Although water covers 70% of the earth's surface, less than 1% of it is freshwater that can be used for drinking. Even in Canada, where there is an abundance of freshwater in groundwater and in rivers and lakes, there are many indigenous communities that lack a sustainable source of drinking water. Such is the case for the Six Nations of the Grand River, the largest indigenous Reserve in Canada, located within an hour drive from major urban centers in southern Ontario and where less than 9% of the residents have access to safe, treated potable water. The major tributaries that drain the Six Nations reserve are part of the McKenzie Creek Watershed, which has been characterized as having the highest loading of sediments and nutrients to the lower Grand River, which eventually drains into the eastern basin of Lake Erie. This research project was initiated by the Six Nations community, who wanted an update on the prevalence of fecal contamination in their drinking water sources (wells, cisterns). Secondly, the community wanted to know the ecosystem health status of tributaries flowing through the Six Nations Reserve (McKenzie and Boston Creeks), and to determine if land uses in the watershed were negatively affecting the health of these streams. A study conducted in the summer of 2018 confirmed that 29% of the tap water tested in 75 households were contaminated with E. coli; 40% of the wells and 15% of the cisterns were contaminated and these were distributed throughout the Reserve with no apparent pattern. A study conducted in the summer of 2019 found that the McKenzie Creek was highly polluted with total phosphorus (P), total suspended solids, turbidity and total-ammonia nitrogen (N), while Boston Creek was highly polluted with soluble reactive P and E. coli as well as total-nitrate N. Nitrogen concentrations at 14 stations were highly and significantly related to percentage of agricultural land in catchments. Elevated levels of pollutants have been observed in the two creeks for three decades, indicating that conditions will not improve without remedial actions. / Thesis / Master of Science (MSc)