Soil erosion and fluxes of sediment within landscapes of the Canadian Prairies

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Zarrinabadi, Ehsan
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Maintaining the future sustainability of agriculture and ensuring soil security is of primary concern across Canada. Understanding the state of soil erosion and determining the vulnerable areas are essential measures in combatting future soil erosion and avoiding soil degradation. Therefore, the general goal of this thesis was to quantify soil erosion rates and develop an improved understanding of erosion processes within the Canadian Prairies. To fulfill the aim of the research project, typical agricultural and native prairie landscapes of the region were studied within three watersheds including the Red River Valley and the Broughton’s Creek watershed in Manitoba, and the Bigstone Creek watershed in Alberta. Initially, passive uni-directional wind erosion sediment samplers were employed to assess wind-eroded soil movement in agricultural lands of the Red River Valley. Cesium-137 (137Cs) measurements were conducted to quantify total soil loss and deposition rates within the wetland landscapes in the Broughton’s Creek and Bigstone Creek watersheds. In addition, soil and sediment properties were characterized to understand tillage-, water- and wind-induced sediment transport dynamics and distinguish between eroded and depositional zones. Landform classification maps of the studied wetland catchments were also created to assist developing sediment budgets of soil loss and accumulation, and quantify sediment flux rates from agricultural fields to wetland environments. Furthermore, soil erosion models were used to characterize spatial patterns of soil loss by tillage, water, and wind erosion and assess relative contribution of these processes towards total soil erosion. This study found that: i) Measured soil loss and sedimentation caused by wind erosion are very small in the Red River Valley. Moreover, abrasion of crops by wind-transported sediment was not observed in this study; ii) Using the measurements of 137Cs, average annual soil losses in cultivated fields were estimated at about 1.2 kg m-2 yr-1 and 0.9 kg m-2 yr-1 in Manitoba and Alberta, respectively, with approximately 70% of cultivated field being classified as eroded zone in both provinces; and iii) On the knoll of hummocky landscapes, tillage erosion dominates the pattern of total soil erosion and the effects of water erosion and wind erosion are minor.
Soil, Erosion, Sedimentation, Modelling, 137Cs