Water Level Changes Associated with Climate Variability in Las Vegas and Coyote

Spring Valley, Southern Nevada

March 2010

David DonovanSNWA Engineering and Operations

Nevada Water Resources Annual Conference

Key Point

• This presentation examines natural groundwater variations immediately adjacent to a large local pumping center

Eastern Nevada

• 3 of 4 Nevada Climate Divisions

• Main focus of presentation Las Vegas and Coyote Spring Valley

Background

• Groundwater is a key component of supply

• Climate variation and surface water resources

• Climate variation and groundwater resources

• Groundwater development in Coyote Spring is imminent (Summer 2010)

Outline

• Examples of wells effected by climate variability inside Las Vegas Valley

• Summary of Las Vegas Valley Hydrology

• Examples of wells effected by climate variability outside of Las Vegas Valley

• Monitoring and management

Previous Work

• Las Vegas

- Reported but not specifically highlighted

- Included in Donovan (2009)

• Coyote Spring

- Extensively discussed in:

Smith and others (2004)

Buqo (2008)

Ayoub and others (2008)

Mayer (2008)

Emery (2008)

Cumulative Departure From Average Precipitation is:

• A standard technique used by the USGS in the Nevada basin reports of the 1960’s

• Calculated by determining the difference between the average and an individual year (or month) then adding the departure value of the previous year (or month)

• If correctly calculated, the last year (or month) is Zero (0)

• Requires a continuous data set

- Has a partial relationship to physical processes (pre-existing conditions)

- Best used to define drought and periods of abundance (dry and wet periods)

- Buqo (2008) recommended using monthly cumulative departure

January 2005 PRISM

Winter 2004-2005

• Most dramatic in southern Nevada

• Also observed throughout eastern Nevada (Ayoub and others 2008)

Divisions 2, 3, and 4

Division 4 (Las Vegas)

Division 2 (Northeastern Nevada)

From Recon Report 33Rush and Kazmi (1965)

Additional Considerations

• Considerations of Buqo (2008) and Weber and Stewart (2004)

- A key consideration is that the real hydrologic conditions have a “shorter memory” than the technique

• Locally collected data and indexed values

• Long term data and evaluate timing of abundant, dry and “normal” periods

• Shorter term records (1-2 years) may be very effective at explaining stream flow, reservoir levels and ground water levels

Precipitation Event of Dec 2004 and Jan 2005

• Water level changes were undetectable in central Las Vegas Valley

• Large water level changes were observed on the periphery

• Effects were observed throughout eastern Nevada including flooding in Las Vegas and major flooding along the Virgin River

Las Vegas Valley (1)

• Hydrologic effects (stream flow and water level changes) in the central part of any large valley are likely to be muted and / or lagged due to geologic discontinuities and general complexity of large hydrologic systems

• In addition, Las Vegas Valley also has:

- A large volume of ground water production

- An active artificial recharge program

- Extensive urbanization with secondary recharge and

- Essentially no “natural” gaged streams

• Post 1990 trends continued however

Las Vegas Valley

Groundwater in Las Vegas

Central LVV Hydrographs

Central Las Vegas (post 1990)

Las Vegas Valley (2)

• Large water level changes (40 to 300 feet) occurred in Blue Diamond, Kyle Canyon and the Snow Mountain Paiute Reservation

• The most surprising (but smallest magnitude) rise occurred at Snow Mountain

• No clear signal was observed at or near Corn Creek

• Of specific interest in Las Vegas Valley – improved definition of natural “lag”

Las Vegas Valley

Las Vegas GMP

• HTS Network

- Cell Modem

- Websites

http://www.lasvegasgmp.com/html/telemetry_help_text.html

http://www.lasvegasgmp.com/html/telemetry_map.html

Humane Well Near Blue Diamond

• Observed water level declines and rises in 1995 and again in 1998 led to closer manual observation in the Winter of 2004-2005

• Rise and decline was several hundred feet and is temporally coincident with precipitation events

• Good example of large ground water level changes associated with climate variability

Blue Diamond

General Considerations for Hydrologic Analysis at Blue Diamond and Other Areas

• Droughts produce slow steady declines

• Abundant years partially reset water levels

- Thus they are somewhat easier to observe

Las Vegas Valley

Upper Kyle Canyon

• Temporal correlation with a small lag was observed

• Kyle Canyon RAWS has a short record with data gaps but it appears to provide a good precipitation record for correlation

• Note same large precipitation event in January 2005 observed elsewhere

Kyle Hydrograph

Change in Water Levels1990 to 2005 and 2006

Change in Water Levels 2008 and 2009

Snow Mountain

• Water level changes could be groundwater production related or a result of increased precipitation

• Is it groundwater production?

• Is it caused by climate variability?

- If climate variability what is the duration of the lag?

Production and Water Levels(Relationship is Not Definitive)

Snow Mountain

Snow Mountain

Snow Mountain With One Year Lag

Coyote Spring Valley

MX-4 Well

MX – 4 Hydrograph

MX-4 USGS Transducer Record

SNWA Transducer Data

January 2010 PRISM

Climate Variability and Ground Water Resources – Concluding Remarks

• It occurs

• It has a small effect

• It can be accommodated either using stationary (current system) or…

• In the future planned for under a “no regrets” strategy

• Natural variation due to climatic variation occurs on a relative short scale 1-2 years

• Must monitor these effects to discern natural variation to enhance management of groundwater development and the influenced environmental resources