Water Temperature Control of 

Reservoir Release Flows

2020 Technology Search Results
Background

• Reclamation must address temperature control of reservoir release 

flows to comply with water quality requirements and biological 

opinions, and to reduce potential impacts to species protected under 

the Endangered Species Act. 

• Reclamation currently employs selective withdrawal devices and 

operational techniques at many facilities to meet downstream 

temperature requirements.

• New ideas and technologies are needed to reduce installation and 

maintenance costs and to better or more easily meet temperature 

objectives.
Glen Canyon Dam Background

• 560 ft water depth when full

• Primary flow release through 8 power penstocks (3470 ft)

• Can also release through spillway (3648 ft) and 4 bypass valves (3374 ft)

• Pre-dam temperatures 0-30 deg C; post-dam releases 7-12 deg C
Research Approach

• Compile information on how water temperature is currently controlled 

at dams (state-of practice)

• Conduct Technology Search to seek all ways that water temperature is 

controlled in any industry that may be applicable to dams (out-of-box 

ideas)

• Determine if Reclamation should run a prize competition to seek 

additional solutions
Current Technologies at Dams

Gated selective withdrawal systems – rigid steel structures on upstream face 

of dam to enclose penstock intakes and release water from various elevations

Examples: Shasta Dam, Folsom Dam, Jordanelle Dam, 

Flaming Gorge Dam, Hungry Horse Dam, Cougar 

Dam, Applegate Lake

Image from USACE
Current Technologies at Dams

Fixed flexible temperature curtains –

submerged curtain positioned for water flow 

over or under to control outflow temperature

Examples: Lewiston Reservoir, Whiskeytown Lake

Adjustable flexible temperature curtains –

pulley system allows raising and lowering of 

submerged curtain

Example: Burrendong Dam (Australia)

Photograph from BCI Construction USA, Inc., Lewiston Reservoir

Photograph from WaterNSW, 

www.waternsw.com.au/projects/burrendong

Sherman, Bradford. 2000. “Scoping Options for 

Mitigating Cold Water Discharges from Dams”. 

CSIRO Land and Water, Canberra, Australia.
Current Technologies at Dams

Surface pumps and draft tube 

mixers – top-down circulation 

approach

Destratification devices –

induces large-scale circulation 

or mechanical mixing

Floating intakes – hinged pipes 

positioned to draw water from 

different levels

Schematic from USACE

Sherman, Bradford. 2000. “Scoping Options for 

Mitigating Cold Water Discharges from Dams”. 

CSIRO Land and Water, Canberra, Australia.

Sherman, Bradford. 2000. “Scoping Options for 

Mitigating Cold Water Discharges from Dams”. 

CSIRO Land and Water, Canberra, Australia.
Current Technologies at Dams

• Warming basins – shallow water bodies that warm water via sun exposure

• Multi-level outlets – fixed openings at several levels above intakes

• Low-level outlets – direct flow release to river that bypasses turbines; 

potential to bifurcate between river outlet and penstock or add turbines in 

river outlets

• Reservoir fill, circulation, and release strategies – guide curve changes, 

inflow routing, supplemental releases, concentration of flow through one 

gate, release strategy optimization, hypolimnetic withdrawal
Technology Search Methodology – yet2

• Define: 

• Ways water temperature is controlled (cooled or heated) in any industry that 

can be related to large water resources projects

• Could involve direct heating or cooling of fluids or methods to prevent 

warming or cooling of fluids

• Any stage of development

• Cost is not a factor

• Scout: Proactively scour global markets through their network and 

database and receive submissions to posted Technology Need.

• Filter: Discuss and refine findings with Reclamation at set-points. 

Determine Reclamation use case and partner potential.

• Engage: Prioritize promising technologies and coordinate introductions.
Summary of Solutions

Provided by yet2
Limiting Reservoir Heating: SkyCool Systems

• Uses radiative cooling to passively cool water. Multi-layer optical film reflects 

about 97% of sunlight while simultaneously emitting the surface’s thermal 

energy to the atmosphere. Currently applications in cooling buildings 

(refrigeration, HVAC).

• Reclamation use case: coat penstocks; large area land-based or floating panels

http://skycoolsystems.com/

Information provided by yet2
Limiting Reservoir Heating: Radi-Cool

• Passive cooling of surfaces with see-through polymer interspersed with glass 

beads that emits energy as infrared radiation and reflects solar light.

