Rethinking Water Storage on the Southern Colorado Plateau

Home , Cataract Canyon, Fontenelle Reservoir, Lake Mead, Lake Mohave, Lake Powell, Lees Ferry

Rethinking water storage on the southern Colorado Plateau

Jack Schmidt

https://qcnr.usu.edu/wats/colorado_river_studies/https://qcnr.usu.edu/wats/colorado_river_studies/ Fill Mead First -- establish Lake Mead as the primary reservoir storage facility; 2015 store water in Lake Powell only when Lake Mead is full.

2016 • Objectives

• Expose Glen Canyon’s sandstone walls • Recreate natural flow, sediment transport, and temperature regime in Grand Canyon • Save water (300,000 – 600,000 af/yr) • Eliminate need for Glen Canyon Dam Adaptive Management Program

Fill Mead First Proposal

• Phase I – reduce storage in Lake Powell to minimum power pool elevation (3490 ft asl) • Phase II – reduce storage in Lake Powell to dead pool (3370 ft asl) • Phase III – drill new diversion tunnels and fully drain Lake Powell New York Times, May 20, 2016 ~0.49 M af/yr evaporated from Powell ~0.37 M af/yr seepage losses

~0.55 M af/yr saved

Myers, 2010, Planning the Colorado River in a changing climate: reservoir loss New York Times, May 20, 2016 rates in Lakes Powell and Mead and their use in CRSS. Consulting report to GCI. Myers, 2013, Loss rates from Lake Powell and their impact on management of the Colorado River. Journal of the American Water Resources Association GRGr

?SRRGr CRC P ??E

?DDRH

?ER E ??tribsungaged

??Gstorage:long + ??Gstorge:short

SJRB

??Gseepage

CR LF = + ±

∆ 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠 𝐼𝐼 𝑃𝑃 − 𝐸𝐸 𝐺𝐺 − 𝑅𝑅 Calculation of Water Savings by Myers (2010, 2013)

= ±

𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙LossesPowell𝐸𝐸 = E 𝐺𝐺+ G 770,000 af/yr (+60,000) = 500,000 af/yr + 270,000 af/yr (+60,000)

LossesMead = E + G

880,000 af/yr = 810,000 af/yr + 70,000 af/yr

LossesTotal = LossesPowell + LossesMead

1,600,000 to 1,700,000 af/yr = 770,000 af/yr (+60,000) + 880,000 af/yr

Losses associated with ~500,000 af/yr present operating rules evaporation loss assumed Evaporation losses

Estimated evaporation rates (1946-1955)

Powell (4.5 ft/yr)

Mead (6.8 ft/yr)

Meyers and Nordenson, 1962, USGS Professional Paper Previous Studies of Evaporation at Lake Mead

• Water budgets Anderson and Prichard (1951) = 5.3 ft/yr • Mass transfer Harbeck et al (1958) = 7.1 ft/yr (in 1953) • Energy budget Harbeck et al (1958) = 7.0 ft/yr ( average for 1941-1953) Westenberg et al (2006)* = 6.7 ft/yr (average for 1953-1973); 6.0 ft/yr (average for 1974-1994) Westenberg et al (2006) = 7.5 ft/yr (average for 1997-1999)

CRSS = 6.6 ft/yr Annual energy-balance corrected evaporation rate, based on eddy covariance method

Jun Au Au O

Moreo and Swancar, 2013; Moreo, 2015 Evaporation = (evaporation rate) X (reservoir surface area)

Moreo and Swancar, 2013; Moreo, 2015 2010-2015 ; average evaporation rate = 6.2 ft/yr Annual Lake Mead evaporation varied between Mar 2010 – F 2011 = [580,000 af] -- 6.8 ft/yr 520,000 and 590,000 af/yr Mar 2011 – F 2012 = [590,000 af] (Mar 2010 – F 2015) Mar 2012 – F 2013 = [590,000 af] Mar 2013 – F 2014 = [520,000 af] -- 5.7 ft/yr Mar 2014 – F 2015 = [500,000 af]

Au Jun Au O Au Lake Mead

Annual energy-balance corrected evaporation rate, based on eddy covariance method

Moreo and Swancar, 2013; Moreo, 2015 Evaporation Studies at Lake Powell

Jacoby et al (1977) = 5.8 ft/yr (average for 1962- 1975)

• Evaporation pans • Mass transfer

Reclamation (1986) used the Jacoby et al (1977) data to estimate an average rate of 5.7 ft/yr for 1965-1979. Evaporation at Lake Powell reported in Interim Shortage Guidelines EIS and in 24-Month Study

Total annual evaporation used in CRSS = 4.0 ft/yr Evaporation at Lake Powell is often reported as “net,” which is total evaporation minus evapotranspiration that occurred before Glen Canyon Dam was constructed

Total annual evaporation used in CRSS = 4.0 ft/yr Predam ET?

