Water Supply Conditions and Outlook October 1, 2018

Transcription

1 Water Supply Conditions and Outlook October 1, 2018 Flow Forecasting & Operations Planning Water Security Agency

2 Overview Water supply conditions across Saskatchewan remain near normal, with most reservoirs and lakes maintaining near typical levels for this time of year. The surface water supply conditions have improved over part of the province with the precipitation received in September. Surface water supply shortages, and drought like conditions, are still being experienced in south central Saskatchewan. The cumulative spring and summer precipitation remains near normal for most of northern and south eastern portions of Saskatchewan. South western and central areas of the province have received below normal precipitation during the growing season in Streamflows across the province generally remain near normal for this time of year. Both the Qu Appelle River and the Saskatchewan River are seeing near normal flows due to the precipitation received in September. Now that the growing season is over, Alberta is no longer diverting as much water for agricultural purposes, allowing flows to return to near normal on the South Saskatchewan Remain in late September. With above normal precipitation received in the Alberta portion of the North Saskatchewan River basin, flows are above normal for this time of year. The continued well above normal precipitation over the Churchill River Basin has resulted in the flows remaining well above normal on the Churchill River and its tributaries. 1

3 2018 Rainfall Figure 1 shows the percent of average cumulative rainfall between April 1 and October 1, Most of southwestern and central Saskatchewan received below normal precipitation so far in the growing season of During the same time period, most of the west central and the south eastern areas of the province received near or above normal accumulations. An area near Lake Diefenbaker, and a portion of the most south western corner of the province received accumulations that are about half of the average for this period. Figure 1: April 1 to October 1, 2018, Percent of Average Precipitation (Map courtesy of Agriculture and Agri-Food Canada) 2

4 Figure 2 shows the cumulative rainfall for September, Most of southern and central Saskatchewan received near average rainfall in September. In northern Saskatchewan, the southern portion of the Churchill River basin again received above average rainfall this month. This increased rainfall resulted in continued well above normal flows and lake levels throughout the Churchill River Basin, but no major flooding occurred. Figure 2: Total Precipitation September 1 to September 30,

5 Soil Moisture Conditions Figure 3 shows cropland topsoil moisture conditions as of October 1 st, With the precipitation received in September, the soil moisture conditions have significantly improved throughout most of the province, with a majority now seeing near adequate conditions. As of October 1, the only major areas of the province that are still experiencing short to very short conditions are the Indian Head region, an area South of Regina, a small area near Swift Current, and an area North of Saskatoon. Figure 3: Cropland Topsoil Moisture Conditions as of October 1, 2018 (Map Courtesy of the Ministry of Agriculture) 4

6 In their September 30, 2018, drought assessment (Figure 4), Agriculture and Agri-Food Canada has identified most of southern and central Saskatchewan as experiencing some form of drought ranging from abnormally dry to severe drought conditions. While conditions have improved in the southwestern portion of the province, drought conditions intensified in the southeast over the past month. With a D2 or Severe Drought area, crop or pasture loss and water shortages can be expected. 5

7 Figure 4: Canadian Drought Monitor September 30, 2018 (Map courtesy of Agriculture and Agri-Food Canada) 6

8 Long Range Forecasts Most long range forecasts are currently predicting near normal precipitation over Saskatchewan, and above normal temperatures between October 1 and December 31. Multi-model ensemble maps for precipitation and temperature over the next three months, which are the average result of seven seasonal weather forecasts, are shown in Figure 5 and 6 respectively. It is important to keep in mind that seasonal weather forecasts are statistically unreliable. Figure 5: North American Multi-Model Ensemble Precipitation Anomaly Outlook for October 1 to December 31, 2018 (Map Courtesy of the US National Weather Service) 7

9 Figure 6: North American Multi-Model Ensemble Temperature Anomaly Outlook for October 1 to December 31, 2018 (Map Courtesy of the US National Weather Service) 8

10 Detailed Water Supply Condition Table 1 provides a summary of the current levels and storages of the major water supply lakes and reservoirs in Saskatchewan. Many reservoirs were above or near median levels as of October 1, Many of the reservoirs in southeastern and southcentral Saskatchewan, including Diefenbaker, Cookson, Avonlea, Nickel, Newton, and Boundary reservoirs, still remain slightly below the 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 During their Crop Report survey at the end of September, the Saskatchewan Ministry of Agriculture asked a question related to the current condition of on-farm surface water supplies. These results are mapped in Figure 7. Figure 7 indicates that even with the added precipitation in the southern and central parts of the province, conditions remain similar to what they were at the end of August. Severe shortages are still being reported in the RM of Indianhead, Number RM s reported moderate shortages occurring, 25 RM s reported localized shortages, and 13 RM s anticipate shortages in 1-2 months if no rainfall occurs. Data collected by Agriculture and Agri-food Canada, mapped in Figure 8, shows a slightly different pattern. This particular map indicates that water supply concerns are most prevalent over the south central areas of the province. With the September precipitation, conditions have improved in the western portions of the province, as well as along the Manitoba border, with most areas now reporting minimal to no impact. 9

