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Groundwater and Drought: How does USGS contribute to our understanding of groundwater and drought?
The USGS provides unbiased knowledge about groundwater to support resource managers and policy makers with essential information they can use to plan for and respond to drought.
The key to success in coping with water-supply drought is drought planning to assure that water can be drawn from storage, including aquifers or surface-water reservoirs, to supply water users with an adequate supply. This planning can include traditional forms of groundwater resource development as well as systems of artificial recharge or aquifer storage and recovery that take advantage of excess water during wet periods or of waste water, and put it into the subsurface to be extracted in times of the greatest need.
Groundwater data and information also can be used to help communities make the best day-to-day management decisions while drought is taking place. Decision-makers need accurate and timely information on the current status and recent trends in groundwater levels.
USGS mathematical groundwater flow and transport models can be used in planning and response activities to simulate the effects of future drought or groundwater management scenarios.
USGS scientists identify, describe, and make available fundamental information regarding groundwater availability and quality in the Nation's major aquifer systems over time.
Water-level measurements from observation wells are the principal source of information about the hydrologic stresses acting on aquifers and how these stresses affect groundwater recharge, storage, and discharge. Long-term groundwater quantity and quality monitoring by USGS and our Cooperators provides information necessary for sustainable management of groundwater supplies to meet current and future human needs, and ecosystem requirements.
The USGS and USGS Cooperators measured groundwater levels at least once in more than 21,000 wells during 2012. This group of wells is referred to as the Active Groundwater Level Network.
The USGS Climate Response Network is a set of about 130 Active Groundwater Level Network wells that are used to monitor the effects of droughts and other climate variability on groundwater levels.
The Below Normal Groundwater Level map presents Active Groundwater Level Network wells with 10 or more years of record in the month of the most recent measurement, when the most recent water-level measurement is in the 24th percentile or lower.
USGS scientists characterize natural and human factors controlling quality, recharge, storage, and discharge in the Nation's major aquifer systems, and improve understanding of these processes.
The USGS conducts regional and national assessments of groundwater availability and quality to provide an understanding of the current status of the Nation's groundwater resources. In addition, assessment of how those resources have changed over time and development of tools to forecast regional response to human and environmental stressors help answer basic questions about the Nation's ability to meet current and future demands for groundwater.
USGS scientists develop and test new tools and field methods for the analysis of groundwater systems and the interactions these systems have with surface water.
As the Nation's concerns over water resources and the environment increase, the importance of considering groundwater and surface water as a single resource has become increasingly evident. The USGS is at the forefront of devising new techniques to solve practical problems in the study of groundwater resources. Many USGS studies explore the relationship between groundwater and surface-water resources, and USGS tools and data are available for water-resources managers to inform their management of these connected resources.
Predictive computer models are needed to make informed decisions in many areas related to groundwater flow, the effects of groundwater development, and groundwater/surface-water exchange. State and local governments as well as groundwater scientists in the private sector also regularly use USGS models as an integral part of their work. Learn more in the fact sheet about USGS groundwater modeling software development.
During drought, groundwater pumping may be increased when surface-water supplies are low. It is important for us to understand how groundwater pumping affects streamflow, which may be important for water supplies or ecosystem health. USGS research can be used by water resource managers to estimate the rate, locations, and timing of streamflow depletion in response to groundwater pumping. Learn more in the fact sheet on streamflow depletion by wells.
USGS WaterWatch provides streamgage-based maps that show the location of more than 3,000 long-term (30 years or more) USGS streamgages. This streamflow drought map presents below normal 7-day average streamflow compared to historical streamflow for the day of year. For the purposes of this map, water levels are considered below normal when the most recent water-level measurement is in the 24th percentile or lower. The map shows daily conditions adjusted for the time of the year.
USGS Local Data Collection and Research
The USGS conducts groundwater activities in every state and in the US territories. Local data collection and groundwater studies inform our understanding of groundwater conditions and changes over time and provide information and data to local water-resource managers can use.
