water level changes associated with climate variability in
TRANSCRIPT
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