Low water levels and hydrological droughts
Although Quebec has an abundance of fresh water and its quality is generally good, it isn’t always sustainably managed.
Climate change and other factors such as population growth and consumer habits are putting increasing pressure on its water regime. This could lead to more severe hydrological droughts and low water periods in certain regions of the province.
This section of the website focuses specifically on the influence of climate change on low water levels and hydrological drought.
Different types of drought
A drought is defined as an abnormally dry period that lasts long enough for the lack of precipitation to cause a serious hydrological imbalance. There are two main types of drought: hydrological drought and agricultural drought.
Hydrological drought affects surface water and groundwater. It occurs when the levels of watercourses drop considerably.
Agricultural drought is characterized by a lack of water in the top layer of soil (around one metre), which adversely affects crop growth conditions. It is caused by a prolonged rainfall deficit, and its impact varies depending on soil properties and crop type. Agricultural droughts are generally associated with reduced crop yields and water scarcity. They are particularly serious if they occur at critical moments in the plant growth cycle, such as during germination. The influence of climate change on agriculture is discussed on the Agriculture page.
Definition | Low water levels
Low water levels, which correspond to the minimum level or flow of a watercourse during dry periods, are a direct consequence of hydrological drought. It’s important to remember that there is no single definition of low water levels, which vary depending on their duration and recurrence, like floods. The thresholds used to identify low water levels may differ from one jurisdiction to another.
Causes of low water levels and hydrological droughts
Several climate factors, such as humidity, wind, and solar radiation, can influence the occurrence of hydrological droughts. However, temperature and precipitation play a key role.
Generally speaking, in the summer, low water levels occur in the absence of rain when there are very high temperatures, favouring evapotranspiration.
Definition | Evapotranspiration
Evapotranspiration is the combination of two natural processes that move water into the atmosphere: the evaporation of water and transpiration by vegetation.
In the winter, part of the precipitation falls as snow, making this season more prone to low water levels. Moreover, winter conditions can have a significant impact on water levels the following summer. A recent study has shown that greater amounts of accumulated snow which persist longer and melt more gradually in the spring favour higher water levels during the subsequent summer.
However, this reality could change as a result of increased precipitation in the form of rain and reduced snow and ice cover in winter, caused by climate change.
