Climate Change and Water Quality

It’s no mystery that the recent drought significantly lowered the quantity of water available in the Pacific Northwest and California. Mountain snowpack disappeared. Reservoir levels dropped while demand increased. Water scarcity ensued until the recent rains filled many reservoirs to the brimming point.

There’s now a decent amount of scientific research linking the recent drought to climate change. (For a taste, check out the CIRCulator’s section on Snow Pack & Drought.) What’s less well known, at least by the general public, is how drought and other extreme climate events are lowering water quality as well as quantity. According to a new study published in Climatic Change, many drinking water providers also haven’t made this important connection in their work.

What’s most interesting in this study—at least from our perspective—is how awareness about the climate connection to water quality differed between types of water providers. Utilities that relied on surface water, the study found, were more aware of the threats posed to water quality than utilities that relied on groundwater. This, however, was more of a side outcome of the research than its initial goal.    Ostensibly, the study’s researchers, Julia Ekstrom and colleagues from the University of California Davis, wanted to determine how an awareness of climate change translated into action. To figure this out, they reached out to 925 California water utilities. They got responses back from 259.

The researchers asked questions designed to glean whether a California utilities’ staff felt that climate change was a threat to water quality globally and locally. (Interestingly enough, a larger number of respondents felt climate change was a threat globally but not locally in California.)

The researchers also asked a series of questions designed to glean if utilities’ awareness about the climate/quality connection had somehow translated into planning and adaptation strategies.

The survey results suggest that while many utilities showed awareness of the climate/quality connection and were taking actions to adapt, there were still large gaps between many utilities’ understanding and actual adaption work. Still, 41 percent of respondents reported taking some kind of adaptive action. But, as we said, that’s not the interesting part.

The degree of adaptation and degree of awareness were both strongly correlated to just how severely the recent drought impacted a given utility’s water supply. Here there was a further divide. The survey respondents showed a clear split between water providers that relied on surface water and water providers that relied on groundwater. Surface water dependent utilities reported more adaptation than groundwater dependent utilities.

Let’s break down why this might be by looking at the different water quality impacts that climate extremes, such as drought and extreme rain, can hammer down on water utilities. We’ll start with surface water.

We know that open surface water in reservoirs can drop in quantity from droughts and increased demand during droughts, but water quality can also drop. One reason has to do with something called “turbidity.” Turbidity is essentially a measure of how much sediment is swirling around in a body of water at any given time. Increased turbidity means an increase in sediment. Low water quantity often leads to high turbidity. This spells poor quality.

Droughts can also lower water quality by creating the right conditions for wildfires. The fires in turn can spread ash and other contaminates into open reservoirs. Surface waters can also suffer from high temperatures that can lead to algal blooms.

Poor surface water quality has also been observed following a very different type of extreme climate event: extreme rains. Heavy rains can stir up sediment in reservoirs, increasing turbidity.

According to their responses, water providers that relied on surface water showed a high level of sensitivity to the climate/quality connection, presumably because they’ve seen it in their work. Surface water providers also reported higher rates of implementing some kind of adaptation strategy to help mitigate the quality-lowering effects.

Groundwater providers, by contrast, have fewer climate/quality concerns, at least in the short-run, but they do have them. Droughts tend to increase demand for water. This means more pumping and, hence, less water in the ground. This can increase the concentrations of contaminants already in the water. Usually these contaminants don’t pose a major threat. You might have heard the old regulatory adage, “The solution to pollution is dilution.” Removing that dilution by lowering the water table tends to increase the concentration of contaminants, which also tend to collect near the intake to the pumps. So that’s not good.

There’s another even bigger climate/quality connection that looms in the future for many California groundwater providers: increased salinity. As sea levels rise under climate change, some coastal aquifers could be inundated by seawater, increasing their waters’ salinity and lowering their quality.

Groundwater providers on the coast, according to the study’s responses, showed a higher level of concern that climate change could affect their water quality. Ekstrom and colleagues suggest this connection might have to do with just how much media attention sea level rise has gotten and, perhaps, because many coastal groundwater providers also tend to be larger and can devote more staff time to examining climate change impacts.

The researchers offer another two possible explanations as to why surface water providers might be more aware and more likely to have taken some kind of adaptation action. One is simply that surface water is more highly regulated and more organizationally complex—often organized on a basin scale—than groundwater. The other possible explanation offered by Ekstrom and colleagues is that there is simply more research on the effects of climate change on surface water than groundwater. (For instance, we’ve written about the climate connection to groundwater just once.)

Our Editorial Opinion: While the stated goal of Ekstrom and colleagues’ survey was to focus on water quality over quantity and parse out a connection between climate awareness and climate adaptation, in our opinion the study seems to point to a more interesting split between types of water providers. This split, in turn, appears to be driven, at least in part, by how much scientific and media attention a given water source has received.

STUDY: Climatic Change

Citation: Ekstrom, Julia A., Louise Bedsworth, and Amanda Fencl. “Gauging climate preparedness to inform adaptation needs: local level adaptation in drinking water quality in CA, USA,” Climatic Change, (2016): 1–15. doi:10.1007/s10584-016-1870-3.

Photo Caption: Applegate Reservoir, July 2012. (Photo Credit: Oregon Department of Fish and Wildlife, some rights reserved.

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