Browsing by Author "John C. Fountain, Committee Chair"

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    A Quantitative Assessment of Water Inputs and Outputs to a Small Watershed in Northwestern Wake County: Evaluating the Effects of Human Water Use on Groundwater Resources.
    (2008-12-12) Keyworth, Amy Jackson; April L. James, Committee Member; John C. Fountain, Committee Chair; David P. Genereux, Committee Member
    Sustained availability of safe drinking water is an increasingly important issue for Wake County planners due to the recent rapid and ongoing population growth in areas of the county that utilize groundwater for domestic water supply. Wake County planners need to know whether existing groundwater resources can be maintained in the event that the expected population increase takes place. Any anthropogenic influence can alter a natural system. The groundwater system responds to pumping with either a decrease in stored groundwater, a decrease in streamflow or both (Bredehoeft et al. 1982, Sophocleous, 2000). Wake County is interested in developing a “risk†map as a planning tool to identify areas of Wake County which are at increased risk of groundwater overuse. There are neither adequate data on water table elevations nor stream flows in Wake County with which to assess the relation of current groundwater use to ground or surface water depletion. This case study considers whether insights into groundwater use and potential overuse could be derived from a watershed water-balance approach using existing data. This study is an exercise in identifying available data and data gaps necessary to fill in order to develop a planning tool. Data limitations (e.g., lack of stream discharge or groundwater level data) resulted in restrictions on specific conclusions regarding the study catchment, however, this aspect makes a case study on a specific, fairly typical Wake county catchment a good tool for quantitatively illustrating the significance of different types of hydrologic and water supply data in understanding the water balance and fluxes on a developed catchment with significant groundwater pumping. The study identifies available data sources, data sources that can be further developed, and existing gaps in the data necessary to increase our understanding of a Piedmont fractured bedrock aquifer system. The results of this case study demonstrate that while the natural water balance components overwhelm the anthropogenic inputs and outputs, the impact of human water use on the catchment water balance does offer some useful insights. The quantification of the developed components of the system indicate that water is being moved within and across catchment boundaries in potentially significant ways. Community water systems may result in interbasin transfer of water on many scales. Water is also being transferred from low elevations to higher elevations as groundwater is removed from deep wells and discharged to onsite wastewater treatment systems just below land surface. The CWS groundwater withdrawals from BTC increase the effective housing density in the catchment. Water recharging the aquifer from onsite wastewater treatment systems may be increasing stream flow during drought and may lead to changes in water chemistry and stream health.
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    Relation of Well Yields to Fracture Patterns and Lineaments in the Rolesville Batholith, Wake County, North Carolina
    (2007-07-18) Garlington, Christopher Alan; John C. Fountain, Committee Chair; David P. Genereux, Committee Member; Edward F. Stoddard, Committee Member
    In Wake County over 140,000 county residents (about 25% of the population) rely on groundwater resources for drinking and other everyday uses. The increasing population of the county is causing an increase in demand for water resources. As surface water supplies for the county reach maximum capacity, groundwater will become an increasingly important source of water. Most drinking water supply wells in the county are completed in the crystalline bedrock. There is little matrix permeability in these rocks, therefore groundwater storage and flow is primarily through secondary fractures. The three goals of this study are 1) to determine via field study the primary surface fracture directions present at pavement outcrops within the Rolesville granite area of Wake County, 2) to perform a larger scale land-surface lineament analysis using aerial photographs and remote sensing data to compare with the field data results, and 3) to use available well yield data to correlate with the observed primary surface fracture directions to identify possible areas within the Rolesville granite of Wake County where the subsurface fracturing will allow for the construction of wells with higher than average yields. A total of 151 individual joints and fractures were identified by field study and were recorded. A rose diagram of these fractures finds the primary fracture azimuth to be 90° ± 5°, with 30.67 % of all measured fractures falling in this range. The secondary fracture azimuth in the field is approximately 0° ± 5° (18 % of all fractures). The third most common fracture azimuth is roughly 280°-290° (14 %), and the fourth most common azimuth is 10°-15° (8.67 %). The computer program ENVI was used to identify a total of 2362 lineaments on aerial photographs of the same geographic area where the fractures were located in the field study. The rose diagram of these land-surface lineaments also supports the E-W trend (90° ± 5°) found in the fracture data measured in the field. Lineaments in this range account for 15.66 % of those found. The second most common direction amongst the computer lineaments is 0° ± 5°. The number of fractures in this direction is roughly half that found in the 90° trend, accounting for 7.28 % of all lineaments found. The consistency between the results of the computer and field data confirm the validity of using the computer program ENVI for identifying lineaments in the Rolesville batholith portion of Wake County. This suggests that the directional filter of the program ENVI may be a useful tool in helping locate optimal sites for new high yielding wells.