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The objective of this study was to investigate the spatial and temporal trends of a phytoremediation system comprised of poplar trees designed to control groundwater flow and remove primarily polycyclic aromatic hydrocarbons (PAHs). Several lab and field studies have demonstrated the success of poplar trees in effectively decreasing concentrations of volatile hydrocarbons, but few have demonstrated effects on PAH concentrations. Thus, the focus of this report will be the response of the poplar trees in relation to hydrophobic, nonvolatile polycyclic aromatic hydrocarbons (acenapthene, acenapthylene, anthracene, chrysene, fluoranthene, naphthalene, phenanthrene, and pyrene) in a shallow, surficial aquifer. This field study was conducted on a 1.7-acre site in Oneida, Tennessee contaminated with creosote that was once used for railroad cross-tie treatment. Spatial analysis was used to divide the site into areas based on contaminant levels and a layer of coal that served as a layer of low permeability at an approximate depth of 2 feet. The semi-impermeable coal layer does have an adverse impact on tree growth, while the contamination does not appear to adversely affect tree growth. The rate of growth is also impacted by the age of the tree at planting where younger trees grow faster than the older trees. A steady decrease in PAH concentrations has occurred at the multi-level samplers surrounded by a root zone that has penetrated the contamination. PAH compounds present at relatively high concentrations in the soil and groundwater do not appear to affect tree growth to a greater or lesser extent than lower PAH concentrations. While further research is required to affirm the positive effects of poplar trees at this site, the tree stand has responded well to the high PAH levels. / Master of Science

A railroad yard in Oneida, Tennessee was contaminated with creosote in the 1950s and 1960s through cross tie treatment. The problem was discovered in 1990 and phytoremediation in combination with an interception trench was chosen as the remediation strategy. Hybrid poplar trees (1,036) were planted in 1997 within 0.7 acres. The goals of the phytoremediation system are to prevent migration of the contaminant off the site and clean up the contaminant in-situ. This study is focused on quantifying the rate of evapotranspiration of the phytoremediation system and then determining the effect on groundwater flow. This will be accomplished by quantifying evapotranspiration using a water budget, applying White's Equation, comparing groundwater recession curves, creating a groundwater flow model, and examining water table elevations obtained at the site. Calculations of water use by the poplar trees in early September 1999 ranged from 0.62 to 1.34 gal/day/tree. The volume of evapotranspiration calculated for the trees during 1999 is 140,292 gallons. Total evapotranspiration determined by the water budget for 1998 is 1,570,064 gallons. Evaluation of the water level data over a period of several years shows significant lowering of the water table (fluctuations of up to four feet) during the summer and fall months due to evapotranspiration. Although calculated evapotranspiration rates are not as high as seen in the literature, continued monitoring of the site should show large increases in evapotranspiration rates in the future as the poplar trees mature. / Master of Science

