Drought Indicators and Effects

 

What is Drought?

 

Drought is a recurrent feature of climate involving a deficiency of precipitation over an extended period of time, resulting in a water shortage for activities, communities or aquatic ecosystems. Droughts can be defined as meteorological, hydrological, agricultural or socioeconomic, each of which implies different impacts.

 

Meteorological Drought

 

Meteorological drought is generally defined by comparing the rainfall in a particular place and at a particular time with the average rainfall for that place. Meteorological drought leads to a depletion of soil moisture and this almost always has an impact on crop production. When drought is defined in this way, only reductions in rainfall are considered. The impacts of the lack of water on water reservoirs, human needs or on agriculture are not taken into account.

 

Hydrological Drought

 

Hydrological Drought is associated with the effect of low precipitation on water levels in rivers, reservoirs, lakes and aquifers. Hydrological droughts usually are noticed some time after meteorological drought.

 

Agricultural Drought

 

Agricultural Drought occurs when there is not enough water available for a particular crop to grow or livestock to thrive at a particular time. This drought does not depend only on the amount of precipitation, but also on the correct use of water. Agricultural drought is typically seen after meteorological drought and before hydrological drought.

 

Socio-Economic Drought

 

Socio-Economic Drought occurs when the demand for economic goods exceeds their supply as a result of a weather-related shortfall in water supply.

 

The Province of BC uses four core indicators and additional supplemental indicators to establish:

• if there is a drought or a possibility of drought
• what the drought level is at a given point in time.

 

Core Indicators

 

The province measures the following four indicators to establish whether there is a drought:

• Basin snow indices
• Seasonal volume runoff forecasts
• 30 percent of average precipitation
• 7-day average streamflow

The drought level is linked to a threshold established for each of the core indicators (see page 14 of the British Columbia Drought Response Plan).

 

In addition, the following supplemental indicators also help assess the situation.

• Aquifer levels
• Individual hydrometric station results
• Multi-year trends
• Reservoir inflows
• Wildfire danger class ratings

For more information:

 

Drought Information, Government of BC

 

Drought affects communities, the environment, and the economy through a reduction of water for communities, agriculture and industry. It also affects the sustainability of aquatic ecosystems.

 

Lower water levels may increase concentrations of nutrients or contaminants, leading to poor water quality.

 

With less available potable surface water, people may make heavier draws on ground water supplies, wells, and springs.

 

Water that is necessary for biological or industrial production processes may be reduced, and agriculture and industry users may lose the ability to produce crops or provide goods and services to communities of the province, impacting the health and economy of an area.

 

Coping with the effects of reduced supplies may cause chronic stress for some individuals and negatively affect the social fabric of a community.

 

Drought conditions will also increase the risk of forest fires and limit water supplies for firefighting.

 

Lower stream flows and the corresponding increased water temperatures threaten the survival of many fish and aquatic species.

 

For more information:

 

Dealing with Drought: A Handbook for Water Suppliers in British Columbia - July 2009

 

Source: Dealing with Drought: A Handbook for Water Suppliers in British Columbia - July 2009

 

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