Helen H. Richardson/The Denver Post via Getty Images Algal blooms, like these on Ferril Lake in Denver, are a nightmare for the environment and could be exacerbated by climate change.

We grasp the connection now between our changing climate and the quantity of water around us. Scientists say that climate change means both more frequent and severe droughts and a heightened risk of flooding.

What about the quality of our water? Crises as disparate as Florida’s “guacamole-thick” algal blooms and the record number of cases of Legionnaires’ disease are linked to the effects of climate change on water safety ― or so a paper published last month in the journal Nature argues.

And problems like these appear to be getting worse.

But the extent to which climate change is working with other factors to muddy the water isn’t clear, said Anna Michalak, a faculty member in global ecology at the Carnegie Institute of Science and author of the paper.

“We tend to think of water quality issues as local phenomena controlled by what people are doing at a relatively local-to-regional scale,” Michalak told The Huffington Post.

The reality, she said, is that water quality depends on the interaction between human behaviors and “things that have to do with weather and meteorology — and they themselves are changing as a result of the climate.”

For instance, when changing climate and weather patterns combine with the excessive use of fertilizer on farmland — which contributes to nitrogen runoff into waterways — the results can be extreme. In the Gulf of Mexico, the toxic algal blooms have created a Connecticut-sized “dead zone” wreaking havoc on both the ecosystem and the local economy.

And algal blooms are just one example of this costly relationship. Here are some others:

Strained water infrastructure

Climate change overall means a greater demand for water amid a decreased supply, according to the Environmental Protection Agency. This will strain our nation’s already compromised water infrastructure. The EPA estimates that just the current infrastructure needs would take more than $600 billion to fix.

Many water systems across the country are nearing the end of their useful lives, the American Water Works Association reports. When extreme flooding hits such a system, water main breaks are more common, which can lead to contaminants entering the water supply. Advisories to boil before you drink will help in only some of those situations.

Greater risk of contamination

Increased flooding associated with climate change can exacerbate the runoff of all sorts of pollutants from farms and residential lawns ― including environmentally harmful nutrients like nitrogen and phosphorous, trash and animal waste ― the EPA points out. Extreme flooding can also overwhelm sewage systems, releasing more untreated sewage into waterways. And that means greater contamination risk and higher treatment costs for water systems.

Waterborne disease outbreaks

Climate change leads to warmer water temperatures, which creates better growing conditions for the viruses, bacteria and protozoa that cause waterborne diseases like Legionnaires’. As the nonprofit Physicians for Social Responsibility points out, the effects of these illnesses range from diarrhea to death.

Legionnaires’ disease is already on the rise, according to recent numbers from the Centers for Disease Control and Prevention. Cases of this form of pneumonia have quadrupled over the last 15 years.

Rising salinity of freshwater

Scientists say climate change is contributing to rising sea levels, which drive more saltwater into the freshwater supply. This, too, increases costs as water systems need to desalinate the water or find another freshwater source, according to the EPA.

What do we do? Michalak calls for more research to assess which combinations of weather, climate, land use and management practices put water quality most at risk. Once the interaction of these factors is better understood, we can figure out how to manage water supplies in a more sustainable, climate change-resistant way.

Meanwhile, we shouldn’t jump to overly simple explanations of extreme situations, like the algal blooms growing in Florida, Colorado and elsewhere.

“It’s not just about climate or land use or agriculture,” Michalak said, “but this intersection between what humans are doing locally and what we’re doing globally is what’s coming back to bite us.”

――

Joseph Erbentraut covers promising innovations and challenges in the areas of food and water. In addition, Erbentraut explores the evolving ways Americans are identifying and defining themselves. Follow Erbentraut on Twitter at @robojojo. Tips? Email joseph.erbentraut@huffingtonpost.com.