Reservoirs Recover, La Niña Exits — Prairie Irrigators Head Into 2026 With Best Water Supply Position in Three Years

Southern Alberta irrigation districts are entering the 2026 season with full allocation restored for the first time since 2023. Saskatchewan’s major reservoirs are at or above normal heading into peak spring inflow. The climate pattern that drove two consecutive drought years on the southern Prairies has ended. None of this means rain is guaranteed — but the structural water supply picture is materially better than it has been at this point in either of the two preceding seasons.

Current Conditions — Near-Term Horizon

Southern Alberta

As of March 27, 2026, total storage across the St. Mary Project reservoirs — the system supplying southern Alberta’s largest irrigation district — stood at 620,000 acre-feet, representing 79% of the Full Supply Level (FSL), according to Alberta Agriculture and Irrigation data published by the St. Mary River Irrigation District. District reservoirs alone sat at 80% FSL; the Headworks system comprising the Waterton, St. Mary, and Milk River Ridge reservoirs registered 77% FSL.

The SMRID board set the 2026 irrigation season allocation at 14 inches from the farm gate — the pre-drought standard, and six inches above the reduced allocation issued in 2024. The allocation had been cut by approximately one-third during the 2024 drought crisis when the Oldman Reservoir — Alberta’s largest — reached historic lows. Supply was again restricted in 2025. The Oldman is now reported above 80% full, according to Alberta Agriculture and Irrigation’s provincial reservoir storage summary.

The unusual feature of this season’s reservoir recovery is its timing. Warmer-than-normal winter temperatures caused early snowmelt and stream flow in the southern Rockies, with water entering reservoirs as early as December 2025 rather than the typical spring peak period. The SMRID update confirms this early inflow added approximately 155,000 acre-feet of stored water to the St. Mary Project over winter 2025–26. Snowpack at Flat Top Mountain — the primary contributor to district water supply — remained above the lower quartile as of late March, though below the levels reported at Akamina and Many Glacier showed well below the lower quartile. Continued spring snowmelt will determine the final seasonal inflow picture.

Provincial water supply modelling from Alberta Agriculture and Irrigation projects normal to above-normal river flows in the Milk, Oldman, Bow, Red Deer, and North Saskatchewan basins for the March–September 2026 period. The mountain snowpack in the Bow system is reported at its highest volume in decades. These are the most favourable early-season water supply conditions for Alberta irrigators since 2022.

Saskatchewan

The Saskatchewan Water Security Agency issued its April 17, 2026 update following manual snow surveys at 12 sites conducted April 9–10. Most major water supply reservoirs in southern Saskatchewan are at or above normal levels for this time of year. The exceptions are McDougald and Harris, which remain below normal.

Lake Diefenbaker — the primary storage hub for Saskatchewan’s irrigation sector — is currently above the seasonal median and within normal operating range. Mountain snowpack feeding the Saskatchewan River Basin remains well above normal and is expected to be the primary driver of May and June inflows. If conditions hold, above-normal runoff into Lake Diefenbaker is anticipated.

Regional variation is significant. Above-normal runoff is expected across central Saskatchewan, including areas around Hudson Bay and north of Yorkton and Wynyard. The Quill Lakes Basin is also forecast for above-normal runoff given snowpack levels. The southwestern corner of the province — from Kindersley to Assiniboia — is the exception: well-below-normal runoff is projected for this corridor. Dryland producers in southwestern Saskatchewan remain the most exposed sub-region in the province heading into seeding.

Snowmelt has concluded in the southern portions of the Qu’Appelle River Basin. In northern areas of that basin, melt began earlier but has slowed due to returning cold temperatures.

Manitoba

Manitoba’s spring 2026 water story is not primarily an irrigation story — it is a flood risk story, and Prairie irrigators and grain producers operating near watercourses need to understand the distinction.

Manitoba Transportation and Infrastructure’s Hydrologic Forecast Centre updated its spring flood outlook on April 11, 2026. Flood risk in the Interlake region, specifically the Fisher River basin, has been elevated to high. Snow water equivalent in the Fisher River basin reached approximately 113 millimetres — nearly double the long-term average — with potential for further accumulation. The Icelandic River carries a high flood risk. The Parkland region carries elevated overland flood risk as temperatures rise and drainage channels remain partially frozen.

