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Minute 319, a binational agreement between the United States and México, authorized environmental flows into the Colorado River Delta, including a high-profile pulse flow delivered in March through May 2014. Reforming water management policy to secure future delivery of environmental flows to the delta hinges on demonstrating the feasibility of delivering environmental water and documenting positive ecological responses of the delta's severely degraded riparian habitat. The design of the flow's hydrograph, the novel utilization of irrigation infrastructure, the preparation and subsequent maintenance of selected restoration sites, and interdisciplinary monitoring at multiple scales combined to show that ecological...
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The Science and Policy of the First Environmental Flows to the Colorado River Delta The first transboundary flow of water for the environment was delivered to the Colorado River Delta in spring of 2014. This engineered mini-spring flood of 130 million cubic meters (105,000 acre-feet) was implemented as part of Minute 319, an addition to the 1944 U.S.-Mexico Water Treaty. Minute 319 is a temporary agreement, expiring in 2017. Teams of scientists from government agencies, universities, and environmental NGOs from both the U.S. and Mexico are measuring the surface flow rates, inundation, ground water recharge, ground water levels and subsurface flows, geomorphic change, recruitment, survival and health of vegetation,...
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A LANDSCAPE-SCALE RESTORATION EXPERIMENT: THE 2014 SPRING FLOOD FLOW RELEASE TO THE COLORADO RIVER DELTA, MEXICO The Colorado River delta was once a several-million acre expanse of marsh wetlands, riparian forest, and estuarine habitat located near the river’s mouth in Northwest Mexico (Glenn et al. 2001). However, the diversion of Colorado River water for human use in the arid western U.S. and northwestern Mexico resulted in the gradual drying of the delta with a subsequent loss of over 90% of original habitat (Glenn et al. 2001). Very little water has reached the delta since the era of dam construction on the Colorado River (Nagler et al. 2005), and the highly altered hydrologic regime and influx of invasive...
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Managing streamflow is a widely-advocated approach to provide conditions necessary for seed germination and seedling establishment of trees in the willow family (Salicaceae). Experimental flow releases to the Colorado River delta in 2014 had a primary objective of promoting seedling establishment of Fremont cottonwood (Populus fremontii) and Goodding's willow (Salix gooddingii). We assessed seed germination and seedling establishment of these taxa as well as the non-native tamarisk (Tamarix spp.) and native seepwillow shrubs (Baccharis spp.) in the context of seedling requirements and active land management (land grading, vegetation removal) at 23 study sites along 87 river km. In the absence of associated active...
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