Water Supply Conditions and Outlook Based on Conditions as of August 1, 2021

Prepared by: Flow Forecasting & Operations Planning - Water Security Agency

Overview operating levels. The remaining lakes in the system are near or close to their targeted summer operating level with the exception Conditions remain dry throughout southern and central of Round Lake, which is expected to remain low throughout the . With the hot and dry July observed across most summer. of the province, soil moisture conditions across the grain belt are generally much drier then normal. Most of southern and central Lake and reservoir levels across much of southern and central Saskatchewan are now experiencing agricultural drought Saskatchewan remain below to well below normal. WSA has conditions that range from severe to extreme. Conditions are experienced an increase in requests to pump water from particularly dry in the area. Southern portions of the alternative sources to replenish dugouts. Churchill River Basin are now also experiencing moderate drought conditions.

As a result of the drier conditions throughout July, flows across most of the Churchill River and Lake Athabasca basins are slowly receding; however, flows remain well above normal primarily due to the wet conditions in 2020. Flows in the north are expected to remain near to above normal for the remainder of the summer.

Inflows to on the remain well below normal for this time of year. The dry conditions across Alberta are expected to continue to have negative impacts to the inflows to Lake Diefenbaker, resulting in continued below normal water levels and outflows throughout the remainder of the summer.

Flows on the North Saskatchewan River remain below normal. Flows on the Saskatchewan River are currently well below normal. Flows are expected to remain well below normal for the remainder of the summer and into the fall.

On the Qu’Appelle River System, all the lakes are experiencing high evaporation loss due to high mean daily temperature. Vegetation growth in the Upper Qu’Appelle channel lowered the release from the Lake Diefenbaker and is causing Buffalo Pound and Last Mountain Lakes remain below their targeted summer

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Spring 2021 Precipitation Summary

Figure 1 shows precipitation accumulations received in July and Figure 2 shows how these amounts compared to normal. Rainfall throughout the month of July was well below normal across the entire province. Rainfall accumulations across the north and the southeast were about 40% of normal. The southwest and most of central Saskatchewan received only 20% of normal accumulations throughout the month. The Saskatoon to Melfort area only received 6 to 12 mm, which is less than 20% of normal.

Figure 1: Accumulated Precipitation July 1 to July 29, 2021

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Figure 2: Percent Normal Precipitation July 1 to July 29, 2021

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Soil Moisture Conditions

Figure 3 shows cropland topsoil moisture conditions as of August 2, 2021. Topsoil moisture conditions range from short to very short across the grain belt. Conditions are particularly dry in the west from Maple Creek up through to the Prince Albert area. The only areas where near adequate topsoil moisture conditions exist is a very small section near the Battle River, just south of Lloydminster, and near Lumsden.

The Canadian Drought Monitor assessment for July 31 is shown in Figure 7. With the dry and hot month of July across most of the rovince, conditions have generally worsened. All the south and central portions of the province are now experiencing drought conditions ranging from severe to extreme. Southern portions of the Churchill River Basin are also now in the moderate drought stage. Conditions are the driest in the Saskatoon area where exceptional drought conditions exist. Conditions that are expected to occur only once in a 50-year period.

Figure 3: Cropland Topsoil Moisture Conditions as of August 2, 2021 (Map courtesy of Saskatchewan Ministry of Agriculture)

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Figure 4: Canadian Drought Monitor – July 31, 2021 (Map courtesy of Agriculture and Agri-Food Canada)

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Long-Range Forecasts

Most long-range forecasts are currently predicting near normal precipitation and above normal temperatures across most of the province between August 1 and October 31, 2021.

Multi-model ensemble maps for precipitation and temperature for this three-month period, which are the average result of seven seasonal weather forecasts, are shown in Figures 5 and 6 respectively. It is important to keep in mind that seasonal weather forecasts are statistically unreliable.

Figure 6: North American Multi-Model Ensemble Temperature Anomaly Outlook for August 1 to October 31 (Map courtesy of the US National Weather Service)

Figure 5: North American Multi-Model Ensemble Precipitation Anomaly Outlook for August 1 to October 31 (Map courtesy of the US National Weather Service)

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Detailed Water Supply Conditions Moosomin, Adams, Nickel, Boundary, and Rafferty reservoirs. Lake Diefenbaker is also well below normal for this time of year. Table 1 provides a summary of the current levels and storages of the major water supply lakes and reservoirs in Saskatchewan. Data collected by Agriculture and Agri-food Canada, mapped in Figure 9, shows that the biggest impact to surface water supply is Reservoir and lake levels remain below normal across much of occurring across south central Saskatchewan, from Saskatoon southern and central Saskatchewan, including Junction, Jackfish, down to Mortlach, and near Melfort. Last Mountain, Buffalo Pound, Roughbark, Moose Mountain,

