On July 18, 2023, 100% of Iowa was experiencing at least abnormally dry conditions. Today, the drought has been erased in all 99 counties. Every week the U.S. Drought Monitor is updated. The U.S. Drought Monitor has been a collaborative effort since its inception in 1999, produced jointly by the National Drought Mitigation Center at the University of Nebraska-Lincoln, the National Oceanic and Atmospheric Administration, and the U.S. Department of Agriculture. Meteorologists and climatologists from the NDMC, NOAA, and USDA rotate as the lead author of the map, typically serving two-week stints. The author’s role is to interpret data in ways a computer cannot. When the data points in conflicting directions, they make sense of it.
How do we know when we're in a drought? When you think about drought, you likely think about water—or the lack thereof. Precipitation is a major factor in creating the Drought Monitor, but the map’s authors consider numerous data sources. Some of the numerical inputs include precipitation, streamflow, reservoir levels, temperature and evaporative demand, soil moisture, and vegetation health. No single piece of evidence tells the complete story, nor do strictly physical indicators. That’s why the USDM isn’t a statistical model; it’s a blend of these physical indicators with drought impacts, field observations, and local insights from a network of over 450 experts. Using various types of data and reconciling them with expert interpretation makes the USDM unique. We call it a convergence of evidence approach.
The U.S. Drought Monitor uses a classification system to categorize the intensity of droughts. The scale runs from 0, abnormally dry to 4, which indicates an exceptional drought. These categories help communicate the severity and potential impacts of drought conditions. Here are the drought categories used by the U.S. Drought Monitor:
D0 - Abnormally Dry:
Short-term dryness slowing planting, growth of crops, or pastures.
Fire risk above average.
Streams, reservoirs, or wells low, some water shortages developing or imminent.
D1 - Moderate Drought:
Some damage to crops, pastures.
Streams, reservoirs, or wells low, some water shortages developing or imminent.
Voluntary water use restrictions requested.
D2 - Severe Drought:
Crop or pasture losses likely.
Water shortages common, water restrictions imposed.
D3 - Extreme Drought:
Major crop/pasture losses.
Widespread water shortages or restrictions.
D4 - Exceptional Drought:
Exceptional and widespread crop/pasture losses.
Shortages of water in reservoirs, streams, and wells creating water emergencies.
We went from widespread drought to no drought in 365 days. This weather whiplash is becoming our new normal. Unfortunately, just because we are out of a drought, does not mean our problems are gone.
In 2022, Dr. Jennifer Francis, of the Woodwell Climate Research Center, published a paper on the impacts climate change is having on weather whiplash. The study's findings highlight an increasing risk of flash droughts in the region due to changing weather patterns and extremes. As high-latitude height anomalies become more frequent, conditions that promote rapid-onset droughts are likely to become more common. These flash droughts, characterized by sudden and severe water deficits, can significantly stress crops, reduce yields, and strain water resources. Higher temperatures and shifting precipitation patterns exacerbate these conditions by increasing evaporation rates and creating longer dry spells. To mitigate the impact, farmers need to adopt drought-resistant crop varieties, improve irrigation techniques, and implement soil conservation practices. Effective water management policies and advanced climate monitoring are also crucial for preparing and responding to flash droughts.
When most of the rain falls in one storm, the amount of rain may be enough to erase the deficit, but it is often time not enough to alleviate all of the impacts of a drought. First, in severe droughts, soil essentially burns and is less permeable. The other issue is the increased intensity of rain events. In both cases, most of the rainwater runs off into area streams and rivers. Back in the late 1800s, Des Moines typically saw one storm event per year that delivered 2” or more of rain during a single storm system. As our planet warms and holds more water, we now average two days per year, where we receive 2” or more inches of rain during a single storm system. While that might not seem like a lot, we have essentially doubled our average over the last year.
Our pattern looks to continue to produce above average precipitation for now. In the longer term, we are looking at La Nina conditions returning in the Pacific. Climatologically that means drier than average conditions across the region. Stay tuned and buckle up for more weather whiplash.
I am happy to be part of the Iowa Writer’s Collaborative.
I'm am SO grateful to have your words, perspective, and knowledge back here in Iowa! Thank you for doing this 😊