This value is the net evaporation and does not include the estimated pre-dam evapotranspiration from the Colorado River and its floodplain Most recent evaporation measurements at each reservoir

Lake Mead (2010-2015) most probable average annual rate = 6.2 ft/yr

Lake Powell (1965-1979 average annual rate = 5.7 ft/yr Surface area of Lake Powell > Lake Mead when reservoir storage is more than 10,000,000 af Under the assumed rule of equalizing the storage contents of Lake Powell and Lake Mead …

when total active storage is 40% of P/M when total active storage is 30% of P/M capacity (~20,100,000 af; ~10.1 maf in capacity (~15,100,000 af; ~7.5 maf in each) each) Evaporation from Powell is 350,000 – Evaporation from Powell is 420,000 – 470,000 af/yr 560,000 af/yr

Evaporation from Mead is 420,000 – Evaporation from Mead is 500,000 – 460,000 af/yr 530,000 af/yr

when total active storage is 50% of P/M capacity (~25,100,000 af; ~12.6 maf in each)

Evaporation from Powell is 490,000 – 650,000 af/yr

Evaporation from Mead is 560,000 – 600,000 af/yr When total active storage is 40% capacity:

Equalization: Powell evaporation = 420,000-560,000 af/yr Mead evaporation = 500,000 – 530,000 af/yr

Fill Mead First proposal*: Powell evaporation = 240,000-320,000 af/yr Mead evaporation = 650,000 – 710,000 af/yr

Evaporation losses might be reduced if water is preferentially stored in Lake Mead rather than distributing the water in both reservoirs, but uncertainty is very high

* Phase I proposal Conclusions

• Under FMF, reduced storage and reduced evaporation in Lake Powell is approximately matched by increased evaporation from Lake Mead.

• Under Phase I or Phase II of FMF, it cannot be demonstrated that the total evaporation from the two reservoirs would be significantly different from the estimated losses under the equalization rule.

• The uncertainty in these estimates is large.

• State- of-the-science measurements of evaporation are made at Lake Mead; a similar measurement program is not in place at Lake Powell. Movement of Reservoir Water into Surrounding Ground Water

Jacoby et al., 1977 Movement of reservoir water into surrounding ground- water system is inevitable Losses Associated with Ground-Water Movement into Surrounding Bedrock

Ground water from the north flows towards Lake Powell

Blanchard, 1986

Thomas, 1986 Reservoir water seeps around Glen Canyon Dam and enters the Colorado River upstream from Lees Ferry Thomas, 1986

Note: USGS measured stream flow below CR below dam = 36.6 mil af GCD and at Lees Ferry (Mar 2000 – Au 2004) CR @ Lees Ferry = 37.0 mil af Gaging studies to determine reservoir seepage delivered back into Colorado River

CR below dam = 28.6 mil af CR @ Lees Ferry = 28.6 mil af S 13, 1989 – Mar 31, 1993

CR below dam = 36.6 mil af CR @ Lees Ferry = 37.0 mil af Mar 1, 2000 – Au 2, 2004 Estimated water savings associated with lowering or draining Lake Powell are based on assuming that past rates of ground-water storage will continue in the future.

This is unlikely.

Future ground-water movement estimated 50,000 af/yr, decreasing to 30,000 af/yr after mid-century. Estimated water savings associated with lowering or draining Lake Powell are based on assuming that past rates of ground-water storage will continue in the future.

This is unlikely.

Future ground-water movement estimated 50,000 af/yr, decreasing to 30,000 af/yr after mid-century. Summary of ground-water modeling studies conducted by USGS in 1980s

Gstorage:short Transient (comes and goes)

Gstorage:long

Gstorage:intermediate 50,000 af/yr, declining to 30,000 af/yr after ~2030 [Thomas, 1986] 700,000 af/yr (1965-1975) [Jacoby et al., 1977] 380,000 af/yr (1965-1985) [Thomas, 1986] Conclusions Concerning Ground Water at Lake Powell

• G round water moves from Lake Powell into the surrounding Navajo sandstone.

• The rate that ground water moves into the surrounding bedrock is relatively slow and is likely to have declined with time.

• Most studies have estimated that equilibrium conditions are likely to take many centuries to develop. A proportion of ground-water storage is better considered long-term bank storage and is not available to meet decadal-scale water supply needs.

