How the Middle Republic Natural Resources District Is Mapping the Ogallala Aquifer From the Air
W
hen the Middle Republican Natural Resources District (MRNRD) in Nebraska wanted to get a better picture of its groundwater supplies, it hired Aqua Geo Frameworks to do an airborne electromagnetic (AEM) survey. The district will use that information to better manage groundwater extraction and irrigated farming on the surface. In this interview, MRNRD Manager Jack Russell and Engineering Hydrologist Alex Boyce tell Irrigation Leader about their experience with the new technology and how it will help them help irrigated farmers in their service area. Irrigation Leader: Please tell us about the MRNRD. Jack Russell: Nebraska’s natural resources districts (NRDs) were created in the early 1970s by the State of Nebraska. The MRNRD is 1 of 23 NRDs across the state. Our service area is about 2.4 million acres and covers 41/3 counties. About 50 percent of that area is cropland, with 12.5 percent being irrigated cropland. Alex Boyce: We have about 240,000 certified irrigated acres that are watered with groundwater, and the majority of that water is pumped from the Ogallala aquifer. We grow mostly corn, milo, and soybeans, along with some winter wheat. The NRDs in the Republican River basin and the State of Nebraska have a compact with the States of Kansas and Colorado called the Republican River Compact, according to which we are only allowed to pump as much irrigation water as we did back in 2004, so we have a moratorium on expanding wells and certified acres. On top of the 240,000 groundwater acres, we have another 40,000 acres or so that are irrigated with surface water. Unlike the case with groundwater, the MRNRD doesn’t have jurisdiction over surface water, but we work closely with surface water companies. We have had to install meters on every one of our wells, and we have to measure deliveries of surface water, so we actually have a full accounting of how much water is pumped in our district.
Aqua Geo Frameworks carries out an AEM survey of the aquifer in the MRNRD’s service area.
understand the factors that influenced those declines. It would be an added benefit to know what areas of our district have available groundwater that could support additional irrigation. Under the terms of the Republican River Compact, no new irrigation can be developed in the MRNRD, so understanding the factors that affect water balance is critical. Alex Boyce: When I first joined the district, we started developing groundwater models and subregional watershed models. We noticed that our geology and 3‑D modeling lacked some information. We decided to start drilling some test holes to figure out where the weak spots in the data were. From there, we stumbled across a company that does AEM surveying and decided that was a more cost-effective way to get an idea of the aquifer’s properties. Instead of going out and drilling hundreds of thousands of test holes, we could just fly a helicopter over the aquifer and collect data rapidly.
Jack Russell: In certain areas of the NRD, there are groundwater declines of up to 20–30 feet. That may not be a lot of decline over decades, but we wanted to better
Irrigation Leader: Were you being proactive in doing this survey, or were you already running into problems with wells going dry or ground subsidence?
46 | IRRIGATION LEADER | July/August 2022
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PHOTOS COURTESY OF THE MRNRD.
Irrigation Leader: Please tell us about your work using AEM to map and measure your aquifer. Why did you want this survey done?
Jack Russell: We already have rough information on the aquifer; now, we’re trying to take it to the next level and come up with a model that will help us predict the effects irrigation will have on it.
