2018 Conditions at Freeze-up Report Based on Conditions as of November 1, 2018

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

2018 Conditions at Freeze-Up Report

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Executive Summary

The Water Security Agency (WSA) issues the Conditions at Freeze-up report to summarize the conditions during the late fall/early winter period. This, in combination with the winter snowpack, becomes the initial conditions for the spring snowmelt runoff. This report gives an early indication of areas which are more vulnerable to potentially above or below normal runoff during the spring period. It is not a spring runoff forecast, as winter snow accumulation is an integral component in the runoff yield during the melt, and are difficult to predict. Above average snowmelt runoff was experienced over much of central Saskatchewan during the spring of 2018. Southern areas of the province experienced below to near normal spring snowmelt runoff in 2018. In northern Saskatchewan spring runoff varied from below normal in western areas to above normal in eastern areas. Southern and central portions of Saskatchewan received below average rainfall in the spring and summer 2018. This resulted in drought conditions being experienced to some degree across most of the grain belt. Further north, conditions were very wet throughout the Churchill River Basin as a result of the well above normal precipitation received in the spring and summer. This caused well above normal flows throughout the system through the year. The Beaver River basin also received above average rainfall in the fall, causing above normal flows throughout the system. The rest of the Churchill River Basin received below to average rainfall in the fall, which allowed flows to recede. Fall brought some much needed precipitation to southern and central Saskatchewan. Although the fall precipitation improved soil moisture conditions across these regions, available depressional storage volumes remain high following the very dry conditions in the spring and summer. This will ultimately reduce next springs runoff potential in these areas. The only areas where increased runoff potential exists for the spring of 2019, is in the Churchill River and the Beaver River basins. In both basins, wetter then normal conditions exist as a result of the above normal precipitation received throughout the year. Even with the dry conditions throughout most of southern and central Saskatchewan throughout 2018, no major water supply shortage occurred. There

is a need to replenish supplies with the spring 2019 snowmelt runoff to ensure adequate supplies throughout 2019. Most ground water levels across the province showed declining levels in 2018. Current long range forecasts and climate indices suggest near normal precipitation and above normal temperatures for the first three months of the winter. The initial Spring Runoff Outlook for 2019 will be issued in early February.

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Precipitation and Conditions Leading into Freeze-up

Spring Runoff Summary

The southeast and southcentral areas of the province experienced a well below normal snowmelt runoff as a result of the dry antecedent conditions and limited snowpack. Central Saskatchewan and the extreme southwest corner of the province (the Cypress Hills area), experienced above to well above normal snowmelt runoff. This was a result of the wet antecedent conditions combined with a near to above normal snowfall that was received. Northern and remaining areas of southwestern Saskatchewan experienced near normal runoff.

Summer Precipitation Summary

As is shown in Figure 1, south and central portions of the province, as well as the far north western area of the province, received well below normal precipitation in the summer months. Northern Saskatchewan, with the exception of the north western area, received normal or above normal accumulations. Accumulations were particularly high over lower portions of the Saskatchewan River Basin. Between April 1 and August 31, conditions ranged from very low in areas around Lake Diefenbaker, to extremely wet near Meadow Lake and north of Hudson Bay along the Manitoba border (Figure 2). Accumulations ranged from less than 150 mm at in the southwest, to more than 500 mm north of Hudson Bay.

Figure 1: 90-Day Percent Normal Rainfall Accumulations June 3 to August 31, 2018

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Figure 2: April to August 1, 2018 Precipitation Compared to Historic (Map Courtesy of Agriculture and Agri-Food Canada

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Precipitation and Conditions Leading into Freeze-up

Fall Precipitation Summary

The fall brought some much needed precipitation to the south and central areas of the province with most of the region receiving near or above normal accumulations in September (Figure 3). Southern portions of the Qu’Appelle River Basin, a good portion of the South Saskatchewan River Basin, most of the Cypress Hills, and the very northern portion of the province received below normal precipitation (60-80 %). Significant rainfall occurred over the Beaver River Basin and an area west of Coronach, where well above normal precipitation was received. October saw much less precipitation (Figure 4) with most of the province experiencing below to well below normal precipitation. The southern portion of the province along the US border saw near normal accumulations, the remaining areas recorded below normal precipitation.

Figure 3: Percent Normal Precipitation, September 2018

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Figure 4: Percent Normal Precipitation, October 2018 Figure 5: Percent Normal Precipitation, Sept-Oct 2018

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Soil Moisture Conditions

Figures 6 and 7 indicate that topsoil moisture conditions were generally described as average to short during the final crop report on November 6, 2018. The only area that was reporting surplus soil conditions, is an area north east of Tisdale. Conditions are still particularly dry south of Regina, south west of Prince Albert and a small area southeast of Wynyard.

