The Impact of Climate Change on Water Resources

The Impact of Climate Change on Water Resources

Climate scientists have been saying all along that one of the primary effects of climate change is the disruption of the water cycle. Since so much of everyday life and planning is determined by hydrological systems, it is important to understand the impact that climate change is having (and will have) on drinking water supplies, sanitation, food and energy production.

Climate Change and Water are Closely Linked

The relationship between water, energy, agriculture and climate is as important as it is complex. Climate change has the potential to tip out of balance the relatively stable climate in which civilization has been built and jeopardize the security of water, food and energy systems. Over time, the effects of global warming due to the human-generated buildup of greenhouse gases (GHGs) in the atmosphere have become more evident. In 2017, major GHGs, like carbon dioxide, methane and nitrous oxide hit record levels. The year’s carbon dioxide concentration reached a global average of 405 parts per million, which was the highest ever recorded, matched only by ice core data stretching back 800,000 years.

The top 20 warmest years on record have come since 1995. The year 2017, according to the NOAA State of the Climate in 2017 report, was the third hottest year since the mid-1800s, and the hottest year ever without El Niño warming the world’s waters. As the earth’s average temperature continues to rise, we can expect a significant impact on water resources with the potential for devastating effects on these resources.

Water and the Climate Shark

One of the sharpest observations on water and climate came from the 2009 launch of the CDP Water Disclosure Project, which was aimed at global businesses, when the project’s CEO, Paul Dickinson, stated that,

“Much of the impact of climate change will be felt through changing patterns of water availability, with shrinking glaciers and changing patterns of precipitation increasing the likelihood of drought and flood. If climate change is the shark, then water is its teeth and it is an issue on which businesses need far greater levels of awareness and understanding.” [emphasis added]

What’s true for business addressing climate change and its water impacts is just as true for all segments of society; from government agencies to water utilities to farmers to residential water users, every sector must prepare for climate risk, especially as it relates to water.

In one influential academic paper, scientists proposed that “stationarity is dead,” which means that over time the expectation of a relatively stable climate and narrow range of precipitation patterns are no longer assured. This is a major paradigm shift because previous assumptions on which decisions were made for long-term activities like building dams and reservoirs and even short-term decisions like selecting crops to grow in a given region, might now be too unreliable for predictable planning.

Below are some of the chief water-related challenges that climate change will force people to contend with in the United States and around the world.

Precipitation Pattern Shifts: Drought and Deluge

Climate change disrupts the water cycle and precipitation. According to scientists from the Intergovernmental Panel on Climate Change (IPCC), “[i]t is likely that anthropogenic influences have affected the global water cycle since 1960,” and such effects are the increased likelihood of more intense droughts and precipitation events. With higher average temperatures and warmer air that can hold more water, a pattern might emerge of lengthy dry spells interspersed with brief but heavy precipitation and possible flooding. The back-and-forth between precipitation extremes is sometimes described as “drought and deluge” or more recently, “precipitation whiplash.”

Climate Change and Droughts

Droughts, intense rains and floods occur naturally and involve many factors, including geography, but climate change can exacerbate these events. For instance, temperature rise leads to greater evaporation rates and plant transpiration, which results in water loss in soil and plants. For example, a Stanford study showed that when higher temperatures coincided with minimal precipitation during the California drought of 2011 to 2017, drought conditions worsened. That drought is now considered one of the more exceptionally dry and extreme in the state’s history.

North America is just a few years removed from the 2012-2013 drought that impacted much of the continent, which turned out to be one of the most severe, multi-state droughts in decades. The Colorado River basin has been embroiled in a

Climate Change and Extreme Precipitation

Recent research has tied certain extreme precipitation events to the fingerprints of climate change. Several studies concluded that climate change created conditions that made torrential rainfall more likely, leading to several recent devastating flooding events, for example, Hurricane Florence in North Carolina in 2018  and Hurricane Harvey over southeastern Texas in 2017. Research suggests that climate change could have boosted the odds of the downpours in 2016 in Baton Rouge.

Water-related extreme weather events have huge costs in terms of loss of life, wrecked infrastructure and economic damage even if climate change’s influence on these extreme weather events cannot be always be directly attributed, the influence remains. Since tracking began in 1980, of the top four most economically costly US weather and climate disasters, three are water-related:

  1. tropical cyclones (hurricanes) at $870.2 billion;
  2. droughts at $241 billion;
  3. severe storms at $219 billion; and
  4. inland flooding at $123 billion.

Water Tower Drawdown: Melting Glaciers and Snow Drought

Sometimes called natural “water towers,” mountains are critical headwaters to numerous rivers and other freshwater sources. In all, mountain meltwater and runoff provide more than 50 percent of the world’s freshwater. Yet as global temperatures elevate, mountain glaciers and snowpack are melting at an unprecedented rate. Many mountain glaciers are in retreat, and some in locations like Glacier National Park, are in danger of disappearing within the 21st century. If glaciers melt away, they can’t be restored. Thus, areas that previously depended on glaciers for freshwater will then have to seek other sources.

Further complicating mountain water storage capability is the greater likelihood that warmer temperatures make precipitation fall as rain rather than snow, sometimes called “snow drought.” Although more rain than snow may seem like a plus, it could mean reduced water availability. When snow and ice collect on mountaintops, the snowmelt releases water slowly – to streams, rivers and reservoirs – throughout the spring and summer. On the other hand, when rain falls on mountaintops, especially during the winter, water runs off and quickly fills reservoirs to capacity, which can result in excess water runoff that can’t be stored. Because rain flows faster than melting snow, levels of soil moisture and groundwater recharge may be reduced. Areas that rely on meltwater as their primary freshwater source could increasingly experience water shortages, especially towards the end of summer, and will have to seek other sources.

Another consideration is that treating and moving public water supplies (sometimes vast distances) requires large amounts of energy which is produced mainly by burning fossil fuels like coal, natural gas and oil. That energy production, in turn, requires massive amounts of water, thereby creating a loop of water use and greenhouse gas emissions that further contribute to climate change.

Greenhouse Gas Emissions

Overall, greenhouse gas emissions must be decreased to prevent climate change and protect threatened water sources. Addressing big sources of GHG emissions is the place to start, which means how and where energy is used is critical. In total, the energy sector emits the vast majority of greenhouse gases – at 72 percent – in the form of electricity generation, transportation, manufacturing and so forth. When it comes to emissions related to food, meat and dairy have both a big climate footprint and water footprint. Worldwide, meat production generates 14.5 percent of total greenhouse gas emissions.

Climate Change and Algal Blooms

Numerous other relationships between climate change and water exist. For instance, climate change has warmed up water bodies and caused harmful algal blooms to become greater problem in rivers, lakes and oceans in the US and around the world. These naturally occurring algal blooms are supercharged by nutrient pollution – worsened by drought and deluge cycles – and warmer waters. Excessive amounts of nutrients act as fuel for toxic algal blooms that arrive there as heavy precipitation washes more nutrients into waters. These blooms, like blue-green algae, can damage aquatic life and can produce toxins that are dangerous for humans and other animals to touch or drink. Florida in 2018 has experienced terrible harmful algal blooms both in freshwater (blue-green algae) and in marine waters off the coast (red tide), which has cost the state economically. These events can hurt the economy and human health by polluting drinking water, hampering tourism and shutting down fisheries and shellfish harvesting.

Image: Flooded farm in North Dakota. USDA (Creative Commons)

Updated: 2/7/19