This report documents methodology and results of a study that estimated groundwater discharge by evapotranspiration (GWET) from phreatophytic vegetation in two desert riparian areas with ephemeral spring discharge in Clark County, southern Nevada. The phreatophytes consisted primarily of western honey mesquite [Prosopis glandulosa var. torreyana (L.D. Benson) M.C. Johnst.] at Stump Spring and mixed shrubs at Hiko Springs. An eddy-covariance station and precipitation gage were established to concurrently measure actual evapotranspiration (AET) and precipitation. Site-scale GWET rates—computed by subtracting measured precipitation from AET—were 239 ±45 millimeters per year (mm/yr) based on measurements over one growing season at Stump Spring and 109 ±27 mm/yr averaged over two growing seasons at Hiko Springs.
The volume of GWET for each groundwater discharge area (GDA) was estimated by developing relations between site-scale computed GWET rates and phreatophytic vegetation represented by a Normalized Difference Vegetation Index (NDVI). A GDA was delineated for the natural drainage in each area by mapping the extent of phreatophytes using high-resolution imagery. A second GDA was delineated at Stump Spring by mapping the extent of phreatophytes in the Area of Critical Environmental Concern (ACEC). Site-scale GWET rates were scaled up by applying the site-based GWET -NDVI relations to NDVI distributions in each GDA. The areas of phreatophytic vegetation within each GDA, area-weighted mean GWET rates, and GWET volumes were as follows: (1) Stump Spring—59 hectares (ha), 126 mm/yr, 7.4 ± 1.4 ×104 cubic meters per year (m3/yr) (60 ± 11 acre-feet/yr); Stump Spring ACEC—49 ha, 98 mm/yr, 4.9 ± 0.9 × 104 m3/yr (39 ± 7 acre-feet/yr); and (2) Hiko Springs—7.2 ha, 112 mm/yr, 0.8 ±0.2 × 104 m3/yr (6.6 ±1.6 acre-feet/yr). The GWET rate computed at Stump Spring compared favorably with published GWET rates for mesquite.
Citation Information
Publication Year | 2020 |
---|---|
Title | Estimates of groundwater discharge by evapotranspiration, Stump Spring and Hiko Springs, Clark County, southern Nevada, 2016–18 |
DOI | 10.3133/sir20205075 |
Authors | Michael T. Moreo, Susan G. Buto, David W. Smith, Nora C. Nelson |
Publication Type | Report |
Publication Subtype | USGS Numbered Series |
Series Title | Scientific Investigations Report |
Series Number | 2020-5075 |
Index ID | sir20205075 |
Record Source | USGS Publications Warehouse |
USGS Organization | Nevada Water Science Center |
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Geospatial Data to Support Estimates of Annual Groundwater Discharge by Evapotranspiration from Areas of Spring-Fed Riparian Vegetation, Stump Spring and Hiko Springs, Clark County, Nevada
This USGS data release, supporting USGS Scientific Investigations Report 2020-5075, Estimates of Groundwater Discharge by Evapotranspiration, Stump Spring and Hiko Springs, Clark County, Southern Nevada, 2016-18, consists of five datasets - Normalized Difference Vegetation Indexes (NDVI) and a mapped groundwater discharge areas (GDA) for two spring areas, and a two-class land cover classificationSupplemental Evapotranspiration Gap-filled Datasets from Stump Spring and Hiko Springs, Clark County, Nevada, 2016-18
This USGS data release represents supplemental tabular data for an annual groundwater discharge by evapotranspiration (ET) from areas of spring-fed riparian vegetation, Stump Spring and Hiko Springs, Clark County, Nevada, 2016-18. The raw ET dataset contained multiple data gaps that were simulated and gap-filled with the water-level model utility in SeriesSEE, a USGS developed Microsoft Excel addi - Connect