Water Resources Engineering (WRE) connects engineering hydrology and hydraulics with global, economic, environmental, and societal issues. Our student Kritika Thapa makes this connection here…
In the news entitled “Relief for a Parched Delta”, reported by the New York Times, on their April 16th, 2013 online news, the history and future of the Colorado River delta is discussed. This news relates to WRE domain of hydrology and the specific issue of the distribution of Colorado River water to the south of the American border. The Colorado River drained into the Gulf of California in the 1950’s. However, due to the increasing demand for water on both sides of the border, through dam diversions, the river no longer flows into the Gulf (Figure 1 and 2). A vast ecosystem that included dolphins swimming 60 miles upstream has been lost and replaced by non-native salt cedar. A treaty amendment between the United States and Mexico is poised to release enough water to restore the river’s flow to the gulf for a short time and to provide for more water to regularly flow down the river’s natural path. The initial burst will simulate the floods of the past and amount to approximately 35 billion gallons over one or two months by 2016; the base flow will be approximately 3.5 billion gallons per year. Based on my understanding of the WRE issue, the news story is accurate in reporting the importance of regular flooding to maintain the ecosystem and the water table. Research has shown that when stream flows become more intermittent, diversity and cover of herbaceous species decline. As groundwater deepens, diversity of riparian plant and landscape patches is reduced and species composition in the floodplain shifts from wetland pioneer trees to more drought-tolerant species (Stromberg et. al, 2007). However, despite the article’s optimism, it is unclear how the indicated amount was determined, especially since there seems to be no record of a historical baseline (Zamora-Arroyo, et. al, 2004) or information on the water table along the corridor (Cohen et. al, 2007). Therefore, chances are that the water might not reach to the Gulf. In my opinion, the news story lacks information on whether a comprehensive surface and groundwater model was used to identify the water needs or if there was any information on water budget to understand the discharge through the system.
Throughout the world water is an essential—and often scarce—resource. Vast ecosystems such as this and the Nile have been lost due to short-sighted attempts to sustain human environments. The issue in this news story impacts the broader WRE context areas of environment and economics. The environment context typically relates to the ecosystem benefits that can be reaped through the restoration of the riparian corridor, such as bank stabilization and water quality protection. It is also related to economics because such efforts will provide support and habitat for fish and wildlife and has the potential of income generation for agricultural and fishing communities in the area. In conclusion, this was an important news story. The environment and economies of downstream of dams depend on the cooperation of governments, engineers, scientists, and stakeholders to formulate reasonable measures to restore the rivers while preserving water supply upstream. This article addresses one such attempt and its expected outcome. According to The University of Arizona’s College of Agriculture and Life Sciences, brackish water at the river’s delta can revitalize the ecosystem (Taller, 2002). Without a vibrant ecosystem as well as a reliable source of water, the agricultural and fishing communities which grew to depend on rivers and their deltas cannot thrive.
Figure1. Dry Colorado River Delta (nytimes.com)
Figure 2. By the time the Colorado River reaches Mexico, most of its water has been diverted by a series of dams. Here, a view of dry riverbed below the Morelos Dam, which is the last dam on the Colorado River. (nytimes.com)
Cohen, Michael J., Christine Henges-Jeck, and Gerardo Castillo-Moreno. “A Preliminary Water Balance for the Colorado River Delta, 1992 – 1998.” Journal of Arid Environments 49 (2001):35-48. Print.
Stromberg, J. C., V. B. Beauchamp, M. D. Dixon, and C. Paradzick. “Importance of Low-ﬂow and High-ﬂow Characteristics to Restoration of Riparian Vegetation along Rivers in Arid South-western United States.” Freshwater Biology 52 (2007): 651-79. School of Life Sciences, Arizona State University, 2007.
Taller De Identificación De Prioridades De Conservación Del Delta Del Río Colorado. Rep. The University of Arizona College of Agriculture and Life Sciences, 22 Nov. 2002. <ag.arizona.edu/colorado_river_delta/images/proceedings.pdf>.
Zamora-Arroyo, Francisco, Jennifer Pitt, Steve Cornelius, Edward Glenn, Pamela Nagler, Marcia Moreno, Jaqueline Garcia, Osvel Hinojosa, Meredith De La Garza, and Ivan Parra. Mapping Conservation Priorities in the Colorado River Delta, Mexico. Rep. University of Arizona Ecology and Evolutionary Biology, 2004.