No description available.

Between 1865 and 1915, arroyos developed in the southwestern United States across diverse hydrological, ecological and cultural settings. That they developed simultaneously has encouraged the search for a common cause-- some phenomenon that was equally widespread and synchronous. There are few southwestern streams for which we have even a qualitative understanding of timelines and processes involved in initiation and extension of historic arroyos. Tucson's Santa Cruz River, often cited in the arroyo literature, offers a unique opportunity to chronicle the arroyo legacy and evaluate its causes. The present study reconstructs both the physical and cultural circumstances of channel entrenchment along the Santa Cruz River. Primary data include newspaper accounts, notes and plants of General Land Office surveys, eyewitness accounts, legal depositions, and repeat photography. On the Santa Cruz River, arroyo initiation and extension happened during relatively wet decades associated with frequent warm episodes in the tropical Pacific (El Niño conditions). Intensified El Niño activity during the period 1864-1891 may be symptomatic of long-term climatic change, perhaps indicative of global warming and destabilization of Pacific climate at the end of the Little Ice Age. During this period all but one of the years registering more than three days with rain exceeding 2.54 cm (1 in) in Tucson were El Niño events. The one exception was the summer of 1890, when the central equatorial Pacific was relatively cold but when prevailing low-surface pressures and low-level winds nevertheless steered tropical moisture from the west coast of Mexico into southern Arizona. In the twentieth century, catastrophic channel widening was caused by floods during El Niño events in 1905, 1915, 1977 and 1983. The Santa Cruz River arroyo formed when climatic conditions heightened the probabilities for occurrence of large floods in southern Arizona. Inadequate engineering of ditches that resulted in abrupt changes in the longitudinal profile of the stream further augmented probabilities that any one of these floods would initiate an arroyo. In the future, changing flood probabilities with low-frequency climatic fluctuations and improved flow conveyance due to intensified land use and channel stabilization will further complicate management of the arroyo in an increasingly urbanized floodplain.

Project Completion Report, OWRT Project No. A-051-ARIZ / Agreement No. 14-31-0001-5003 / Project Dates: July 1974 - June 1975 / Acknowledgement: The work upon which this report is based was supported by funds provided by the United States Department of the Interior, Office of Water Research and Technology, as authorized under the Water Resources Research Act of 1978. / Bio-physicochemical measurements were made on treated sewage effluent releases at established locations within the channel of an ephemeral stream, the Santa Cruz River of Southern Arizona. Water samples were taken in chronological sequence as the effluent moved downstream, to trace changes in quality parameters during low and high hydrograph stages. Results indicate that dissolved oxygen (DO) concentrations at low effluent flows were higher than DO concentrations at high effluent flows; while, conversely, biochemical oxygen demand (BOD) concentrations at low effluent flows were generally lower than BOD concentrations at high effluent flows. Biochemical oxygen demand concentrations are affected by waste loadings, flow conditions, phytoplankton growth and nitrification. Mean river deoxygenation rates (k ) in sewage flows after six river miles from the Tucson Sewage Treatment Plant were always negative or increasing, indicative of nitrification, algal growth, and concentration of organic constituents through seepage losses.

Wastewater generated in the Tucson metropolitan region is conveyed to and treated at the Roger Road Wastewater Reclamation Facility (WRF) and Ina Road WRF. From 2005 to 2012, approximately 15,000 acre-feet per year of effluent was returned to the City of Tucson for additional filtration and reuse in the reclaimed water system. The remaining 48,000+ acre-feet per year of treated effluent was discharged to the Santa Cruz River, where a variable portion of the effluent infiltrates the streambed. The effluent that infiltrates the streambed contributes to recharge credits for participants invested in the Managed Underground Storage Facilities. In the effluent-dependent river, physical, chemical, and biological processes work in combination to develop a clogging layer near the streambed surface, which reduces infiltration. Previous studies have shown that large storm events have the ability to scour away the clogging layer and are the most significant processes contributing to establishing infiltration rates. Without the occurrence of large storm events, other variables such as effluent discharge and effluent concentrations affect infiltration to a lesser degree. Effluent discharge, biochemical oxygen demand, and total suspended solids are monitored and recorded daily at the outfalls of the WRFs. The parameters were investigated individually and in combination using statistical analyses to determine their correlations with streambed infiltration in the Santa Cruz River. The dry spring-early summer seasons from 2005 to 2012 were analyzed. A water balance was constructed for non-stormflow days during each time period. Evapotranspiration was calculated using riparian vegetation surveys and detailed delineations of aerial photography of the surface water and streamside herbaceous vegetation. Infiltration was derived as the residual of the water balance. At the daily time scale, correlations among variables were unobtainable due to the extremely variable characteristics of infiltration. The seasonal time scale analyses demonstrated an inverse relationship between both the effluent concentrations of biochemical oxygen demand and total suspended solids with infiltration and a direct correlation between effluent discharge and infiltration under extreme conditions. Under normal conditions, the distribution of discharge between Roger Road WRF and Ina Road WRF had a critical effect on infiltration as a result of the different deposition and erosive regimes through the Santa Cruz River.

