U.S. Department of the Interior U.S. Geological Survey Analysis and Comparison of Selected Water-Budget Components of the High Plains, and Steven M. Peterson Lead Hydrologist Nebraska Water Science Center Coauthors: Jennifer Stanton, Coauthors: Jennifer Stanton, Sharon L. Qi, Derek W. Ryter, Sarah E. Falk, Natalie A. Houston, Stephen M. Westenbroek, and Scott C. Christenson

Presentation Outline  Overview of USGS Groundwater Resources Program and Regional Availability Studies  Soil-water-balance models  Other water-budget component methods  Water-budget component estimates

Mission: To provide objective scientific information and develop interdisciplinary understanding necessary to assess and quantify the availability and sustainability of the Nation’s groundwater resources. U.S. Geological Survey Groundwater Resources Program

GWRP Regional Groundwater Studies  Need for information about the availability of the Nation’s groundwater resources  Depletion, droughts, concerns about climate change  Multi-disciplinary studies across the U.S. will provide resource managers and policy makers with essential information needed for management Octobe r 13, 2011 Water, Climate, and Ecosystems

 Groundwater-management decisions in the United States are made at a local level, such as the State, municipality, etc.  Many aquifer systems cross these political boundaries.  A key role of National and regional assessments is to provide consistent and integrated information across political boundaries that is useful to those who use and manage the resource. Context of Regional Groundwater Studies Octobe r 13, 2011

 Groundwater-management decisions in the United States are made at a local level, such as the State, municipality, etc.  Many aquifer systems cross these political boundaries.  A key role of National and regional assessments is to provide consistent and integrated information across political boundaries that is useful to those who use and manage the resource. Context of Regional Groundwater Studies Octobe r 13, 2011

Assessment goals  Assess effects of human activities on water levels, groundwater storage, and discharge to streams and other surface-water bodies  Explore climate-variability impacts on regional water budget  Evaluate adequacy of data networks to assess impacts at a regional scale October 13, 2011 Water, Climate, and Ecosystems

Regional-Scale Approach to a National Assessment

High Plains Groundwater Availability Study major components  Assess selected water budget components for 1940s and 2000s for the entire High Plains aquifer  New groundwater flow model of the Northern High Plains  Provide refined and updated framework data  Assess Water Availability

High Plains Groundwater Availability Study major components  Assess selected water budget components for 1940s and 2000s for the entire High Plains aquifer  New groundwater flow model of the Northern High Plains  Provide refined and updated framework data  Assess Water Availability

 SOWAT—SOil-WATer-Balance Model  SWB—Soil-Water-Balance Model Precipitation + Irrigation – Runoff – ET – Deep Percolation = Change in soil moisture Soil-Water-Balance Models

Soil Moisture Storage Soil-Moisture Target Available-Water Capacity Actual Evapotranspiration Irrigation Precipitation/Snowmelt Surface Runoff Exchange with Unsaturated Zone or Groundwater

SOWAT—SOil-WATer-Balance Model  Available-water capacity (soil)  Land use  Irrigation water source  Irrigation efficiencies  Soil-moisture target Run SOWAT model Precipitation ET from satellite imagery Convert to effective precipitation Runoff Snowmelt Irrigation Recharge

SWB—Soil-Water-Balance Model Run SWB model Precipitation Evapotranspiration RechargeIrrigation Runoff  Air temperature  Available-water capacity (soil)  Land cover  Surface-water flow direction  NRCS runoff-curve number  Root-zone depth  Plant interception amount  Crop coefficient  Soil-moisture target

Benefits of Soil-Water-Balance Models Spatially variable outputs Short time step (monthly or daily) Some can be coupled with groundwater-flow models Accounts for variable soil characteristics

SOWAT and SWB Limitations Doesn’t consider processes between the root zone and water table Each model cell can have only one land use category Does not account for the effects of a shallow water table on recharge or ET Not calibrated to hydrologic measurements

SWB in/yr SOWAT in/yr Average from 43 previous studies in/yrRecharge

Irrigation Demand SOWAT in/yr SWB in/yr **USGS Water Use in/yr EXPLANATION Average annual irrigation demand, inches per year

Other Water-Budget Component Methods

Precipitation Methods Parameter-Elevation Regressions on Independent Slopes Model (PRISM) Precipitation and elevation relationships National Weather Service Next Generation Weather Radar (NEXRAD) data and measured precipitation from weather stations Inverse-Distance Weighted (IDW) Interpolation Less sophisticated

Evapotranspiration Methods National Weather Service Sacramento Soil Moisture Accounting Model Simplified-Surface-Energy-Balance (SSEB) model SWB model

Simplified-Surface-Energy-Balance (SSEB) Model ET fraction Hot pixel Cold pixel dry field watered plant 0 AET Max AET Actual ET (AET)  Reference ET  “ET fraction” Reference ET USGS Global Data Assimilation Systems model

Recharge Methods SOil-WATer-Balance (SOWAT) Model Soil-Water-Balance (SWB) Model 43 previously published studies

Irrigation Methods SOil-WATer-Balance (SOWAT) Model Soil-Water-Balance (SWB) Model USGS Water-Use Program

Runoff and Groundwater Discharge to Streams Major sources of water in streams are from overland runoff and groundwater discharge (base flow) Base-flow index program (U.S. Bureau of Reclamation) Determined at gaging stations along the edges of the High Plains

Other Aquifer-Budget Components Groundwater in storage ( ) -USGS High Plains Water-Level Monitoring Study Groundwater discharge to springs -Several studies in SHP Flow to and from underlying geologic units -Several studies in CHP and SHP

Water-Budget Component Estimates

Range of Water Budget Volumes: Units = Million ac-ft/yr

Range of Water Budget Volumes: Units = Million ac-ft/yr

Summary SOWAT and SWB provide spatially and temporally variable recharge and irrigation demand Different methods are available for estimating water- budget components Water-budget component estimates were variable among methods

CONTACT INFORMATION USGS Nebraska Water Science Center (402) South 19 th St. Lincoln, NE Robert B. Swanson Director (402) Jason M. Lambrecht Associate Director for Hydrologic Data (402) Richard C. Wilson, P.E. Associate Director of Hydrologic Studies (402) Ronald B. Zelt Associate Director for NAWQA (402) Steve Peterson(402)