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Colorado River Delta Project: A compilation of vegetation indices, phenology assessment metrics, estimates of evapotranspiration and change maps for seven reaches of the delta's 150 km region, for nearly the last two decades

September 7, 2020

These data were compiled for monitoring riparian zone trends and changes in the Lower Colorado Delta as part of the Minute 139 of the 1944 Water Treaty between the United States and Mexico. The quality and quantity of the Delta's riparian and aquatic ecosystems have been dramatically reduced over the past century, due largely to significant alterations to natural hydrologic and sediment regimes. The Minute 319 Agreement states that 130 million cubic meters of water was to be released during the spring of 2014. Water was released from Morelos Dam at the Northern International Border (NIB) near Yuma, Arizona, to the river's delta in Mexico, allowing water to reach the Gulf of California for the first time in 13 years since 2000. Our study evaluated the short and long-term effects of environmental flows to hydrological processes in this borderland delta region. Because of the landscape changes and the anticipated impacts of added water in 2014 from Minute 319 water release, we explored remote sensing-based change analysis techniques and data to develop time series data of the Colorado River delta riparian corridor vegetation greenness and water use since the year 2000. We divided the river into 7 Reaches (R1..R7) to separate between the different land covers, management conditions, and general geospatial and hydrological conditions. We generated a variety of vegetation index, ET, anomalies, and trends using time series for all reaches combined then separately. Our data shows Landsat and MODIS derived EVI and EVI2 as well as time-series data of ETLandsat-EVI (mm/day), using a modified (EVI mod) equation, and ETMODIS-EVI with both EVI and then EVI 2 as the input variable to the ET algorithm were extremely consistent across sensors and methods and covaried well with vegetation, climate, and hydrological conditions of each reach and the whole region.