In lieu of a full-day, in-person event, the Nebraska Water Center hosted a 2020 Mini-Conference – from 2-4 p.m. CDT on August 3 – with two virtual sessions on the hydrogeology and sociology of water resources in western Nebraska.
Together with partners at the UNL Panhandle Research and Extension Center, the first session features Nebraska researchers Steve Sibray and Troy Gilmore who presented western Nebraska's unique hydrogeology. The second session features the Water for Agriculture Project, a USDA-NIFA-funded effort focused on stakeholder engagement for addressing critical issues at the nexus of water and agriculture. Presenters included Nebraska team members Mark Burbach and Jessica Groskopf, and collaborators Wes Eaton, Penn State University, and Jason Farnsworth, Platte River Recovery & Implementation Program.
Please see below for more details, including session abstracts and speaker information. Both sessions will be posted to NWC’s YouTube channel.
Hydrogeology Session – 2-3 p.m.
Hydrogeology and Groundwater Quality Issues of the North Platte Valley
Steve Sibray
The principal aquifer in the North Platte Valley is the shallow alluvial aquifer which consists of sands and gravels deposited by the North Platte river. These sands and gravels are up to two hundred feet in thickness in the deepest parts of the aquifer. There are multiple channels in this aquifer that trend from northwest to southeast. The underlying Brule Formation is a bedrock aquitard unless it is fractured. Age dating of water and water chemistry from the fractured Brule aquifer has shown it is hydrologically connected with the alluvium. Both are part of the High Plains Aquifer system which is sometimes referred to as the “Ogallala Aquifer”.
Research at University Lake and Dutch Flats areas has shown that recharge to the shallow aquifer is largely due to leakage from the unlined surface water irrigation canals. The anion chemistry of the groundwater above the canal is dominantly bicarbonate. Below the canal, the groundwater has a significant sulfate component, similar to the North Platte river water. The shallow unconfined alluvial aquifer is vulnerable to surface contamination, and nitrate is found at elevated levels throughout the valley. Surface water is usually low in nitrate, while higher levels of nitrate tend to be found in those areas where recharge from leaking canals is absent. Uranium levels are high with some exceeding the maximum contaminate level (MCL) in some municipal wells. Nolan and Weber [2015] noted a statistical correlation between nitrate and uranium levels in the High Plains Aquifer. They proposed that nitrate increased the solubility of uranium as a possible mechanism for increasing the concentration of uranium in the groundwater. This presentation explores additional data and alternate mechanisms that better explain the observed high concentrations of uranium in the alluvial aquifer of the North Platte Valley.
Revisiting Groundwater Nitrate and Recharge in the Dutch Flats area of North Platte Natural Resources District
Troy Gilmore
Groundwater studies in the late 1990s showed two distinct types of recharge in the Dutch Flats area of the North Platte Natural Resources District (NPNRD). The two sources were (1) focused recharge through the leaky beds of irrigation canals and (2) diffuse recharge across the landscape, which was enhanced by inefficiency of surface irrigation. Based on estimates of the age of groundwater collected from multiple well nests, it was determined that groundwater moved relatively quickly through the unconfined aquifer. The average groundwater age (travel time since recharge, excluding the travel time from land surface to the water table) was about 9 years. These results suggested that, although groundwater nitrate was high in some wells, nitrate concentrations could be improved in a relatively short time, at least compared to other shallow aquifers with much greater average groundwater ages (e.g., >20 years). As with any agricultural area, the potential for decreasing groundwater nitrate concentrations would depend on both water and nutrient management. In 2017, approximately 20 years after the initial study, we observed that a significant portion of the Dutch Flats area had been converted to center pivot irrigation. Given the potentially greater efficiency of center pivot systems, we hypothesized that groundwater nitrate concentrations in shallow groundwater would improve. It was also possible that improved irrigation efficiency could lead to lower recharge rates. When we tested these hypotheses, our results suggested a slight downward trend in nitrate concentrations, and the majority of groundwater age-dating results suggested lower recharge rates. However, the differences were generally not statistically significant. We followed this an additional study of unsaturated zone (vadose zone) and groundwater transport rates based on a statistical machine learning approach. Using this approach, which was based on historical nitrate concentrations, we found travel times and transport rates that were consistent with previous work, including differences in types of recharge (focused versus dispersed) across the Dutch Flats area.
Stakeholder Engagement and Sociology Session – 3:15-4:15 p.m.
From Knowledge to Understanding: Lessons Learned from Integrating Research and Stakeholder Engagement in a Water & Agriculture Project
Mark Burbach
Jessica Groskopf
Wes Eaton
Jason Farnsworth
What changes can occur in the people, community, and environment as a consequence of community-led stakeholder engagement? The aim of the multidisciplinary USDA funded Water for Agriculture is to answer these questions as a means to address complex water problems in agricultural working landscapes. To do this, team members are facilitating, studying, and supporting stakeholder working groups, aka local leadership teams, in 5 projects sites across diverse water contexts in Arizona, Nebraska and Pennsylvania. This seminar will share insights on stakeholder engagement gleaned from the local leadership team experience addressing issues that matter most to the teams. Panelists will provide a brief overview of the goals and mechanics of the project before reflecting on several themes. These include a) the practical challenges of bringing together new groups of diverse stakeholders to participate in the project; b) how we fostered an inclusive process to identify locally salient water issues and practical action steps; and c) challenges therein. Panelists will then invite session attendees to share in a broader discussion of collaborative approaches to address complex natural resource problems—what does it take to successfully navigate disparate disciplinary cultures in pursuit of both practical and scholarly goals? Where was growth, learning, or some sort of change needed to keep the project moving—did it happen and to what end? What worked well, and less so? The goal of the panel session then is to identify, share, and foster dialogue that can form the basis for a more robust framework for undertaking community-led engagement on water in agricultural landscapes in collaborative fashion, that is grounded in the experiences of stakeholders whose lives are directly tied to the issues.