Oil and gas development across the western United States has increased substantially in recent decades, including within the Colorado Plateau. The Colorado Plateau is a high desert region of grasslands, shrublands, and woodlands and is home to a large number of world-renowned national and tribal parks and monuments (e.g., Grand Canyon, Zion, Bryce, Arches, Canyonlands, Monument Valley, and Mesa Verde). Energy development on the Colorado Plateau is of concern regionally due to potential environmental impacts, including water and air pollution, habitat fragmentation, dust emissions, and soil loss from erosion, all of which can have cascading impacts on human health. Oil and gas well pads are often developed and then abandoned when they are no longer sufficiently productive. However, the rate and degree of recovery of these abandoned sites to a relatively natural state remains unclear.
The Soil-Adjusted Total Vegetation Index (SATVI), calculated using the red and shortwave infrared (SWIR) bands from Landsat, provides consistent estimates of total vegetation cover in drylands, and is used to assess pad changes over time. We develop dense time series (1984-2011) of Landsat SATVI on abandoned well pads as well as nearby control areas of similar environmental conditions, which helped to standardize the assessment. The statistical package Breaks For Additive Season and Trend (BFAST) was used to identify breaks in the time series related to initial site disturbance and active pad use, and to quantify the magnitude, duration, and rate of vegetation change after abandonment. We analyzed change rates relative to climate and other spatial variables and found vegetation increases are most strongly related to wet and cool conditions of winter-spring months during the year of abandonment. However, high-resolution aerial imagery and Landsat-based phenology indices indicate that many abandoned pads where vegetation increased over time are dominated by exotic grasses and annual plants.
Future work: We are currently developing SATVI time series for a smaller subset of well pads that have been reclaimed relatively recently (ca. >2000) such that the pad management reflects modern methods, including recontouring, saving and spreading topsoil, addressing soil contamination, and seeding. We are working closely with BLM to select sample sites based on known pad history and reclamation practices used (dates, seed mixes, application, and others). A subsample of pads will be selected for extensive field data collection of vegetation and soil information.
- Overview
Oil and gas development across the western United States has increased substantially in recent decades, including within the Colorado Plateau. The Colorado Plateau is a high desert region of grasslands, shrublands, and woodlands and is home to a large number of world-renowned national and tribal parks and monuments (e.g., Grand Canyon, Zion, Bryce, Arches, Canyonlands, Monument Valley, and Mesa Verde). Energy development on the Colorado Plateau is of concern regionally due to potential environmental impacts, including water and air pollution, habitat fragmentation, dust emissions, and soil loss from erosion, all of which can have cascading impacts on human health. Oil and gas well pads are often developed and then abandoned when they are no longer sufficiently productive. However, the rate and degree of recovery of these abandoned sites to a relatively natural state remains unclear.
The Soil-Adjusted Total Vegetation Index (SATVI), calculated using the red and shortwave infrared (SWIR) bands from Landsat, provides consistent estimates of total vegetation cover in drylands, and is used to assess pad changes over time. We develop dense time series (1984-2011) of Landsat SATVI on abandoned well pads as well as nearby control areas of similar environmental conditions, which helped to standardize the assessment. The statistical package Breaks For Additive Season and Trend (BFAST) was used to identify breaks in the time series related to initial site disturbance and active pad use, and to quantify the magnitude, duration, and rate of vegetation change after abandonment. We analyzed change rates relative to climate and other spatial variables and found vegetation increases are most strongly related to wet and cool conditions of winter-spring months during the year of abandonment. However, high-resolution aerial imagery and Landsat-based phenology indices indicate that many abandoned pads where vegetation increased over time are dominated by exotic grasses and annual plants.
Future work: We are currently developing SATVI time series for a smaller subset of well pads that have been reclaimed relatively recently (ca. >2000) such that the pad management reflects modern methods, including recontouring, saving and spreading topsoil, addressing soil contamination, and seeding. We are working closely with BLM to select sample sites based on known pad history and reclamation practices used (dates, seed mixes, application, and others). A subsample of pads will be selected for extensive field data collection of vegetation and soil information.
Sources/Usage: Public Domain.Figure 1.1.1. Density of oil and gas well pads per km2 in the Colorado Plateau ecoregion (including parts of Utah, Colorado and New Mexico) as counted in 2016. Oil/gas wells are particularly concentrated in this region with ~100,000 abandoned and current wells spanning 60 years of activity. These numbers are dramatically increasing with time. (Public domain.)
Sources/Usage: Public Domain.Figure 1.1.2. An active oil and gas well pad and an abandoned pad being reclaimed (top left inset).
Sources/Usage: Public Domain.Figure 1.1.3.Graph showing A) Landsat time series of the Soil-Adjusted Total Vegetation Index (SATVI) from 1984-2011. Phases include pre-drilling from 1984-2002, active from 2002-2006, and post-abandonment 2006-2011, B) Bfast model of trends used to estimate breaks in the time series, and C) orhtophotos showing the site during different points in time and where those dates fall on the Landsat time series. The rapid cover change from 2006-2009 and the appearance of dense green.
Sources/Usage: Public Domain.Figure 1.1.4. USGS scientists visiting an old abandoned well pad site. - Data
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