Climate Change Impacts to Groundwater, Springs Hydrology and Aquatic Communities

Amargosa Desert and Death Valley National Park, Nevada and California Terry Fisk1, Greg Pohll1, Don Sada1, Mark Stone2

1Desert Research Institute, Division of Hydrologic Sciences, Reno, NV

2University of New Mexico, Department of Civil Engineering, Albuquerque, NM

LOCATION

INTRODUCTION

Springs are created where groundwater reaches the surface through natural processes. They provide much of the aquatic wetland environment in arid lands as well as a substantial portion of regional aquatic and riparian biodi-versity. Arid land springs are distinct from springs in more humid regions because they are typically isolated, more susceptible to climate change, and are strongly influenced by aquifer characteristics. However, insight into how aquatic and riparian communities will respond to climate change is currently limited to speculation.

At least one dozen springs in the Furnace Creek province of Death Valley National Park, including Travertine Springs, historically flowed onto the floor of Death Valley. These springs are the terminal discharge points for the lower carbonate aquifer, a regional aquifer of approximately 100,000 km2 underlying much of southern Nevada. The National Park Service has recently changed the delivery system for Furnace Creek water so that direct diver-sion from Travertine Springs has ceased. Instead, domestic water is pumped from wells upgradient from Tra-vertine Springs and irrigation water will be collected from downgradient infiltration galleries. This change pro-vides an ideal study platform for research into spring ecology and the effects of changing flow regimes – analo-gous to conditions that may be seen in response to climate change.

Springs in Ash Meadows National Wildlife Area in the Amargosa Desert are intermediate discharge points from the lower carbonate aquifer. The combination of decades of spring discharge and water level data from Furnace Creek, Ash Meadows, and Devils Hole (adjacent to Ash Meadows), new Furnace Creek production and monitor-ing wells, and monitoring networks in the Amargosa Desert provide a very suitable infrastructure to evaluate how aquifer dynamics and spring discharge may be affected by climate change.

METHODS Climate Impacts The Southwestern U.S. faces general temperature increases with largest warming in the summer months, and a likely decrease in precipitation. Due to the aridity of southern Nevada and Death Valley, small changes in water availability may translate into significant alterations in evapotranspiration, recharge, and runoff. Projections for changes in recharge (and also temperature, evapotranspiration, and precipitation) will modify boundary condi-tions of the groundwater and ecological models, described below.

Groundwater Modeling A groundwater flow model will be developed for portions of the Amargosa Desert and Travertine Springs area to evaluate affects on the groundwater flow system resulting from climate change. The model will be based on the U.S. Geological Survey Death Valley Regional Groundwater Flow System model. Simulations will be con-ducted to evaluate how changes in climate, expressed primarily as changes in recharge, affect spring discharge. In addition, response of the aquifer and Travertine Springs to pumping from production wells located upgradi-ent from Travertine Springs will be simulated as an analogue for potential future reduction in spring discharge caused by climate change.

Ecological Modeling Changes in the aquatic environment affecting benthic macroinvertebrate abundance and community structure will be examined by quantifying physical characteristics of the spring brook environment during full discharge and at several lower discharge rates. We will utilize a physical habitat model to determine discharge rates that sustain habitats that support the existing benthic macroinvertebrate assemblage structure. We will integrate field experiments and habitat modeling to quantify thresholds where decreases in discharge affect the abun-dance and distribution of benthic macroinvertebrates, and the structure of this community.

