Groundwater Discharge from Phreatophyte Vegetation, Humboldt River Basin, Nevada

Groundwater Discharge from Phreatophyte Vegetation, Humboldt River Basin, Nevada

Groundwater Discharge from Phreatophyte Vegetation, Humboldt River Basin, Nevada

Project Description

Groundwater evapotranspiration (ETg) from phreatophyte vegetation is the primary component of natural groundwater discharge within the Humboldt River Basin. This report summarizes previous study estimates of ETg, and details methods and results of updated groundwater discharge areas, ETg rates, and ETg volume estimates developed in this study. Estimates derived in this study are summarized for the period of 1985-2015 and were based on a consistent place-based approach that relies on Geographic Information System and groundwater level data and a least-squares regression model that relates Landsat vegetation indices with evaporative demand, precipitation, and in-situ estimates of phreatophyte ET. Median annual ETg rates and volumes reported in this study are representative of pre-development conditions. Where irrigated areas were identified, ETg rates were adjusted to reflect the phreatophyte vegetation that likely occupied irrigated areas prior to cultivation. Results from this study were used to inform groundwater modeling studies by the U.S. Geological Survey and the Desert Research Institute, in cooperation with Nevada Division of Water Resources, to support conjunctive water management.

Results and datasets are summarized and documented in the form of maps, graphs, tables, geodatabases, and metadata following Federal Geographic Data Committee standards and are available at www.dri.edu/humboldt-etg. Estimated pre-development total annual ETg volumes for the upper, middle, and lower Humboldt River basin are 158,500, 361,600, 55,900 ac-ft/yr, and 85,700, 248,400, and 46,100 ac-ft/yr when riparian lands are excluded, respectively. Discharge areas and median annual ETg rates and volumes were compared to previous estimates for respective ET Units and Hydrographic Areas. Results reported for the upper Humboldt River Basin indicate that potential areas of groundwater discharge are generally lower, and ETg rates and volumes are generally less than one half of the ETg rates and volumes reported by Plume and Smith (2013). Results reported for the middle Humboldt River Basin indicate that ETg volumes are higher in six, and lower in seven HAs when compared to previous estimates reported in Water Resource Bulletin and Reconnaissance Series reports. ETg rates and volumes in the middle Humboldt River Basin are also generally less than one half when compared to those reported by Berger (2000). Differences in ETg volumes are primarily due to differences in ETg rates and differences in groundwater discharge areas.

This study used place-based satellite remote sensing, climate and GIS datasets, groundwater levels, and in-situ based phreatophyte ET empirical regression models to estimate potential areas of groundwater discharge, and ETg rates and volumes within the Humboldt River Basin. Future study estimates of ETg within the Humboldt River Basin could be improved by refining delineation of groundwater discharge areas, variability in ETg with respect to climate and land use change, and collection of in-situ ET estimates in areas where large uncertainty exists.

Report – Groundwater Discharge from Phreatophyte Vegetation, Humboldt River Basin, Nevada

Appendix A – Previously Reported Groundwater Discharge Areas, ETg Rates, ETg Volumes, and Study Source Information

Appendix B – Meteorological Station Mean Annual Ratios of Station Calculated ASCE Grass Reference ET (ETo) to Estimated Gridmet ETo

Appendix C – Percent Change in Median ETg for Select Basins

Appendix D – Groundwater Discharge Areas and Median ETa Volumes for Each ET Unit and HA

Appendix E Part 1 – Annual time series of median EVI, ET, ETg, ETo, and PPT rates from 1985-2015 for all groundwater discharge areas inclusive of riparian discharge areas

Appendix E Part 2 – Annual time series of median EVI, ET, ETg, ETo, and PPT rates from 1985-2015 for groundwater discharge areas excluding riparian discharge areas

Appendix F – Bar Charts Illustrating Estimated Discharge Areas, ETg Rates, and ETg Volumes

 

GIS Data – Potential areas of groundwater discharge

GIS Data – Geotiff raster of median annual groundwater evapotranspiration

GIS Data – Groundwater discharge areas digitized from NDWR Water Resource Bulletin and Reconnaissance Series reports

 

