TY - JOUR
T1 - Ecohydrological responses to surface flow across borders
T2 - Two decades of changes in vegetation greenness and water use in the riparian corridor of the Colorado River delta
AU - Nagler, Pamela L.
AU - Barreto-Muñoz, Armando
AU - Chavoshi Borujeni, Sattar
AU - Jarchow, Christopher J.
AU - Gómez-Sapiens, Martha M.
AU - Nouri, Hamideh
AU - Herrmann, Stefanie M.
AU - Didan, Kamel
N1 - Funding Information:
This research is dedicated to Dr. Edward Glenn, whose idea it was to bring life back to the delta of the Colorado River using small, consistent environmental flows from this important yet altered dryland river. The Colorado crosses from one nation to another and touches myriad land ownerships along the way, from tribal to privately held lands to federal- and state-owned lands, and is managed by various agencies on both sides of the border. Having been mentored by Ed Glenn for more than two decades (1998?2017), I was inspired to provide an analysis of the research and monitoring for nearly the same years (2000?2019) because studying this land brought Ed much hope that this arid and vast region would be returned to a state where native plants were regenerated by new surface flows, providing a hydrological ecosystem for plants and animals to thrive for future generations. Funding was provided by the U.S. Geological Survey (USGS) under Minutes 319 and 323, Desert Southwest Cooperative Ecosystem Studies Unit agreement #G18AC00321 (P. I. Kamel Didan), and the National Aeronautics and Space Administration agreement #80NSSC18K0617 (P. I. Kamel Didan). I want to thank Jody Waugh for suggesting the naming of the Phenology Assessment Metric. We thank our many partners from the Delta Science Team for their ongoing dedication and hard work in these changing times. We are particularly grateful to our reviewers, and Karl Flessa, for suggesting important changes to the organization of this manuscript that improved its readability. Any use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Funding Information:
This research is dedicated to Dr. Edward Glenn, whose idea it was to bring life back to the delta of the Colorado River using small, consistent environmental flows from this important yet altered dryland river. The Colorado crosses from one nation to another and touches myriad land ownerships along the way, from tribal to privately held lands to federal‐ and state‐owned lands, and is managed by various agencies on both sides of the border. Having been mentored by Ed Glenn for more than two decades (1998–2017), I was inspired to provide an analysis of the research and monitoring for nearly the same years (2000–2019) because studying this land brought Ed much hope that this arid and vast region would be returned to a state where native plants were regenerated by new surface flows, providing a hydrological ecosystem for plants and animals to thrive for future generations. Funding was provided by the U.S. Geological Survey (USGS) under Minutes 319 and 323, Desert Southwest Cooperative Ecosystem Studies Unit agreement #G18AC00321 (P. I. Kamel Didan), and the National Aeronautics and Space Administration agreement #80NSSC18K0617 (P. I. Kamel Didan). I want to thank Jody Waugh for suggesting the naming of the Phenology Assessment Metric. We thank our many partners from the Delta Science Team for their ongoing dedication and hard work in these changing times. We are particularly grateful to our reviewers, and Karl Flessa, for suggesting important changes to the organization of this manuscript that improved its readability. Any use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
PY - 2020/12/15
Y1 - 2020/12/15
