No description available.

Forest harvesting is blamed for a perceived increase in the flashiness and turbidity of the Cascapedia River's water. This has raised questions over the source of the sediment (harvest parcels, roads, or stream banks) and its potential impact on the sedimentology of the river. The objectives of this research are twofold. The first is to ascertain if harvesting operations are associated to a widening of low-order tributaries, creating a source of sediment. The second is to determine if variations in the sedimentology along four segments of the Cascapedia can be associated to harvesting operation intensity. Firstly, analysis of stream width in low-order tributaries shows that, once the variations associated with basin area and D50 are removed and within the range of harvesting in our dataset, there appears to be a 25% increase in width associated with the harvesting activities of the last five years, as well as with road density, both in a 60 m stream buffer for a number of the sampled streams. Secondly, the models relating harvesting intensity and changes in sedimentology are sensitive to a few sites or contrary to theory. Future studies should determine the underlying hydrological processes responsible for stream enlargement and the process of sediment deposition.

The objective of this study was to apply the WEND model, a nutrient mass balance model, to the Castor watershed in southern Quebec to evaluate phosphorus movement, storage and export over time. The WEND model was customized to run on a field-scale and then individually applied to 266 fields on the watershed for a 30-year simulation period. Field-specific information for the period of 1997-1999, was used as basic inputs to the model. Climatic information was obtained from local sources. The additional information required to run the model was derived from the literature. Model outputs were analysed at three different levels: (i) the overall watershed impacts, (ii) by cropping system, and (iii) for field management practices presenting a high risk of P losses. Specific outputs examined were: soil test Mehlich-III P, soil P saturation with aluminium, RUSLE soil loss potential and TP export. / The model was used to examine the impacts of crop rotations, fertilizer application and tillage management on TP export. For the Castor watershed, the soil test P increased at a mean rate of 3.71 kg Mehlich-III P ha -1 yr-1, equivalent to a mean input of about 32 kg P2O5 ha-1 yr-1 in excess of plant requirements, assuming current field management practices remain constant. / If TP export is considered the most important parameter in terms of P contamination, crop rotations are a good alternative to continuous corn monocropping under which losses could reach as high as 3.36 kg TP ha-1 yr -1. Crop rotations were shown to be an important management practice that should be more carefully examined when establishing field management practices. Just one year of grassland within a rotation can greatly improve the overall environmental health of a watershed. The management of P inputs is also an important target for improvement, as fertiliser inputs often surpassed plant requirements by two- or three-fold.

“What I have tried to do in this and in all my writing on the early days of this country is what the artist does when he paints a sketch of a Canadian scene or a Canadian person. I have tried to select something that is beautiful or significant or interesting or essential to an understanding of ourselves. I have tried to tell the stories of personalities, men and women who have by their human qualities, aspirations, and activities, given substance to our history, whose loves and hates and fears and achievements have been woven into the very fabric of our Canadian consciousness. I have tried to say, as the painter says, ‘here is something I think you would like to know,’ ‘here is something that has significance’ or ‘here is something that may evoke your love or pride or indignation I as the case may be.” (IO:x) This, in very simple terms, has been my aim here - to paint a picture, or rather a series of pictures of the North Shore, past and present, from the viewpoint of the human geographer. I make no claim to be a historian, nor to have encompassed the full range of material available. Rather, I have selected from the accounts of yesteryear certain aspects which have an attraction for me personally, in the hope that these might also be of interest to others. In brief, I have attempted to write an academic treatise which will yet prove acceptable to the ‘reading public.‘ [...] / fr

No description available.

This study is, primarily, a presentation of a "re-exploration" of the physiography and vegetation of a large portion of Northern Ontario. At the same time, it serves as an illustration of a method of multiple survey through the use of aerial photographs.