Figure 7: Water Supply Impact Map as of August 2, 2021(Map courtesy of Agriculture and Agri-Food Canada)

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Table 1: Water Supply

Full Departure Current Current Date of Elevation Lower Quartile Median Upper Quartile Reservoir Supply from Full Storage Percent Observation (m) Elevation (m) Elevation (m) Elevation (m) Level (m) Supply (m) (dam3) Full Altawan August 1, 2021 898.59 899.71 -1.12 4,740 72% 894.24 897.74 898.42 Avonlea August 1, 2021 597.49 597.90 -0.41 7,910 89% 596.57 597.28 597.73 Boundary August 1, 2021 558.93 560.83 -1.90 49,900 83% 558.75 560.35 560.71 Buffalo Pound August 1, 2021 509.35 509.47 -0.12 90,400 96% 509.28 509.39 509.45

Cookson August 1, 2021 751.57 753.00 -1.43 31,100 76% 751.15 752.09 752.57 Cypress August 1, 2021 975.21 975.97 -0.76 110,000 86% 971.44 972.91 974.68 Diefenbaker August 1, 2021 553.50 556.87 -3.37 8,090,000 86% 554.49 556.15 556.64 Downie August 3, 2021 877.73 878.89 -1.16 9,410 77% - - - Eastend August 1, 2021 917.98 918.06 -0.08 2,400 94% 916.68 917.20 917.93 Grant Devine August 1, 2021 560.88 562.00 -1.12 92,900 88% 561.21 561.64 561.92 Highfield August 1, 2021 721.67 722.99 -1.32 8,650 58% - - -

Huff August 1, 2021 815.31 815.72 -0.41 3,380 78% 813.70 814.47 815.43 Junction August 1, 2021 754.81 757.28 -2.47 4,670 36% - - - Newton August 1, 2021 802.36 803.28 -0.92 7,730 63% 801.19 801.85 802.54 Nickle August 1, 2021 562.26 563.00 -0.74 10,300 77% 562.55 562.83 563.03 Rafferty August 1, 2021 548.28 550.50 -2.22 339,000 77% 548.06 549.27 550.01 Reid/Duncairn August 1, 2021 806.49 807.72 -1.23 86,400 82% - - - Thompson/Lafleche August 1, 2021 713.93 714.76 -0.83 30,000 81% - - -

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Major River Systems Gardiner is resulting in low flows on the Saskatchewan River. The current lake level in Cumberland Lake is below its lower quartile. Saskatchewan River System Flows on the North Saskatchewan River have been near the lower quartile since June. Beginning on July 22, TransAlta has been releasing more water at its Bighorn Dam to manage higher water levels in Lake Abraham. This has helped to improve flows in Saskatchewan recently.

Inflows to Lake Diefenbaker have remained well below normal with the persistent hot and dry conditions over southern Alberta This is resulting in below normal runoff over headwater areas and above normal irrigation water use. As irrigation demands drop off over the coming weeks, we do expect to see inflows improve some.

Lake Diefenbaker is about 2.6 m below normal levels and is now Figure 8: Lake Diefenbaker Observed and Forecasted receding after peaking at 553.60 m on July 22. Reservoir levels are Inflows expected to drop at a rate of about 1 cm per day in early August. With outflows and inflows nearly balanced, the bulk of the reductions in Lake Diefenbaker levels are due to evaporation with a lesser amount attributed to water use.

Outflows from Lake Diefenbaker will remain below normal, with weekly averages of 75 m3/s, for the foreseeable future. Below normal flows on the North Saskatchewan River and lower release from

Figure 9: Lake Diefenbaker Observed and Forecasted Elevations

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change or rainfall is observed. Round Lake will not be operated in 2021 as Agriculture and Agri-Food Canada does not have land control in place.

