watershed

Wildfires and water quality

August 11, 2025 By EarthWise Leave a Comment

Hotter and drier conditions driven by climate change are leading to an increasing number of wildfires in North America and around the world. The damage wildfires cause – to forests, homes, and communities – is well-known. But long after the flames are gone, the effects can linger, especially in rivers and streams, where water quality may suffer for years.

A new study by scientists at the CIRES institute at the University of Colorado Boulder analyzed more than 100,000 water samples from more than 500 sites across the Western U.S. and found that wildfires can degrade water quality for up to eight years after a fire. The research, which was recently published in the journal Nature Communications Earth & Environment, found elevated levels of organic carbon, nitrogen, phosphorus, sediment, and turbidity – the cloudiness of water – in basins affected by fire.

This large-scale analysis reveals watersheds take longer to recover from wildfires than previously thought, with widespread, long-lasting impacts often going undetected for years.

Organic carbon, phosphorus, and turbidity remain elevated for one to five years after a fire. Nitrogen and sediment levels stay notably high for up to eight years. Fire-driven impacts are worse in more forested areas.

Each watershed in the study responded differently depending on local conditions. In some places, sediment levels surged to as much as 2,000 times normal levels, while others remained relatively unchanged.

The research team hopes its findings can help guide future planning efforts to improve wildfire resilience.

**********

Web Links

Wildfires threaten water quality for years after they burn

Photo, posted April 6, 2017, courtesy of Bonnie Moreland via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Saving the Great Salt Lake

January 27, 2025 By EarthWise Leave a Comment

For many years, scientists have warned that the Great Salt Lake in Utah is headed toward a catastrophic decline. While the size of the Great Salt Lake fluctuates naturally with seasonal and long-term weather patterns, the lake has been experiencing significant and steady declines for decades. In fact, the Great Salt Lake has lost more than 15 billion cubic yards of water over the past three decades, and it’s getting shallower at the rate of four inches a year.

This reduction is primarily due to excessive water diversions from rivers and streams that feed into the lake for agricultural, industrial, and municipal use. These diversions, combined with prolonged drought and rising temperatures due to climate change, have significantly reduced the lake’s water level.

According to a new study led by researchers from Oregon State University, 62% of the river water bound for the Great Salt Lake is diverted for human use, with agricultural activities responsible for nearly three-quarters of that percentage. The analysis, which was recently published in the journal Environmental Challenges, found that reducing irrigation is necessary to save the lake.

In order to stabilize and begin refilling the lake, the research team proposes cutting human water consumption in the Great Salt Lake’s watershed by 35%. The researchers emphasize that farmers and ranchers facing income losses from using less water would require taxpayer-funded compensation.

The Great Salt Lake is a biodiversity hotspot, sustaining more than 10 million migratory birds. The lake also directly supports 9,000 jobs and fuels $2.5 billion in economic activity annually.

**********

Web Links

Reducing irrigation for livestock feed crops is needed to save Great Salt Lake, study argues

Photo, posted January 14, 2024, courtesy of Olaf Zerbock via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

A Below-Average Dead Zone In The Gulf of Mexico | Earth Wise

July 20, 2023 By EarthWise Leave a Comment

The Gulf of Mexico dead zone, or hypoxic area, is an area of low oxygen content that can kill fish and other marine life. It occurs every summer and is mostly a result of excess nutrient pollution from human activities in cities and farms throughout the Mississippi River watershed. The nutrients carried by the river into the gulf stimulate an overgrowth of algae, which eventually die and decompose, which depletes oxygen in the water as the algae sink to the bottom.

The resultant low oxygen levels near the bottom of the gulf cannot support most marine life. Fish and shrimp often leave the area seeking better places to be. Animals that can’t swim away – like mussels and crabs – can be stressed by the low oxygen level or even killed.

The National Oceanic and Atmospheric Administration produces a dead zone forecast each year based on a suite of models developed by NOAA and partners at multiple universities.

