine, glacial outwash, and alluvial materials. The monitoring of some selected chemical characteristics of the Salmon River revealed in general the mean values of pH, specific conductivity, temperature, total alkalinity, total HC03 alkalinity, total hardness (CaCO₃ equivalent), total dissolved solids, total Kjeldahl N, organic C, NO₃ -N, CI, Na, and K were consistently higher at low streamflows than at high (>750cfs) streamflows. Oxidation reduction potential and dissolved oxygen mean values were consistently higher at high flows than at low flows. The other variables measured remained relatively constant on average across all levels of streamflow. There was, however, considerable variation at specific point samples. Data derived from collection of atmospheric precipitation indicated a significant input of many chemical factors to the watershed. Bed sediment and soils chemical characteristics give a general indication of the amounts and distribution of the various chemicals potentially available for contribution to stream waters. Analysis of the results obtained in comparison with water quality standard acceptable levels revealed water quality problems with pH, temperature, phosphorus, iron, copper, and manganese. Significant statistical correlation exists between water quality variables and glaciomarine, marine and beach overlying marine or glaciomarine materials; glacial outwash materials; agricultural field crops; low density residential areas; and schools. In order to identify specific point and non-point sources more detailed information is needed on groundwater characteristics and the streamflow characteristics of tributary streams. Some general management alternatives are recommended bearing in mind that each site must be evaluated on its own merits and specific suggestions made on-site.

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