Table 2: Observed and Forecasted Qu’Appelle Lake Levels

Desirable Projected Summer August September Operating Lake 1, 2021 1, 2021 Range Buffalo Pound 509.34 509.42 509.17 - 509.47 Last Mountain 489.75 489.62 489.66 - 490.27 Figure 10: Lake Diefenbaker Observed and Forecasted Pasqua-Echo 479.08 479.08 478.84 - 479.15 Outflows Mission-Katepwa 478.26 478.25 478.08 - 478.38 Crooked 451.64 451.62 451.41 - 451.71 Round 441.67 441.60 442.11 - Qu’Appelle River 442.42 All the lakes in the Qu’Appelle River System are experiencing high evaporation loss due to high mean daily temperature during July. As Souris River a result, Buffalo Pound and Last Mountain Lakes remain below their The Souris River Basin received well below normal precipitation targeted summer operating levels. Extraordinary vegetation growth throughout the month of July. As a result of the dry and hot in the Upper Qu’Appelle channel above Eyebrow Lake has reduced conditions in the basin, flows at Sherwood Crossing dropped the conveyance capacity of the channel. In July, we constructed a steadily throughout the beginning of the month. On July 15 a release dyke on the low points of the channel to contain the flow within of 0.1 m3/s was initiated from Grant Devine Dam to help supplement channel. We are planning to maintain a constant release of 6.5- flows and maintain the 4 ft3/s (0.11 m3/s) minimum requirement at 7.0 m3/s from Qu’Appelle River Dam unless the flow containment is the USA border. at risk. We are releasing water through the fishway of and will maintain it until the lake’s water level reaches to the Quill Lakes targeted summer operating level of 509.45 m. Due to evaporation losses throughout the month of July, and minimal

3 precipitation in the area, the Quill Lakes dropped another 9 cm in Flow on the Qu’Appelle River near Lumsden is about 2.2 m /s and July and are now down to 519.78 m. This is the lowest level for July release from the Craven Control structure is close to 3.0 m3/s, which 3 since 2014. If conditions remain dry, the lakes are expected to drop suggest about 0.8 m /s outflow from the . The a further 0.2 m prior to freeze-up. northern tributaries of Last Mountain Lake are contributing minimum. The current release from the Craven Control Structure is maintaining Pasqua-Echo, Mission-Katepwa, and Crooked lakes and conditions are expected to remain steady unless any significant temperature

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Churchill River Flows remain near to above normal throughout the Churchill River System. Due to dry conditions throughout July, flows are generally receding throughout the basin. Without significant rain, flows are expected to continue to slowly recede throughout the remainder of the summer; however, flows are expected to remain near to above normal as the water levels remain high from the rainfall received in 2020.

Construction work at La Ronge is underway. To facilitate this work, Lac La Ronge will continue to be maintained near the lower end of its operating range (possibly as low as 364.1 m) throughout the remainder of the summer and into the fall.

Southwest Rainfall in the southwest for the month of July was 20-40% of normal. Despite the extremely dry conditions, water supply from reservoirs has been sufficient to provide full delivery of water for irrigation in all areas except the Big Stick Lake Basin, where irrigation has been limited due to low reservoir levels. Reservoir releases were completed in July for the purpose of paying back international apportionment deficits on the Frenchman River and Battle Creek in the Missouri River Basin. Rain and groundwater-fed streamflow across the southwest have declined to nearly zero flow in many areas.

Table 3 contains July 1st water levels for a cross section of Saskatchewan lakes.

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Table 3: Lake Level Summary

August 1, Summer 2021 Projected Normal Summer Level Recorded Historical Extreme Lake Levels (m) Level (m) (m) Level (m) Year Anglin 515.37 515.36 515.35 515.99** 2013 Big Quill 519.75 520.0 515.00 520.93** 2017 Boundary Reservoir 558.93 558.9 560.50 561.15 1979 Buffalo Pound 509.35 509.45 509.47 511.45 1974 Candle Lake 494.34 494.4 494.40 495.25 1973 Cookson Reservoir 751.57 752.0 752.50 753.35 1979 Crooked 451.65 451.6 451.70 454.40** 2014 Echo and Pasqua 479.07 479.1 479.10 480.98 2011 Fishing 529.57 529.8 528.50 530.92 2011 Good Spirit 483.88* 484.2 484.60 485.68** 2010 Grant Devine 560.88 560.8 561.50 556.58** 2011 Jackfish 529.30 529.6 529.40 530.00 1985 Katepwa and Mission 478.26 478.25 478.30 479.58 2011 La Ronge 364.23 364.1 364.30 364.98** 2011 Last Mountain 489.74 489.8 490.20 492.09 1955 Moose Mountain 619.69 619.9 620.40 621.90 2011 Rafferty 548.28 548.4 550.50 554.05** 2011 Round 441.66 441.5 442.4*** 445.70** 2014

* Estimated **Occurred after spring runoff during summer event(s) ***With outlet structure operated. Without the outlet structure the normal summer level is 441.3m

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Ongoing Water Supply Outlook

Up to date flows and lake levels are available at www.wsask.ca.

The WSA will issue Water Supply Conditions Reports monthly until November 2021.

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