The latest forecast, completed in May, found that the discharge of nutrients in the rivers was about one-third below the long-term average between 1980 and 2022. Nitrate loads were down 42% and phosphorous levels down 5%.

Based on these measurements, the scientists forecast a summer dead zone that will cover an estimated 4,155 square miles, which is 22% lower than the 36-year average of 5,364 square miles. Ongoing efforts by the Interagency Mississippi River and Gulf of Mexico Hypoxia Task Force to reduce nutrient levels seem to be paying off.

**********

Web Links

NOAA forecasts below-average summer ‘dead zone’ in Gulf of Mexico

Photo, posted September 6, 2013, courtesy of NOAA Photo Library via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Metals In Western Water Supplies | Earth Wise

October 29, 2021 By EarthWise Leave a Comment

A new study published by the University of Colorado Boulder looked at the problem of rivers being contaminated by acid rock drainage. Rocks that include sulfide-based minerals, such as pyrite, oxidize when exposed to air and water. The resulting chemical reaction produces sulfuric acid which, when present in water, dissolves metals like lead, cadmium, and zinc. The recent study found that rare earth elements are also leached out of rock by this process.

Rock drainage occurs naturally throughout the western United States, but historic mines that disturbed large amounts of rocks and soil have dramatically increased this process and have led to growing downstream water pollution. Upwards of forty percent of the headwaters of major rivers in the West are contaminated by some form of acid mine or rock drainage.

The warming climate has brought longer summers and less snow in winters. Longer, lower stream flows make it easier for metals to leach into watersheds and concentrate the metals that would otherwise be diluted by snowmelt.

Rare earth elements are essential components of many high-tech devices such as computers, hard drives, and cell phones. There is not a long history of studying the hazards they might represent when they enter the environment.

The study looked at the Snake River watershed in Colorado and found that increasing amounts of rare earth elements are entering Colorado water supplies. Concentrations of rare earth elements are not ordinarily monitored and there are no water quality standards set for them.

According to the researchers, once rare earth elements get into water, they tend to stay there. Traditional treatment processes don’t remove them. It is a growing problem that needs to be addressed.

**********

Web Links

Rare earth elements and old mines spell trouble for Western water supplies

Photo, posted October 27, 2007, courtesy of Dion Gillard via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Road Salt Pollution

January 8, 2020 By EarthWise 1 Comment

Mirror Lake is a popular recreational lake located in the Village of Lake Placid. It is the most developed lake within the Adirondack Park, which is a publicly protected area that is actually larger than Yellowstone, Yosemite, Glacier, and Grand Canyon National Parks combined.

New research has revealed that road salt runoff into Mirror Lake is preventing natural water turnover which poses a risk to the balance of its ecology. The study, which was published in Lake and Reservoir Management, found that road salt runoff is preventing spring mixing of the water column. This creates more anoxic water conditions, meaning there is less oxygen in the water, and limits the ability of the habitat to support the native lake trout.

Mirror Lake is the first lake in the Adirondack Park to show an interruption in lake turnover due to road salt. Many lakes in northern climes experience so-called “dimictic turnover”, which is a natural process where wind and less stratified water conditions of spring and fall allow mixing of the water column that redistribute oxygen and nutrients throughout the lake. High levels of surface-water chloride introduced into the lake from road salt runoff inhibit the mixing of the water column.

The lack of mixing and oxygenation is bad news for fish species such as lake trout, which require cold, oxygenated water to survive. It may also put the lake at a greater risk of algal blooms.

Mirror Lake is small, surrounded by concentrated development, and receives the direct discharge of stormwater. So, it is particularly vulnerable to road salt contamination. Other lakes elsewhere in New York may experience similar conditions. The researchers are confident that natural turnover conditions could be restored to the lake if road salt application in the watershed is reduced.

**********

Web Links

Road salt pollutes lake in one of the largest US protected areas, new study shows

Photo, posted January 5, 2018, courtesy of MTA of the State of NY via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.