CONTACT

Justin Huntington, PhD
Justin.Huntington@dri.edu

LOCATION

Desert Research Institute
2215 Raggio Parkway
Reno, NV 89512

DIVISION

Hydrologic Sciences

Groundwater Dependent Ecosystem Assessments

Groundwater Dependent Ecosystem Assessments

Groundwater Dependent Ecosystem Assessments

Project Description

Groundwater supports a variety of ecosystems in Nevada and the Great Basin, including springs, rivers, lakes, meadows, and wetlands, as well as trees and shrubs that tap into groundwater through deep roots (called phreatophytes). Many of these groundwater dependent ecosystems (GDEs) have small footprints on the landscape, but outsize ecological, economical, and cultural importance —  they provide water storage and purification, store carbon, provide recreational and economic benefits, many of them are considered sacred to indigenous peoples, and they provide habitats to a wealth of species, including many rare and endemics species that are found only in this region. As water demands for agriculture, mining, energy development, and potable water uses continue to increase, understanding the potential impacts of groundwater withdrawals on these ecosystems can assist efforts to sustainably manage limited water resources to meet economic and livelihood, wildlife habitat, recreation and other needs. Furthermore, understanding the influence of variability in climatic conditions on groundwater dependent vegetation will enhance our ability to better tease apart effects of climate from those associated with water management.

The DRI studies highlighted below seek to enhance this understanding by assessing historical patterns of vegetation variability and trends in relation to climate and management using 35+ years of Landsat satellite imagery, climate data, groundwater levels, unmanned aircraft systems (UAS), and field surveys for selected areas across the Great Basin. Reports and all data compiled for each of these studies are available below for download.

 

CONTACT

Christine Albano, PhD
Christine.Albano@dri.edu

Blake Minor, MS
Blake.Minor@dri.edu

Justin Huntington, PhD
Justin.Huntington@dri.edu

LOCATION

Desert Research Institute
2215 Raggio Parkway
Reno, NV 89512

DIVISION

Hydrologic Sciences

map of Nevada highlighting groundwater
Photo of Grass Springs with mountain in the background

Baseline Assessment of Groundwater Dependent Vegetation in relation to Climate and Groundwater Levels in select Hydrographic Basins of Nevada 

Objective:  To establish a baseline for monitoring and assessing the potential impacts of groundwater developments on GDEs in selected hydrographic basins of Nevada by quantifying the current status and historical trends in the condition of groundwater dependent vegetation relative to trends in both climate and groundwater levels. Analyses were completed for Pueblo, Continental Lake, Mud Meadow, Dixie, Railroad-North, Steptoe, Goshute, and Independence Valleys in Nevada. 

Key Findings: 

  • In several valleys, the areal extents of groundwater dependent vegetation (phreatophyte areas) were substantially smaller than was estimated historically, suggesting that either the historical extents were overestimated or that there have been substantial losses of groundwater dependent species due to lowered groundwater levels. These differences are important and merit further investigation, as real losses in groundwater dependent vegetation indicate large-scale ecological change, while historical overestimation of the phreatophyte area may suggest historical overestimation of the groundwater discharge, which has served as the basis for determining the perennial yield and groundwater appropriations for each valley.
  • Analysis of Landsat satellite data over 35 years revealed that vegetation outside the phreatophyte areas – especially forest and woodland vegetation was, on average, trending more positively than phreatophyte area vegetation, which tended to have only slightly positive to slightly negative trends. Areas classified as riparian, wetland, and low-intensity agricultural vegetation consistently had larger magnitude trends and tended to have a larger proportion of negative trends relative to dryland vegetation types. The trends observed in this study deserve careful consideration and future research to better isolate their causal factors.
  • Permitted groundwater rights are higher than the current estimated perennial yield in half of the eight basins assessed. Lack of consistent and long-term groundwater data was the most limiting factor in this study. Given the available data, over 25% of wells in each of five basins had statistically significant declines in groundwater levels. The largest declines in groundwater levels were most often observed in direct association with irrigated agriculture (up to 10’s of feet over 35 years) and mining activities (up to 100s of feet). 
  • Substantial human impacts were documented at all GDE sites that were visited in the field, but trends in vegetation over time varied from negative to neutral to positive. In most cases, there was insufficient groundwater levels data available to quantify groundwater-vegetation relations. This is an important data gap that will be essential to fill in order to understand the effects of water development on these ecosystems.

    Download the report and associated datasets here: 

    Status and Trends of Groundwater Dependent Vegetation in Relation to Climate and Shallow Groundwater in the Harney Basin, Oregon 

    Objective:  To increase understanding of relations between variations in climate, shallow groundwater, and groundwater dependent vegetation in the Harney Basin, OR. 

