Skip to main content

Chihuahuan desert impacts water decisions


December 07, 2007

Southern Arizona’s Chihuahuan desert and the semi-arid riparian reaches of the San Pedro River serve as the laboratory for researchers, including ASU ecologist Juliet Stromberg. She and her graduate students in the School of Life Sciences traverse the area examining the effects of flood, fire, groundwater pumping, and wetlands restoration on plant communities and water balance.

“Desert rivers are very diverse, biologically. Many conservation groups are concerned about maintaining habitat quality for endangered riparian plants and animals,” Stromberg notes. “And watershed groups are striving to achieve sustainable groundwater management – inclusive of maintaining riparian biotic communities and the amenities they provide to society.”

With more than one-third of earth’s landscapes being semi-arid or arid, studies such as Stromberg’s not only further local understanding of water distribution, movement, and quality, but could also support water resource decision-makers thousands of miles away.

“The San Pedro has a highly variable stream flow regime characterized by extremes of flood and drought, sometimes referred to as ‘boom and bust hydrology,’” Stromberg says. “Much like dry land rivers worldwide.”

How do gains in regional understanding translate to global decision-making?

Stromberg’s group is part of a consortium of researchers and institutions brought together by the Science and Technology Center for Sustainability of Semi-Arid Hydrology and Riparian Areas (SAHRA) supported by the National Science Foundation. The SAHRA Center, administered by Jim Shuttlefield at the University of Arizona, promotes “basin-focused” research to “drive science integration.” It partners understanding of the hydrology of a semi-arid region with a broad spectrum of stakeholders and provides information, tools and methods to aid scientists, elected officials and water resource management professionals develop public policy.

The impact is both regional and global. The upper San Pedro river basin is one of the two primary semi-arid Southwest river basins in which SAHRA projects are based. Other studies examine areas in the Rio Grande/Rio Bravo, Salt, Verde, and Colorado river basins, the sum total of whose flows affect Arizona, Utah, Colorado, New Mexico, and parts Nevada, Texas, and northwestern Mexico. Since the early 1990s, Stromberg, an associate professor in the College of Liberal Arts and Sciences, and her group have contributed to expanded and integrated understanding in the San Pedro, as well as the Salt, Hassayampa, Verde and other riparian areas.

With support from SAHRA (since 2001), The Nature Conservancy, The Arizona Water Institute, and the Environmental Protection Agency, Stromberg’s group has pursued five lines of inquiry: quantifying relationships between dryland stream hydrology and riparian plant communities, understanding how changes in stream flow (dewatering, rewatering, ground water pumping, river damming) affects riparian vegetation, determining the effects of fire and flood disturbance on riparian plant communities, predicting effects of climate change on riparian ecosystems, and developing and implementing riparian ecosystem assessment tools.

“Our studies examine how riparian plant communities in dryland regions change in response to shifts in the driving physical forces of flood disturbance and periodic water limitation, and also provide information on the environmental flows needed to sustain valued biotic communities,” says Stromberg. “Because of their very unpredictability and quixotic nature, desert rivers are fascinating to study; it is also rewarding to work within the framework provided by SAHRA to provide information of direct value to stakeholders,” Stromberg adds.

The combined efforts of Shuttlefield, Stromberg, and other SAHRA partners led to the center’s receipt of the International Great Man-made River Prize in November 2007 – shared with the Center for Hydrometeorology and Remote Sensing (CHRS) at University of California, Irvine, directed by Soroosh Sorooshian.

The award, presented by the United Nations Education, Science and Culture Organization (UNESCO), and sponsored by the Libyan Arab Jamahiriya honors “remarkable scientific research and scientific studies and discoveries in the field of exploration of groundwater and surface water usage in arid zones subject to drought and desertification and contributing to environmental and human development.”

The Prize’s name comes from the Great Man-Made River Project in Libya begun in the 1980s, now in its third phase (of five), pumping water from four basins that are part of a fossil aquifer (Nubian Sandstone Aquifer) that stretches under Chad, Sudan, Libya and Egypt. Stromberg’s work supported by SAHRA has been published in peer-reviewed journals, such as Freshwater Biology, River Research and Applications, Global Ecology and Biogeography, Wetlands, Restoration Ecology, Diversity and Distributions, Biological Conservation and Environmental Monitoring and Assessment, and acquired a global footprint.

Who knows? That next dip of well-water metered half a world away, may owe its flow to understanding coming from Stromberg’s riparian studies just down the river from ASU. Other SAHRA member institutions include: Northern Arizona University; New Mexico Institute of Mining and Technology; Scripps Institution of Oceanography; the United States Geological Survey; the University of New Mexico, Albuquerque; Pennsylvania State University; Los Alamos National Laboratory; USDA-Agricultural Research Services; the Desert Research Institute; the University of California, Irvine; the University of California, Merced; the University of California, Riverside; the U.S. Army Corps of Engineers; the University of California, Los Angeles; and Sandia National Laboratories.