• Reclamation use case: coat penstocks; large area land-based or floating panels

http://radi-cool.com/

Information provided by yet2
Limiting Reservoir Heating: PARC

• “Self-cooling”paint consisting of engineering metaparticles

• Reclamation use case: coat penstocks; large-area land-based or floating panels

https://www.parc.com/technologies/self-cooling-paint/

Information provided by yet2
Limiting Reservoir Heating: P4P Energy

• Lightweight solar panel suspension system for canal shading prevents 

evaporation water loss

• Reclamation use case: covering canals

http://p4penergy.com/

Information provided by yet2
Energy Storage: Highview Power

• Liquid air energy storage technology uses 

electricity to cool air until it liquified. The 

liquid is stored in tanks and then reheated to 

its gaseous phase such that the gas can turn a 

turbine to generate electricity.

• Reclamation use case: use liquid air energy 

storage to store excess energy from dam and 

use to cool downstream water

https://www.highviewpower.com/ 

Information provided by yet2
Energy Storage: CryoHub

• Liquid air energy storage technology using 

cryogenic liquids currently applied to 

industrial refrigeration.

• Reclamation use case: use liquid air energy 

storage to store excess energy from dam 

and use to cool downstream water

https://cryohub.eu/en-gb/

Information provided by yet2
Energy Storage: PCM Products

• Phase Change Materials (PCMs) allow for temporary storage of thermal 

energy through the process of freezing and melting. Heat or cold can be 

stored from one process and used later for another application.

• Reclamation use case: energy storage

FlatICE Container Design TubeICE Container Design

http://www.pcmproducts.net/

Information provided by yet2
Energy Storage: Energy Vault

• Gravitational energy store uses a crane to lift 

composite blocks to create a tower. Energy is stored in 

the elevation gain.

• Reclamation use case: energy storage system can be 

used to power heating/cooling systems

https://energyvault.com/

Information provided by yet2
Heat Exchange: Makai Ocean Engineering

• Specializes in marine pipelines with applications in ocean thermal energy 

conversion, seawater air conditioning systems, desalination, powerplant cooling, 

wastewater, and transmission pipelines. Designed deepest large diameter 

seawater pipe intake in the world.

https://www.makai.com/

Information provided by yet2
Heat Exchange: Makai Ocean Engineering

• Reclamation use case: floating intakes and cold water pumping

https://www.makai.com/

Information provided by yet2
Heat Exchange: CRH

• Underground concrete earth tubes use 

geothermal energy to reduce 

heating/cooling load on buildings using 

earth-air heat exchanger processes.

• Reclamation use case: harness 

temperature of earth to passively cool 

or heat water 

https://www.crh.com/

Information provided by yet2
Heat Exchange: Thermal Transfer Systems

• Specializes in heat exchangers such as cooling towers using evaporative cooling.

• Reclamation use case: use heat exchangers to cool reservoir water depending on 

water volume and temperature reduction required.

Cooling Tower Heat Exchanger

https://www.thermaltransfersystems.com/

Information provided by yet2
Heat Exchange: Evaptech

• Cooling tower designer that uses evaporative cooling to reduce water 

temperature. Textured PVC sheets strips away heat.

• Reclamation use case: evaporative cooling for reservoir release flows

https://www.evaptechinc.com/

Information provided by yet2
Heat Exchange: Danfoss

• District-wide systems heat water at central location and distribute it through 

a system of underground pipes.

• Reclamation use case: heat or cool water by routing water through district 

heating system

https://www.danfoss.com/en-us/markets/district-energy/

dhs/district-heating/

Information provided by yet2
Destratification Devices: CLEAN-FLO

• Water aeration systems using a ceramic diffusers to completely mix surrounding 

water and even distribute dissolved oxygen. Application of 120 ft deep water 

body in Puerto Rico.

• Reclamation use case: near-dam aeration systems for reservoirs; partial mixing 

achievable by varying speed of motor to manage desired change in temperature

https://www.clean-flo.com/winter-pondaeration-for-ice-prevention/

Information provided by yet2
Destratification Devices: Griffith University

• Dynamic Reservoir Simulation Model (DYRESM), a one-dimensional 

hydrodynamic model, used to predict the vertical distribution of temperature 

in reservoirs. Used to determine the effectiveness of artificial destratification by 

air-bubble plumes to reduce evaporation loss from reservoirs.

• Reclamation use case: employ hydrodynamic modeling for artificial 

destratification

Helfer, Fernanda, Fernado P. Andutta, Jose A. Louzada, 

Hong Zhang, Charles Lemckert. 2018. Artificial 

destratification for reducing reservoir water evaporation: 

Is it effective? Lakes & Reservoirs. Volume 23, Issue 4.

https://onlinelibrary.wiley.com/doi/abs/10.1111/lre.12241

Information provided by yet2
Destratification Devices: UW-Madison

• Gradual Entrainment Lake Inverter (GELI) homogenizes lake temperature using a 

large flat disk with a geomembrane that moves vertically through the water 

column. Centralized air bladder drives movement.

