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Spring Water Runoff: What to Expect

​​​What happens when there is an increase in water runoff?

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 we try to keep up at the Water Treatment Plant:

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

How can I prepare for these events?​

You can prepare by:

  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


Spring runoff can also mean excess runoff in your neighbourhood, and it is important that during these spring runoff events, and all throughout the year, you ensure that 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


How Many Treatment Plants do we Have?

The City of Lethbridge consists of one 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.


SHORT TERM issues at the Water Treatment Plant due to water quality concerns:

What is turbidity?

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.

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 thunderstorms.  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:

  • First is the 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).
  • Second is 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.

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. 




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 

Causes: Different taste and odour 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.​​


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.


Who should be conserving water?

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.

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.

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.


Need more information? Contact​