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

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Elderly recreational vehicle campers are attracted to the Lower Colorado River area during the winter season. Their numbers have grown in recent years and many are seeking alternatives to the usual practice of establishing residence in private trailer parks. As a result, various public land sites in the region are being subjected to concentrated winter use. Units in these camping areas represent users who are retired couples or individuals on fixed or limited incomes, living in "self-contained" campers, travel trailers or motor homes. Some of these visitors are utilizing designated campgrounds; others are squatting on the public domain where there are few, if any, sanitary or other facilities. The impact of elderly winter visitors on the public land resource of the Lower Colorado River basin area is varied. An understanding of environmental effects is important, but proposed solutions depend upon our ability to understand the people causing environmental deterioration. Answers have been sought to basic questions about winter visitor characteristics and behavior. The findings were applied toward the development of basic policy recommendations pertinent to appropriate public land management for the desert areas of the Southwest. Of theoretical interest was the evaluation of the relative importance of camping socialization experiences in explaining user behavior. Data were gathered from 580 visitor units during the winter of 1973-74 with a personal interview schedule. Important classes of variables included socio-economic characteristics, camping experience, and users' campground behavior and preferences. Interviews were conducted in seven sites representing various kinds of public and private camping facilities in the region. Discriminant function, correlational, multiple regression and bivariate analyses were utilized to render the collected data meaningful. The basic sub-groups in the sample were distinguished by significant differences in various socio-economic and experiential characteristics. The most important of these were income, education, age, value of mobile quarters, and pre-retirement adult camping experience. Length of stay in public land camping areas was not explained by differences in site characteristics. Differences in visitor characteristics accounted for 40-50% of variation in length of stay. Important predictor variables included income, age, average annual pre-retirement camping experience and the amount of previous recreational vehicle camping without utility and sewerage hookups. Support was evidenced for a basic theoretical orientation: that post-retirement behavior is, in part, a reflection of pre-retirement recreational socialization and leisure life style patterns and persistence. The results suggested certain implications for public land management. Recommendations include the desirability of moving elderly winter camper use to sites away from the Colorado River. High fees imposed along the river would discourage extended-stay winter use and restore a unique resource to the short-term water-oriented visitor. The establishment of a spectrum of "inland" camping sites with varying levels of facilities and fees would serve as a positive inducement to the older winter camper, and restore some order to what has been, in some areas, an uncontrolled camping environment. A public campground on Bureau of Land Management land in Why, Arizona, offers a possible solution to the problems posed by the limited resources available to most public land management agencies. There a parcel of public land has been leased by a non-profit community association and developed into a public campground with basic facilities for elderly winter visitors. Management expenses are met through the imposition of a modest graduated fee schedule which favors the extended-stay camper. In this case a squatting problem has been resolved through local initiative; the public land management agency, with its limited budget, has been spared the expense of development and that of direct management responsibility.

Spatially-distributed water consumption was modeled over a segment of the Lower Colorado River, which contains irrigated agricultural and Tamarisk-dominated riparian ecosystems. For the irrigation scheme, distributed evapotranspiration data were analyzed in conjunction with point measurements of precipitation and surface flow in order to close daily and annual water balance. The annual closure error was less than 1% of the total water diversion to the area. In addition, it was found that the soil water storage component of the water balance cannot be neglected if the analysis is performed over time frames shorter than annual (e.g. growing season). Water consumption was highly uniform within agricultural fields, and all the full-cover fields were transpiring close to their potential rates. Mapping several new and existing drainage performance indicators showed that neither soil salinization nor water-logging would be of concern in this irrigation scheme. However, the quality of high-volume return flow must be studied, especially since the degraded water quality of the western US rivers is believed to act in favor of the invasive riparian species in outcompeting native species. Over the Tamarisk forest, the remotely-sensed evapotranspiration estimates were higher than the results of an independent groundwater-based method during spring and winter months. This was chiefly due to the fixed satellite overpass time, which happened at low sun elevation angles in spring and winter and resulted in a significant presence of shadows in the satellite scene and consequently a lower surface temperature estimate, which resulted in a higher evapotranspiration estimate using the SEBAL model. A modification based on the same satellite imagery was proposed and found to be successful in correcting for this error. Both water use and crop coefficients of Tamarisk estimated by the two independent methods implemented in this study were significantly lower than the current approximations that are used by the US Bureau of Reclamation in managing the Lower Colorado River. Studying the poorlyunderstood stream-aquifer-phreatophyte relationship revealed that diurnal and seasonal groundwater fluctuations were strongly coupled with the changes in river stage at close distances to the river and with the Tamarisk water extraction at further distances from the river. The direction of the groundwater flow was always from the river toward the riparian forest. Thus the improved Tamarisk ET estimates along with a better understanding of the coupling between the river and the riparian aquifer will allow the Bureau of Reclamation to re-asses their reservoir release methodology and improve efficiency and water savings.

Master of Science / Department of Biology / Craig Paukert / I investigated the influence of anthropogenic threats and hydrologic alteration on fish assemblages within the Lower Colorado River Basin (LCRB). Life history traits of fish assemblages for individual stream segments were summarized by species presence/absence data of current (1980-2006) records. To assess anthropogenic threats, I developed a series of ecological risk indices at various scales (e.g., catchment, watershed, aquatic ecological system and upstream of aquatic ecological system) and related each index to fish life-history traits to determine the method and scale that best related to biotic metrics. Hydrologic alteration was quantified using the Indicators of Hydrologic Alteration software to calculate hydrologic alteration values using the range of variability approach. Ecological risk indices within all scales were strongly correlated (r[superscript]2>0.54, p<0.0001) to one another. Relationships between fish life history traits and ecological risk indices occurred only at the catchment and watershed scales. Strongest relationships were at the watershed scale where increased levels of anthropogenic risk were related to reduced occurrences of native, fluvial dependent species (r[superscript]2=0.12, p<0.0001) and increased occurrences of nonnative generalist species (r[superscript]2=0.22, p<0.0001). The percent agriculture was positively related to indices of alteration of low flows (r=0.401, p=0.006) while forested land cover was negatively related to alteration of low flow events (r=-0.384, p=0.008). Relationships between indices of hydrologic alteration and fish traits indicate the occurrence of piscivorous, nonnative fishes increased with alteration of low flow events whereas occurrence of fluvial dependent fishes that preferred rubble substrate decreased with alteration of low flow events (r=0.64, p=0.001). Our analysis suggests that ecological risk indices and hydrologic alteration in the LCRB are related to composition of biotic communities. Incorporating cost-effective risk indices into conservation planning will likely increase the effectiveness of conservation efforts while understanding biotic responses to modified flow regimes are a necessity in sustainable development of water resources as human populations grow and water resources decrease in the LCRB.

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Periodic releases from an upstream dam cause rapid stage fluctuations in the Colorado River near Austin, Texas. These daily pulses modulate fluid exchange and residence times in the hyporheic region, where biogeochemical reactions are pronounced. We installed two transects of wells perpendicular to the river to examine in detail the reactions occurring in this zone of surface-water and groundwater exchange. One well transect recorded physical water level fluctuations and allowed us to map hydraulic head gradients and fluid movement. The second transect allowed for water sample collection at three discrete depths. Samples were collected from 12 wells every 2 hours for a 24-hour period and were analyzed for nutrients, carbon, major ions, and stable isotopes. The results provide a detailed picture of biogeochemical processes in the bank environment during low flow/drought conditions in a regulated river. Findings indicate that a pulse that causes a change in river stage of approximately 16-centimeters does not cause significant mixing in the bank. Under these conditions, the two systems act independently and exhibit only slight mixing at the interface. / text

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