• Reclamation use case: localized destratification

Smith, Colin A., Jordan S. Read, M. Jake Vander 

Zanden. 2018. Evaluating the “Gradual Entrainment 

Lake Inverter” (GELI) artificial mixing technology for 

lake and reservoir management. Lake and Reservoir 

Management. Volume 34, Issue 3.

https://www.tandfonline.com/doi/abs/10.1080/1040238

1.2018.1423586

Information provided by yet2
Destratification Devices: Three Gorges 

Corporation

• Intelligent water temperature destratification device that self-adjusts within 

the thermocline and performs up-and-down reciprocating movement to 

break the thermocline.

• Reclamation use case: improvement of aeration systems

https://www.ctg.com.cn/

IP:CN103572733B

Information provided by yet2
Destratification Devices: PowerChina

• Intelligent destratification device decides best position in thermocline 

based on water density and breaks stratification by aeration.

• Reclamation use case: improvement of aeration systems

http://ghidri.powerchina.cn/

IP:CN208834191U(publishedon05/07/2019)

Provided by yet2
Destratification Devices: Destratification 

Pump

• Water destratification through pumping surface water down to bottom layer. 

• Reclamation use case: localized destratification

Paper published in Nanjing, China, 2007

https://wenku.baidu.com/view/47c58044

ad02de80d4d840a6.html

IP: TBD

Provided by yet2
Destratification Devices: Intellectual Ventures

• Invention “Salter Sink” harnesses energy from 

waves to cool ocean surface temperatures in 

hurricane-prone areas. Ocean waves overtop a 

large, buoyant ring which forces cooler water 

from the bottom. Temperature mixing occurs.

• Reclamation use case: similar application in 

reservoirs

https://www.intellectualventures.com/

Information provided by yet2
Surface Aerator: Environment Agency

• Spray ponds use spray coolers as an improvement to reduce area of the pond 

and cool pond temperatures.

• Reclamation use case: improvement on cooling ponds

https://assets.publishing.service.gov.uk/gover

nment/uploads/system/uploads/attachment_

data/file/291077/scho0610bsot-e-e.pdf

Information provided by yet2
Surface Aerator: Fluence

• Surface aerators (paddle wheel, bubblers, fountains, agitators) and subsurface 

aerators to destratify lakes and improve water quality

• Reclamation use case: temperature and oxygen mixing

https://www.fluencecorp.com/aerators/

Information provided by yet2
Selective Withdrawal Systems: Fengxi

Reservoir

• Inclined pipe with multiple inlets at different depths placed on the upstream 

slope of dam or bank slope of a reservoir.

• Reclamation use case: alternative for selective withdrawal system

https://www.59baike.com/a/181960-46

Information provided by yet2
Selective Withdrawal Systems: Siphon 

Withdrawal

• Withdraw warmer water from top layer of the reservoir with a siphon pipe 

that bypasses turbines

• Reclamation use case: increase downstream temperatures

Review paper “Reservoir stratification and 

improvement methods”, by Lili Wu from Hohai

University, Nanjing, Jiangsu, China.

Published in Hydropower Station Design 09/2007

https://wenku.baidu.com/view/47c58044ad02de

80d4d840a6.html

Information provided by yet2
Heating Devices: Environmental Solar 

Systems

• Parabolic solar troughs concentrate solar energy to heat up water pumped 

through the receiver tube.

• Reclamation use case: use solar troughs to heat up release water

https://www.parabolicsolartrough.com/

Information provided by yet2
Heating Devices: SolarVap

• Uses solar systems to power sustainable water desalination systems.

• Reclamation use case: use concentrated, industrial scale solar power to heat or 

cool downstream water

https://solarvap.net

Information provided by yet2
Heating Devices: Wattco

• Direct heat transfer using immersion heaters with electric heating elements. 

Currently used in industrial tanks.

• Reclamation use case: heaters inside penstocks or immersion heaters in tailrace

https://www.wattco.com/product_category/

immersion-heaters/

Information provided by yet2
Geothermal Systems: Underground Energy

• Aquifer Thermal Energy Storage – Open-loop geothermal technology relies on 

seasonal storage of cold and/or warm groundwater in a suitable aquifer with 

thermal wells.

• Borehole Thermal Energy Storage – Closed-loop geothermal technology using 

drilled boreholes as ground heat exchanger.

ATES Summer Operation – Cooling BTES Summer Operation – Cooling

https://underground-energy.com/ourtechnology/

Information provided by yet2
Conclusions

• Technology Search was successful in finding out-of-box ideas

• No single solution will be successful at all sites

• Many solutions from other industries were not scalable for large applications

• Passive solutions may not meet temperature goals by themselves, but could 

be paired with active solutions

• Next Steps:

• Knowledge transfer to spread results

• Local staff will need to determine if use case makes sense at specific dams

• Prize competition is not planned
Connie Svoboda

csvoboda@usbr.gov

303-445-2152