N2 - Hydrological and bioclimatic processes that lead to drought may stress plants and wildlife, restructure plant community type and architecture, increase monotypic stands and bare soils, facilitate the invasion of non-native plant species and accelerate soil erosion. Our study focuses on the impact of a paucity of Colorado River surface flows from the United States (U.S.) to Mexico. We measured change in riparian plant greenness and water use over the past two decades using remotely sensed measurements of vegetation index (VI), evapotranspiration (ET) and a new annualized phenology assessment metric (PAM) for ET. We measure these long-term (2000–2019) metrics and their short-term (2014–2019) response to an environmental pulse flow in 2014, as prescribed under Minute 319 of the 1944 Water Treaty between the two nations. In subsequent years, small-directed flows were provided to restoration areas under Minute 323. We use 250 m MODIS and 30 m Landsat imagery to evaluate three vegetation indices (NDVI, EVI, EVI2). We select EVI2 to parameterize an optical-based ET algorithm and test the relationship between ET from Landsat and MODIS by regression approaches. Our analyses show significant decreases in VIs and ET for both the 20-year and post-pulse 5-year periods. Over the last 20 years, EVI Landsat declined 34% (30% by EVIMODIS) and ETLandsat-EVI declined 38% (27% by ETMODIS-EVI), overall ca. 1.61 mm/day or 476 mm/year drop in ET; using PAM ETLandsat-EVI the drop was from 1130 to 654 mm/year. Over the 5 years since the 2014 pulse flow, EVILandsat declined 20% (13% by EVIMODIS) and ETLandsat-EVI declined 23% (4% by ETMODIS-EVI) with a 0.77 mm/day or a 209 mm/year 5-year drop in ET; using PAM ETLandsat-EVI the drop was from 863 to 654 mm/year. Data and change maps show the pulse flow contributed enough water to slow the rate of loss, but only for the very short-term (1–2 years). These findings are critically important as they suggest further deterioration of biodiversity, wildlife habitat and key ecosystem services due to anthropogenic diversions of water in the U.S. and Mexico and from land clearing, fires and plant-related drought which affect hydrological processes.
AB - Hydrological and bioclimatic processes that lead to drought may stress plants and wildlife, restructure plant community type and architecture, increase monotypic stands and bare soils, facilitate the invasion of non-native plant species and accelerate soil erosion. Our study focuses on the impact of a paucity of Colorado River surface flows from the United States (U.S.) to Mexico. We measured change in riparian plant greenness and water use over the past two decades using remotely sensed measurements of vegetation index (VI), evapotranspiration (ET) and a new annualized phenology assessment metric (PAM) for ET. We measure these long-term (2000–2019) metrics and their short-term (2014–2019) response to an environmental pulse flow in 2014, as prescribed under Minute 319 of the 1944 Water Treaty between the two nations. In subsequent years, small-directed flows were provided to restoration areas under Minute 323. We use 250 m MODIS and 30 m Landsat imagery to evaluate three vegetation indices (NDVI, EVI, EVI2). We select EVI2 to parameterize an optical-based ET algorithm and test the relationship between ET from Landsat and MODIS by regression approaches. Our analyses show significant decreases in VIs and ET for both the 20-year and post-pulse 5-year periods. Over the last 20 years, EVI Landsat declined 34% (30% by EVIMODIS) and ETLandsat-EVI declined 38% (27% by ETMODIS-EVI), overall ca. 1.61 mm/day or 476 mm/year drop in ET; using PAM ETLandsat-EVI the drop was from 1130 to 654 mm/year. Over the 5 years since the 2014 pulse flow, EVILandsat declined 20% (13% by EVIMODIS) and ETLandsat-EVI declined 23% (4% by ETMODIS-EVI) with a 0.77 mm/day or a 209 mm/year 5-year drop in ET; using PAM ETLandsat-EVI the drop was from 863 to 654 mm/year. Data and change maps show the pulse flow contributed enough water to slow the rate of loss, but only for the very short-term (1–2 years). These findings are critically important as they suggest further deterioration of biodiversity, wildlife habitat and key ecosystem services due to anthropogenic diversions of water in the U.S. and Mexico and from land clearing, fires and plant-related drought which affect hydrological processes.
KW - evapotranspiration
KW - minute 319
KW - minute 323
KW - pulse flows
KW - remote sensing
KW - restoration
UR - http://www.scopus.com/inward/record.url?scp=85092391660&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85092391660&partnerID=8YFLogxK
U2 - 10.1002/hyp.13911
DO - 10.1002/hyp.13911
M3 - Article
AN - SCOPUS:85092391660
VL - 34
SP - 4851
EP - 4883
JO - Hydrological Processes
JF - Hydrological Processes
SN - 0885-6087
IS - 25
ER -