Award Date

August 2016

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Water Resource Management

First Committee Member

Dale A. Devitt

Second Committee Member

David K. Kreamer

Third Committee Member

Lynn Fenstermaker

Fourth Committee Member

Lloyd Stark

Number of Pages

74

Abstract

Groundwater in the basins of east central Nevada (Great Basin Desert, NV) has been permitted for export to southern Nevada. These basins are also vulnerable to changes in climate that could lead to declining recharge. Any decline in groundwater levels no matter the driving force could significantly impact phreatophytes (deep rooted shrubs), which utilize water from both the vadose zone and the capillary fringe to meet plant water needs, to support growth, and for overall health. A reduction in groundwater due to these forces could have a significant impact on the decoupling of phreatophytes from what is normally a reliable source of water. Some climate models predict a reduction in annual precipitation over the next 20-30 years throughout much of the western United States (Barnett and Pierce, 2008). Therefore, extensive research is needed to gain a stronger understanding of the coupling of phreatophytes to groundwater prior to pumping and possible climate change. In March 2010, field research was initiated to gain a better understanding of the hydrologic connections between phreatophytes and their environment in Spring Valley, NV. Isotope and soil moisture data collected to 340 cm suggested that the phreatophytic shrub was responding to both groundwater and soil moisture in the vadose zone, with greater reliance on groundwater later in the summer period. Eddy covariance full stand level evapotranspiration (ETEC) estimates were used in conjunction with multiple plant parameters to assess contributions from groundwater using water balance techniques. Results suggested that the phreatophyte Sarcobatus vermiculatus (common name greasewood) was accessing and utilizing groundwater resources while the other three species on site, Chrysothamnus nauseosus (rabbitbrush), Artemisia tridentata (sagebrush), and Atriplex confertifolia (shadscale), appeared to be accessing water only within the upper 100 cm. Data also indicated that rabbitbrush maintained a more favorable water status than other species at this site suggesting rabbitbrush, a non-halophyte, may have been accessing water deeper within the upper 100 cm that other species were not accessing, but was probably not accessing groundwater due to the presence of high levels of soluble salts (> 50 dSm-1 in soil solution) beyond 100 cm.

Keywords

greasewood; groundwater; isotope; NDVI; phreatophyte; rabbitbrush

Disciplines

Ecology and Evolutionary Biology | Natural Resources and Conservation | Natural Resources Management and Policy | Water Resource Management

Language

English