Groundwater Avail. Study: One of most productive aquifers in world

Groundwater Availability podcast
Rachael Hoagland:  Welcome to the 11th episode of Nebraskast, where we talk with real USGS scientists about the important water-resources work they're doing all over Nebraska. My name is Rachael Hoagland, and I'm here with Steve Peterson, a lead hydrologist at the USGS Nebraska Water Science Center. Today we're talking about the High Plains portion of a nationwide study that is assessing groundwater availability.
Steve, explain briefly what the High Plains aquifer is and what groundwater is.
Steve Peterson:  The High Plains aquifer is a large regional aquifer, which underlies parts of eight states, including Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming. It's largely comprised of the Ogallala Aquifer, but does include younger deposits in the northern section that are in hydraulic connection with the Ogallala Aquifer. Groundwater is actually the water that fills in the pore spaces in between the grains of sediment that comprise the aquifers.
Rachael:  What is meant by groundwater availability? Are we just talking about how much groundwater is in the aquifer or is it more than that?
Steve:  The groundwater availability studies are meant to assess the status and availability of groundwater as a resource, also to help identify what the future availability of the resources will be under things such as climate change or continued development or what the forecast of what the groundwater resource will be if developments were to change in the future, in terms of how much groundwater gets pumped or other things like that.
Rachael:  Why is it important to have that information?
Steve:  Groundwater is very important because the High Plains aquifer is one of the most productive agricultural regions in the United States. The aquifer sustains more than one quarter of the nation's agricultural production, and groundwater is the primary source for irrigation water for agriculture.
Rachael:  What determines how much groundwater is available? What sort of factors are involved?
Steve:  There's several factors, some of which include the geology of the aquifer, in terms of how much space is in between the different sediment sizes that comprise the aquifer, how fast the water can flow through the aquifer, the saturated thickness of the aquifer in terms of how many feet of the aquifer there actually are saturated beneath the land surface, as well as regulatory and other factors.
Rachael:  This is a longer-term effort, several studies together combined to make the assessment. Where are we in terms of the timetable in the assessment process of the High Plains aquifer?
Steve:  We're in the fourth year of the study. Our first big report came out in October of 2011, so last fall. Now we're actually in the process of finalizing the groundwater-flow model, the new groundwater-flow model, for the northern High Plains and beginning to write the report and do the actual assessment of the availability of the aquifer using the new model as a tool.
Rachael:  When are you expecting that to come out and be available to the public?
Steve:  The report on the modeling and the digital data series will be coming out later in 2012. The final report that is actually the reporting on the assessment of water availability will come out in 2013.
Rachael:  What are some of the tools that you need to make sure that you get the best groundwater availability assessment possible?
Steve:  For the northern High Plains, we have built a new groundwater-flow model which is the primary tool to use to assess groundwater availability. The reason that we use the groundwater-flow model: It's able to capture features such as spatially variable recharge, interaction of the groundwater with streams, and variability of the aquifer in terms of its geology and physical dimensions and characteristics and how those things change in space and time. The groundwater-flow model is able to incorporate all of these features and therefore it is the tool to use to assess water availability.
Rachael:  You said that the final report won't be available until sometime in 2013. What can you say about what we've learned so far?
Steve:  The first report is a comparison of estimates of selected water-budget components for the 1940s and 2000s. That report, while it doesn't recommend one particular estimation method over another, provides a very useful and comprehensive comparison of different estimation techniques for water-budget components such as recharge or evapotranspiration or even precipitation. The comparison of those factors and the difference between the numbers that you get with different estimation techniques is a pretty important outcome.
Rachael:  The High Plains portion of the study is just one part of this nationwide study. Can you give us an idea of the other aquifer systems that are being assessed as part of the overall nationwide study?
Steve:  The Central Valley aquifer in California and the Mississippi Embayment in the lower Mississippi area and the Denver Basin are studies that have already been completed. The Columbia Plateau, Southwest Basin and Range Aquifer, High Plains, Southeast Coastal Plains, and the glacial aquifers are all studies that are either wrapping up or are currently underway.
Rachael:  Who are we partnering with in order to make the study possible?
Steve:  The studies are all funded and chartered through the Groundwater Resources Program of the U.S. Geological Survey. All of these water availability studies, every five years or so, get summarized in a large report that then goes to Congress to report on availability of water resources for the nation.
Rachael:  If you want to get more information about the water availability assessment for the High Plains, you can go to our home page at ne.water.usgs.gov. You'll find a link to the fact sheet that you can download and which also provides more information about this. It will also include links to other related reports that are coming out as part of this ongoing assessment. Steve, I'd like to thank you for taking the time to talk to me today.

Steve:  Thank you.