Moderate flood risk continues along portions of the Red, Assiniboine, Souris, Saskatchewan, and Carrot rivers. Inflow to the Portage Reservoir was approaching the ice management threshold of 5,000 cubic feet per second at the time of the update.

Manitoba’s irrigation sector operates largely on captured on-farm snowmelt storage rather than formal district allocation systems comparable to Alberta’s. Above-normal snowpack translates to better on-farm reservoir fill for operations relying on supplemental irrigation — a positive indicator for potato and vegetable producers in the province’s southwest. However, the more immediate water management concern for Manitoba grain and livestock producers this spring is flood-related seeding delay and field access, not water supply adequacy.

Canadian Drought Monitor context (December 2025 — most recent published map): As of December 31, 2025, 79% of the Prairie Region remained classified as D0 (Abnormally Dry) or in D1–D3 drought conditions, including 62% of the Prairie agricultural landscape. Drought conditions improved through December across most of Alberta and Saskatchewan following above-normal snowfall, but long-term moisture deficits — particularly in southern Alberta and southwestern Saskatchewan — had not been eliminated. The next CDM update will reflect conditions through the end of March 2026; that release will provide the first definitive read on whether December and winter precipitation has resolved the structural deficit picture across the southern Prairies. Agriculture and Agri-Food Canada publishes updated drought maps monthly at agriculture.canada.ca .

Climate Pattern Context — Strategic Horizon

ENSO: La Niña Has Ended

The NOAA Climate Prediction Center issued its Final La Niña Advisory on April 9, 2026. ENSO-neutral conditions are now in place and are favoured through April–June 2026, with an 80% probability. El Niño is likely to emerge in the May–July 2026 window, with a 61% probability, and is expected to persist through at least the end of 2026.

This transition matters for Prairie producers on two timescales.

For the 2026 growing season, the operative condition is ENSO-neutral. The La Niña phase that amplified drought risk across the southern Prairies during 2024 and 2025 is no longer active. ENSO-neutral reduces the drought-amplifying signal that characterized recent seasons, returning summer precipitation probability closer to climatological norms. This does not guarantee adequate in-season moisture — it means the climate pattern is no longer stacked against it in the way it has been.

For winter 2026–27 and the 2027 growing season, an El Niño emergence through summer and fall would carry the typical Prairie implications: a warmer and drier winter, reduced snowpack, and lower spring flood risk. Early El Niño years historically carry lower drought risk for the following growing season than La Niña years, though this is probabilistic. NOAA notes that the possible strength of any developing El Niño ranges widely — from ENSO-neutral persisting, to a very strong event by October–December 2026. Monitoring the NOAA ENSO Diagnostic Discussion through the summer will be critical as the El Niño probability and strength picture develops.

The equatorial Pacific subsurface temperature anomalies have been increasing since early March 2026 — a leading indicator that supports the El Niño emergence forecast.

Historical ENSO analogue context: The 2015–16 El Niño transition year saw southern Prairie conditions that were variable during the growing season but dramatically reduced drought risk compared to the preceding La Niña period. The 2009–10 La Niña exit produced near-normal Prairie growing season conditions. No two ENSO transitions follow the same trajectory, and the strength of any emerging El Niño remains highly uncertain at this stage. These analogues are informative context, not prediction.

PDO context: The current Pacific Decadal Oscillation index value was not available from a verifiable NOAA Tier 1 source at the time of publication. The next NOAA PDO update should be checked and this section updated before republication. PDO phase would either amplify or moderate the El Niño signal on the Prairies; at this stage the ENSO-neutral condition limits the PDO’s amplifying role regardless.

Production and Planning Implications

Southern Alberta irrigated operations

The return to 14-inch allocation restores the operational capacity that irrigators have not had since 2023. For potato, sugar beet, corn, and high-value cash crop rotations in the Lethbridge–Medicine Hat corridor, this removes the water constraint that forced defensive cropping decisions in both 2024 and 2025. The planning question is no longer whether water is available from the reservoir — it is whether in-season precipitation supplements or strains irrigation requirements.

