Research and Engagement for New Water Allocation for Irrigation from Duncairn Reservoir
About Duncairn Reservoir
Duncairn Reservoir is located on Swift Current Creek, 30 kilometers southwest of Swift Current. Duncairn Dam was constructed, and Reid Lake was created in 1942 by the Prairie Farm Rehabilitation Administration (PFRA).
The reservoir was formed to supply the Rush Lake, Waldeck, and Herbert irrigation projects. It has also become a supply reservoir for the City of Swift Current and irrigation close to the reservoir and along Swift Current Creek. Water released from the reservoir maintains the flow in the creek for stock watering, domestic use, and maintains fish habitat. The reservoir has also seen more recreational use, especially boating and fishing.
The reservoir is supplied predominantly from runoff from the east slope of Cypress Hills.
The dam is operated to provide flood control to downstream residents, including the City of Swift Current.
Expanding Irrigation in the Southwest
In 2023, the Water Security Agency (WSA) conducted a water availability assessment of the Duncairn Reservoir. The assessment identified additional water available for irrigation development, achievable without altering the current operating guidelines. Following this assessment, WSA continues work to determine how much water can be allocated for food production in one of the province’s driest areas.
Current Irrigation from Duncairn Reservoir
The reservoir currently supplies 30,000 acre-feet for licensed water use, with 16,000 acre-feet allocated for existing irrigation. An additional 4,000 acre-feet would represent a 13 per cent increase in total usage.
The reservoir’s operating guidelines set an irrigation cut-off level at 803.72m. When the reservoir reaches this level, all irrigation at the reservoir and downstream releases for irrigation must stop. This maintains roughly half the reservoir’s capacity for municipal use and to support the lake’s fisheries.
Historically, flood irrigation has been the primary method used in the region. Producers are adopting more efficient practices, including the use of center pivots.
There has been no new water allocation for irrigation development in the Swift Current Basin since 1981. Irrigation demand around the Duncairn Reservoir has been high for several decades. Over that time, WSA has received interest in developing more than 14,000 acres.
The infographic below illustrates effects of withdrawing 4000 acre-feet at once from the top of the Duncairn Reservoir. This reservoir has a capacity of 85,300 acre-feet and an irrigation cutoff level is set to ensure about half this capacity remains to supply municipal water use and reduce negative impacts to wildlife habitat.
Figure 1: Effects of New Allocation
Disclaimer: This figure does not represent the actual shape of the reservoir and is intended to illustrate capacity in terms of volume only.
Real-Time Hydrometric Data
WSA maintains a network of hydrometric stations across Saskatchewan, which collect lake levels in real-time.
Click here for real-time data for Reid Lake. The monitoring station is located at the dam structure on the north end of the reservoir.
Water Modelling & Hydrology Study
WSA used updated modeling technology (Water Resource Management Model) and 98 years of flow data, including both drought and excess precipitation periods. The model operates under the assumption of full utilization of all existing licensed allocations within the Swift Current-Rush Lake System.
In Saskatchewan, irrigation Water Rights Licences typically assume a 70% availability rate. This means that irrigators can expect to receive their full water allocation in 7 out of every 10 years. However, during 3 out of 10 years, they should anticipate receiving less than the full allocation. In contrast, municipalities and industrial users are assured their full allocation with at 100% availability.
When the basin was frozen in 1981, this modeling technology did not exist, and the period of flow data was not as comprehensive.
The results indicate an additional 4,000 acre-feet for expanded irrigation maintains current license parameters.
The model produced conservative results by simulating the full utilization of all current licenses, ensuring future demands can be met and safeguarding for times of water shortages. In practice, licensed users rarely utilize their entire allocation. However, it is crucial to consider the maximum potential usage to ensure that any new allocations do not adversely affect the other needs dependent on this water supply.
WSA also undertook a hydrology study to assess the feasibility of allocating downstream from the Duncairn Reservoir. The study found that partial allocations from the Swift Current Canal and Highfield Reservoir are achievable while staying within the parameters of the original study that looked at diverting water directly from the reservoir.
Reservoir levels will see a slight decrease in average levels and will fluctuate within the operating range, as they have historically.
Graph 1 displays the simulated effects of levels at Duncairn Reservoir. The top blue dashed line shows the full supply level. The bottom grey dashed line displays the conservation drawdown limit, also known as the irrigation cut-off level. The black line illustrates the simulated elevations of the reservoir, assuming that all the current licensed allocation is fully utilized. The red line represents the change in lake levels if an additional 4000 acre-feet were allocated. WSA’s historical flow data allows for a modeled simulation predating the construction of the dam.
Graph 1: Impact of additional 4000-acre feet on Duncairn Reservoir Levels
Scoring Matrix
WSA and the Ministry of Agriculture are developing a scoring matrix to prioritize applications. This matrix considers factors such as soil suitability, location and water source. The scoring process ensures that any released allocation is prioritized for locations where water efficiency in the system can be maximized. An allocation cap will be established, limiting the maximum amount of water a single entity can apply for. This approach is designed to ensure that a greater number of producers can benefit from irrigation development in the region.
WSA will publish the criteria of the scoring matrix and the details of the allocation cap before accepting any new applications for water rights licenses to guarantee a fair and transparent application process.
Stakeholder Engagement
Since the study was completed, WSA hosted 12 stakeholder engagement sessions about the proposed expansion. WSA recognized the need for a comprehensive engagement process to better integrate stakeholder input into the project.
Responding to stakeholder feedback, WSA undertook additional work since these engagement sessions, including:
- Completing a Fishery Assessment Duncairn Reservoir.
- Completing hydrology scenarios that verify the identified allocation can be partially allocated downstream of Duncairn Reservoir while maintaining the same parameters of the original study.
- Clarified that a 12-inch allocation will initially be provided, and flexible allocation will be offered based on producer demand.
In addition, WSA is currently working on:
- A reservoir elevation study using Bathymetry and LiDAR.
- Studying the effects of a partial release of the identified 4,000 acre-feet of allocation.
- Implementing an intensive water use monitoring approach for current irrigators, starting in 2024.
For more information, send your inquiries to sccbasinirrigation@wsask.ca or phone 866.727.5420.
Fish Habitat Assessment
Duncairn is a popular fishing spot, with high demand for stocking and interest about water levels. WSA’s assessment considered impacts to the fish population, including Walleye, Northern Pike and Yellow Perch.
Practical solutions have been identified that will enable us to simultaneously manage risks to fish habitat and expand irrigation. Some options being considered include creating a comprehensive reservoir operating plan and proactively engage with Fisheries and Oceans Canada to assess and mitigate any potential risks on a frequent basis. These actions will balance the sustainability of the environment and the growth of our economy and increasing local food production.
For more information, send your inquiries to sccbasinirrigation@wsask.ca or phone 866.727.5420.