No description available.

A two-dimensional, finite difference model was used to simulate the lowering of the water table below a floodplain in order to affect water conservation by reducing phreatophyte transpiration. Evapotranspiration capture percentages and unit water costs associated with alternative well network designs were calculated in order to determine those factors which are most important in designing an evapotranspiration capture project.

The Gila River Indian Reservation lies in the Sonoran Desert of south-central Arizona, with an elevation range from 941 to 4512 feet (287 to 1375 m). Three major desert streams (the Salt, Gila, and Santa Cruz Rivers) have their confluences on the reservation. The human occupancy of the Gila floodplain is believed to have been continuous for the past two millenia. In the past century loss of stream flow and deterioration of riparian and marsh habitats have resulted from drastic changes in hydrologic regimes of the major streams. Documentation of original habitat conditions is based on Hispanic accounts (1694-1821) and subsequent Anglo accounts, together with oral history from the Pima Indians. Riparian timber and emergent vegetation were gone by 1950 due to destructive floods and lowered water table. Irrigation run-off and Phoenix sewage effluent have reestablished locally riparian communities and marshes. Eleven major habitats occur today on the reservation. Their predominant vegetation is described. Field work on the reservation was conducted from 1963 to 1976. Modern distributional data are compared with evidence from archaeological, ethnographic, and historical sources. The total avifauna (all time horizons) consists of 232 species, of which 207 are supported by specimen evidence. At least 101 species are breeding or have bred in the past; five other species are probably breeding. On geographic grounds an additional seven species are suspected of having bred aboriginally. The taxonomy and migration are discussed in accounts of 46 species with two or more subspecies occurring on the study area. The Piman ethno-taxonomy of birds distinguishes 67 taxa, most of which correspond to Linnaean (biological) species. In the past 100 years 28 species (21 as breeding species) have been extirpated from the reservation. Of these 24 are directly related to loss of riparian woodlands or open water and marshes. Since 1958 at least 13 species have recolonized as a result of the redevelopment of riparian communities with willow, cottonwood, and cattail. The present reservation habitat and avifauna are contrasted with two modern analogs with perennial surface water and intact riparian communities. These are at similar elevations, less than 30 miles (48 km) from the reservation. Ten Neotropical species have colonized Arizona within the 20th century and an additional eight have extended their breeding ranges northward. Four Neotropical species have occupied the reservation during this period. Formerly allopatric subspecies of two species (Great-tailed Grackle, Quiscalus mexicanus, and Horned Lark, Eremophila alpestris) are now interbreeding on the reservation in areas of secondary intergradation. The northward movements are attributed to post- Pleistocene recolonizations, in part facilitated by human modifications of habitats. At least 15 wintering species are departing earlier in spring than they did at the turn of the century. This is attributed to habitat deterioration. The habitats with the greatest avifaunal diversity, both summer and winter, are the traditional Pima farms (rancherlas) and the recently redeveloped riparian communities along the Salt River. The least diversified and most disturbed habitats are the Gila River channel and the large-scale mechanized farms on lands leased to non-Indians. The future of both the natural habitats and the avifauna of the reservation is in the hands of tribal leaders.

In experimental pools open to emigration, mosquitofish (Gambusia affinis) resided at higher densities than topminnow (Poeciliopsis occidentalis). When Gambusia were introduced to Poeciliopsis pools, all topminnow maintained residency. Only 11% of the Gambusia emigrated from the mixed populations before the plant cover was removed; with no cover, 59% left. A significant number of Gambusia in single species pools also responded to a loss of cover by emigrating. Continuing residency of Poeciliopsis after introduction of Gambusia supports findings that displacement by mosquitofish is not an immediate process. Frayed fins on resident topminnow suggest short-term agonistic interactions. Coexistence of an exotic species (Gambusia) and an endangered desert fish (Poeciliopsis) may depend on the complexity, or spatial variation, of the Southwest's few remaining cienegas. The opportunity to disperse from pools in these habitats may be an important factor in Poeciliopsis survival; such emigratory behavior can be tested in open experimental systems.

No description available.

No description available.

