Low-level helicopters allow companies and agencies to find aquifers on the Mississippi Alluvial Plain, which is distributed on seven US states, from southern Louisiana to southern Illinois, including Illinois, Missouri, Kentucky, Tennessee, Arkansas, Mississippi and Louisiana.
By executing high-resolution, airborne geophysical surveys, local agencies can obtain critical data to evaluate and manage groundwater resources in the region. Surveys follow initial flights and data acquisition over the Mississippi Alluvial Plain. Helicopters are deployed in-focus areas to acquire high-resolution survey grids.
“Airborne geophysical data fill a critical role in aquifer mapping studies since such large-scale data cannot be acquired effectively on the ground,” says Dr. Burke Minsley, a Denver-based USGS research geophysicist who is helping to lead the airborne geophysical effort. “We are excited to add cutting-edge airborne geophysical technologies to advance groundwater modeling and decision-making efforts in this study.”
Low-level flights cover more than 20 million acres within the Mississippi Alluvial Plain. Trained pilots, who are certified for low-level flying, coordinated flights.
Mississippi Alluvial Plain
The Mississippi Alluvial Plain, which is one of the most fruitful agricultural regions in the US, relies upon groundwater for irrigation. It is the third-largest area of irrigated cropland in the US, comprising roughly 29,000 square miles, or 19 million acres.
Helicopter surveys capture high-resolution, three-dimensional representations of the groundwater resources using instruments that collect data on the geology in shallow aquifers of the region. When the data analysis is finalized the maps allow agencies to better understand the aquifer system that supports groundwater resources at depths of roughly 300 feet underground.
Helicopter surveys are conducted along east-west lines at approximately 200 feet above the ground. The helicopter features an electromagnetic instrument housed in a cylinder, known as a bird that is towed about 100 feet below the aircraft.
The helicopter also includes scientific instruments such as a magnetometer and a gamma-ray spectrometer, which are both safe for the environment, animals and humans.
Water exploration and agricultural industries have begun using airborne geophysical surveys to ascertain water and food security. The minimum daily requirement of water for domestic usage is 200 liters per person in developing countries.
The exploration of freshwater sites through geophysical surveys will increase the demand for magnetic, gravity, resistivity, and electromagnetic based geophysical services in the future.
The global water exploration industry is starting to use geophysical surveys before starting groundwater drilling activities. These will help develop a clear picture of underground formations to understand the hydrologic cycle and groundwater quality; and distinguish the nature, number, and type of aquifers.
“This represents the largest-to-date public-sector initiative to acquire airborne electromagnetic data for hydrologic applications in the United States,” said Don Cline, Associate Director for the USGS Water Resources Mission Area. “The data collected from these surveys will greatly improve our knowledge of water resources in the MAP study area.”