    Key Findings: 

    • Trend analyses of groundwater levels indicate widespread declines in groundwater levels across the basin; in most cases these declines were determined to be occurring independently of antecedent climate conditions. 
    • Substantial changes in surface water extent, vegetation vigor, and land use, indicated by the Landsat Normalized Difference Vegetation Index (NDVI), were evident over the course of the 35-year study period, with positive trends in NDVI indicating lake level declines since the mid-1980’s and subsequent encroachment by sparse vegetation as well as increases in irrigated cropland. Negative trends in vegetation vigor were most prominent in riparian and wetland vegetation types and low-intensity agricultural lands used as pasture and/or hayfields. 
    • Site-specific analyses of field survey and remote sensing data identified transitions from mesic (i.e., riparian and wetland) to dryland vegetation along the edges of Malheur Lake in response to declining lake and shallow groundwater levels since the 1980’s. Other areas where trends in vegetation were evident have limited evidence of groundwater declines and are places where non-native plant species invasions and intensive vegetation management activities such as mowing, prescribed fire, invasive plant management, and agricultural water management are likely influencing vegetation trends. 

    Download the report and associated datasets here: 

    Spatiotemporal Reconnaissance Investigation of Phreatophyte Vegetation Vigor for Selected Hydrographic Areas in Nevada 

    Objective:  Identify patterns of phreatophyte vegetation vigor change through space and time and qualitatively assess relations between these changes and variability in precipitation, evaporative demand, and depth to groundwater for selected hydrographic basins where significant declines in groundwater are known to have occurred due to pumping for irrigation. Analyses were completed for Kings River, Quinn River (Orovada subarea), Upper Reese River, Paradise, Grass, and Edwards Creek Valleys in Nevada. 

    Key results: 

    • Findings from this study illustrate that phreatophyte vegetation vigor changes can be observed from Landsat satellite imagery and confirmed with field investigations. 
    • Groundwater levels have substantially declined over the last 50 years in many basins, and vegetation species have become less mesic from historical observations made in the 1960s and reported in USGS Reconnaissance Series Reports 
    • An important conclusion from this study is that while declines in vegetation vigor and localized stress and mortality was observed in areas with declining water levels, facultative phreatophyte vegetation such as greasewood persists where groundwater levels were historically at or near land surface (i.e., 0 to 30 ft) and currently exceed the typically reported range of rooting depths (~20 to 60 ft) for this species, suggesting that precipitation has been sufficient to sustain these vegetation communities over the long term. 

    Download the report and associated datasets here:

     

    Groundwater Discharge from Phreatophyte Vegetation, Humboldt River Basin, Nevada

    Remote Sensing Estimates of Evapotranspiration from Irrigated Agriculture, Northwestern Nevada and Northeastern California

    Remote Sensing Estimates of Evapotranspiration from Irrigated Agriculture, Northwestern Nevada and Northeastern California

    Project Description

    Accurate historical evapotranspiration (ET) information for agricultural areas in the western U.S. is needed to support crop and pumpage inventories, water right applications, water budgets, and development of water management plans. Annual and monthly ET from irrigated agriculture is largely a function of water availability, atmospheric water demand, crop type, crop conditions, and land use. Landsat thermal and optical satellite imagery is ideal for monitoring the spatial and temporal variability of crops given its spatial and temporal resolution, making it ideal for monitoring crop ET.

    The objective of this study is to estimate and summarize monthly, seasonal, and annual ET from agricultural areas in northwestern Nevada and northeastern California from 2001 through 2011 using Landsat satellite imagery. ET estimates from 57 Hydrographic Areas (HAs) are summarized in multiple ways including a geodatabase, maps, figures, and tables. Monthly and annual ET estimates for select HAs are discussed with respect to variations in climate, water supply, and land use changes, through visualizations and summaries of spatial and temporal ET distributions. Landsat based ET was estimated using a land surface energy balance model, Mapping EvapoTranspiration at high Resolution with Internalized Calibration (METRIC), using Landsat 5 and Landsat 7 imagery combined with reference ET.