FUTURE WORK

The specific model domain remains to be selected, as well as how the local model will be embedded within the existing U.S. Geological Survey model. Options include (1) a very localized model focusing on the Travertine Springs/Furnace Creek area of Death Valley, and (2) a domain encompassing the southern portion of the Amargosa Desert, including Ash Meadows and Devils Hole. Death Valley National Park and the National Park Service Water Rights Branch in Fort Collins, Colorado have been collecting spring discharge and groundwater level data for decades from Travertine Springs and other springs in the Furnace Creek area, and from a variety of monitoring well networks inside and out-side the park. In addition, the park has been collecting water level and pumping data from the new pro-duction wells, and associated monitoring wells since the advent of pumping. These data will form the core set that will be used to model changes to the local groundwater flow system and spring discharge, and to better define aquifer characteristics in the vicinity of Travertine Springs. Data from a variety of monitor-ing well networks in the Amargosa Desert and from Devils Hole will be used in the groundwater flow model for both steady-state and transient calibration, and to evaluate potential climate-related changes in water levels in the Amargosa Desert and Ash Meadows areas.

REFERENCES Belcher, W. R. (ed.) 2004. Death Valley regional ground-water flow system, Nevada and California – Hydro-

geologic framework and transient ground-water flow model: U.S. Geological Survey Scientific Investigations Report 2004-5205, 408 p.

Hershler, R. and D.W. Sada. 2002. Biogeography of Great Basin freshwater snails of the genus Pyrgulopsis. Pages 255 – 276. In, R. Hershler, D.B. Madsen, and D.R. Currey (eds.). Great Basin aquatic systems history. Smith-sonian Contributions to Earth Sciences, Number 33.

Sada, D.W. and D.B. Herbst. 2006. Ecology of aquatic macroinvertebrates in Travertine and Nevares Springs, Death Valley National Park, California, with an examination of water diversion effects on their abundance and community structure. Unpublished report to U.S. National Park Service, Death Valley National Park.

Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K. B. Averyt, M. Tignor, and H. Miller, eds. 2007. The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovern-mental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Stonestrom, D. A., Constantz, J., Ferré, T.P.A., and Leake, S.A., eds. 2007. Ground-water recharge in the arid and semiarid southwestern United States: U.S. Geological Survey Professional Paper 1703, 414 p.

Winograd, I. J., and W. Thordarson. 1975. Hydrogeologic and hydrochemical framework, south-central Great Ba-sin, Nevada-California, with special reference to Nevada Test Site. U.S. Geological Survey Professional Paper 712-C, 123 p.

ACKNOWLEDGEMENTS

This research is funded by the National Science Foundation Nevada EPSCoR Program under Cooperative Agreement No. EPS-0814372. We are grateful to the National Park Service and U.S. Geological Survey for their support with data acquisition and modeling.

Travertine Springs

Amargosa Desert

Spring Mountains

Travertine Springs

Amargosa Desert

Ash Meadows

Recharge to the Lower Carbonate Aquifer is primarily from precipitation in the higher mountains of south-ern Nevada. For Ash Meadows, the Amargosa Desert, and Travertine Springs, a substantial portion of re-charge is from the Spring Mountains. Additional recharge is from Pahute Mesa and the Sheep Range.

RESEARCH QUESTION AND HYPOTHESIS “How will aquatic ecosystems respond to climate change, and can we develop a quantitative

understanding of groundwater – spring dynamics so that we may predict changes to aquatic ecosystems?”

Understanding how spring ecosystems respond to climate change is the initial requirement in being able to develop predictive models of these ecosystems. Our overall hypothesis presumes that climate change in southern Nevada will result in decreased precipitation, increased temperatures, increased evapotranspira-tion, and a decrease in recharge to the groundwater system (IPCC 2007). Further, we assume that a reduc-tion in spring discharge will occur because of decreased groundwater recharge, and this reduction in dis-charge will affect dependent aquatic ecosystems.

Annual precipitation and ground water re-charge

Prop

ortio

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Meters From Source

Endemic macroinvertebrates, excluding spring snails

NonEndemic macroinvertebrates, excluding spring snails

Meters From Source

Abu

ndan

ce

Example: Map of hydraulic conductivity bases on lithologic properties, aquifer test data, and water level monitoring data.

Example: Travertine Spring water column analyses for macroinvertebtates.