National Strategy for the
Assessment of Water Availability
and Use in the United States
Kevin F. Dennehy
Reston, VA
USA
U.S. Department of the Interior
U.S. Geological Survey
Philippine National Workshop
Water Availability Enhancement (WAVE) Project
March 1-4, 2011
Does the United States have enough
water?
We do not know, however….
Scientific and Technical Challenges
to Meet US Demands for Water
• Measure and account for the
Nation’s water resources
• Develop methods to
understand existing water
resources while using those
supplies more efficiently
• Develop and improve
predictive water management
tools
What do we know about the Nation’s
water availability?
Build on Previous Work
Previous national and regional evaluations
have improved our knowledge, however
repeated evaluations of the resource are
needed:
• new information on water resources becomes available;
• new methods and technologies are developed;
• the places water is used, water demands, and the
issues of concern change with time; and
• the systems change in response to development.
Goals for a National Assessment
Clarify our understanding of water availability
status and trends and improve our ability to
forecast the balance between water supply and
demand for future economic and environmental
uses.
“Can’t effectively manage
what don’t measure or understand”
• Status
• Trends
• Forecast
Will there be sufficient freshwater resources in
the future to sustain economic growth and
quality of life in the United States?
Water Availability and Use:
Great Lakes Basin Pilot
• Funded in 2005, five-year project
• Respond to Great Lakes Issues
• Develop methods for National Assessment
Groundwater, surface water, water use
Image from NOAA, Great Lakes Environmental Research Laboratory,
AVHRR satellite imagery, 1995
Water
Availability
Water Quality
Water Law And
Regulations
Economic
Factors
Ecology,
Recreation, and
Instream Use
Water Quantity
Infrastructure
And Existing
Water Use
What is Water Availability?
To determine water availability
need to know…
• Quantify resource (supply)
and
• Information about its use (demand).
Source: U.S. Geological Survey National Atlas of the
United States; http://nationalatlas.gov/atlasftp.html
Water Resources Regions
Principal Aquifers
Framework for a National Assessment
• What are current
streamflows and how
have they changed over
time?
• How will new
withdrawals affect
streamflow?
Surface Water Analysis
• Stream gage data not
available everywhere
• Developed new method
to estimate streamflow
over time at any stream
even where there is no
stream gage
Surface Water Analysis
• How much water is withdrawn
and how much water is used?
• How does water use vary in time
and space?
Water Use in the Great Lakes
Future water availability depends on groundwater,
surface water and current water use.
Public-supply
withdrawals:3,800 million gallons per day
17.7 million people
Self-supply domestic
withdrawals:410 million gallons per day
5.2 million people
Groundwater
12%
Surface
Water88%
Groundwater
99%
Surface
Water1%<
• How has development
changed groundwater
levels and availability?
• What are potential
constraints limiting
groundwater availability?
Groundwater Availability
• Groundwater divides move
because of pumping
Groundwater Availability
Forecast 2005-2040
Detail Look at
Approach/Tasks
Taken to Assess the
Groundwater
Component of
Water Availability
Organize Geospatial Data LibraryRelation and Flow of Information
Source: Faunt, 2009
Compile Geospatial Data Sets and
Metadata
California’s Central Valley
Diversity of Data Types and Categories Detail of One Data Type
Source: Faunt, 2009
Assemble 3-D Hydrogeologic FrameworkFloridan Aquifer System
• Based on 8,500 drillers logs
• Interpolated to one-mile spatial grid at 50 foot depth intervals
• Coarse near river channels
• Finer in low energy environments (Corcoran Clay)
Source: Faunt, 2009
Assemble 3-D Hydrogeologic Framework
California’s Central
Valley aquifer system
Groundwater modeling is useful for the evaluation of historic
changes in water budgets and provides a tool to understand
system response to stresses from future human and
environmental uses.
Development of Regional
Groundwater Modeling Tool
1962-2003/Engineered
Engineered
Complex
12 million acre-feet/year recharge /discharge
Pre-development
Natural
Simple
2 million acre-feet/year recharge /discharge
Source: Faunt, 2009
Source: Faunt, 2009
Spatial & Temporal Variability in
Groundwater Budgets
Source: Faunt, 2009
Source: Faunt, 2009
Groundwater budgets
change in response
to human and
environmental
stresses (large-scale
pumping and climate
variability).
Source: Alley and others, 2002 and Johnston, 1999
Trends in
Water Budget
Components
Cumulative Change in Storage
Source: Faunt, 2009
Human Effects
Climate Effects*
Middle Claiborne aquifer (Sparta)
How long will groundwater supplies last?
Tool capable of forecasting system response
Clarke and others, 2011
Products/Outcomes• Water budgets of major aquifers systems
• Trends in groundwater use, storage, recharge, and discharge
• Groundwater models that provide
– Regional context for more local studies
– Tools to make future projections of groundwater availability
• Region-wide estimates of key hydrologic variables
• Assess climate variability effects on future groundwater availability
• Evaluation of existing networks for monitoring groundwater availability
Regional Design Flexibility
Scaling Up --Periodic National Synthesis/
National Assessment
Scaling Down --Regional to Local Scales
Scale Area (mi2) Cells per
layer
Cell size (ft)
Regional 180963 102051 5000 x 5000
Intermediate 454 50600 500 x 500
Local 22 118336 72 x 72
Model Area107,000 mi2
277,000 km2
Developing a Sound Approach
for a National Assessment
• Characterize water resources at multiple spatial and
temporal scales. Answer questions at scales that are
relevant to local, State, tribal, and Federal decisions makers
and provide the information and tools used to those
stakeholders.
• Find effective means to deliver national-scale products/water
information while recognizing that these same resources are
commonly managed on a local scale.
Developing a Sound Approach
for a National Assessment (cont.)
• Educate water-resource managers and the public to think of
regional water resources in an integrated way.
• Incorporate understanding of how future changes to a
system—driven by human uses, climate variability, or land-
use change may be accommodated by informed water-
resources management.
For More
Information
http://water.usgs.gov/ogw/gwrp/
Kevin Dennehy
Program Coordinator
703-648-5018
