How Climate Change Is Affecting Your Tap Water Quality

Warmer temperatures, drought, and wildfires are degrading water sources nationwide.

Warming Water

Rising air temperatures are warming surface water sources -- rivers, lakes, and reservoirs -- that supply drinking water to most Americans. Warmer water holds less dissolved oxygen and supports faster microbial growth, which means treatment plants must use more disinfectant (typically chlorine or chloramine) to keep water safe. More disinfectant means more disinfection byproducts (DBPs) like trihalomethanes and haloacetic acids, which are linked to increased cancer risk at elevated levels.

USGS data shows that stream temperatures in the continental US have increased by an average of 1-2 degrees Fahrenheit over the past 50 years, with some regions warming faster. This may sound small, but microbial activity roughly doubles with every 10-degree Celsius increase. Utilities in the Southeast and Southwest are already seeing seasonal DBP levels approach or exceed EPA limits during summer months.

Warmer water also accelerates the breakdown of aging pipes and increases the rate at which lead, copper, and other metals leach from plumbing into drinking water. Higher water temperatures make corrosion control -- the chemical treatment that prevents pipe deterioration -- less effective, creating a compounding problem for utilities already struggling with aging infrastructure.

Drought

Drought degrades water quality in two ways: it concentrates contaminants and it forces utilities to tap lower-quality backup sources. When reservoir and river levels drop, the same amount of agricultural runoff, industrial discharge, and naturally occurring minerals is dissolved in less water, driving up concentrations of nitrate, arsenic, manganese, and other contaminants. Utilities may need to increase treatment intensity just to maintain the same water quality.

In extreme drought, some communities lose their primary water source entirely. In 2022, several small towns in Texas and Mississippi ran out of water and had to truck it in. Larger cities like Phoenix and Las Vegas are drawing down Lake Mead to historically low levels, approaching the point where water can no longer flow through Hoover Dam's intake pipes. These cities have invested in deep-well backup systems and water recycling, but the water chemistry from alternative sources often differs significantly from the original supply.

The hardness of your water can also increase during drought, as groundwater levels drop and wells pull from deeper, more mineral-rich strata. If you have noticed your water feeling harder or leaving more scale than usual, drought conditions may be the explanation. Check your city's current water data to see how your local numbers compare to historical averages.

Wildfires

Wildfires are emerging as one of the most severe threats to drinking water quality in the western US. When fires burn through watersheds that feed reservoirs, the runoff carries ash, sediment, heavy metals, and organic compounds into water supplies. Post-fire runoff has been shown to spike levels of manganese, iron, nitrate, and turbidity by 10 to 100 times normal levels. Standard water treatment was not designed for contamination at this scale.

The 2021 Marshall Fire in Colorado, the 2020 CZU Lightning Complex in California, and the 2025 Palisades and Eaton fires in the Los Angeles area all caused significant water contamination. In some cases, the heat from wildfires melted plastic water pipes and meters, releasing benzene and other volatile organic compounds directly into the distribution system. After the Camp Fire destroyed Paradise, California in 2018, the town's water system was contaminated with benzene at levels 8 times the federal limit, and the system remained unusable for over a year.

Watershed contamination from wildfire can persist for years. Burned landscapes lose their vegetation and topsoil, so every rainstorm washes new sediment and contaminants into reservoirs. Utilities downstream of fire scars are investing in additional treatment capacity, but these upgrades cost millions and take years to build. For residents in fire-prone areas, a home filtration system with activated carbon provides an additional layer of protection against volatile organics and sediment.

Algal Blooms

Harmful algal blooms (HABs) are increasing in frequency and severity across the US, driven by warmer water temperatures and excess nutrient runoff from agriculture. Cyanobacteria (blue-green algae) produce toxins called microcystins that can cause liver damage, neurological effects, and skin irritation. Standard chlorine disinfection does not reliably remove these toxins, requiring utilities to deploy advanced treatment like activated carbon or ozone.

In 2014, a massive algal bloom in Lake Erie forced Toledo, Ohio to issue a do-not-use order for 500,000 residents -- they could not even boil the water, because boiling concentrates microcystins rather than destroying them. Similar events have occurred in Salem, Oregon (2018), and multiple Florida communities that draw from Lake Okeechobee. These are not rural backwaters; these are major metro water supplies.

The Great Lakes, Mississippi River basin, and Florida's freshwater systems are the most affected regions, but algal blooms are expanding into areas where they were previously rare, including New England reservoirs and Pacific Northwest lakes. Climate projections suggest HABs will become more frequent and intense through mid-century, putting increasing pressure on treatment systems that were not designed to handle them.

Adaptation

At the utility level, adaptation means investing in treatment flexibility. Utilities that rely on a single treatment process are most vulnerable to climate-driven water quality swings. The most resilient systems use multiple barriers: source water protection, conventional treatment, advanced oxidation or activated carbon, and distribution system monitoring. The Bipartisan Infrastructure Law's $55 billion in water funding is partially directed toward these upgrades, but adoption is uneven.

At the household level, the case for point-of-use filtration is stronger than ever. A quality filter provides consistent protection regardless of seasonal water quality fluctuations, wildfire contamination events, or algal bloom emergencies. Reverse osmosis systems offer the broadest protection, removing virtually all dissolved contaminants. Activated carbon filters (including pitcher filters) handle disinfection byproducts, volatile organics, and taste/odor issues effectively.

Stay informed about your local conditions. Check your city's data on CheckMyTap to understand your baseline water quality, and sign up for your utility's notification system so you are alerted to any advisories or quality changes. Climate impacts on water quality are not a future problem -- they are happening now, and the trends point in one direction. Knowing your water and having a filtration plan is practical adaptation for the water system we actually have, not the one we wish we had.