Agriculture and Agri-Food Canada produces soil moisture products using data from the European Space Agency’s Soil Moisture Ocean Salinity (SMOS) satellite mission (Figure 8). This data, indicates topsoil moisture conditions were generally much drier than normal across southern and central Saskatchewan in late October. The exception is the area along the US border, and the area around Meadow Lake, where conditions are near or slightly wetter then average.

Figure 6: November 6, 2018 Cropland Topsoil Moisture Conditions

(Map Courtesy of the Saskatchewan Ministry of Agriculture) Figure 7: November 6, 2018 hay and Pasture Topsoil Moisture

Conditions (Map Courtesy of the Saskatchewan Ministry of Agriculture)

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Figure 8: October 22 – October 28, 2018 Percent Normal Soil Moisture (Map Courtesy of Agriculture and Agri-Food Canada)

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Fall Streamflow

Fall streamflow is an indication of antecedent flow conditions within a basin prior to freeze-up. Historically most creeks in southern Saskatchewan are ephemeral, typically only flowing for a short duration during the spring freshet or during periods of above normal rainfall. When conditions are wet these creeks can flow at elevated rates over extended durations as water stored within the basin is slowly released, indicative of basins susceptible to higher runoff yields the following spring. Table 1 provides a summary of the preliminary flow, rank, and historical statistics for select streamflow gauges across the province for October 31, 2018. October 31 is used for this table as many of these streamflow gauges are only operated from March 1 to October 31. Table 1 shows that October 31 flows were generally around normal across the grain belt, and above normal in the Churchill River Basin at freeze-up.

Pre-Spring Runnoff Lake Level Projections

Table 2 shows the current lakes on the Qu’Appelle River, and where they are projected to be on March 1, 2019. Last Mountain, Mission-Katepwa, and Crooked lakes are expected to be near their normal levels on March 1, 2019. Pasqua-Echo Lake is expected to be at above normal levels as dry conditions have resulted in some stop logs being left in the Echo Lake control structure to retain storage within the lakes. At Round Lake, levels are expected to remain below normal as the control structure at its outlet is not being operated. Fishing Lake and the Quill Lakes are expected to see small gains over the winter period due to snow loading and potentially groundwater inflows. Other closed basin lakes, many of which are not gauged and not included in the above table, remain high and will also go into 2019 spring runoff at elevations higher than what is considered normal. In the Souris River Basin, Grant Devine Reservoir is being drawn down to its normal February 1 level of 561.0 m through a 0.85 m3/s release which was initiated on October 31. This release at Grant Devine Dam will continue into January 2019. No winter release from Rafferty Reservoir is anticipated at this time as the reservoir is at 549.22 m which is 0.28 m below its required February 1 level of 549.5 m. Beginning on February 1, 2019, spring runoff forecasts for the Souris River Basin will be prepared in consultation with our United States partners for both of these reservoirs on a semi-monthly basis. The reservoirs may be drawn down further in advance of spring runoff, if warranted by these forecasts, in

accordance with the 1989 Canada-US Agreement on Water Supply and Flood Control in the Souris River Basin. Flows on the North Saskatchewan River have been above normal over the past few months. Flows on the river are anticipated to recede to near median over the winter. The reduced release from Lake Diefenbaker this summer has resulted in water levels being near median for this time of year. SaskPower will be staging up releases during the second week of November and then holding flows on the South Saskatchewan River steady to allow a stable ice cover to form on the River prior to commencing with the planned winter releases from Lake Diefenbaker. Average releases from Lake Diefenbaker are currently planned this winter to draw down Lake Diefenbaker to near its median level by the end of March. WSA will be monitoring snow pack conditions in the alpine region and adjusting operations plans throughout the winter as needed.

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Table 1: October 31 Flows, Historical Statistics and Rankings

Station 2018 Flow

(m3/s)

2018 Rank

Years of

Record

Lower Quartile

Flow (m3/s)

Median Flow

(m3/s)

Upper Quartile

Flow (m3/s)