The goal of this thesis was to examine the sources and ecological behaviour of genotoxic organics in the St. Lawrence river system. A rapid and effective version of the SOS Chromotest was developed to accomplish the task of genotoxicity assessment. The method, validated with standard reference materials, is particularly well suited to complex environmental extracts. The endpoint investigated throughout the thesis, SOS genotoxicity, is empirically related to more familiar endpoints such as mutagenicity and carcinogenicity. Analyses of literature data confirmed correlations between SOS genotoxicity and both Ames/Salmonella mutagenicity and animal carcinogenicity. Analyses of industrial and municipal wastewaters revealed that organic and inorganic chemical production facilities, metal refining and founding facilities and petroleum refineries release high potency wastes. Loading values indicate that low potency sources (e.g. municipal wastewater and pulp & paper facilities) often have exceptionally high loadings. A substantial portion (2.3-99.8%) of industrial genotoxins are associated with suspended particulates. Sorption partition efficients (K$ sb{ rm d-genotox}$) indicate that municipal wastewater and pulp & paper facilities release particularly soluble genotoxins. Extracts of suspended particulate matter collected near industrial discharges are direct-acting. Bottom sediment extracts are less potent and usually require S9 metabolic activation. Genotoxicity of both bottom sediment and suspended particulates are empirically related to the genotoxicity of regional industrial emissions. Direct-acting substances in the water column appear to be less stable and may be converted to more stable pro-genotoxic substances present in the bottom sediments. A mass balance of genotoxicity for St. Lawrence surface waters revealed that domestic, rather than industrial sources make the largest contribution to observed genotoxicity. The importance of domestic wastes was confirmed

