FACT SHEET
SOURCE WATER
PROTECTION
LAKE AND RESERVOIR
MANAGEMENT
Tools help utilities predict and respond
quickly to water quality change
QUICK FACTS
• Reservoir managers can run models—even
simple ones—to predict many water quality
conditions and changes
• Advances in monitoring technology allow
near-real time detection of contaminants and
water quality characteristics
• In-reservoir strategies can be very effective
at preventing anoxia and algal blooms and
improve other processes
OVERVIEW
Water treatment costs, finished water quality, and
ultimately public health are directly influenced
by lake and reservoir management. A proactive
approach includes modeling, monitoring, and
in-reservoir management strategies. Water providers often do not have control over nutrient inputs
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and other non-point contamination sources.
Management tools and strategies can help utilities
predict, track, and respond quickly to changes in
water quality.
Watersheds are complex systems with multiple
entities that introduce inputs and pollution into
the water. Downstream reservoirs are impacted
by municipal, industrial, or agricultural activities
upstream, which can introduce nutrients, pathogens and other contaminants. Local seasonal
variations, weather, and other geographic factors
can impact water quality as well. See WRF Topic
Overviews, “Land Use and Water Quality” and
“Wildfire, Drought, and Flood.”
Simple water quality modeling and monitoring,
along with common in-reservoir management
strategies, can assist with overall impacts and help
avoid future treatment costs.
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WATER QUALITY MODELING
MODEL SELECTION PROCESS DIAGRAM
Dynamic/Mechanistic
Model Selection
Reservoir Water Quality Model
Problem Formulation
Limited funds (e.g., $25–30k)
short timeframe (e.g., 3–4 months)
Yes
No
Minimal modeling experience
and expertise
Yes
OME empirical models
No
Screening level study broad
brush answers
Yes
No
Limited site, watershed
data & information
Yes
No
Sufficient information for decisions
No
Yes
Design & implement
management options
1. Model applied to your reservoir
and problem types and results
used in making management
decisions.
2. Comprehensive user’s manual
3. Model currently supported and
being updated
4. Graphical user interface
available for displaying and
analyzing results
5. State accepts model results if
used for regulatory decisions
6. Model schematic of reservoir
water quality problems
Time and resources needed for
model application available
Revise expectations
Obtain needed funds and data
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Yes
Model selection
No
No
Source: Wagner et al. 2013
Models are useful tools for testing the results of
a potential land use or management change on
reservoir water quality. They quantify the relationship between watershed characteristics to create
a mathematical representation of reality. Reservoir
managers can run models to predict water quality
changes such as:
• Effects of changing storage
• Effects of mixing or oxygenation
• Effects of nutrient loading or management
• Influence of different water sources
• Bacterial transport and die-off (Wagner 2015a)
Decision-makers can assess the expected range of
results from a given management action and the
probability of achieving a desired result. Although
modeling requires effort and funding, it can help
utilities predict and adapt quickly to water quality
changes (Wagner et al. 2013). Even simple order of
magnitude estimations can often provide answers
to assist with overall impacts.
Yes
Apply simpler models
Yes
Modeling should always begin with a clear understanding of the problem to be addressed. Utilities
can consider the type of data, decision timeframe,
complexity, and scale. Adequate data can be
gathered through a robust, long-term monitoring
program. A model is reliable only if the data and
linkages are close to reality. Reservoir managers
should be part of the modeling team. Even if an
outside contractor is hired, reservoir managers
lend information and experience to minimize
assumptions by the modelers. The WRF project,
Water Quality Modeling to Aid Water Supply ReserSOURCE WATER PROTECTION
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A proactive management
approach can help
utilities reduce treatment
costs and mprove
environmental conditions.
voir Management (Wagner et al. 2013), provides
further information.
RAPID WATER QUALITY MONITORING
Rapid water quality monitoring systems can
provide data in near-real time. A variety of instruments can quickly obtain data on specific characteristics, including velocity, temperature, dissolved
oxygen, turbidity, nitrogen, chloride, and toxicity.
These systems may be particularly important for
reservoirs vulnerable to extreme weather events
such as forest fires (Stanford et al. 2014), those that
experience quick or unpredictable water quality
changes, and reservoirs with low oxygen, algae, or
compliance challenges (Wagner 2014).
