Transferable Research Capabilities and Interests

Unsaturated-Zone Research Techniques Applied in the High Plains Ground-Water Study

• Incremental drilling, core and sediment recovery and processing, water and chemical extraction
• Unsaturated-zone chemical profiling, mass balance, and flux estimation
• Unsaturated-zone water flux estimation and modeling
• Recharge estimation
• Understanding natural climate variability and long-term climate change effects and aquifer response.
• Soil-water analysis and chemical transformations, denitrification microcosms
• Real-time monitoring of weather, evapotranspiration, and unsaturated-zone wetting-front migration
• For detailed information about these efforts, please see McMahon and others, 2003, McMahon and others, 2006, and Gurdak and others, 2007.

Research on Vertical Gradients in Water Chemistry and Age in the High Plains Aquifer

• Provide information on differences in ground-water quality and ground-water age relative to depth within the aquifer and the underlying bedrock.
• Assesses potential for changes in the quality of produced water as the aquifer declines and the influence of the underlying bedrock becomes more important.
• Ground-water age data helps to define the stratification and residence time of water in the aquifer.
• Age data can be used as an independent calibration for predictive ground-water flow models.
• Age data can be used to estimate biogeochemical reaction rates.
• Chemical and age data can be used to reconstruct paleorecharge conditions.
• For detailed information about these efforts, please see McMahon, 2001, McMahon and Böhlke, 2006, and McMahon and others, 2004.

Ground-Water Vulnerability Research

• Ground-water vulnerability model and map development for the prediction of nonpoint-source contamination, which aid ground-water resource management decisions.
• Delineatation of well-contributing areas and determination of well-screen depths that intercept recently recharged ground water for vulnerability prediction.
• Estimation of uncertainty associated with propagation of inherent errors introduced into ground-water vulnerability models and maps, for improved confidence using vulnerability assessments during resource management decisions.
• For more detailed information about this effort, please see Gurdak and Qi, 2006, Qi and Gurdak, 2006, and Gurdak and others, 2007.

Research on Climate Change within the High Plains Region

• HPGW's findings regarding recharge variability and climatic controls on chemical and water movement represent a novel investigation of the impact of climate variability and climate change on ground-water resources and aquifer sustainability.
• Agricultural community and local and federal agencies (water conservation districts, USDA, BOR, etc.) that manage the ground-water resource are most interested in sustainability issues related to water-level declines and water-quality impacts across the High Plains aquifer (HPA).
• At a recent UNESCO sponsored meeting (International Symposium on GRAPHIC -Groundwater Resource Assessment under the Pressures of Humanity and Climate Change, April 4-6 2006, Kyoto Japan) HPGW researchers presented preliminary findings on climate controls impacting aquifer recharge and chemical quality.
  • The goals of the United Nations sponsored GRAPHIC program: i.) identify major ground-water resources on each continent that are highly stressed by human activities climate variability/change; and ii.) coordinate future global research efforts to understand future climate impacts and management options to enhance global ground-water sustainability.

Remote Sensing Research

• Classification of irrigated land from Landsat imagery using supervised classification and band-ratio techniques.
• Change analysis in amount of irrigated agriculture from 1980 to 1992
• For detailed information about these efforts, please see Qi and others, 2002.

Future Research Possibilities

• Understanding and predicting the effect of climate change on ground-water resources is a relatively new area of climate research and the HPA system provides an ideal field laboratory for these investigations.
• The substantial body of existing geologic, hydrologic, climatologic, and geographic information for the High Plains provides the necessary foundation for expanding research into natural climate variability, climate change, human impacts, and aquifer recharge and sustainability.
• Gradients in temperature (north-south) and precipitation (east-west) in the High Plains allow for studies of the influence of natural climate variability under current conditions on the HPA, in addition to studies of future climate change.
• A High Plains ground-water modeling effort to revise the current "pre-MODFLOW" model.

Peter B. McMahon Project Manager - High Plains Regional Ground-Water Study
USGS Colorado Water Science Center
Denver Federal Center
P.O. Box 25046, MS-415
Denver, CO 80225
pmcmahonusgs.gov
Ph: (303) 236-4882