Regional Drainage

Horsefly Regional Emergency Spillway Project

Phase 1 in Construction

The expansion of an existing emergency spillway to divert overland floodwaters and stormwater runoff from the St. Mary River Irrigation District's main canal to the Oldman River. The project is located mainly on private lands near Taber, Alberta. The expansion would increase the diversion capacity of the existing spillway from approximately 7.6 m3/s to 47 m3/s.


Over a decade in the making.

From human development to farming, irrigation, and land modifications, Southern Alberta has witnessed a significant increase in agricultural production, accompanied by numerous residential and industrial land development opportunities. Spanning from the City of Lethbridge to the City of Medicine Hat, this region contributes $1.8 billion to the agricultural Gross Domestic Product, supporting more than 120 agri-food processing industries. However, these developmental advancements have not occurred without consequences.

The intensified development has led to alterations in the natural drainage of the landscape, reducing its absorptive capacity. Consequently, this has created challenges in managing stormwater, posing threats to homes, businesses, public infrastructure, farmland, crops, and the vital drinking water supply. Moreover, the lack of natural drainage exacerbates the situation, as many drainage corridors in various parts of the region are intercepted and conveyed by the existing irrigation canal system. This system was not originally designed to handle the excess volume resulting from heavy rainfall and snowmelt runoff. Given the potential for future weather events resembling those experienced in 2010, 2011, 2013, 2014, and 2018, the establishment of an emergency discharge corridor becomes critical for the economic stability and growth of the region.

In 2012, the Southern Regional Stormwater Drainage Committee (SRSDC) was established to formulate a long-term solution to address the ongoing threat posed by stormwater runoff events. Collaborating partners of the drainage committee encompass the Towns of Coaldale, Taber, and Bow Island, the Village of Barnwell, the City of Medicine Hat, the Counties of Lethbridge, 40 Mile, and Cypress, the newly amalgamated St. Mary River and Taber Irrigation Districts (SMRID), and the Municipal District of Taber, which serves as the managing partner.

Under the purview of the SRSDC, the Southern Regional Stormwater Management Plan was devised, identifying seven pivotal flood mitigation projects spanning from south Lethbridge to Medicine Hat, with a cumulative budget exceeding $170 million. Among these seven projects, the Horsefly Regional Emergency Spillway Project yields the most significant benefit in enhancing the flood attenuation capacity of the entire regional system.

By strategically setting an emergency spillway near the midpoint of the 312 km-long SMRID main canal—a major point of capacity reduction—this project will safeguard water/wastewater systems, transportation networks, and public infrastructure from recurrent damage. The 15 km-long Regional Emergency Spillway will divert water from the main canal near Taber, Alberta, and channel it through the existing irrigation infrastructure to the Oldman River at a rate of 47 m3/s.

Upon becoming operational, the regional emergency spillway will ensure the ongoing safety and security of residents throughout the region, while concurrently generating up to 150 new construction jobs. The enduring economic impact of these infrastructure upgrades promotes long-term community resilience and establishes the requisite foundation for attracting additional investments in the agri-food processing industry, thereby heralding a brighter future for all residents of Southern Alberta.



Location: From the Taber Lake Reservoir to the Oldman River 

Construction start date: December 6, 2022

Engineers: MPE Engineering Ltd, Stantec Engineering

Contractors: DeGraaf Excavating Ltd

Completion date: Summer 2024


Location: From the Horsefly Lake Reservoir to the Taber Lake Reservoir

Construction start date: 2024

Engineers: MPE Engineering Ltd, Stantec Engineering


Completion date:


Location: From the SMRID main canal to the Horsefly Lake Reservoir

Construction start date: 2024

Engineers: MPE Engineering Ltd, Stantec Engineering


Completion date:


Government of Canada

Phase 1


Investing in Canada Infrastructure Program (ICIP)

Phases 2 & 3


Disaster Mitigation and Adaptation Fund (DMAF)
Government of Alberta

Phases 1, 2 & 3


Alberta Community Resilience Program (ACRP)
Southern Regional Stormwater Drainage Committee Partners

Phases 1, 2 & 3


Partners are seeking further funding from the Provincial Government

St. Mary River Irrigation District

Phases 1, 2 & 3


+ Land and right-of-way acquisition contribution


Southern Regional Stormwater Drainage Committee Partners

Land Management Plan
Land Management Plan