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Title: Assessing the role of climate and resource management on groundwater dependent ecosystem changes in arid environments with the landsat archive

item HUNTINGTON, JUSTIN - Desert Research Institute
item MCGWIRE, KENNETH - Desert Research Institute
item MORTON, CHARLES - Us Geological Survey (USGS)
item Snyder, Keirith
item PETERSON, SARAH - Bureau Of Land Management
item ERICKSON, TYLER - Google
item NISWONGER, RICHARD - Us Geological Survey (USGS)
item CARROLL, ROSEMARY - Desert Research Institute
item SMITH, GUY - Desert Research Institute
item ALLEN, RICHARD - University Of Idaho

Submitted to: Remote Sensing of Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/5/2016
Publication Date: 7/20/2016
Citation: Huntington, J.L., Mcgwire, K., Morton, C., Snyder, K.A., Peterson, S., Erickson, T., Niswonger, R., Carroll, R., Smith, G., Allen, R. 2016. Assessing the role of climate and resource management on groundwater dependent ecosystem changes in arid environments with the landsat archive. Remote Sensing of Environment. doi: 10.1016/j.rse.2016.07.004.

Interpretive Summary: Landsat imagery is now available from 1984 to the present. This paper looks at using powerful new rapid cloud computing developed in conjunction with the Google Earth Engine, to process these images rapidly and calculate vegetation “greenness” (i.e. vigor) indices. Normalized Difference Vegetation Index (NDVI) and climate datasets were analyzed for a five groundwater dependent ecosystems within the Great Basin to better understand how changes in NDVI relate to annual precipitation, evaporative demand, and anthropogenic impacts, including both riparian restoration and groundwater development. These ecosystems provide critical habitat for many sensitive species. The Landsat archive showed significant correlations between changes in vegetation vigor, evaporative demand, depth to groundwater and land and water management. These are tool that can assist resource managers in make science-based decisions about the extent and health of these important groundwater dependent systems.

Technical Abstract: Groundwater dependent ecosystems (GDEs) rely on the presence of subsurface or surficial expressions of groundwater. These systems are receiving more attention as temperature increases, droughts are more extreme, and where groundwater development captures natural discharge for anthropogenic use. Phreatophyte shrublands, meadows, springs, and riparian areas are GDEs that provide critical habitat for many sensitive species, especially in arid and semi-arid environments. While GDEs are vital for ecosystem services and function, their long-term (i.e. ~30 years) spatial and temporal variability is poorly understood with respect to local and regional scale hydrometeorology, groundwater management, and rangeland management. In this work we analyze time series of vegetation vigor from Landsat 5, 7 and 8 for evaluating the effectiveness of GDE restoration and conservation efforts, and identifying potential impacts from changing hydroclimatology, land management, and groundwater development. Changes in vegetation vigor based on groundwater availability and land management in arid landscapes are detectable with Landsat. However, the effective quantification of these ecosystem changes can be undermined if changes in spectral bandwidths between different Landsat sensors introduce biases in derived vegetation indices. Utilizing the Landsat 8 “under-fly dataset”, differences in spectral reflectance and vegetation indices between Landsat 7 and 8 are quantified for a range of vegetation communities in arid and semiarid regions of the southwestern United States. Google’s Earth Engine cloud computing and environmental monitoring platform is used to rapidly access and analyze the Landsat archive along with downscaled North American Land Data Assimilation System (NLDAS) gridded weather data of solar radiation, surface air temperature, humidity, windspeed, and precipitation, which are used for both atmospheric correction and correlation analysis. Results of continuous Landsat time series analysis clearly illustrate that there are strong correlations between changes in vegetation vigor, hydroclimatology, depth to groundwater, and land management. This work has resulted in supporting land and water managers to evaluate long-term vegetation change in arid environments.