| Summary: | It is understood that intensive agricultural activities can adversely impact surface-water quality
resulting in risks to ecosystem and human health. What is less clear are the links between agricultural
land use (type and intensity), environmental conditions and surface-water quality at varying spatial and
temporal scales. There are also challenges with detecting agricultural influence on surface waters in a
timely and accurate manner. This is of concern in the Lower Fraser Valley as this region has experienced
significant agricultural intensification and population growth in recent years. This study examined
influences of agricultural land use, climate and hydrology on water quality in three watersheds to identify
land-use practices and environmental conditions producing the greatest risk of contamination. This was
accomplished through an intensive surface-water sampling program to assess nutrient and bacterial
dynamics in the Hatzic, Elk Creek and Salmon watersheds, combined with hydrometric and
meteorological monitoring from 2002-2005. Spectroscopic techniques (absorption and fluorescence) were
also evaluated as tools to detect and quantify agricultural influence.
Consistent correlations between agricultural land use and contamination (nutrient and bacterial
concentrations) were observed across all watersheds. Seasonal trends were consistent, with nutrient
concentrations peaking during winter months (illustrating strong hydrological control over mobilisation and
transport) and bacterial concentrations peaking during summer months (illustrating the supply-constrained
nature of bacterial stores). Contaminant concentrations correlated with measures of
agricultural intensity. Livestock operations represented the highest-risk land use for contamination, with
even small operations producing observable impacts on water quality. Temporally, the greatest risk of
bacterial contamination was associated with storm events preceded by periods of dry weather during
summer months.
Absorption and fluorescence were effective measures of agricultural influence as they quantify
and characterize agriculturally-derived dissolved organic matter. Advantages of these techniques include
rapid sample processing, minimal requirements for sample treatment and volume. Further, they provide
qualitative information regarding water quality, water source and land use that is not available from
nutrient or bacterial analyses alone. These techniques do not accurately detect contaminants in areas
with minimal agricultural influence and therefore are limited as direct indicators of bacterial or nutrient
concentrations. === Science, Faculty of === Resources, Environment and Sustainability (IRES), Institute for === Graduate
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