A drought is when there is less water available over a large physical area for a long period of time. It happens when precipitation (for example, rain or snow), river flow, and ground water are below average levels.

Drought can generally be described as a prolonged period of dry weather that depletes water resources. Water resources may include:

• natural sources such as rivers, streams, lakes, wetlands, and groundwater,
• human-made storage such as reservoirs and dugouts, and
• soil moisture.

For The City of Calgary, drought occurs when the water required for municipal supply, irrigation, and minimum environmental flows diminishes below The City drought triggers and supporting indicators.  

Unlike floods, which can happen very quickly, droughts develop slowly over time. A drought can last anywhere from weeks to months and can evolve into multi-year droughts if the region is consistently not getting enough moisture.

Calgary is most at risk of experiencing a drought from mid-July to the end of September.

The reason why drought is a top climate hazard for Calgary is because regional warming trends will result in seasonal shifts in the type and timing of precipitation. This means that there will be less water in the rivers when we need it most – during our hotter, drier, and longer summers.

These impacts are compounded by growth and an increasing development footprint – as you can see on the right - which replaces our natural landscapes with, typically, less drought resilient landscape types that require irrigation.   

In addition to impacts on our drinking water supply and local agriculture, droughts can cause:

• negative health impacts to plants, wildlife, wetlands, forests, parks, open spaces, recreational facilities, and private yards,
• drying out of forests and grasslands and an increase in the risk of wildfires, which impact both local air quality and water quality, and
• increased pests and disease outbreaks (for example pine beetles) in trees and plants. Lack of water can stress trees, limiting their ability to react to these attacks.

The City of Calgary defines water security as having enough water for human well-being, ecosystem resilience, and economic activity now and for future generations. Calgary’s Water Security Framework outlines The City’s top risks to water security (climate change, population growth, and water license limits), key initiatives underway, and priority actions that address questions of future long-term water security out to the year 2100. The creation of the Drought Resilience Plan is a key action identified in this strategy.

The City has taken several proactive steps to explore ways to increase our water storage and manage our demand to ensure we have a year-round reliable water supply.

For example, the addition of higher gates at the Glenmore Dam doubles the storage of the reservoir, which not only increases flood protection but also improves our climate resilience to future droughts so we can store more water in the winter when flows on the Elbow River are at their lowest.

Also, significant progress has been made to help reduce our water demand by nearly 30 per cent despite a growing population. This includes investments in leak detection, water main replacements, water metering, and the adoption of low-flow toilets and faucets.

Glacial melt is important. On average, glacier melt makes up approximately three per cent of Calgary’s annual river runoff with most of our water supply coming from precipitation (snowmelt and rain).

However, if we were to experience a drought extending into August, when precipitation is at its lowest, glacial melt would contribute 8-20 per cent of our water supply when there isn’t as much precipitation to rely on.

With rising temperatures due to climate change, glaciers will continue to shrink, meaning we won’t have the same steady supply in our rivers to sustain us over the driest months of the year.

Drought has received renewed attention over the last decade as climate change and urban growth reshape supply and demand in the Bow River watershed.

History shows that our region is prone to prolonged, severe droughts which will be intensified by climate change in the future. A multi-year drought impacting Calgary is one of our city’s top climate hazards, and improved climate modelling and risk analysis has provided new technical knowledge of how droughts will impact Calgary, and strategies needed to mitigate those impacts. This plan is timely to demonstrate accelerated action for climate adaptation.

Persistent water scarcity can erode investor confidence in a city's economic prospects, potentially deterring investment in both local businesses and infrastructure projects. Implementing the holistic suite of strategies for drought resilience is critical for supporting long-term growth and city building in a semi-arid and drought-prone region.

To build drought resilience, some of the strategies we are considering need the participation of all Calgarians and businesses to reduce how much water we need and use.

Demand Management–a broad term for managing how much water we use as a municipality–is a priority goal within the Drought Resilience Plan. Maintaining a thriving city and economy in a drought-prone location requires a continuously evolving relationship with water and climate change through an update to the current City of Calgary Water Efficiency Plan. This is foundational work and connects to the other goals from the water supply, readiness and response, ecosystem, and people perspectives.  

Key actions include updating the targets and actions in our Water Efficiency Plan, addressing the potential financial impacts of drought, and updating the water restrictions section within the Water Utility Bylaw. Enacting water restrictions this summer and fall has offered an opportunity to have real-time data and customer experiences to draw on.

In Calgary, our 2022 demand was 351 litres per person per day (lpcd), and our net residential consumption was 174 lpcd, which includes both single family and multifamily.

The City is part of a national benchmarking initiative for water utility performance indicators. This reporting shows that among other Canadian municipalities, Calgary ranks in the median for residential daily consumption.

Calgary’s Climate Strategy identifies drought as one of Calgary’s eight main climate hazards, and the adaptation action plan directs the development of the Drought Resilience Plan to identify pathways and strategies to address drought-related impacts.

The Drought Resilience Plan’s implementation schedule lists the alignments between the drought strategic actions and the climate strategy adaptation theme areas of People, Built Infrastructure, Natural Infrastructure and Water. 

The Drought Resilience Plan articulates the intersections of drought and city building, and the impacts of growth and urban form on water uses. Through the Land Use Bylaw renewal and City Building program, an opportunity is presented to review and update landscape regulations to encourage or require more native and drought-tolerant plant species and other resilient landscaping features, that will support better outcomes for drought resilience on private landscapes.    

The plan identifies in-stream flows (meaning, the quantity, timing, and quality of water flow required to sustain freshwater ecosystems) as one of the systems with the highest vulnerability to drought. Flows, water quality, the potential for reduced biodiversity, and the influx of invasive species were the most vulnerable components.

The Healthy Landscape goal looks at strategies that protect our aquatic ecosystem in low flow and drought conditions, as well as ensuring our built and restored landscapes use drought-tolerant species that ensure they can thrive during drought and minimize potential disturbance from other invasive species.

The City of Calgary already assumes responsibility for authorizing water reuse projects on a case-by-case basis, including the use of reclaimed water from our wastewater treatment plant for a key industrial customer.

The City also irrigates some parks around Calgary with non-potable water. Currently, seven large sites are using either untreated river water (Bowness Park, Prince's Island, Baker Park), well water (Valley View) or storm water from run off (Inverness Storm Pond, Nose Creek Recreation Centre).