Reservoir status heading into the season means irrigators can make seeding and crop selection decisions based on agronomic merit rather than water supply hedging. That said, the mountain snowpack picture is mixed: Flat Top Mountain, the primary supply contributor, remains above the lower quartile but is not exceptional. If the spring and early summer are drier than normal — which ENSO-neutral does not preclude — the 14-inch allocation may be fully drawn down by mid-summer in a hot, dry year. Irrigators should plan irrigation scheduling with that scenario in mind, not assume that improved reservoir levels eliminate in-season pressure.

Dryland producers in the southern Alberta brown soil zones, particularly south and east of Lethbridge, should note that the December CDM still showed D1 pockets near Medicine Hat and along the Alberta–US border. Soil moisture carryover into spring in those areas is limited. Growing season precipitation will be the primary determinant of yield outcomes for dryland operations in this zone.

Saskatchewan irrigated and dryland operations

For irrigators on the Lake Diefenbaker system, above-median reservoir storage combined with above-normal mountain snowpack creates the best pre-season water supply position in several years. The WSA long-range forecast for southern Saskatchewan — normal precipitation and warmer-than-normal temperatures for May through July — is consistent with ENSO-neutral conditions but warrants monitoring. Warmer temperatures increase evapotranspiration demand; if precipitation comes in at the lower end of the normal range, irrigation demand will be elevated.

The Westside Irrigation Rehabilitation Project (WIRP) expansion near Lake Diefenbaker is scheduled to begin construction in late 2026, with approximately 100,000 acres of new irrigated area targeted. The current above-median reservoir position strengthens the case for moving ahead with that project timeline.

For dryland producers in the Kindersley–Assiniboia southwest corridor, the WSA’s projection of well-below-normal runoff is a direct warning: subsoil moisture in this corridor going into the growing season is likely to be limited, and that zone carries the highest drought exposure in the province for 2026. Crop selection and input decisions in this corridor should account for elevated production risk.

Manitoba grain and livestock producers

The primary near-term concern is seeding timing and field access, not water supply. Elevated flood risk along the Red, Assiniboine, and in the Interlake region could delay spring field operations by one to two weeks in affected areas. Canola seeding in flood-affected zones should be monitored closely for timing pressure against frost risk windows. Pasture recovery in low-lying areas near river systems will lag if flooding extends through May.

Livestock producers in the Parkland and Interlake regions should have contingency plans for delayed spring turnout if overland flooding delays pasture access. Feed inventory management through the risk window is the relevant planning action now.

For Manitoba irrigated potato and specialty crop producers relying on on-farm snowmelt storage, the above-normal snowpack across much of the province translates to better reservoir fill than in recent dry springs. The risk is rapid melt concentrating runoff too quickly to capture effectively — worth monitoring as temperatures rise in late April and May.

What to Watch

Canadian Drought Monitor — March 2026 update: Expected from AAFC by approximately April 10, 2026. This map will be the first to capture winter snowpack effects on soil moisture and the first definitive assessment of whether long-term drought designations in southern Alberta and southwestern Saskatchewan have been downgraded. Published monthly at agriculture.canada.ca .

NOAA ENSO Diagnostic Discussion — May 14, 2026: The next scheduled release will provide the first post-spring assessment of whether El Niño has formally emerged and, critically, early-strength modelling for summer and fall 2026. This release will refine the winter 2026–27 planning signal. Published at cpc.ncep.noaa.gov .

Saskatchewan Water Security Agency — ongoing monthly updates: WSA will continue publishing reservoir and runoff condition updates through the spring and summer. Lake Diefenbaker inflow tracking through May and June is the key indicator for Saskatchewan irrigator confidence through the growing season. Published at saskatchewan.ca .

Alberta Agriculture and Irrigation — provincial reservoir storage summary: Updated weekdays. Tracks storage volumes across the Milk, Oldman, Bow, Red Deer, North Saskatchewan, and Athabasca basins. Critical to monitor as spring runoff develops and as the May–June growing season demand ramp begins. Available at rivers.alberta.ca .

Tags: ENSO neutral, La Niña, El Niño watch, irrigation water allocation, Prairie drought, southern Alberta reservoirs, Lake Diefenbaker, Saskatchewan runoff, spring soil moisture, Manitoba flood risk

This post was produced with AI assistance. All sources are attributed and linked. Western Farm Report editorial standards apply.