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Spring Water Runoff: What to Expect

The water remains safe for drinking, cooking and bathing. 

Chlorine levels may be increased to address this issue. Chlorine is used to disinfect water so it is safe for drinking purposes. This chemical destroys micro-organisms such as bacteria and viruses that can pose a threat to public health.

Water in Lethbridge is always safe for human consumption - the community will always be notified if the water is UNSAFE to drink.​​

When this happens, residents may notice a stronger than usual chlorine odor and taste to the City's water supply. Again, the water remains safe for drinking, cooking and bathing. 

Spring runoff can also mean excess runoff in your neighbourhood, and it is important that you make sure your property is safe from intense water events. Be sure to check your home to prevent flooding, and clear gutters and stormdrains in your neighbourhood of leaves, garbage, other debris, or snow to help water drain.


Why there are changes in water quality

1. Increased temperatures can cause high turbidity levels due to quick melt and ice jams on the Oldman River.

What is turbidity? Turbidity is the measure of how cloudy a river or lake is. High turbidity is caused by changes in the water flow, such as spring runoff, ice melting on the river, or intense rainstorms.  Turbidity​ is measured by the amount of light that is able to shine through the turbid water, measured in NTU's (Nephelometric Turbidity Units).

Higher NTU's  mean higher turbidity in the water, which makes it more difficult to treat the inflow of water from the Oldman River.

Turbid water is a challenge when there are high river flows in May and June, but there are two reasons that it may be especially challenging in February and March:

  1. Water temperature: The chemical reactions that we depend on during water treatment are slower in cold water. Further, the settling process prior to filtration is less effective, as cold water is denser than warm water
    (ex. 3 degrees C vs 15 degrees C).
  2. The rate at which river conditions can change: Ice jams can result in the river turbidity changing in just one hour from less than 500 NTU (Nephelometric Turbidity Units) to more than 5,000 NTU. In comparison, June high water, even during the flood of 1995, can result in similar changes but over a period of three or four days.
Why does this happen? In Southern Alberta, we see this a lot​! The snow accumulation in the mountains, cities, and towns can create large amounts of runoff when we see temperatures drastically change or increases in precipitation in a short amount of time.

2. Increased turbidity leavels means the Water Treatment Plant can't keep up with demand and storage levels are depleted.

Increased turbidity levels makes it more difficult to clean the incoming water at the Water Treatment Plant. This causes the water in the storage reservoirs throughout the City of Lethbridge to decrease (diagram explaining location of storage reservoirs below), if we do not use caution with the amount of water we use. 



3. Increases in Natural Organic Matter (NOM) in the water. 

Natural Organic Matter (NOM) is the organic material present in surface or ground water, coming from plants and animal waste products within the environment. Sources include agriculture, forested areas, plants, open fields, etc. 

This causes different tastes and odours in our water supply.

As flow and turbidity increase during spring runoff, we may need to add chlorine to ensure that we are reaching quality standards​​​​, and ensuring safe drinking water. 

Water in Lethbridge is always safe for human consumption - we will always notify the community if the water is UNSAFE to drink.​​


Requests to conserve water

Water concerns can mean that the community needs to help conserve water. The reason water conservation would be required could be due to:

  • high turbidity in the water,
  • the Water Treatment Plant cannot keep up with demand (storage reservoirs decrease), and
  • increased Natural Organic Material (NOM) in the water.


What does this mean for the community?

We cannot control annual snowmelt, runoff, or weather, but we can prepare and respond as necessary.  The following may be required during these times, as city employees try to keep up at the Water Treatment Plant:

  1. Voluntary water conservation may be asked of the community 
  2. Mandatory water conservation, as outlined in the Water Rationing Action Plan
Note: with voluntary or mandatory water conservation, a Boil Water Order​ may also be declared.

Boil Water orders are issued when the water is unsafe to consume, or likely to become unsafe at any time. This reduces the risk of water-borne illnesses. 


How can I prepare for water conservation events?​

  1. Ensuring you are prepared for a 72 hour emergency
  2. Reviewing the Water Rationing Action Plan​, in the case that water conservation becomes mandatory
  3. Pre-plan within your home or business about what actions can be taken if water conservation is voluntary, or mandatory. Create an Action Plan for water conservation.
    1. You can also visit the following pages for ideas:


What the community should NOT do!​

1. Please do not panic. We are working on the problem and safety is our first priority. 

2. Please do not hoard water; we will inform the community of any issues that will require the saving of water.

Be assured that we are working around the clock each and everyday, to ensure safe drinking water is available to the community.



  1. Who should be conserving water during a water conservation event?

    Answer: If voluntary water conservation is requested, we ask that all Lethbridge water users do what they can to conserve water. It is anticipated that the need for water conservation will be short, and therefore ask that everyone pitch in, including residential, commercial, and institutional settings.

  2. What are some ways that I can conserve water?

    Answer: All Lethbridge water users can reduce water usage and conserve by looking for areas within your business or household where you can reduce water use. Some actions can include: flushing the toilet only when necessary, not running the water, limiting showers (or reduce shower time in half), etc.

  3. How do I know if my water is safe to drink? (what if it has a different smell and/or taste?)

    Answer: It is always safe to drink unless the City of Lethbridge notifies the community of a Boil Water Order, or another health warning.


How many Water Treatment Plants do we have?

The City of Lethbridge consists of one Water Treatment Plant, located in the river valley, across the river from the University. Treated water is pumped from the plant to reservoirs, then to water customers via underground pipes.

There are two water reservoirs in each of the south, north and west. A portion of the water at each reservoir is dedicated to fire protection, and the remainder is used to meet community demands.


Other Information

Water Conservation

Outdoor Water Conservation

Indoor Water Conservation


For more information

Phone: 311 or 403-320-3111 (if outside of Lethbridge)
Online: Submit a service request