During the spring of 2014, 130 million m3 of water were released from Morelos Dam on the lower Colorado River, allowing water to reach the Gulf of California for the first time in 13 years. Nearly two years later, scientists continue to analyze the effects of this historic experiment, the result of a new U.S.-Mexico agreement. To assess the response of vegetation to the pulse flows, remote sensing techniques were used to measure greenup and evapotranspiration (ET) of vegetation within the delta’s riparian corridor. ET was assessed with an algorithm derived from MODIS Enhanced Vegetation Index (EVI) data, while greenup was measured using Landsat 8 Normalized Difference Vegetation Index (NDVI) data. There was a small but significant increase (3%) in ET and a significant increase (17%) in NDVI from 2013 (pre-pulse) to 2014 (post-pulse) within the delta’s riparian corridor (P 0.05). While NDVI declined in 2015, it was still significantly higher than in 2013 (P 0.05). This increase reverses an overall decline in NDVI and ET since the last major flood in 2000. Using the ET findings coupled with salinity data collected during the pulse flows, USGS researchers developed a conceptual model explaining the role of groundwater and surface flows in maintaining the riparian corridor in Mexico. Based on preliminary findings, pulse flows could be an effective tool for restoring the lower Colorado River’s riparian zone.
The difference in greenup between 2013 (pre-pulse) and 2015 (post-pulse); this change reversed a 13-year decline in green vegetation between 2000 and 2014. Image first appeared in Jarchow, C. J., Nagler, P. L., Glenn, E. P. 2016. Greenup and evapotranspiration following the Minute 319 pulse flow to Mexico: An analysis using Landsat 8 Normalized Difference Vegetation Index (NDVI) data. Ecological Engineering.