The goal of this work is to contribute to the understanding eutrophication in large rivers with a detailed study of the Grand River, an impacted river in highly agricultural and urbanized Southern Ontario. It focuses on the role of nitrogen (N) and phosphorus (P) in the distribution and abundance of benthic submersed macrophytes, which are important actors in river N and P cycles. Chapter 1 uses data from the Provincial Water Quality Monitoring Network to examine seasonal, long term and spatial patterns in total P (TP), soluble reactive P (SRP), nitrate and nitrite (NO3- + NO2-) and ammonium (NH4+). The monitoring of many sites in the Grand River began in 1965, and I examine data from the period from 1965 to 2009. The monitoring program began prior to the Canada-USA ban on the use of phosphate in detergents, which came into effect in 1973, and also before major improvements to municipal waste water treatment. The phosphate ban is analyzed as an example of a whole-system nutrient manipulation experiment, and the seasonal and long term response of the river system, from headwaters to mouth, is examined. TP and SRP declined over the monitoring period, with the greatest response found in TP, which declined by 120 µg/l/y immediately downstream of the of the watershed’s largest treatment plant in the years 1972-1975. Thereafter, TP and SRP continued to decline over most of the lower river, with rates of decline in nutrient concentration accelerating with distance from the wastewater treatment plants (WWTPs). NO3+NO2 increased during the monitoring period in the upper portion of the river with the highest increase of 158 µg-N/l/y observed in the 10 year period of 1975-1985. It did not change in response to WWTP upgrades that occurred in the early 1970s. WWTPs were a clear source of TP, SRP and NH4+ to the river system, but not NO3 +NO2 , and the continual increase in NO3 +NO2 was due to increases in diffuse sources. The seasonal and spatial data suggest that non-point sources of N and P dominate in the Grand River watershed. However, the largest WWTP in the region at Kitchener is an important source of nutrients, and was an especially large source of P prior to changes in detergent standards and wastewater treatment. The submersed macrophyte biomass in the Grand River was examined as a function of proximity to WWTPs in chapter 2. Spatial surveys were conducted in 2007 and 2009 on three reaches of approximately 10 km in length each, with two reaches having an upstream and downstream section, separated by a WWTP. Macrophyte patches were mapped, biomass was estimated, and plants were analyzed for N and P. Tissue N and P were compared to published thresholds for evidence of nutrient limitation. Biomass was greater downstream of the WWTPs than upstream in both reaches and both years, indicating that nutrient loading leads to increased biomass downstream, evidence that even in a heavily agricultural watershed, point sources have a demonstrable effect on macrophyte biomass. Depth was important in explaining some of the variation, while river width and orientation were not important. Even though macrophyte biomass was elevated downstream of the WWTPs, there was no strong evidence of N or P limitation upstream based on tissue concentrations and a laboratory determined critical nutrient threshold, and I hypothesize that the nutrient limitation affecting biomass occurs earlier in the growing season, before peak biomass. This suggests that the eutrophication process in rivers is distinct from that in lakes, and future work should view eutrophication in rivers in the context of seasonal succession. Drivers of seasonal and inter-annual variability in submersed macrophyte biomass were examined in chapter 3 with a multi-year, reach-scale spatial survey of three reaches near the WWTPs of Waterloo and Kitchener. Biomass differed among reaches, years and sites, and showed distinct seasonal patterns. The reach downstream of the WWTPs had the highest biomass, and peak biomass came soonest in the growing season, while the upstream reach had the smallest and latest peak biomass. Weather was significantly correlated to both the quantity and the time of the peak biomass, with higher temperatures associated with larger and earlier peak biomass and precipitation and higher flow associated with later and lower peak biomass. Therefore, the eutrophication response in rivers can depend on weather, and these drivers of variation should be accounted for when forecasting responses to future changes in nutrient loading. The effect of nitrogen discharged by WWTPs on the riverine submersed macrophyte community, and the suitability of macrophyte tissues as indicators of point source impact, were quantified in chapter 4 using δ15N as a tracer of WWTP effluent impact. Macrophytes and water for NO3- and NH4+ concentration and isotope analysis was collected by canoe along two 10 km reaches of the river, up and downstream of two WWTPs. Macrophytes incorporated effluent nitrogen into their tissues downstream of the WWTPs, using effluent NH4+ rather than NO3-. Impacts of the effluent on macrophytes can be traced as far as 10 km downstream, while daytime chemical evidence of the plume disappeared much sooner. The δ15N-NH4+ value rapidly increased downstream of the WWTP, changing in one instance from +13‰ to +31‰ over 1 km, with macrophyte δ15N values changing from +6‰ to +24‰ over 5 km, while δ15N- NO3- values showed no such change. These data lead to the conclusion that riverine submersed macrophytes record the influence of WWTP effluent, specifically effluent NH4+, but that using two end-member mixing models to determine N sources would be inappropriate in such dynamic environments. Nitrogen cycle processes such as nitrification and denitrification are influenced by dissolved oxygen (DO) and rapid transformations occur in environments with strong DO gradients. Because development of dense macrophyte beds in eutrophic rivers has the potential to greatly alter daily oxygen cycling, producing strong redox potentials, macrophytes could influence microbial nitrogen cycling. In Chapter 5, nitrogen uptake by macrophytes using a 15N-NH4+ tracer and N2O production was investigated using in situ chamber incubations upstream and downstream of a WWTP. NH4+ uptake occurred in chambers, while measurable net N2O production occurred in some chambers only. Neither N2O production nor NH4+ uptake differed between chambers with and without PO43- addition, nor did they differ between light and dark treatments. NH4+ uptake was higher at the upstream site, indicating that above the WWTP there was NH4+ demand in the macrophyte community. NH4+ uptake was a hyperbolic function of mean chamber NH4+ concentration. Turnover time for the macrophyte N pool due to NH4+ uptake was as long as 47 d, while the turnover of the dissolved NH4+ pool was as rapid as 14 h. Because net uptake was a small fraction of gross uptake, calculated release rates were almost as high as uptake rates, again indicating rapid NH4+ cycling. Eutrophication of rivers has elements that make it a process distinct from that in lakes. I showed that, in the Grand River, N and P were both high in concentration throughout the river, with a distinct increase downstream of the largest WWTPs in the watershed. The biomass of benthic submersed macrophytes was elevated below the WWTPs, but there was no evidence of nutrient limitation upstream during the time of peak biomass. Macrophyte biomass development followed a seasonal pattern, but was also influenced by seasonal temperature and precipitation patterns. Thus, the riverine eutrophication process has an important seasonal component, much as the plants themselves do, peaking in the summer and senescing in the fall. As part of the eutrophication response, macrophytes altered the chemical cycles of nutrients that fuel their growth. Though changes in benthic biomass themselves are part of riverine eutrophication, this thesis provides evidence that changes in macrophyte biomass produces chemical and ecological changes that are characteristic of increased trophic conditions.

