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2. Introduction

Natural ecosystems provide human beings with many services ranging from aesthetic enjoyment to water, food, and timber (Bieling, 2014). Human lives are enriched with such goods and services, which contributes to security, economies, and well-being in many ways. Introducing changes to natural ecosystems through human activities can reduce delivery of those services. It can undermine the ecosystem to continue providing the goods and services necessary for the well-being of humans in terms of culture and livelihoods. When ecosystems are altered, the production of fish and wildlife can be affected through the loss or destruction of their habitats. The availability and quality of water are also affected through withdrawal, diversion, and pollution (Bieling, 2014). Altering complex ecosystems like wetlands that provide many goods and services can lead to negative impacts on human livelihoods that rely on these ecosystems.

Many large freshwater deltas in the Canadian north lie downstream from hydropower dams that have altered the hydrology of the deltas for over 50 years now (Beltos, 2014 and Sagin et al., 2015 ). Due to the significance of the natural flow of water for biological processes, the alteration of these processes has significant implications for the ecosystems in these downstream deltas. Most important is the fact that most of the inhabitants of these inland deltas are Indigenous peoples. Hence, the changes in the biophysical structure of these ecosystems have negative consequences for the communities living along the delta regions (Abu 2018) . The Saskatchewan River Delta (SRD) is one complex inland delta located in the central lowlands of Canada.

The Saskatchewan River is a major continental river and the source of drinking water for most of the population of Saskatchewan. It covers five different ecoregions. The EB Campbell Dam was built on the Saskatchewan River in the year 1962. Downstream of this dam the river becomes the Saskatchewan River Delta. This delta is the largest fresh water delta in North America.

Many alluvial water bodies are specified as balanced systems, which means that the geomorphology of the water body neither aggrades nor degrades. Therefore, construction of dams disrupts the natural processes of the river thus altering the geomorphology of the channel and resulting in forced modification in downstream parts of the river. There are three reservoirs in the Saskatchewan River that have altered sediment fluxes (Ashmore and Day 1988) and interrupted sediment supply to the delta. The first reservoir is Diefenbaker Lake which is 225 km long and is formed by the Gardiner and Qu’Appelle Dams. The second is Codette Lake which is upstream of Nipawin and the Francois Finlay Dam, and the third reservoir is Tobin Lake, formed by E.B. Campbell Dam which is east of Nipawin (Vandall et al., 2012). Together, these dams are believed to trap sediment that once reached the delta (Ashmore and Day 1988).

The Saskatchewan River Delta has been significantly modified by the construction of dams upstream. The flow regime of the delta has been particularly modified. It was a system that once produced summer floods, but today, it has truncated levels in the spring and summer season (Sagin et al., 2015), and its levels are elevated in unnatural ways during the winter (Abu 2018). EB Campbell Dam also modifies the daily flows into the delta, and this implies that there is no longer natural flow occurring in the delta, which can in part explain the impact caused (Waldram 1988; Waldram 1989).

2.1 The Saskatchewan River Delta Siltation Deficiency

Apart from changes in hydrology, the Cumberland House communities in the delta have also identified the lack of sediments as a critical threat to the long term productivity and sustainability of their ecosystem. Sediment transport to the delta is interrupted by upstream dams (Ashmore and Day 1988).This has resulted in the deepening and widening of the river channel below EB Campbell Dam (Smith et al., 2016) . There is now less frequent connection to many of the wetlands and productive side channels to the main river during flooding. The Old Channel of the Saskatchewan River is of particular concern as it now only receives water at highest flows. The channel was at one time a Goldeye spawning ground, and it acts as the primary source of water for Cumberland Marshes which is a nationally designated important Bird Area and a onetime productive wetland complex for muskrats that is jointly managed by Ducks Unlimited and the N90 (Delta) Trappers Association. However, both the groups have a fear for long-term water supply viability.

Together these changes mean lowered capacities of water reaching the downstream of the delta especially during the summer months. Besides that, the other significant change is the heavy flows of eroded soils into Cumberland Lake. Generally, this sedimentation has over time left some areas dry with low access of waters as other areas are left flooded, the imbalance has been caused by the excess sedimentation which in turn affects the way of life of those depending upon the waters. Also the dry areas become less productive due to the upper fertile soils being carried away. Cumberland Marshes is a good example of this effect of sedimentation. According to the future projections, it suggests that the channel erosion accelerated process caused by sediment starvation will eventually lead to the widening of a single channel’s way through a former delta (Smith et al., 2016), leading to the alteration to the delta ecosystem.

2.2 Aim of Study

The study seeks to investigate the sediment loss due to construction of EB Campbell dam in upstream and downstream of the Saskatchewan River.

2.3 Specific Objective

In line with the above mentioned aim, the study seeks to achieve the following objectives:

  1. Determine seasonal profiles of sediment load in the Saskatchewan River Delta using a record of 15-minute turbidity readings in 2014 and 2017.

  2. Calculate and interpret the sediment loss due to construction of EB Campbell Dam using data from above and below the dam in 2014.

  3. Compare spot measurements of total suspended solids with continuously recorded turbidity data.

  4. Analyse multi-decadal change in concentration of sediments in the Saskatchewan River immediately below E.B. Campbell Dam by comparing the sediment load in the 1980s (Ashmore and Day 1988) with measurements from 2014.