• Changes in ground-water storage are likely to occur as far as 20 miles from the reservoir.

• There is no evidence of bank seepage losses from Lake Powell, except around the north side of Glen Canyon Dam. That water seeps back into the Colorado River upstream from Lees Ferry.

• No studies have described ground-water movement south from Lake Powell or around the south side of Glen Canyon Dam. Lake Mead

Accounting surface defines those wells distant from the river and reservoirs whose water partly comes from the Colorado River

Wiele et al., 2009 Although the spatial extent of the saturated alluvium has been defined, no modern studies of ground-water movement have been conducted.

Wiele et al., 2009 What would happen in Grand Canyon if Lake Powell were partially drained? waterfall

waterfall

Lake Powell surface area:

Full – 251 mi2 Minimum power pool – 77 mi2 Dead pool – 32 mi2 June 2003 March 2004 8-17-04 Fine sediment remobilization in Lake Powell under drawdown

6-29-02 2-10-03 8-16-03 8-17-04 Dohrenwend, unpubl Pratson et al., 2008

Phase I

Phase II

The lower reservoir levels of Phase I and Phase II would cause the San Juan and Colorado Rivers to incise into their deltas. The mobilized fine sediment would form new deltas within the lowered reservoir. Downstream releases would be clear water. Phase I

Phase II

Phase I

Phase II

Phase I

Phase II

The capacity of the infrastructure limits the ability to reestablish a natural flow regime.

capacity of penstocks ~31,500 ft3/s

capacity of river outlets is 15,000 ft3/s when reservoir is above minimum power pool elevation; below mppe, capacity is much less

Data: Bureau of Reclamation Inflow Evap (observed hydrology)

Power-plant release rule: match inflows; maximum Rule curve for release is Minimum power pool releases through 31,500 ft3/s river outlets

Dead pool

River outlets: maximum release 15,000 ft3/s What might happen if Lake Powell goes below minimum power pool elevation and water can only be evacuated through the river outlets? Spillways – 3648’ (Warm)

Powerplant – 3470’ (Cold/Warm)

River Outlets – 3374’ (Cold)

As reservoir level declines, releases downstream will warm. 0°C a) July thermal conditions in CRB

15°C

Fontenelle Reservoir !! 30°C ! !!!!!!!!!!!!! -1.2°C !!!!!!!! !!!! !!!!!!!!!!! !!!!!!! Flaming Gorge !!!!!!!!! Reservoir !!!!!!!!!!!!! !!!!!!!!!!!!!!!!! -7.1°C !!! !!! !!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!! !!!!!!!! !!!!!!!!!!!!!!!!!!! !!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!! !!!!!!!!!!!! !!!!!!! !!!!!!!!!!!!!!!!!! !!!!!!!!!!!! !!!!!!!! !!!!!!!!!!! !!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!! !!!!!! !!!!!!!!!!!!!!!! !!!!!!!!!!!!!! !!!!!!!! !!!! ! !!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !! !!!!!!!!! !!! !!!!!!! !!!! !! !!! !!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!! !! !!!!!! !!!!!!!!!!!!!!!!!!!! !!!!!! !!!!!!!!! !!!!! !!!! !!! !!!!!!! !!!!!!!!! !!!!!!!!! !!!!!!!!!!!!!!! !!!!!!!!!! !!!!!!!! !!!!!!!!!! !!!!!!! !!!!!! !!!! !!!!! !!!!!!!!!!!!!! !!!!!!!!! Lake Powell

!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!! !!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!! !! !!! !!!!!!! !!!!! !!!!!!!! !!!!!!!!!!!!!!!! !!!!!!!!!! !!!!!!!! !!!!!!! !!!! -15.2°C !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!! !! !!!! Navajo Reservoir !!!!!! Lake Mead !!!! -14.3°C !!!!!!!!!! !!!!!!!!!! !!!!! !!!!!!!!!!!!!!!!!! !!!!!!!!!!! !!!! -4.6°C !!!!!!!!!! !!! !!!!!!! !! !!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!! !! !!!!! !! !! !!!!!!! !!! !!!!!!!!!!!!!!!!!!!!! Lake Mohave Ü 0 100 200 km

Thermal conditions below Glen Canyon Dam are unusually cool in summers … Dibble et al., In Prep., BioScience 0°C b) December thermal conditions in CRB