Historical Rankings

1 2 3 4 5

ASSINIBOINE RIVER AT KAMSACK 0.66 39 75 0.27 0.68 1.8 2010 2016 2014 1954 1995

BATTLE CREEK AT ALBERTA BOUNDARY 0.20 25 44 0.15 0.21 0.26 2010 2016 2011 2012 1993

BATTLE RIVER NEAR THE SASKATCHEWAN BOUNDARY 2.28 14 40 1.1 1.9 2.9 1980 1982 1981 1986 2005

BIRCH CREEK NEAR ELFROS 0.00 34 56 0.000 0.001 0.006 2016 2010 2006 1995 2005

BOGGY CREEK NEAR LUMSDEN 0.00 59 64 0.003 0.006 0.009 2016 2010 2009 1956 1977

CARROT RIVER NEAR TURNBERRY 19.4 11 53 5.0 9.1 15 2016 2006 2005 2010 1978

CHURCHILL RIVER ABOVE OTTER RAPIDS 488 7 56 198 304 401 1974 2005 1997 2017 1996

CUTARM CREEK NEAR SPY HILL 0.18 24 77 0.021 0.096 0.21 2016 2010 2014 1953 1954

DORE RIVER NEAR THE MOUTH 8.10 4 48 0.99 1.9 5.4 2017 1974 2007 2018 1975

FRENCHMAN RIVER AT INTERNATIONAL BOUNDARY 0.15 68 96 0.052 0.23 0.51 2016 2014 2010 1983 1927

IRONSPRING CREEK NEAR WATSON 0.00 32 57 0.000 0.009 0.042 2016 2006 2010 2005 2014

LANIGAN CREEK ABOVE BOULDER LAKE 0.00 20 61 0.000 0.000 0.020 2010 2006 2015 2016 2005

LIGHTNING CREEK NEAR CARNDUFF 0.00 18 46 0.000 0.001 0.010 1975 2014 2016 1985 2013

LONG CREEK NEAR NOONAN 0.03 31 90 0.002 0.021 0.045 2013 1911 2011 2014 2015

MOOSE JAW RIVER NEAR BURDICK 0.13 33 66 0.039 0.12 0.24 2016 1959 1993 2002 1954

MOOSE MOUNTAIN CREEK ABOVE GRANT DEVINE LAKE 0.03 42 82 0.000 0.027 0.17 2014 2010 2011 1954 1955

NOTUKEU CREEK NEAR VANGUARD 0.11 22 71 0.034 0.067 0.14 2016 2011 1963 1916 1965

PIPESTONE CREEK ABOVE MOOSOMIN LAKE 0.01 24 46 0.000 0.011 0.17 2014 2011 2010 2016 2001

QU'APPELLE RIVER NEAR WELBY 6.00 28 57 3.7 5.4 10 2014 2010 2011 2016 1954

RED DEER RIVER NEAR ERWOOD 6.13 20 65 2.1 4.4 7.3 2016 2010 1954 1970 2006

STURGEON RIVER NEAR PRINCE ALBERT 1.31 14 42 0.20 0.38 1.8 2010 2016 2015 2012 2011

SWAN RIVER NEAR NORQUAY 3.29 14 44 1.2 2.2 3.5 2016 1970 2010 1993 2009

SWIFT CURRENT CREEK BELOW ROCK CREEK 0.62 12 64 0.25 0.31 0.50 2016 2015 2014 2013 2011

TORCH RIVER NEAR LOVE 5.13 30 62 2.7 4.9 7.3 2016 2005 1954 2015 2004

WHITESAND RIVER NEAR CANORA 0.31 28 72 0.004 0.20 0.61 2016 2010 2014 1995 1954

WOOD RIVER NEAR LAFLECHE 0.02 15 62 0.00 0.00 0.01 2016 2014 2013 2015 2002

YELLOW GRASS DITCH NEAR YELLOW GRASS 0.00 11 62 0.000 0.000 0.000 2011 2010 2000 2014 2009

YORKTON CREEK NEAR EBENEZER 0.19 19 74 0.022 0.075 0.18 2016 2014 1954 2010 1995

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Table 2: November 1, 2018 Observed Levels and Projections for March 1, 2018

Lake

November 1, 2018 March 1, 2018

Observed 2018

(masl)

Median (masl)

Departure from

Median (m)

Projected 2018 (masl)

Median (masl)

Departure from

Median (m)

Last Mountain 489.85 489.88 -0.03 489.87 489.90 -0.03

Echo-Pasqua 478.85 478.56 0.29 478.80 478.50 0.30

Mission-Katepwa 478.26 478.35 -0.09 478.21 478.27 -0.06

Crooked 450.76 451.07 -0.31 450.59 450.80 -0.21

Round 441.68 441.83 -0.15 441.27 441.55 -0.28

Fishing 529.77 529.00 0.77 529.80 529.00 0.80

Quill Lakes 520.43 515 5.43 520.45 515 5.45

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Climatic Conditions and Long-Range Weather Forecast

Large Scale Climate Influences

The hydroclimate of Saskatchewan is heavily influenced by teleconnections with recurring large-scale climate patterns such as the Pacific Decadal Oscillation (PDO), Pacific North American mode (PNA), and the El Nino-Southern Oscillation (ENSO). These large scale climatic influences can provide insight, but should be considered within the context of past experiences rather than a forecast of upcoming conditions.

PDO

The PDO is an index of sea surface temperatures over the northern portion of the Pacific Ocean. This index shifts from warm (positive) to cool (negative) phases on inter-decadal time scales, typically 20-35 years. During negative phases, Saskatchewan typically experiences above normal snowfall and consequently experiences larger spring runoff events. Conversely, we tend to see lower than normal snowfall when the PDO is in its positive phase.