New knowledge gained over the past 15 to 20 years on the management of riparian zones in Arizona for water yield improvement has been organized and analyzed. Hydrologic processes and principles applicable to riparian zones, the distribution and nature of riparian vegetation in Arizona, and new resource management methods, needs, and constraints have been evaluated, The relationship between vegetation management for water yield improvement and other resource based products and uses of riparian zones such as timber, range for livestock, wildlife and fish, recreation, and aesthetics was also assessed. Past studies and surveys indicate that Arizona has approximately 280,000 to 320,000 acres of riparian vegetation, However, pertinent information such as species composition, vegetation density, depth to groundwater, groundwater quality, and landownership have not been mapped accurately for many riparian zones in Arizona, A continuous survey of riparian vegetation cover by remote sensing supplemented by ground truth is suggested to remedy this situation. Analysis of hydrologic studies indicated the following identifiable trends in water use by riparian species, Saltcedar, arrowweed, cottonwood, and hydrophytes are the heaviest users of water (between four and eight feet of water annually). Intermediate water users (annual use between two and five feet) are seepwillow, mesquite, quailbrush, four-wing saltbush, and greasewood. Lesser amounts of water are transpired by grasses and sedges and evaporated from bare soil (0,5 to three feet annually). Five water yield improvement methods applicable to riparian zones are evaluated; conversion of one vegetation type to another, channelization, cottonwood thinning, antitranspirant and biological control treatments. Conversion treatments to grasses or crops may yield water savings of up to 2,5 acre-feet per acre annually during the first year, However, some or all of this water may eventually be used by replacement vegetation, Several constraints including possible loss of wildlife habitat, contamination of water supplies by chemical herbicides, lowered aesthetic quality, and increased soil erosion with the removal of riparian vegetation reduce the opportunities for converting a large percentage of riparian vegetation in Arizona, To justify operational conversion programs in Arizona follow up studies of current conversion projects should be instituted, Rates at which revegetation takes place, declines in water salvage as revegetation occurs, amount and value of increased herbage production, and long term effects on plant distribution and animal life need to be determined. Channelization projects in the Southwest have been credited with increasing water yields; however, methods for determining these increases are poorly documented. Channelization for flood control purposes is limited because flow of flood water is accelerated in the vicinity of the excavation and may contribute to flooding and sedimentation on unchanneled segments. Cottonwood thinning designed to reduce evapotranspiration and flood hazards has been conducted along the Verde River, Increased water yields have not been measured, Adverse effects on fish and wildlife have been reported as a result of thinning cottonwoods. Limited thinning of cottonwoods to prevent bridges from washing out or to protect existing structures on the floodplain may be beneficial. Application of antitranspirant foliar sprays to reduce plant water use is a potential treatment method for increasing water yield in riparian zones. Antitranspirants were effective in reducing transpiration rates of saltcedar plants by up to 38 per cent for three to five weeks in greenhouse and limited field studies, Research on the feasibility of obtaining supplementary water from riparian vegetation through the application of antitranspirants should be expanded, Antitranspirants, if proven safe and effective, may be mutually acceptable to water, recreation, and wildlife interests. Biological control of saltcedar is not effective at present.

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.

From the Proceedings of the 1976 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 29-May 1, 1976, Tucson, Arizona / Energy budget evaluations of evapotranspiration from saltcedar were carried out on the flood plain of the Rio Grande River, near Bernardo, New Mexico. The site was adjacent to the Bureau of Reclamation's lysimeter study of water use by saltcedar. The energy budget for the cloudless day of June 14, 1975, revealed that energy gains from net radiation totaled 432 cal/cm² , while energy losses (in cal/cm2 ), were 14 to stored energy, 31 to convection, and 387 to evapotranspiration (ET). The energy loss to ET is equivalent to the latent energy contained in about 6.5 mm of water. The energy budget values are reasonable for a phreatophyte community in a semi-arid environment. The latent energy loss compares favorably with 401 cal/cm² measured by three lysimeters, although there were discrepancies in timing and amounts of loss among the individual lysimeters. The mean canopy diffusion resistance was 1.90 sec/cm over a 10-hour daytime period on June 14. The mean resistance was combined with vapor pressure deficit to predict lysimeter ET on three subsequent days. The agreement was within 12 percent, which suggests that diffusion resistance may be useful for simple ET predictions.

From the Proceedings of the 1977 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 15-16, 1977, Las Vegas, Nevada / Transpiration rates (T) of riparian phreatophytes can be high. Antitranspirant (AT) sprays can curtail T without the ecological imbalance made by eradication. Saltcedar (Tamarix sp.) and cottonwood (Populus sp.) in 15-gal. drums enabled replicated trials on isolated plants or on canopies. T of isolate saltcedar plants could be 2x that of plants in a fairly dense canopy. T for a unit ground area of saltcedar varied from 2.2 (sparse -) to 15.8 (dense-stand) mm/day in July at Davis. Extrapolation of experimental T data to field sites must, therefore, be made carefully. Wax -based ATs increased foliar diffusive resistance (R), and reduced T of saltcedar and cottonwood 32-38% initially and 10% after 3 weeks. R increased naturally in the afternoon when evaporative demand was high and if soil water was low. Nocturnal T of salt cedar was 10% of day T. AT effectiveness increased with a higher ratio of day: night hours, and with lower soil water stress. Therefore, AT will be most effective on long summer days in riparian areas where ground water is available.