11 Figure 7: On Farm Surface Water Supply Conditions (Dugouts and Small Reservoirs) as of September 30,

12 Figure 8: Water Supply Impact Map as of September 30, 2018 (Map courtesy of Agriculture and Agri-Food Canada) 11

13 Reservoir Name Date and Time of Last Observation Table 1: Water Supply Reservoir Current Condition Report Current Elevation (m) Full Supply Level (m) Departure from Full Supply (m) Current Storage (dam 3 ) Current Percent Full Lower Quartile Elevation (m) Median Elevation (m) Upper Quartile Elevation (m) Grant Devine October ,000 95% Altawan October ,120 62% Avonlea October ,130 58% Boundary October ,300 85% Buffalo Pound October , % Cookson October ,000 76% Cypress October ,000 86% Downie* October N/A N/A N/A N/A Duncairn* October ,200 83% Diefenbaker October ,800,000 94% Eastend October ,320 91% Highfield* October ,600 51% Huff October ,150 73% Junction October ,300 72% Lafleche/Thompson October ,900 91% Newton October ,230 26% Nickle October ,400 86% Rafferty October ,000 87% *Data courtesy of Agriculture and Agri-Food Canada 12

14 Discharge - m 3 /s Water Supply Outlook Conditions as of October 1, 2018 Major River Systems Saskatchewan River System With the fall irrigation season in Alberta coming to an end, diversions within the basin have decreasing significantly. This, combined with additional runoff from recent precipitation, has resulted in increased flows into Lake Diefenbaker, with the inflow now sitting near upper quartile for late September/early October. With the added inflows, the operation plan is to release a daily average of 100 m 3 /s, with plans to increase the average releases to 120 to 130 m 3 /s in October. These release values are still slightly below median; thus flows on the South Saskatchewan River below Lake Diefenbaker remain slightly below median. The elevation of Lake Diefenbaker remains approximately only 0.6 m below the median for this time of year. With inflows increasing and outflows remaining slightly below normal, near normal reservoir levels at Lake Diefenbaker are expected prior to freeze-up. As a result of the above normal precipitation in September over much of the basin, flows on the North Saskatchewan River are near upper quartile for this time of year. With the increased outflow from Lake Diefenbaker, and above median flows on the North Saskatchewan River, flows on the Saskatchewan River are now above median. Figures 9, 10, and 11 show recorded and projected inflow, elevation and outflow to Lake Diefenbaker Observed 10-Day Forecast 6-Month Forecast Low Inflow Estimate Mid. Inflow Estimate High Inflow Estimate Lower Quartile Median Upper Quartile Figure 9: Lake Diefenbaker Observed and Forecasted Inflows 13

15 Discharge - m 3 /s Elevation - m Water Supply Outlook Conditions as of October 1, Observed 10-Day Forecast 6-Month Forecast Low Inflow Estimate Mid. Inflow Estimate High Inflow Estimate Lower Quartile Median Upper Quartile Figure 10: Lake Diefenbaker Observed and Forecasted Elevations Observed 10-Day Forecast 6-Month Forecast Low Inflow Estimate Mid. Inflow Estimate High Inflow Estimate Lower Quartile Median Upper Quartile Figure 11: Lake Diefenbaker Observed and Forecasted Outflows Qu Appelle River Although summer precipitation has been below average across the majority of the upper portion of the Qu Appelle River Basin, with the September precipitation and the augmentation of flows from the Qu Appelle River Dam, flows and lake levels remain at near normal levels for this time of year. 14

16 In the Upper Qu Appelle, construction of rock riffles is still planned for late October. The termination of outflows from the Qu Appelle River Dam will be required for the duration of this work. As a result, Buffalo Pound Lake is being held higher than normal leading up to this work. Last Mountain Lake continues its typical fall decline and is projected to go into winter at typical freeze-up levels. All of the stop logs have now been removed from Crooked Lake and some logs have been removed at the Echo Lake Control. Depending on October s precipitation, some logs may be left in the Echo Lake Control structure to conserve water for next year since conditions in the basin are drier than normal. Lake Table 2: Qu Appelle Lakes 2018 Levels and Operating Ranges (metres) 2018 Spring Peak October 1, 2018 Projected November 1, 2018 Desirable Summer Operating Range Buffalo Pound Last Mountain Pasqua-Echo Mission-Katepwa Crooked Round Souris River The majority of the Souris River Basin received near normal summer rainfall, and near typical fall conditions persist. As a result, all of the major water supply reservoirs are near typical fall levels with the exception of Boundary Reservoir which is a little below normal levels due to well below normal snowmelt inflows. A small winter release is planned from Grant Devine Lake to lower its level to the required February 1 level of m. This flow will be initiated in late October and will be approximately 0.8 m 3 /s. Quill Lakes Despite a relatively dry summer, the Quill Lakes remain high. The level has declined approximately 0.4 m from this year s spring peak level and is projected to go into freeze up slightly lower than last fall. Churchill 15

17 Due to the continued above normal precipitation in the basin, flows and levels in the Churchill River Basin remain near or above upper quartile for this time of year; however, the headwater and tributary flows are generally receding. Flows are projected to remain near upper quartile for the fall and into the winter. Table 3 contains September 1 st water levels for a cross section of Saskatchewan lakes. 16

18 Lake October 1 Level (metres) Table 3: Lake Level Summary Fall 2018 Projected Level (metres) Normal Summer Level (metres) Recorded Historical Extreme Level Year (metres) Grant Devine ** 2011 Anglin ** 2013 Big Quill ** 2017 Boundary Reservoir Buffalo Pound Candle Lake Cookson Reservoir Crooked ** 2014 Echo and Pasqua Fishing Good Spirit ** 2010 Jackfish Katepwa and Mission La Ronge ** 2011 Last Mountain Moose Mountain Rafferty ** 2011 Round *** ** 2014 **Occurred after spring runoff during summer event(s) *** with outlet structure operated. Without the outlet structure the normal summer level is 441.3m Ongoing Water Supply Outlook Up to date flows and lake levels are available at The WSA will issue a Conditions at Freeze-up Report in November or early December. 17