The Impacts to Water from Wildfire
Wildfires cause devastating heat, fire, and burning destruction. After the wildfire’s ash settles and the rain pours, mudslides quickly erode the burned land, carrying a swath of debris and muddy sludge downhill. As runoff pours downhill, it enters into waterways such as streams and lakes, degrading the water quality. This impact to water is the focus of part three in our wildfire series.
We will discuss where our water supply comes from, how wildfire affects it, what contaminates it, and water pollution solutions for preventing and treating it. We will demonstrate how the Thomas Fire in southern California has affected the water supply in the county of Ventura, and how they are responding. Part one, which focuses on water storage preparation, is here. Part Two, which focuses on erosion control, is here.
The Importance of Clean Water
Clear and clean water is one of the most basic of human necessities. We need it to drink and replenish our bodies. We need it to irrigate crops to grow food. Aquatic life needs it to breathe, and to swim freely and see clearly. Clean water matters and enables us to function and flourish.
Where Does Our Water Supply Come From?
The majority of our water sources originate from forested land. Since forests provide so much of our water supply, it’s important to protect the forests’ watersheds .
According to the U.S. Geological Survey:
- 50% of southwestern U.S. water supply comes from forests
- 80% of freshwater in the U.S. begins in forest lands
- 3,400 public drinking water systems are in national forest watersheds
Contaminants in Runoff from Wildfire
Contaminants from post-wildfire runoff harm aquatic life in ecosystems, killing fish and plants. They also compromise water quality in water district municipalities, causing boil water alerts and a diversion of water sources which leads to unsafe low water pressure. The severity of the wildfire determines the degree to which the water quality degrades. It is based on several factors: post-wildfire precipitation, watershed topography and ecology of the local region.
Some of the common contaminants found in water runoff are elevated heavy metals (including iron, lead, nickel, and zinc), phosphorous and nitrates, pesticides, remnants from flame retardant, and chemicals. Ash and debris can also contaminate water bodies. The debris accumulates and travels in stormwater runoff to new locations. It can also be blown by the wind into water sources. The communities surrounding the Thomas Fire burn area understand this contamination all too well.
The Thomas Wildfire’s Effect on Water Quality
On January 9th, torrential rains fell in Ventura County, close to the southern California Thomas Fire burn area. The recent fires burned at such high temperatures through the upper watershed that it left behind a significant amount of ash and debris. The muddy runoff gathered debris as it rolled downhill and into the water ways. It overwhelmed the Matilija Dam, which flows into the main tributary of the Ventura River. This caused the Casitas Municipal Water District to stop pumping water from the river to prevent potential water quality impacts to their Lake Casitas reservoir.
While this prevented contamination, it also decreased the available water supply. The water pressure and supply had already been lower from power outages and from firefighters drawing water to fight the Thomas wildfire. This pollution only made the problem worse.
The Matilija Dam Webcam on January 9th.
Severe turbidity entering the water supply.
A normal day for the Matilija Dam
The Casitas Municipal Water District has plans to use water pollution prevention products to help. The products will clean up and filter the ash and debris, allowing the water district to begin pumping again from formerly polluted waterways, such as the Ventura River. According to Ron Merckling, a spokesperson for the water district, turbidity curtains will block sediment from flowing downriver and drop it to the surface. They are being placed on Santa Ana and Coyote Creeks and near an intake structure for Castaic Dam. Booms that are up to 20 feet wide will skim the surface and will block floating material such as wood and brush.
Ventura County is just one of the many communities facing these challenges. Neighboring communities such as Montecito have also had water breaks, power outages, and disruptions to their water supply. Fixes for these water quality issues can take weeks or even months. Fortunately, there are many options for minimizing the effects to water quality.
Solutions for Improving or Maintaining Water Quality after a Wildfire
There are several solutions to minimize your contribution to contaminated stormwater runoff. These products can be used either before or after a rain event.
Erosion Control to Minimize Impact to Water Quality
The first solution is to prevent the sediment, debris and contaminants from entering the waterways. Soil erosion control products slow and filter the spread of the runoff before it enters water bodies.
- Straw Wattles can help prevent toxic urban runoff from entering water streams. They are placed perpendicular to the flow of the water.
- Straw or coir mats replace the hardened, burned earth with an absorbent ground cover.
- Silt fences collect sediment and slow the speed of water.
Protecting Stormwater Drains and Other BMPs
Another solution is to use stormwater best management practices (BMPs), such as drain guards and ditch checks. These filter or stop the flow of water. If the stormwater drains are not maintained, it can lead to costly cleanup. Avoid expensive fixes by maintaining the drains.
- An Overgrate Drain Cover is placed over the drain to keep sediment and debris out of the drain.
- An Undergrate Drain Cover hangs underneath the drain cover to catch the debris below the drain.
- A Ditch Check acts like a temporary dam to filter sediment runoff.
Water Pollution Prevention: Turbidity Curtains and Debris Booms
Another effective preventative solution for water-side property owners, associations and municipalities is the use of turbidity barriers. Turbidity curtains and booms are used as a last resort, once the turbidity and sediment has already entered the waterways. They float in the water, containing and slowing the settle of the sediment as it passes through the water.
We have many variations of turbidity curtains and booms depending on needs and situation.
- Turbidity Curtains slow the spread of sediment so it has time to settle to the bottom. Several types are available depending on water conditions.
- Debris Booms collect floating branches and trash debris.
- Staked Silt Barriers can be placed in shallow water (30” deep or less) to collect sediment and redirect the flow of water.
An Investment for the Future
The government is also finding ways to help. The U.S. Department of Agriculture (USDA) announced recently on January 17th that it’s investing almost $32 million this year to mitigate wildfire risk, improve water quality, and restore healthy forest ecosystems. It will include supporting important watersheds, and reconnecting ecosystems that are vital reservoirs of biodiversity. The U.S. Forest Service is an agency of the USDA.
The Future of Wildfire
Wildfires are a complicated and dangerous phenomenon. They can swiftly burn thousands of acres leaving behind charred earth and destroying communities, properties and lives. They can lead to massive mudslides and flooding, steep erosion of hillsides, and polluted runoff. They can affect the water supply and contaminate public and private water sources.
Understanding the process of wildfires can help us in the future. Using preventative measures before, during, and after the wildfire can help control and mitigate its effects. Working together as a community, we can become more knowledgeable and better prepared for the future of wildfire.
If you have questions about any of the wildfire solutions we discussed, please contact us at 772-646-0597 or visit us at GEI Works.
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