Cheap water, massive federal subsidies and political clout have sustained rice farming in the lower Colorado River basin for decades, but now the industry is in a precarious situation. Drought, population growth upstream and economic boom in Austin are pushing out the practice because of increasing demand for Texas’ scarce water resources. The tightening supply of water raised questions about the sustainability of producing such a water intensive crop in the state. Drought has cut off the cheap water to farmers for three years, and a mobilized coalition of upper river basin interests is calling for a permanent end to subsidized water. It’s increasingly clear that the politics of water in a drought-prone future is likely to side with cities, where voters are heavily concentrated. Rice farmers have scrambled to adapt. Larger rice farms have switched to groundwater. Some farmers have swapped rice for corn, milo or soybeans to keep their income. Crop insurance, which made up for at least 55 percent of the money lost in drought, softened the blow for rice farmers. But revenues in rice-related industries in Wharton, Matagorda and Colorado counties have dropped sharply and some businesses have already packed it in. These new realities cast uncertainties throughout the lower river basin, where locals fear this way of life is disappearing. / text

2 pp. / This fact sheet briefly describes the socioeconomic and cultural aspects of the Colorado River Indian Tribes reservation.

I evaluated the spatial and temporal patterns of the avian communities in the Colorado River delta, Mexico, and their relationship with vegetation type and surface water. I also developed plausible conservation and restoration guidelines for riparian areas and native birds in the region. The study included monthly point counts at 30 transects (240 points) from May 2002 to July 2003, breeding counts at 175 sites (3 times per year) during 2002 and 2003, and habitat measurements at the survey points.The most common species were Mourning Doves, Red-winged Blackbirds, and Brown-headed Cowbirds, but another 64 species were commonly found, including Verdins, Song Sparrows, Yellow-breasted Chats and Abert's Towhees. Surface water was the most important habitat feature related to avian richness and density regardless of vegetation type or land cover (P < 0.005). During summer, species richness was explained by variations in water and the cover of cottonwoods (r2 = 0.56, P < 0.001), and the variation in bird densities was explained by variations in water and the cover of willows (r2 = 0.35, P = 0.003).When comparing native versus saltcedar dominated sites, both with the presence (wet) or absence (dry) of surface water, the diversity of birds was more influenced by the presence of water than by vegetation type. Bird abundance was more influenced by vegetation type, but water also had an important effect, as wet sites had higher bird abundance than dry sites with the same vegetation type, and saltcedar wet areas had similar avian abundance to native dry sites. On all cases, the presence of water was an important factor determining the ecological value, in terms of avian richness, abundance, and diversity, of both native riparian and saltcedar areas. Saltcedar areas with surface water had avian characteristics similar to native riparian sites.The dedication of instream flows and pulse floods, the maintenance of vegetation cover and structural diversity, and an increase of older riparian stands will secure the viability of existing bird populations and will increase the probability of recovery of the species that are still extirpated from the floodplain of the Colorado River in Mexico.

Salinity issues in the Upper Colorado River Basin have been a serious concern to the western United States and northern Mexico. The Colorado River salinity is mainly come from geologic materials located in the Upper Colorado River Basin. Natural weathering and human activities, such as irrigation, accelerate the dissolution of saline materials. Economic damages due to salinity in the Colorado River Basin are estimated at $295 million in 2010, for example, reduced crop yield, plugging of water pipes and fixtures, and ecological health of rivers. In order to manage salinity in the Upper Colorado River Basin, SPARROW model has been applied to simulate salinity sources and transport. However, the model application discontinued during recent past due to lack of data. Given the motivation and importance of salinity issues in the Colorado River Basin, the overall goal of this research is to develop a decision-making framework for an effective salinity management in the Upper Colorado River Basin. First, this research introduced a methodology for reliable analysis of salinity sources and transport in the Upper Colorado River Basin. However, recent decreasing trend of number of monitoring stations may cause increase of model uncertainty. Therefore, a decision-making methodology for an effective water quality monitoring network was developed. From the results of monitoring network analysis, the redundancy or scarcity of monitoring stations in each watershed can be identified under the given operational costs. Finally, salinity management scenarios considering cost and equity were developed. Management options considering cost only can neglect the fairness in the allocation of salinity control responsibilities among stakeholders. To overcome this limitation in management, the methodology developed in this research considers cost of salinity control, equitable distributions among stakeholders, and cost efficiency. The methodologies developed in this research provide a comprehensive decision-making framework for an effective salinity management in the Upper Colorado River Basin. Moreover, this framework is not limited to the management of salinity in the Upper Colorado River only, but also can be applied to other water quality management problems.

