Weather whiplash, a phenomenon in which extreme seesawing between drought and flood occurs, is now driving deterioration of water quality and forcing municipalities to seek expensive solutions so their residents can have clean and safe drinking water. Modern agriculture is inextricably tied to declining surface water quality, with associated national and global ecological and economic problems.
Agriculture is a major source of reactive nitrogen and interacts with hydrology to control nitrogen loading to aquatic ecosystems. Future hydrological changes that are associated with climate will alter nitrogen loading to freshwater ecosystems in ways that are just beginning to emerge.
That’s according to research which indicates that U.S. Midwest agricultural regions will experience more drought and periods of excessive rainfall, and these will be “really big storms,” according to Terry Loecke, the study’s lead author and an assistant professor of environmental studies at the University of Kansas. He and his team of researchers have created a weather whiplash index, which is calculated as the total precipitation from January to June of each year (1951–2099) minus the total precipitation from July to December of the previous year (1950–2098), divided by the total precipitation over that entire period.
And they’ve found that extreme weather events change the storage of nutrients in the agricultural landscape, especially nitrogen used in fertilizing farms.
“Farmers put on their normal amount of fertilizer, but when we have a drought, plants don’t grow as big and don’t take up as much nitrogen,” Loecke said. “Instead of going into the plants, which would be harvested, it stays in the soil — and no water is flushing it away.” Floods carry the nitrogen into rivers, which often supply local communities with drinking water.
With climate change predicted to increase the frequency and severity of growing-season drought and produce more extreme precipitation in the spring, agricultural crop yield will be reduced but soil nitrate concentrations will be enriched.
And who will pay for the nitrogen remediation? You guessed it: the taxpayer. Water departments are finding themselves forced to build new facilities to eliminate nitrogen from municipal water supplies.
The team scrutinized a 2012-2013 drought and flood cycle that led to a nitrogen spike in Midwest surface waters. “We looked at observations of the 2012 drought that ended in a flood and asked how frequently that has occurred across upper Midwest across in the last 10-15 years,” Loecke said. “We found that the connection between drought-to-flood conditions and high nitrate was pretty common.”
The extreme nitrate levels in the Des Moines and Raccoon Rivers gave the Des Moines Water Works no choice: they had to construct a $4.1 million nitrate removal plant that costs $7,000 per day to operate. “The drinking water is a real problem, especially in Des Moines,” Amy Burgin, one of the study’s co-authors and associate professor of environmental studies at the University of Kansas, said. “It has one of most expensive nitrate-removal facilities that we know about. In recent years, they’ve been running it from 25 to 150-plus days each year. That’s really adding up, because the money isn’t in the budget they have to spend to get clean drinking water to citizens.”
And the need to create a nitrate removal infrastructure has a cumulative effect. The Des Moine Water Works sued Iowa counties upriver from the city, as they were centers of agriculture, in an effort to capture some of denitrification costs.
Loecke and Burgin argue that surface water nitrate elevation levels will become more common across the agricultural Midwest with weather whiplash. “The average person will pay more to have clean drinking water,” Loecke outlined. “A city can’t predict how many days they’ll have to run a nitrate-removal facility. When they run it a lot, it’s a huge hit to their budget, and they have to pass it on to their citizens, and it will spread out to rest of the Midwest. Midwesterners will have to pay more for drinking water going forward.”
According to analysis by the Des Moines Register, 30 percent of Midwest cities and town will have this problem, and, according to Loecke, “Most don’t have the tax bases to support huge nitrate-removal facilities.”
Additional Images courtesy Associate Professor Amy Burgin