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Wildfires: How Do They Affect the Water Cycle ?

• 20.08.2021
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Wildfires: How Do They Affect the Water Cycle ?

Dursun Yıldız

Water Management  Specialist

Hydropolitics Academy

August 7 2021

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Urgent action is needed to safeguard the biodiversity of the world’s forests amid alarming rates of deforestation and degradation, according to the latest edition of  The UN Report  “State of the World’s Forests” .

It highlights that some 420 million hectares of forest have been lost through conversion to other land uses since 1990, although the rate of deforestation has decreased over the past three decades.Forests are the most important elements of ecosystem balance  In the last period, increasing fires increase this imbalance.

The increase in forest fires creates adverse effects on water resources. Fires cause changes in vegetation-soil-water balance of water resources.

Wildfires are keystone components of natural disturbance regimes that maintain ecosystem structure and functions, such as the hydrological cycle, in many parts of the world. Consequently, critical surface freshwater resources can be exposed to post-fire effects disrupting their quantity, quality and regularity. Although well studied at the local scale, the potential extent of these effects has not been examined at the global scale

The amount of water used in the fire generally does not generate water pressure

Water used by air vehicles such as aircraft and helicopter in extinguishing forest fires are taken from the sea, lakes and pools. From time to time, it is used to be drawn from the streams and groundwater in suitable areas and are used for extinguishing and cooling. In addition, chemical substances are also used in forest fires.

In the fire-fighting aircraft,  about 5 tons water can be stored . These aircrafts can withdraw water from the source  two times  per hour. Even if thousands of sorties are made, the water used for this purpose will not exceed 5000-10000 tons. The helicopters in mountainous areas can take water faster than airplanes and move to forest fire. Although the aircraft can carry   10 tons of water in 1 hour, it is known that the helicopters can perform approximately 12 sorties  and carry 2.5 tons of water each case .The water-carrying capacity of fire-fighting helicopters reached up to 7.5-10 tons in recent years.

In addition to the fire fighting by aircrafts and helicopters , it is powered to be widely used in the terrestrial struggle to the fire regions of fresh water due to mountainous woodland conditions and fire conditions.

In the fight against forest fires  water resources play a significant role . But optimum amount of water is used in a plan together with other measures. For all these reasons, the water used during the forest fire, which usually does not generate a pressure on the water sources.

The main effect occurs after fire. The balance of the ecosystem is broken.

According to experts one of the reasons that trigger the forest fires is  hotter air masses and decrease humidity resulting from meteorological drought. However, only the climate is not effective on fire, but also the fire may also cause changes to the climate. This is the part of the work that concerns the water policies

The presence of forests that are lost or lost in various ways is directly or indirectly effective in the hydrological cycle.

• Raindrops  fall in that land  with a greater energy creating more sediment transport

• Forests lost by fire  increase run off  flow by lost of  evapotransporation

• Burned forest area reduces the permeability of the land and causes water resources in the quantity and quality of water resources and leads to erosion.

• The infilitration  capacity of the land in the burned forests area decreases  by 10-15%.Therefore precipitation  is run of in shorter time

The large fires of experts suggest that the vegetation may affect the energy balance and micro-air conditioner with the disappearance of the vegetation.

The studies show that changes in land surface characteristics have also changed the micro air conditioner in that region

In summary, forest fires bring many environmental changes.

 This change differs depending on the severity of the fire, the time, its frequency, the shape and its size. The degree of this change is also due to the seasons and the type of flammable substance, land and soil properties.

Nature's self-renewal feature is moving after a fire. However, it takes a long time to reconstruct all the deteriorated ecosystem balances.

Wildfires are essential to ecosystem function across the globe , influencing a wide spectrum of ecosystem components and natural processes , among which is the hydrological cycle. Accordingly, an abundant literature has described the effects of vegetation burning and post-fire recovery on local hydrology in different biogeographic areas . Vegetation cover, litter and soil organic matter can be dramatically reduced by large fires and can lead to higher surface runoff and soil erosion, increasing water quantity, but decreasing water quality. The water requirements of rapidly growing post-fire vegetation can subsequently limit water quantity , even though water quality may improve[2].

We need broader  scale  approach

The timing, extent, and severity of forest wildfires have increased in many parts of the world in recent decades. These wildfires can have substantial and devastating impacts on water supply, ecohydrological systems, and sociohydrosystems. Existing frameworks to assess the magnitude and spatial extent of these effects generally focus on local processes or services and are not readily transferable to other regions. However, there is a growing need for regional, continental, and global scale indices to assess the potential effect of wildfires on freshwater availability and water supply resilience.[1].

References

[1] Hallema, D. W., Robinne, F.-N., & Bladon, K. D. (2018). Reframing the challenge of global wildfire threats to water supplies. Earth’s Future, 6. https://doi.org/ 10.1029/2018EF000867

[2] François-Nicolas Robinne , Carol Miller, Marc-André Parisien , Monica B. Emelko , Kevin D. Bladon , Uldis Silins  and Mike Flannigan (2016) A Global Index for Mapping the Exposure ofWater Resources to Wildfire Forests 2016, 7, 22; doi:10.3390/f7010022 www.mdpi.com/journal/forests 13 January 2016