Browsing by Subject "water use"
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Item Changing patterns and perceptions of water use in east central texas since the time of anglo settlement(2009-05-15) Patzewitsch, Wendy WinbornPatterns and perceptions of water use have changed since Anglo settlement in Texas in the early nineteenth century. Change has not been constant, gradual, or linear, but rather has occurred in fits and spurts. This pattern of punctuated equilibrium in water use regimes is the central finding of this dissertation. Water use is examined in terms of built, organizational, and institutional inertias that resist change in the cultural landscape. Change occurs only when forced by crisis and results in water management at an increasing scale. Perception is critical in forcing response to crisis. Four water use regimes are identified. The agrarian regime was characterized by individual family and plantation units that were self-sufficient in their water supply. Water was perceived as abundant, but used sparingly. The agrarian regime began with Texas?s declaration of independence from Mexico in 1836 and lasted for the remainder of the nineteenth century. The waterworks regime was characterized by the introduction of piped water. During this second regime, water was still perceived as abundant, but was also taken for granted. The crisis forcing the waterworks regime was the need for better fire protection in cities. The almost constant threat of flood and drought, underscored by the Drought of the 1950s, in conjunction with a demographic shift, brought about the dam and levee regime. As a consequence of the Drought of the 1950s, water was for the first time perceived as scarce. We have just entered the groundwater regime. Recent water legislation and a state supreme court decision in favor of a bottled water company are putting new emphasis on groundwater sales from rural property owners to municipal water companies. Empirical studies supporting this theoretical framework are drawn from the heretofore unpublished 1868 journal of Pleasant B. Watson, from municipal bond records in the archives of the Texas Comptroller, from the early history of the waterworks at Bryan, Texas, from newly discovered records of a levee along the Brazos River, from an overview of dam and reservoir construction, and from a recent proliferation of groundwater districts.Item Dynamics of water use and responses to herbivory in the invasive reed, Arundo donax (L.)(2010-07-14) Watts, David A.The first objective of this study was to investigate the role of an invasive grass species, Arundo donax (L.), on the hydrologic cycle. At a site on the Rio Grande in South Texas, we measured the gas exchange of carbon dioxide and water vapor at the leaf scale and structural characteristics, such as leaf area and shoot density, at the stand scale. In order to assess the effect of water availability, this study was conducted along transects perpendicular to the edge of the river along a potential moisture gradient. The second objective was to quantify the effect of two herbivores, an armored scale, Rhizaspidiotus donacis (Leonardi), and a stem-galling wasp, Tetramesa romana (Walker),on the photosynthetic and transpiration rates of A. donax. Leaf gas exchange measurements were made to determine the direction and magnitude of the effect on physiological processes and by what mechanisms any effects arose. Stands of A. donax used approximately 9.1 ? 1.1 mm of water per day. This rate of water use was at the high end of the spectrum for plants. The major controls on stand scale transpiration were evaporative demand, leaf area index, and water availability. During two summer seasons, stand scale transpiration varied greatly, following the pattern of variability in precipitation, suggesting that recent rainfall constituted a significant proportion of the water taken up by this species. Herbivory by a stem-galling wasp and a sap-feeding scale, both separately and together, reduced the rates of leaf scale physiological processes in A. donax. The efficacy of the wasp was density dependent, and this herbivore reduced the carboxylation rate of Rubisco. The effect of the scale took approximately five months to manifest, which coincided with generation time. Scale reduced photosynthesis by decreasing the maximum rate of electron transport. When the two insects were both present, the effect of their herbivory seemed to be additive. These results will assist the responsible management agencies in evaluating the propriety of using one or both of the insect herbivores as biological control agents.Item Relationship of salinity and depth to the water table on Tamarix spp. (Saltcedar) growth and water use.(Texas A&M University, 2004-09-30) Schmidt, Kurtiss MichaelSaltcedar is an invasive shrub that has moved into western United States riparian areas and is continuing to spread. Saltcedar is a phreatophyte that can utilize a saturated water table for moisture once established and is also highly tolerant of saline soil and water conditions. Literature has indicated that depth to the water table and salinity have a significant effect on growth and water use by saltcedar. Several studies were initiated to help develop a simulation model of saltcedar growth and water use based on the EPIC9200 simulation model. A study was initiated at the USDA-ARS Blackland Research Center Temple, Texas in the summer of 2002 to better understand the effects of water table depth and salinity on (1) saltcedar above and below ground biomass, root distribution, leaf area and (2) water use. Five different salinity levels (ranging from 0 ppm to 7500 ppm) and three different water table depths (0.5m, 1.0m, and 1.75m) were studied. Results indicated that increasing depth to the water table decreased saltcedar water use and growth. For the 0.5m water table depth, saltcedar water use during the 2002 growing season averaged 92.7 ml d-1 while the 1.75m depth averaged 56.6 ml d-1. Both root and shoot growth were depressed by increasing water table depth. Salinity had no effect on saltcedar growth or water use except at the 1250 ppm level, which used 110 ml of H2O d-1. This salinity had the highest water use indicating that this may be near the ecological optimum level of salinity for saltcedar. A predictive equation was developed for saltcedar water use using climatic data for that day, the previous day's climatic data, water table depth and salinity that included: previous day total amount of solar radiation, water table depth, previous day average wind speed, salinity, previous day total precipitation, previous day average vapor pressure, minimum relative humidity, previous day average wind direction, and maximum air temperature. Data from the field study and a potential growth study were integrated into the model. The model was parameterized for the Pecos River near Mentone, Texas. Predicted saltcedar water use was slightly lower than results reported by White et al. 2003.