Geospatial Mapping Study Shows Drought Trend in Ag-Dominated Arkansas Delta
Satellite imagery used to analyze vegetation health over past two decades
By John Lovett – Nov. 15, 2024
DROUGHT EXPLORER: Hamdi Zurqani, an assistant professor of geospatial science, developed the Arkansas Vegetation Drought Explorer v.2.0 as part of a drought mapping study looking at short and long-term trends in Arkansas. (U of A System Division of Agriculture photo)
FAYETTEVILLE, Ark. — The Delta, a regional powerhouse for Arkansas agriculture built by river flows, is showing a trend of increasing droughts.
Using satellite imagery, Arkansas Agricultural Experiment Station researchers comprehensively analyzed drought dynamics over five years to reveal this and other short and long-term climate trends in Arkansas.
Hamdi Zurqani, an assistant professor of geospatial science for the College of Forestry, Agriculture and Natural Resources and the Arkansas Forest Resources Center at the University of Arkansas at Monticello, developed the Arkansas Vegetation Drought Explorer v.2.0 as part of a drought mapping study. The user-friendly web app gives users access to maps showing drought levels in Arkansas by county, year and month.
“One of the reasons we did this study was that there is no state climatologist and no state climate office in the state of Arkansas,” Zurqani said. “This kind of data set can show the trend. For example, if you select from 2000 to 2024 within sub ranking, you can see what’s going on within that specific region to determine what you may expect next year because we predict the future on the past.”
The results from the drought mapping study were published last month in the Ecological Indicators journal as an article titled “Google Earth Engine application for mapping and monitoring drought patterns and trends: A case study in Arkansas, USA.” The lead author was UAM forest resources graduate student Shadia Alzurqani. Co-authors included Zurqani, Don White, Jr. and Kathleen Bridges all colleagues at UAM’s College of Forestry, Agriculture, and Natural Resources. Shawn Jackson with the Arkansas Department of Agriculture’s Division of Natural Resources was also a co-author.
Improving drought management
“Overall, the study and the associated app have the potential to significantly improve drought management, water resource planning and climate change adaptation in Arkansas and other regions facing similar challenges,” Zurqani said.
The data and combined interactive map provide an essential foundation for policymakers, environmental scientists, and agricultural stakeholders looking to mitigate drought impacts and safeguard against future climate uncertainties, Zurqani added.
The Arkansas Water Resources Center, a part of the University of Arkansas System Division of Agriculture, funded the study through the U.S. Geological Survey 104(b) program with matching funds provided by the Division of Agriculture and University of Arkansas Monticello. The experiment station is the research arm of the Division of Agriculture.
How it works
The Arkansas Vegetation Drought Explorer is a user-friendly web application, which leverages MODIS satellite imagery to display drought severity across Arkansas. Users can select county and timeframes for which they want to observe and the app generates drought severity maps based on Vegetation Health Index.
The Vegetation Health Index is a metric that combines satellite-based observations of vegetation conditions and temperature. Healthier vegetation reflects more sunlight, while stressed or drought-affected plants reflect less, indicating potential drought conditions.
By analyzing these patterns over time, the Vegetation Health Index can distinguish between normal and drought-affected areas, with the color-coded map displaying levels of severity —ranging from green for healthy vegetation to red for extreme drought. This allows users to track how drought conditions evolve and impact vegetation health across Arkansas.
Wet and dry contrasts
Zurqani said it was essential to keep in mind that using spatial distribution maps to evaluate droughts may only reveal general trends.
Some of the insights gained by using the Arkansas Vegetation Drought Explorer include:
Short-term meteorological data shows more frequent droughts, while long-term trends suggest possible improvement in some areas.
Arkansas experiences a higher frequency of droughts during March and August.
Droughts are most frequent in eastern and southern Arkansas, especially in the Mississippi River Alluvial Plain.
Flash droughts strongly affect vegetation, with agricultural lands and grasslands being the most vulnerable.
A flash drought includes a sharp decline in soil moisture below its normal conditions in the first 16 days, decreasing to its minimum within 24 days.
Zurqani and his team noted increasing drought conditions in agricultural land across time scales of 14 to 180 days. Other land cover types exhibited similar trends, with drier short-term conditions and wetter long-term spans.
However, they saw progressively wetter conditions over two to five years.
“As we look at drought trends across different time scales, we see an interesting contrast,” Zurqani said. “In the short term — over periods of 14 to 180 days — we observe increasing drought stress in agricultural areas, as well as other land cover types. This is largely due to immediate factors such as crop needs and seasonal weather patterns.
“When we extend the time frame to two to five years, many regions, especially in areas like the southwest part of the state, show a trend toward wetter conditions, which suggests that these ecosystems have the capacity to recover and balance out over time,” he said.
So, while droughts may be more frequent in the short run, there is evidence that longer-term climate cycles can bring about improvements, offering some relief to both the land and the communities that rely on it, he noted.
In simple terms, Zurqani said, the state’s short-term drought signals can often be severe and widespread. Still, there’s evidence that longer-term patterns could bring some areas back into balance.
Drought in March and December
The research suggests that even areas with seemingly abundant rainfall can experience drought events, particularly during periods of below-average precipitation or when evaporation rates exceed precipitation. Zurqani said that this threat has increased in recent years.
Arkansas experienced varying levels of drought throughout the years 2000 to 2022. March typically saw the most widespread drought conditions, with around 32 percent of the state’s land mass impacted, including 1 percent and 12 percent experiencing severe and moderate drought, respectively.
November and October showed relief with the least drought activity.
The most intense drought period was in the southeastern and northeastern regions in December, with 15 percent of the area experiencing mild drought, 8 percent moderate drought, and 2 percent facing severe drought. Severe drought conditions were seen in 14 counties. The U.S. Drought Monitor Program also observed a trend of increasing drought in the northern and eastern regions of the state.
While Chicot County in the southeast suffered the most, with 10 percent of its area experiencing extreme drought, Garland County in the southwest quadrant saw the highest concentration of extreme drought within a single county, reaching 18 percent.
To learn more about the Division of Agriculture research, visit the Arkansas Agricultural Experiment Station website. Follow us on 𝕏 at @ArkAgResearch, subscribe to the Food, Farms and Forests podcast and sign up for our monthly newsletter, the Arkansas Agricultural Research Report. To learn more about the Division of Agriculture, visit uada.edu. Follow us on 𝕏 at @AgInArk. To learn about extension programs in Arkansas, contact your local Cooperative Extension Service agent or visit uaex.uada.edu.
About the Division of Agriculture
The University of Arkansas System Division of Agriculture’s mission is to strengthen agriculture, communities, and families by connecting trusted research to the adoption of best practices. Through the Agricultural Experiment Station and the Cooperative Extension Service, the Division of Agriculture conducts research and extension work within the nation’s historic land grant education system.
The Division of Agriculture is one of 20 entities within the University of Arkansas System. It has offices in all 75 counties in Arkansas and faculty on five system campuses.
The University of Arkansas System Division of Agriculture offers all its Extension and Research programs and services without regard to race, color, sex, gender identity, sexual orientation, national origin, religion, age, disability, marital or veteran status, genetic information, or any other legally protected status, and is an Affirmative Action/Equal Opportunity Employer.
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