I studied habitat preferences of Gila chub in a canyon-bound system (Bonita Creek) and a marsh system (Cienega Creek). Gila chub in Bonita Creek, frequently occurred in a broader range of habitat types and conditions than Gila chub in Cienega Creek. Gila chub in Cienega Creek were highly pool oriented. In contrast, Gila chub in Bonita Creek generally preferred, or used in proportion, swifter shallower habitat types. Segregation between size classes in relation to habitat variables was noted, but was less than expected. I studied other life-history characteristics as well and found reproduction commencing in February, peaking in spring, and dropping off as summer begins. Spawning in the fall is suggested by the presence of small YOY and gonad development. I also evaluated methods to spawn and rear Gila chub. Following initial spawning, Gila chub spawned consistently in the laboratory without hormonal, chemical, photoperiod, or drastic temperature and substrate manipulation, during all times of the year. Spawns were noted at temperatures ranging from about 15 to 26°C but spawning above 24°C occurred infrequently. Larval Gila chub fed a commercial diet grew the same or slightly better than those fed thawed Artemia sp. nauplii, and significantly better than those fed chicken Gallus domesticus egg-yolk powder, but survived significantly better when fed Artemia. Despite the latter, observations suggest Artemia nauplii may be difficult for first-feeding larval Gila chub to handle. Thawed chironomid sp. larvae clearly outperformed prepared commercial feeds for small and large juvenile Gila chub with respect to growth. Growth of larval Gila chub was highest at 28ºC and lowest at 32ºC, while survival of larval Gila chub was highest at 24ºC and lowest at 20ºC. Spinal deformities were common (about 47%) for larval Gila chub reared at 32ºC but generally uncommon for those reared at lower temperatures. Water temperatures from 20-28ºC appear suitable for rearing larval Gila chub, with temperatures from 24-28ºC more optimal. Water temperatures from 20-29ºC appear suitable for rearing juvenile Gila chub. My data strongly support increasing rearing density having a negative effect on growth and survival (larval only) of Gila chub. Although populations of Gila chub share many natural history traits, my data suggests habitat use can vary among systems. It is possible unique preferences and strategies exist between different populations of Gila chub. Thus managers should be cautious about applying information based on one population to others. The future of Gila chub may someday depend in part on hatchery propagation to provide specimens for restocking formerly occupied habitats and establishing refuge populations. Information from my study can aid future efforts to successfully spawn and rear Gila chub and related species.

Thesis (M. S. - Renewable Natural Resources)--University of Arizona, 1978. / Includes bibliographical references (leaves 64-71).

Section 1: Watershed-based Plan, Section 2: Pollutant Risk Ranking, Section 3: Watershed Management and Improvements, Appendix A: Soil Classification, Appendix B: Water Quality Data and Assessments, Appendix C: AGWA Tool, Appendix D: Suggested Readings

Traditional flood-frequency techniques are based on the assumption that the observed flood record represents a sample that has been drawn from a single climatically homogeneous population of floods. A hydroclimatic approach was used to evaluate this assumption by identifying the circulation patterns and atmospheric flood-generating mechanisms which control the temporal and spatial variability of flooding. Mean monthly discharges and instantaneous peak flows of the partial duration series were analyzed for thirty gaging stations in the climatically sensitive, semiarid, Gila River basin for the period 1950 to 1980. Correlation fields and composite maps were constructed to define the relationship between 700 mb height circulation anomalies and mean monthly streamflow. Individual flood events were linked to climate by analyzing daily synoptic weather maps and classifying each flood event into one of eight hydroclimatic categories on the basis of the atmospheric mechanisms which generated each flow. The analysis demonstrated that floods and anomalously high streamflow in the Gila River basin originate from a variety of atmospheric processes which vary spatially, seasonally, and from year-to-year. The mechanisms most important for generating floods included winter fronts, cutoff lows, tropical storms, snowmelt, and widespread and localized summer monsoon-related circulation patterns. When flood discharges were grouped into hydroclimatically homogeneous categories, histogram plots of their frequency distributions exhibited means and variances that differed from those of the overall frequency distribution of the entire flood series. The means of the discharges generated by frontal precipitation and tropical storms tended to plot above the mean of the overall series, while the means of floods generated by snowmelt tended to plot below the overall mean. Flood estimates computed from a series containing mixed distributions were not the same as flood estimates computed from climatically homogeneous subsets of the same series. These results have implications for traditional flood-frequency analysis and other stochastic methods of analyzing hydrologic time series. The hydroclimatically-defined subgroups in the flood series of the Gila River basin indicate that nonhomogeneity and nonstationarity can be imparted to a hydrologic time series by differing atmospheric mechanisms alone.