No description available.

No description available.

No description available.

The fluvial geomorphology of the Colorado River cutting across the Colorado Plateau in the western United States is bedrock controlled and largely governed by rapids. Rapids on the Colorado River control the water-surface profile and influence the bathymetry, the storage of sand, and the aquatic ecology. Despite their importance, little data on the hydraulics, sediment transport, and long-term stability of rapids have been collected. By comparing water-surface profiles, the average rate of aggradation at the head of 91 rapids in Grand Canyon between 1923 and 2000 was calculated to be 0.26 ± 0.15 m. In addition, while in 1923, 50% of the cumulative drop through the river corridor occurred in just 9% of the distance, by 2000, the cumulative drop over the same distance increased to 66%. A new hydraulic model, incorporating one-dimensional step-backwater theory, was constructed for the Colorado River in Grand Canyon. The model includes 2,690 cross sections and simulates discharge up to 5,600 m³/s, offering the opportunity to simulate large floods, rare under the current regulated flow regime. Flow velocities were measured directly in rapids using three separate flow measurement instruments. An acoustic Doppler velocimeter (ADV) was used to measure velocity in five Grand Canyon rapids. While the instrument was able to measure velocity in three dimensions up to 3.0 m/s, limitations rendered data unusable for flow above 3.0 m/s. An acoustic Doppler current profiler (ADCP) was used to measure the flow field in rapids throughout the water column in Cataract Canyon. The peak average velocity measured by the ADCP was roughly 4.0 m/s. Similarly, average flow velocity of 5.2 m/s was measured in a Cataract Canyon rapid using a pitot-static tube. The pitot-static tube measured instantaneous flow velocities up to 6.5 m/s, one of the fastest velocity measurements made in a river. Using the combination of the ADCP and pitot-static tube, the flow structure and nature of turbulence within rapids were analyzed. Finally, techniques were developed to enable the measurement and construction of detailed water surface, shoreline, and bathymetric maps directly in rapids on the Colorado River.

I use microchemistry in fish otoliths to test the hypothesis that diverting Colorado River flow from reaching the Gulf of California has impacted two endemic fish: the threatened gulf Corvina, (Cynoscion othonopterus) and the endangered totoaba (Totoaba macdonaldi). The oxygen and carbon stable isotope ratios in otoliths help to reconstruct conditions of the environment during key life history stages before and after the damming and diverting the Colorado River. The δ¹⁸O in otoliths illustrate that both C. othonopterus and T. macdonaldi seek out brackish habitat provided by the Colorado River during their early life history. The δ¹⁸O of C. othonopterus otolith have a strong negative correlation with Colorado River flow. I found that previously published relationships between otolith δ¹⁸O and ambient temperature along with δ¹⁸O of the water are sufficient to predict ranges of expected δ¹⁸O values for T. macdonaldi in the field. The δ¹⁸O in pre-dam T. macdonaldi otoliths show significant divergence from modern T. macdonaldi otoliths’ values, indicating that these fish used the brackish waters of the Colorado River estuary. The δ¹³C in T. macdonaldi otoliths has a significant proportion of its δ¹³C derived from diet. Pre-dam T. macdonaldi juveniles have a significantly different diet, which reflects that the Colorado River estuary had higher productivity before diversion of the river. Lastly, T. macdonaldi grew faster before the dams and in association with Colorado River flow measured by the δ¹⁸O.

Thesis (M.S. - Geosciences)--University of Arizona. / Includes bibliographical references.