Winter, Jennifer Gabriele2006-07-282006-07-2819991999http://hdl.handle.net/10012/419Since eutrophication became a widely used term in the late 1940s, much research effort has been directed towards understanding eutrophication in lakes. Comparatively little, however, is known about the eutrophication process in rivers despite large increases in the concentrations of nitrogen and phosphorus measured in rivers worldwide. Consequently, there is a real need to address the problem of increased nutrient loads delivered to lotic systems. To investigate nitrogen and phosphorus loading to streams in the Grand River watershed, empirical models were constructed to predict diffuse sources of these nutrients and assessments were made of epilithic diatom and macroinvertebrate communities to determine relationships with water quality and land use. The streams selected for investigation were chosen based on land use in their watersheds. Theupper half of the Laurel Creek watershed and the Carroll Creek watershed are rural and land use is mainly agricultural, whereas the lower half of the Laurel Creek watershed is under urban development. An export coefficient modeling approach was used to assess the influence of land use on phosphorus and nitrogen loading to Laurel Creek and Carroll Creek. Models were constructed for the 1995-1996 water year and calibrated with a +3% of observed concentrations. Runoff from urban areas contributed most to the loading of phosphorus to Laurel Creek and atmospheric deposition was an important source of nitrogen. In the Carroll Creek watershed, runoff from non-row crops contributed most to both nitrogen and phosphorus loading. When the Laurel Creek models were assessed by running them for the 1977-1978 water year, using water quality and land use data collected independently, predicted concentrations were within +7% of observed concentrations. The Carroll Creek phosphorous model was developed using the export coefficients chosen for Laurel Creek, with slight modifications, and it is likely that these coefficients will perform well in other areas of the Grand River watershed, with similar catchment characteristics and land use. This requires confirmation by testing the coefficients in other subcatchments. Different export coefficients were used in two nitrogen models, however, because the measured nitrogen concentration in Carroll Creek was much higher than in Laurel Creek. It is thus clear that further study is required to investigate the use of export coefficient modeling to model nitrogen inputs in this area. The taxonomic structure of epilithic diatom and macroinvertebrate communities in Laurel Creek and Carroll Creek was related to both water chemistry and watershed land use. These communities can thus be used as indicators of stream water quality and surrounding land use. Although land use and water chemistry predictors were independently related to diatoms and macroinvertebrates, a close link was observed between land use, water chemistry and the biota. Relationships between epilithic diatoms and total nitrogen and total phosphorus concentrations were sufficiently strong to develop weighted-averaging regression and calibration models for inferring steam water concentrations of these nutrients. The models were accurate within +2.4ug/1 for phosphorus and +2.0mg/l for nitrogen. The models were found to be reliable and performed better than other nutrient diatom-inference models. Epilithic diatoms can clearly be used to monitor total nitrogen and total phosphorus in these streams. Overall, there is potential for the results of export coefficient modeling and bioassessment to be related. Nutrient concentrations predicted empirically could thus be used further to predict impacts on the strucutre and functioning of stream communities. Furthermore, these relationships could be used to assess the impact of proposed developmet, changes in land use or nutrient control strategies, on stream health as determined by the biota. These approaches have utility for evaluating eutrophication, in particular nonpoint sources of nutrients, in temperate watersheds.application/pdf11970099 bytesapplication/pdfenCopyright: 1999, Winter, Jennifer Gabriele. All rights reserved.Harvested from Collections CanadaDoctoral Thesis