While the PDO had been predominantly in a strong negative phase from late 2007 through to the end of 2013, which corresponds with the wetter hydroclimate we experienced over this period, it has primarily been in the positive phase since the beginning of 2014. It is too early to tell if this is a longer term shift or simply a short term blip. Currently, the PDO index is not overly strong and close to neutral. The United States National Oceanic and Atmospheric Administration expect the PDO to remain near neutral during the winter 2018-19. As such, the PDO is not expected to have a strong influence on our snowpack and spring runoff in 2019.

PNA

The PNA is one of the most prominent modes of low-frequency variability in the Northern Hemisphere extratropics and is associated with fluctuations in the strength and location of the jet stream. During the positive phase, warmer and drier conditions typically persist over western North America. The PNA is difficult to forecast beyond one month. The PNA is currently near neutral, and is expected to remain there over the next month.

ENSO

The El Niño-Southern Oscillation (ENSO) is a naturally occurring phenomenon that involves fluctuating Pacific Ocean temperatures near the equator. During El Niño (Warm Phase) years, Saskatchewan typically experiences warmer and drier winters. The converse generally occurs during La Niña (Cool Phase) years. ENSO Neutral conditions are currently present; however, a weak El Niño event is favored through the upcoming winter. Based on model outputs, there is about an 55-60 percent probability that El Niño conditions will continue through to the spring of 2019, and 25 percent probability that neutral conditions will be observed into the spring of 2019.

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Seasonal Outlooks

The US National Weather Service host a webpage with seasonal forecasts from seven models, including two Environment and Climate Change Canada models, and produces multi-model ensemble products. These models are all forecasting near normal precipitation over Saskatchewan between November 1 and January 31, and above normal temperatures. Three month spatial anomalies maps for precipitation (Figure 9) and temperature (Figure 10) covering the November 1 to January 31 forecast period are provided here.

Summary of Winter Precipitation Outlook

Most indices and models suggest that over the next three months Saskatchewan will receive near normal precipitation and experience warmer then normal temperatures. However, there are no long range precipitation or temperature forecasts with appreciable accuracy or reliability, and the effects of climate cycles on mid-continental precipitation is complex, variable, and inconsistent. In addition, noteworthy precipitation events that can have a significant effect on runoff often occur in late winter, beyond the current long term forecasts.

Figure 9: Multi Model Ensemble Precipitation Anomaly Forecast

(November 1, 2018 to January 31, 2019)

Figure 10: Multi Model Ensemble Temperature Anomaly Forecast (November 1, 2018 to January 31, 2019)

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Current Groundwater Conditions

The Saskatchewan groundwater monitoring program was initiated in the early 1960’s and monitors groundwater levels for 70 observation wells. Wells are completed in bedrock and glacial drift deposits ranging from six metres to 555 metres deep and are located throughout the Province. The observation wells showed an overall increase in groundwater levels throughout the Province since 2010 and 2011. Water levels in the observation wells completed in the bedrock aquifers have decreased in 2018. Bedrock aquifers are generally deeper and less susceptible to climatic variations compared to shallower glacial aquifers. Surficial sand aquifers are most responsive to variations in the magnitude and timing of snowmelt and rain at the surface. For example, the observation well near Saskatoon shows seasonal fluctuations were at the highest level recorded in summer 2014 (Figure 11), and have been decreasing since. Regionally, shallow groundwater levels have increased in the northwestern portion of the Province, but decreased for the remaining areas in 2018. The buried valley-type aquifers occur in the form of long and narrow, highly permeable sand and gravel units incised into valleys in the low-permeability bedrock sediments and covered by glacial sediments. Water levels in most buried valley type aquifers have been steadily increasing since 2010-2011. However, groundwater levels in these buried valley aquifers showed a decrease since 2017 and continued to decrease in 2018. (Figure 12). In general, the groundwater levels show a decreasing trend for most of the aquifer systems in the Province in 2018.

Figure 11: Groundwater Levels near the City of Saskatoon

Figure 12: Groundwater Levels in the Hatfield Valley Aquifer near Nokomis

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Current Water Supply Conditions

Most lakes and reservoirs were generally in good shape following spring runoff in 2018 and sufficient water was available to meet the demands throughout the summer months. However, many of the reservoirs in southeastern and southcentral Saskatchewan, including, Cookson, Avonlea, and Boundary reservoirs, remain slightly below normal levels for this time of year. This is a result of the below normal snowmelt runoff in 2018, and the hot and dry conditions during the summer of 2018.

Monitoring of Runoff Conditions and Spring Runoff Forecasts

The Water Security Agency will continue to monitor conditions throughout the winter of 2018/2019. Beginning in early February, Spring Runoff Outlooks will be released on www.wsask.ca.