Rapid monitoring data support early warning
systems, compliance, and water treatment cost
savings/avoidance. In the WRF project, Rapid Water
Quality Monitoring to Aid Water Supply Reservoir
Management (Wagner 2014), the utilities studied spent an average of $13,750 on capital costs,
$5,000 on deployment, and $3,334 on operation
and maintenance. Rapid monitoring systems
require data organization and experienced field
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staff; some instruments may need frequent calibration and maintenance.
IN-RESERVOIR MANAGEMENT STRATEGIES
Water quality concerns for reservoirs include temperature, dissolved oxygen, turbidity and nutrient
loading. Ideally, utilities should be proactive in
improving the quality of waterbodies that empty
into their reservoirs and lakes through coordinated land and watershed management. See WRF
Topic Overview, “Land Use and Water Quality.” After
water is transported to a water treatment facility,
in-reservoir management options can help avoid
treatment costs (Dortch 1998). The WRF project,
Oxygenation and Circulation to Aid Water Supply
Reservoir Management (Wagner 2015), contains
discussions of different types of these two systems.
Circulation (Destratification)
Pumps and jets force the movement of water
to disrupt the stratification of oxygen levels in
a reservoir, helping to prevent anoxia and algal
blooms. While circulation can provide a consistent
quality and pH equilibrium, it can be disruptive to
fisheries because it disrupts thermal stratification
(Dortch 1998).
substances and disinfection byproduct precursors,
and help reduce the release of iron, manganese,
sulfides, and phosphorus.
Phosphorus inactivation
When aluminum sulfate or sodium aluminum is
added to the reservoir, phosphorus binds to the
aluminum and precipitates to the lake floor. This
treatment can be very effective at reducing algal
blooms, but is expensive and possibly toxic if overdosed (Dortch 1998).
Biological control
For drinking water reservoirs, biological controls—
introducing certain insects, plants and fish—may
help control algae. They are generally favored over
chemical controls, but effectiveness depends on
many variables. (Jeppesen et al. 1990, Leventer
and Teltsch 1990, Quin 2013).
Oxygenation
In this strategy, oxygen is added to deep water
by releasing oxygen gas or submerged chambers
directly into the water, which does not disrupt
thermal stratification. The increase of oxygen
levels in deeper, colder layers can create a refuge
for zooplankton that eat algae. It can also help
oxidation processes involving oxygen-demanding
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REFERENCES
Dortch, M.S. 1998. Water Quality Considerations in Reservoir Management. Journal of Contemporary
Water Research and Education 108: 32-42. http://ucowr.org/files/Achieved_Journal_Issues/V108_
A3Flood%20Control%20Operations.pdf
Jeppesen, E., J.P. Jensen, P. Kristensen, M. Sondergaard, E. Mortensen, O. Sortkjaer, and K. Olrik. 1990.
Fish Manipulation as a Lake Restoration Tool in Shallow, Eutrophic, Temperate Lakes 2: Threshold Levels,
Long-term Stability and Conclusions. Hydrobiologia 200-201(1):219-227. doi: 10.1007/BF02530341.
Leventer, H., and B. Teltsch. 1990. The Contribution of Silver Carp (Hypophthalmichthys molitrix) to the
Biological Control of Netofa Reservoirs. Trophic Relationships in Inland Waters, Developments in Hydrobiology 53: 47-55. doi: 10.1007/978-94-009-0467-5_7.
Qin, B. 2013. A Large-scale Biological Control Experiment to Improve Water Quality in Eutrophic Lake
Taihu, China. Lake and Reservoir Management 29(1): 33-46. doi: 10.1080/10402381.2013.767867.
Stanford, B.D., B. Wright, J.C. Routt, J.F. Debroux, and S.J. Khan. 2014. Water Quality Impacts of Extreme
Weather-Related Events. Denver, Colo.: Water Research Foundation.
Wagner, K.J., K. Thornton, L. Christina, and D.F. Mitchell. 2013. Water Quality Modeling to Aid Water Supply
Reservoir Management. Denver, Colo.: Water Research Foundation.
Wagner, K. J. 2014. Rapid Water Quality Monitoring to Aid Water Supply Reservoir Management. Denver,
Colo.: Water Research Foundation.
Wagner, K.J. 2015a. Oxygenation and Circulation to Aid Water Supply Reservoir Management. Denver,
Colo.: Water Research Foundation.
Wagner, K.J. 2015b. Webcast: Reservoir Management. January 27, 2015. http://www.waterrf.org/
resources/webcasts/pages/Webcasts-detail.aspx?ItemID=104
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