Stakeholder participation is a foundation of good water governance. Good groundwater governance typically involves the co-production of knowledge about the groundwater system. Models provide a vehicle for producing this knowledge, as well as a boundary object around which scientists and stakeholders can convene the co-production process. Through co-production, stakeholders and scientific experts can engage in exchanges that create system knowledge not otherwise achievable. The process involves one-way transfer of information, active two-way conversations, and integration of multiple kinds of knowledge into shared understanding. In the Upper Santa Cruz River basin in Arizona, USA, the University of Arizona Water Resources Research Center (WRRC) convened a project aimed at providing scientific underpinnings for groundwater planning and management. This project, entitled Groundwater, Climate, and Stakeholder Engagement, serves as a case study employing the first two stages of knowledge co-production using a hydrological model. Through an iterative process that included two-way communication, stakeholders provided critical input to hydrologic modeling analyses. Acting as a bridging organization, the WRRC facilitated a co-production process, involving location-specific and transferability workshops, which resulted in new knowledge and capacity for applying the model to novel problems.

Thesis (Ph. D.)--University of Arizona, 1993. / "In addition to chapters [leaves 20-57] unique to the dissertation, ten papers are included that were published during the period of doctoral enrollment"--Leaf 19. Includes bibliographical references.

The interplay between social and productive spheres in arid land agrarian societies with non-mechanized technologies is exemplified in a case study of the prehistoric Hohokam Indians of southern Arizona. In addition to chapters unique to the dissertation, ten papers are included that were published during the period of doctoral enrollment. Results from a variety of investigative techniques are combined to characterize Hohokam agriculture and its relationship to societal forms and dynamics. Among these are archaeological survey and settlement pattern analysis, technical studies of prehistoric fields, palynological analysis for reconstruction of agricultural environments, and comparison with methods and concepts employed by historic and modern traditional farmers in the southwestern United States and northwestern Mexico. Hohokam farming is examined at sequential scales, beginning with the setting, layout, and yield of individual fields and ending with comparison between Hohokam agricultural configurations and those of other arid land cultures. Topics receiving emphasis within the broader dissertation theme are the nature of Hohokam agrarian landscapes, the recently recognized role of cultivated agave in subsistence systems, and the social and economic framework for agricultural decision-making and strategies.

Almost 90% of the treated sewage effluent processed by the two treatment plants serving the greater Tucson area is available for passive recharge through the Santa Cruz River streambed north of Tucson. In the absence of any major disturbance of the effluent channel, the recharge capacity of the streambed materials decreases over time as microbial activity, and possibly suspended sediments settling out of solution, act to clog the surficial sediments under the effluent stream. Effluent stream transmission-loss measurements made over the period from November 1994 to August 1995 provided data used to determine the average vertical hydraulic conductivity of the low-flow channel in the study reach through simulations using the computer model known as KINEROS2. Saturated hydraulic conductivity (KSAT) served as the calibration parameter in the model. The appropriate KSAT value was chosen for each set of field data by matching the observed and simulated downstream hydrographs for the study reach. KSAT values were corrected for viscosity changes resulting from changing average daily surface water temperatures over the study period. Saturated hydraulic conductivity values for the effluent stream channel ranged from a maximum of 37 mm/hr in January, 1995, following several major winter storms, to a minimum of 11 mm/hr in August, 1995, after a nearly six-month interstorm period. The saturated hydraulic conductivity values decay exponentially with time after the last major winter storm. The mathematical model describing this decay may be used to estimate effluent recharge rates under similar future meteorological and climatological conditions.

From the Proceedings of the 1975 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 11-12, 1975, Tempe, Arizona / Since 1955 secondary treated effluent from the city of Tucson treatment plant has been released into the Santa Cruz River, the principal drainage tributary of the Tucson basin. Because the river is ephemeral, it has functioned essentially as an artificial recharge facility for sewage effluent. In past years the total volume of effluent artificially recharged amounted to about 31,000 ac-ft per year. Such recharge has affected not only the groundwater levels in the vicinity of the river, but also water quality. Recharge of nitrate is of particular concern.