WRRC-Funded Research Projects Produce Results

The University of Arizona Water Resources Research Center administers Section 104B of the Water Resources Research Act, funded by the U.S. Geological Survey. Funds support small research projects that focus on state and regional water issues, reflecting the WRRC mission of promoting understanding of critical state and regional water management and policy issues. Only faculty at Arizona state universities are eligible for 104B funding. Following are research results of recent 104B projects:

Preliminary Evaluation of Perchlorate Contamination of Ground Water In The Lower Colorado River Region; Charles Sanchez, University of Arizona, Yuma Agricultural Center.
There is a concern that years of irrigation with perchlorate-contaminated Colorado River water may have contaminated the Yuma aquifer with perchlorate, and that communities around the greater Yuma region using groundwater as their source of potable water may be exposed to perchlorate by drinking perchlorate-contaminated groundwater. The results of a conducted survey showed that well waters being used by PWS and rural households are well within regulatory limits of perchlorate. Detectable perchlorate concentrations are mostly limited to wells less than 20 ft in depth, and the concentration ranges seen reflect concentrations seen in the Colorado River water, which is within the calculated EPA DWEL of 24.5 µg/L.

An outdoor multi-stage, continuous-flow photobioreactor (MCP) for groundwater nitrate removal.

An Outdoor Multi-stage, Continuous-flow Photobioreactor for Bioremediation of Nitrate-contaminated Groundwater; Qiang Hu, Dept. of Applied Biological Sciences, Arizona State University East, Milton Sommerfeld, School of Life Sciences, ASU.
Groundwater makes up more than 40 percent of Arizona’s drinking water supply. Widespread and persistent nitrate contamination in the groundwater poses a concern to health and the state’s and region’s economic prosperity. Several conventional chemical and physical technologies have been proposed or tested for groundwater nitrate removal. The projected high capital and operational costs, however, have prohibited commercial applications of these approaches. In this study, a pilot-scale Multiple-stage, Continuous-Flow Photobioreactor has been successfully designed, fabricated, and operated under outdoor conditions for groundwater nitrate removal. Preliminary results indicate that MCP can be a cost-effective, sustainable nitrate removal system for use as a centralized facility for large cities such as Phoenix and Tucson; a scaled-down model would be suitable for small communities in remote areas. Furthermore, algal biomass produced as a by-product from the photobioreactor can be used as an organic fertilizer or animal feed, providing additional value to this advanced environmental clean-up green biotechnology.

Big Chino 3-D Digital Hydrogeologic Framework Model, Abe Springer, Dept. of Geology, Northern Arizona University.
The objectives of the study were to further define the subsurface geology of Big Chino Basin and to create an interactive three-dimensional digital hydrogeologic framework model using EarthVision. Well logs re-interpreted for lithology, in combination with geophysics data and a geologic map prepared by the U.S. Geological Survey were used as the basis for the hydrogeologic framework. A hydrogeologic framework is similar to a geologic framework except that unit designations are based on hydrogeologic properties rather than stratigraphy. The completed model will be presented to relevant stakeholders this summer.Opportunities for Passive Restoration of the Salt River Riparian Corridor, Juliet C. Stromberg, School of Life Science, Arizona State University.

Portions of the urbanized Salt River have been dewatered and are now targeted for ecosystem restoration by measures such as tree planting. Little attention has been paid to the potential for natural redevelopment of plant communities along this river reach. We investigated the vegetation and soil seed banks of three reaches of the Salt River in and near Phoenix to determine 1) how the riparian plant community has been altered by diversion of stream flow and 2) how the pockets of riparian vegetation that developed naturally at rewatered urban reaches compare to those in the upstream perennial reach.

Results indicate that long-term diversion of the Salt River has converted a species-rich hydromesic riparian forest/shrub community to a species-poor xeric shrub community. Yet, riparian species, such as cattail (Typha domingensis) and umbrella sedge (Cyperus odoratus) are present in the seed bank of these xeric shrublands. Species richness and functional group composition of the riparian patches in the rewatered urban reach (near urban storm drains) were very similar to values in the upstream rural perennial reach.

These findings have implications for the way riparian restoration is approached. These small riparian storm drain communities provide anecdotal evidence for the resilience of this system, given adequate restoration of stream flows and sediments. The species composition of these sites provides an example of a plant community that can establish and maintain itself with limited intervention under these altered conditions. Also, these communities, if left intact during the planned restoration interventions, could function as source of propagules for the establishment of riparian species in adjacent reaches.