FACT SHEET
WATER SUPPLY
DIVERSIFICATION
MANAGED
UNDERGROUND
STORAGE
Managed Underground Storage Systems
Techniques and Considerations
QUICK FACTS
• Managed Underground Storage can be a
viable and cost-effective source for reliable
drinking water supplies
• MUS recharge wells and surface basins are
dependent on site-specific hydrogeologic
conditions
• System challenges include water quality,
operation and maintenance, regulations, and
water rights
OVERVIEW
Achieving a sustainable, reliable drinking water
supply is an increasingly important challenge.
Managed Underground Storage (MUS) can be
viable and cost-effective. MUS (also called Sustainable Underground Storage) is defined as the
purposeful recharge of water into an aquifer for
WATER RESEARCH FOUNDATION
later recovery and use. During times when water
is available and of suitable quality, it is recharged
into an aquifer, using either infiltration through
surface materials, or direct injection through wells.
The aquifer acts as a large reservoir, storing water
for periods from a few hours to many years.
Managed aquifer recharge schemes are used for
purposes other than water storage, including
hydraulic barriers for saline intrusion, and environmental restoration.
MUS TECHNIQUES
There are variations in MUS techniques, which in
general involve recharging an aquifer and later
recovery of the stored water through wells.
Recharge
Recharge wells and surface basins are the primary
methods for aquifer recharge, and the selection
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FIGURE 1. SECTION SHOWING A TYPICAL
GROUNDWATER RECHARGE SYSTEM
Water Sources
MUS systems utilize a wide variety of source
waters, including surface water, groundwater, stormwater and treated wastewater. The
choice of water source depends on availability, quality, end use and regulatory constraints. For example, if treated wastewater
is used for drinking water, special pre- and
post-treatments may apply. See Potable
Reuse Topic Overview.
HYDROGEOLOGIC CONSIDERATIONS
(source: Bouwer et al. 2008)
of method is determined by aquifer type, depth
and characteristics. Research wells may be used
for both recharging and recovering stored water.
Vadose zone wells, which recharge water that then
infiltrates the target aquifer, combine some of the
advantages of both well and surface basin recharge.
Wells are also used instead of surface basins to prevent evaporation losses, and/or at sites where the
land is not suitable for surface infiltration.
Recovery
Except for a very few MUS systems, recovery of
stored water occurs through wells. Recovery wells’
location, depth and design are based on factors
such as the aquifer’s hydraulic gradient and proximity to the stored water’s final use.
WATER RESEARCH FOUNDATION
Hydrogeologic conditions for MUS are very
site-specific. A critical step in designing an
MUS system is the development of an aquifer
model, including analytical and/or numerical
flow modeling.
WATER QUALITY CONSIDERATIONS
The chemical, physical and microbiological properties of the source water, native groundwater,
stored water and recovered water all must be
characterized and monitored. A critical step in any
MUS system is understanding the potential water
quality changes associated with mixing often
chemically- and microbiologically-different waters.
Water quality changes can emerge from the subsurface environment, or MUS system impacts such
as leaching, or mixing with impaired groundwater.
Common source water contaminants of concern
for MUS systems include disinfection by-products,
trace amounts of pharmaceuticals and personal
care products, and viruses. Among potential water
quality transformations in stored water, a particular
concern is arsenic (Miller 2001, Vanderzalm 2009).
OPERATION AND MAINTENANCE
CONSIDERATIONS
Recharge facilities are the primary Operation and
Maintenance (O&M) considerations for MUS systems. For a detailed review, see WRF report, Design,
Operation, and Maintenance for Sustainable Underground Storage Facilities.
Surface Recharge
Recharge basins can rapidly degrade with clogging materials, both inorganic (e.g., silts and clays)
and biologic (e.g., algae). Periodic draining and
scraping the basin and controlling weeds are necessary O&M because even a thin layer of materials
can reduce a basin’s effectiveness.
Well Recharge
Key O&M issues for recharge wells are clogging,
cascading and corrosion. Clogging may be caused
by physical factors (e.g., suspended sediments or
air entrainment) or chemical factors (e.g., precipitation on the well screen). Clogging is typically
Development of an aquifer
model is a critical step in
the development of a MUS
system due to variations in
site-specific conditions.
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managed through pretreatment of the recharged
water and well-cleaning or redevelopment.
Cascading occurs when the well’s water level
does not rise to ground surface during recharge.
It can lead to structural and plugging problems. A
variety of conditions can cause corrosion, which
is mitigated through appropriate selection of
recharge well materials, and controlled through
pretreatment to stabilize the recharge water.
REGULATORY AND INSTITUTIONAL
CONSIDERATIONS
Most regulations and institutional controls were
not designed for MUS scenarios. They are highly
HYDROGEOLOGIC FACTORS
AQUIFER FACTORS
•Spatial constraints
•Hydrologic properties
•Matrix properties
•Available storage
POTENTIAL AREAS OF CONCERN
•High probability of clogging
•Potential loss of stored water
•Seasonal/temporal variations
•Potential degradation of stored water/
groundwater quality
WATER RESEARCH FOUNDATION
site-specific and vary widely
between states and jurisdictions. Well recharge systems
are regulated at the federal
level by Underground Injection
Control regulations, which
designate MUS wells as Class 5
wells, a category that includes
such wide-ranging uses as car
wash effluent disposal and
agricultural drainage. The lack
of regulation specifically for
MUS wells leads to inconsistent
application from state to state.
Surface recharge systems are
regulated at the state level, generally through a combination
of existing water quality, quantity and land use regulations.
New regulations are currently
under development in a number of states, notably California
and Florida.
Water rights pose unique challenges for MUS systems. Because
of the movement of surface
water into groundwater, issues
can arise due to separate management of those two rights, in
combination with existing water
rights ownership.
REFERENCES
Bouwer, H., R. David, G. Pyne, J. Brown, D. St. Germain, T.M. Morris,
C.J. Brown, P. Dillon, and M.J. Rycus. 2008. Design, Operation, and
Maintenance for Sustainable Underground Storage Facilities. Denver,
Colo.: AwwaRF.
Dillon, P., and S. Toze. 2005. Water Quality Improvements During
Aquifer Storage and Recovery. Denver, Colo.: AwwaRF.
Fox, P., S. Houston, P. Westerhoff, J.E. Drewes, M. Nellor, W. Yanko,
R. Baird, M. Rincon, R. Arnold, K. Lansey, R. Bassett, C. Gerba, M.
Karpiscak, G. Amy, and M. Reinhard. 2001. Soil Aquifer Treatment for
Sustainable Water Reuse. Denver, Colo.: AwwaRF.
Hahn, W.F., H. Thompson, J. Forbes, and M. Ankeny. 2003. Comparison of Alternative Methods for Recharge of a Deep Aquifer. Denver,
Colo.: AwwaRF.
Miller, T. 2001. ASR in Wisconsin Using the Cambrian-Ordovician Aquifer. Denver, Colo.: AwwaRF.
NRC (National Research Council). 2008. Prospects for Managed
Underground Storage of Recoverable Water. Washington, DC:
National Academies Press.
Pyne, R., P. Singer and C. Miller. 1996. Aquifer Storage Recovery of
Treated Drinking Water. Denver, Colo.: AwwaRF.
Vanderzalm, J., J. Sidhu, E. Bekele, G.G. Ying, P. Pavelic, S. Toze, P.
Dillon, R. Kookana, J. Hanna, K. Barry, X.Y. Yu, B. Nicholson, J. Morran,
S. Tanner, and S. Short. 2009. Water Quality Changes During Aquifer
Storage and Recovery. Denver, Colo.: Water Research Foundation.
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