15°C

Fontenelle Reservoir !! 30°C !!!!!!!!!!! +2.5°C !!!!!!!! !!!! !!!!!!!!!!! !!!!!!! Flaming Gorge !!!!!!! Reservoir !!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!! !!!!! Yampa R. +6.9°C !!! !!!!!!!!! !!!!!!!!!!!!!! !!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!! !!!!!!!!! !!!!!!!!!!!!!!!!!!!! !!!!!!!!! !!!!!!!!! !!!!!!!!! !!!!!!! !!!!!!!!!!!!!! !!!!!!!! !!!! ! !!!! !!!!!!!!!!!!!!!!! !!!! !!!!!!!!!!! !! !!!!!!!!! !!! !!!!!!! !!!! !! !!! !!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!! !! !!!!!! !!!!!!!!!!!!!!!!!!!! !!!!!! !!!!!!!!! !!!!! !!!! !!! !!!!!!! !!!!!!!!!! !!!!!!!!! !!!!!!!!!!!!!!! !!!!!!!!!! !!!!!!!! !!!!!!!!!! !!!!!!! !!!!!! !!!! !!!!! !!!!!!!!!!!!!! !!!!!!!!! Lake Powell

!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!! !!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!! !!! !!! !!!!!!!!! !!!!! !!!!!!! !!!!!!!!!!!!!!! !!!!!!!!!! !!!!!!!! !!!!!! !!!!! !!!!!!!!!!!!!!!!!!!!! !!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!! +9.2°C Navajo Reservoir !!!!! Lake Mead !!!! !!!! +4.9°C !!!!!!!!!!!! !!!!!! !!!!!! +3.5°C !!!!!!!!!!!!!!!!!! !!!!!!! !!!!!! !!!! !!!!!!!!!! !!! !!!!!!! !! !!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!! !! !!!!! !! !! !!!!!!! !!! !!!!!!!!!!!!!!!!!!!!! Lake Mohave Ü 0 100 200 km

… and unusually warm in winter Dibble et al., In Prep., BioScience It is likely that there would be significant within-year temperature fluctuation under Phase I and Phase II. There would be significant warming during summers, with unknown ecological impacts

Minimum Power Pool

Dead Pool Losses

Evaporation: Mead is slightly more evaporation than Powell

Seepage: losses at Powell persist but are small

Environmental Considerations

Sediment will be redistributed within Lake Powell, but releases downstream will be devoid of sediment

Flow regime will not be run-of-the-river

Thermal regime will be more like unregulated condition Hoover Dam Lake Powell

Glen Canyon Dam

Lake Mead Upper Basin

Lower Basin

Note: 1990-2016 Average annual flow at Lees Ferry = 9,300,000 af/yr Average annual flow at Diamond Creek = 10,000,000 af/yr Projected elevation of stored water in Lake Powell

Colorado River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations for Lake Powell and Lake Mead (adopted 2007) …

Projected elevation of stored water in Lake Mead Cataract Canyon Hoover Dam

Glen Canyon Glen Canyon Dam Lake Powell Lake Mead

Marble Canyon Grand Canyon

Numerous studies in Grand Canyon demonstrate that the volume of releases greatly affects sediment transport, sediment mass balance, sand bar stability, and rate of downstream warming of dam releases. Water source

All water that enters Lake Powell passes through the southern Colorado Plateau and is released from Lake Mead to Lower Basin users Bottleneck

Lower Basin and MX water users David Brower, Sierra Club Cataract Canyon

Hoover Dam Glen Canyon Lake Powell

Lake Mead Glen Canyon Dam

Marble Canyon Grand Canyon

Water storage and environmental river management in the southern Colorado Plateau are one integrated management challenge: How to we achieve watershed-scale water supply reliability while also enhancing the opportunities for Confluence of the Grand and rehabilitation of the Grand Canyon ecosystem? Green Rivers to the Grand Wash Cliffs ~500 miles Findings:

Implementation of FMF is unlikely to re-establish a natural flow regime of the Colorado River in Grand Canyon

Water released from a partially drained Lake Powell is likely to be devoid of fine sediment. Impacts to the aquatic and riparian ecosystem are potentially significant due to increases in water temperature.

There is likely to be no change in total reservoir evaporation losses if FMF was implemented.

The long-term future rate of movement of ground water into the bedrock surrounding Lake Powell is likely to be less than ~50,000 af/yr.

Now is the time to initiate new measurement and modeling programs of losses at Lake Powell and Lake Mead so that future policy discussions have access to less uncertain data regarding evaporation and ground-water storage . Modeling studies are needed to predict fine sediment redistribution in a partially drained Lake Powell.

Decisions about future management of Powell/Mead should consider water supply reliability and ecosystem rehabilitation as a joint problem. River rehabilitation should be considered when Interim Guidelines are renegotiated.