The USGS Pennsylvania Water Science Center collaborates with the Pennsylvania Department of Environmental Protection (PA DEP) to create a Pennsylvania Groundwater Indicator Map reflecting current groundwater conditions and the PA DEP definitions of drought watch, warning, and emergency. Every day, groundwater levels in USGS observation wells are used to compute an average level of the last 30 days preceding that day that serves as a ground water indicator. The groundwater indicators are then compared with statistical groundwater-level values derived from historic observation-well records.
The USGS California Water Science Center has undertaken a study to develop a greater understanding of the location, extent, and magnitude of land subsidence along the California Aqueduct, as well as to help understand the relationship of groundwater levels and land subsidence. By 1970, significant land subsidence (more than one foot) had occurred in about half of the San Joaquin Valley due to aquifer-system compaction from over pumping and groundwater-level declines. During the droughts of 1976-77, 1987-92, and 2007-09, groundwater pumping increased to meet irrigation demands. This increased pumping resulted in water-level declines reaching near historic lows and periods of renewed compaction. Learn more about the evaluation of groundwater conditions and land subsidence along the California Aqueduct.
Drought Recovery Rate
Work by the USGS North Carolina Water Science Center has shown the time lag among precipitation, streamflow, and groundwater levels as hydrologic conditions move into and out of drought (USGS SIR 2005-5053 by J.C. Weaver, 2005). Weaver explains that "streamflows respond more quickly to changing climate conditions than ground water, and the time lag between the beginning of a drought and the start of declining ground-water levels is longer than for streamflow. This time-lag pattern continues following the end of drought when streamflows are returning to normal and ground-water levels may still be declining."
Sample graphs demonstrating time lag among precipitation, streamflow, and groundwater levels as hydrologic conditions move into and out of drought. Graph shows cumulative monthly departures of streamflow, groundwater, and precipitation for sites near Paw Creek, Mecklenburg County, North Carolina, during (A) 1998-2003 water years and (B) 2002-2003 water years. From USGS SIR 2005-5053 by J.C. Weaver, 2005.
Local USGS Water Science Centers
For more information about USGS activities in your state or territory, visit your local USGS Water Science Center online:
Selected USGS Project Reports on Drought and Groundwater
Bedinger, M.S., 1980, Hydrologic Response of Aquifers to Droughts in the Great Plains, U.S.A.: U.S. Geological survey Open-File Report 80-7, 16 p.
Busciolano, R.J., 2005, Statistical Analysis of Long-Term Hydrologic Records for Selection of Drought-Monitoring Sites on Long Island, New York: U.S. Geological Survey Scientific Investigations Report 2004-5152, 47 p.
Cohen, Philip, Franke, O.L., and McClymonds, N.E., 1969, Hydrologic Effects of the 1962-66 Drought on Long Island, New York: U.S. Geological Survey Water-Supply Paper 1879-F.
Czarnecki, J.B., and Schrader, T.P., 2013, Drought and Deluge: Effects of recent climate variability on groundwater levels in eastern Arkansas: U.S. Geological Survey Fact Sheet 2012-3135, 6 p.
Gatewood, J.S., Wilson, Alfonso, Thomas, H.E., and Kister, L.R., 1964, General Effects of Drought on Water Resources of the Southwest: U.S. Geological Survey Professional Paper 372-B, 55 p.
U.S. Geological Survey, 1991, National water summary 1988-89 Hydrologic events and floods and droughts: U.S. Geological Survey Water-Supply Paper 2375, 591 p.
Weaver, J.C., The drought of 1998-2002 in North Carolina — Precipitation and hydrologic conditions: U.S. Geological Survey Scientific Investigations Report 2005-5053, 88 p.
Zimmerman, T.M., and Risser, D.W., 2005, Drought-sensitive aquifer settings in southeastern Pennsylvania: U.S. Geological Survey Scientific Investigations Report 2005-5169, 21 p.
You can also search the USGS Publications Warehouse for reports summarizing specific USGS studies.