Fertilizer runoff can have harmful downstream effects, such as poisoned drinking water and toxic algae blooms. As detailed in a USA TODAY and Investigate Midwest story published Wednesday, heavy rainfall contributes to a disproportionate amount of this runoff into U.S. waterways.

Rainfall is only expected to get heavier and more intense, especially in the spring. 

[Read more: Excess fertilizer washed from Midwestern fields is slowly poisoning the Gulf of Mexico]

For instance, springs in Champaign County, Illinois — the area the newsrooms focused their analysis on because it had all the required data — have gotten wetter over the past 40 years.

Year to year, the spring rain totals vary. However, the county saw 30.5% more rain in the 2010s than in the 1980s, according to federal weather data.

It’s a potent recipe for runoff, especially given that Champaign County has the third-highest nitrogen surplus in the nation, according to one study.

Over the past seven springs, nitrogen spiked in the county’s Spoon River 42 times, and 36 of those times came after rainfall.

The three heaviest storms dumped one-third of all the nitrogen during this time period into the Spoon River.

USA TODAY is funding a fellowship at Investigate Midwest for expanded coverage of agribusiness and its impact on communities.

Top image: A storm hovers over an Illinois rural landscape on May 29, 2015. Extreme weather is likely to become more common in the Midwest under climate change conditions, according researchers and federal reports.