“What I have tried to do in this and in all my writing on the early days of this country is what the artist does when he paints a sketch of a Canadian scene or a Canadian person. I have tried to select something that is beautiful or significant or interesting or essential to an understanding of ourselves. I have tried to tell the stories of personalities, men and women who have by their human qualities, aspirations, and activities, given substance to our history, whose loves and hates and fears and achievements have been woven into the very fabric of our Canadian consciousness. I have tried to say, as the painter says, ‘here is something I think you would like to know,’ ‘here is something that has significance’ or ‘here is something that may evoke your love or pride or indignation I as the case may be.” (IO:x) This, in very simple terms, has been my aim here - to paint a picture, or rather a series of pictures of the North Shore, past and present, from the viewpoint of the human geographer. I make no claim to be a historian, nor to have encompassed the full range of material available. Rather, I have selected from the accounts of yesteryear certain aspects which have an attraction for me personally, in the hope that these might also be of interest to others. In brief, I have attempted to write an academic treatise which will yet prove acceptable to the ‘reading public.‘ [...] / fr

Hydraulic and morpho-sedimentary differences between pools and riffles have always intrigued fluvial geomorphologists. Surprisingly, earlier explanations of pool-riffle morpho-sedimentology dynamic focus too exclusively on hydraulic patterns and neglect analysis of sediment transport. Understanding the mechanisms governing pool-riffle morpho-sedimentary dynamics, such as the sediment transport patterns represent a big challenge in fluvial geomorphology, considering the stochastic nature of bedload transport in gravel-bed rivers. The main objective of this thesis is to understand the two-dimensional relationship between hydraulic patterns, sediment transport patterns and morpho-sedimentary changes in pool-riffle sequences and to use these insights to understand how pool-riffle sequences maintain their form over time. / This thesis is organized into four chapters. These chapters analyze hydraulic, sediment transport and morpho-sedimentary measurements collected on a riffle-pool-riffle sequence of the Des Coeurs river during seven controlled experimental floods. Chapter 2 tests the velocity reversal hypothesis (Keller, 1971), with results demonstrating that no velocity reversal was observed in the field, for peak flow up to 123% of the bankfull discharge. Chapter 3 demonstrates the existence of a bedload transport reversal: below 60% of bankfull discharge, sediment transport on the riffle exceeds transport in the pool; as discharge increased, more sediment was exported from the pool than imported, thereby maintaining the pool. Chapter 4 demonstrates that the bedload transport reversal is caused by the spatial heterogeneity of the sediment transport patterns (sediment supply, particle displacements and sediment sorting), which underlies the importance of developing two-dimensional bedload transport formulae. Chapter 5 tests the two-dimensional applicability of well-known bedload transport formulae developed in a one-dimensional environment. None of the formulae could be applied with accuracy in a two-dimensional environment. However, site-specific calibration considerably improves bedload transport rate and grain-size distribution prediction. / This thesis improves the understanding of the morpho-sedimentary dynamics of pool-riffle sequence; it argues that a purely hydraulic view of pool-riffle sequence is insufficient to understand their stability. It explains pool-riffle maintenance as a result of a bedload transport reversal caused by the spatial heterogeneity of the sediment transport patterns, and raises the importance of acquiring two-dimensional sediment transport data to improve two-dimensional bedload transport formulae.