    Results highlight that a range of geographic, climatic, hydrographic, and anthropogenic factors influence ET. For example, irrigators in Mason Valley have the ability to mitigate deficiencies in surface water by pumping supplemental groundwater, resulting in low annual ET variability. Conversely, irrigators in Lovelock are subject to limited upstream surface water storage and are not able to irrigate with groundwater due to high salinity. These factors result in high annual ET variability due to drought. ET estimates derived from METRIC for well-watered fields generally compare well to previous estimates derived from traditional reference ET – crop coefficient methods. Although there are limitations and uncertainties with the METRIC model, METRIC ET estimates are within 10 to 20 percent of ET reported from micrometeorological studies in Nevada for commonly grown crops of alfalfa and pasture grass. Landsat derived ET estimates reported in this study have many immediate applications relevant to water managers, researchers, and practitioners.

    A report is available for download here: Remote Sensing Estimates of Evapotranspiration from Irrigated Agriculture, Northwestern Nevada and Northeastern California 

    The dataset is available for download here: GeoDatabase Download (Separate Database Appendices Download)

    Justin Huntington
    Research Professor, Hydrology
    Division of Hydrologic Sciences
    Desert Research Institute
    2215 Raggio Parkway
    Reno, NV 89512
    775-673-7670
    Justin.Huntington@dri.edu

    CONTACT

    Justin Huntington
    Research Professor, Hydrology

    775-673-7670 

    LOCATION

    Desert Research Institute
    2215 Raggio Parkway
    Reno, NV 89512

    DIVISION

    Division of Hydrologic Sciences

    Drought Sensitivity and Trends of Riparian Vegetation in Nevada

    Drought Sensitivity and Trends of Riparian Vegetation in Nevada

    Drought Sensitivity and Trends of Riparian Vegetation in Nevada

    Project Description

    Maintaining the ecological integrity of riparian areas and other groundwater-dependent ecosystems (GDEs) is an important objective for natural resource and water managers, given the role of these systems in sustaining biodiversity and the other ecosystem services they provide. Long-term monitoring data are required to understand status and trends in these systems, which are often confounded by the influences of interannual climate variability. Yet, these data are expensive to collect and maintain and have historically not been widely available. Recent advances in cloud computing can now help to address these challenges, by allowing efficient and cost-effective processing and analysis of multiple decades’ worth of satellite remote sensing and climate datasets over large geographic extents.

    In this study we analyzed climate-adjusted trends in riparian vegetation across the state of Nevada from 1985 to 2018 based on the 30 meter resolutionMap of Riparian Vegetation in Nevada. To accomplish this, we established relations between the Standardized Precipitation-Evapotranspiration Index (SPEI; a drought index representing the difference between precipitation and potential evapotranspiration for a select time period) and Landsat-derived normalized difference vegetation index (NDVI, an indicator of vegetation vigor) using linear regression. We then used this relationship to adjust for the influence of drought on NDVI and assessed the NDVI trend over time using a non-parametric Mann-Kendall trend test.

    Our results highlight areas where changes in riparian vegetation have occurred that are likely due to natural disturbances or human impacts, as opposed to drought or interannual climate variability. This information helps to clarify and quantify the effects of management actions and can be used to target locations for field investigation or alternative management. We have coupled this work with targeted analyses of groundwater well trends and drone-based field assessments in high priority GDEs to interpret our results and identify potential causal factors of change.

    The dataset is available for viewing here: https://dri-apps.earthengine.app/view/nv-riparian-trends

    A publication describing the study is available here: https://www.mdpi.com/2072-4292/12/9/1362 – Albano, C.M.; McGwire, K.C.; Hausner, M.B.; McEvoy, D.J.; Morton, C.G.; Huntington, J.L. Drought Sensitivity and Trends of Riparian Vegetation Vigor in Nevada, USA (1985–2018). Remote Sens. 2020, 12, 1362.

    The 30-meter resolution (1 GB) dataset is available upon request.

    Please contact fill out the form below for access.

    Christine M. Albano
    Postdoctoral Fellow, Ecohydrology
    Division of Hydrologic Sciences
    Desert Research Institute
    2215 Raggio Parkway
    Reno, NV 89512
    Christine.Albano@dri.edu

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    CONTACT

    Christine M. Albano
    Postdoctoral Fellow, Ecohydrology

    775-673-7689 

    LOCATION

    Desert Research Institute
    2215 Raggio Parkway
    Reno, NV 89512

    DIVISION

    Division of Hydrologic Sciences