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Stable isotopes of delta(18)O, delta(2)H, and (13)C, radiogenic isotopes of (14)C and (3)H, and ground water chemical compositions were used to distinguish ground water, recharge areas, and possible recharge processes in an arid zone, fault-bounded alluvial aquifer. Recharge mainly occurs through exposed stream channel beds as opposed to subsurface inflow along mountain fronts. This recharge distribution pattern may also occur in other fault-bounded aquifers, with important implications for conceptualization of ground water flow systems, development of ground water models, and ground water resource management. Ground water along the mountain front near the basin margins contains low delta(18)O, (14)C (percent modern...
Water introduced to surface drainages, such as agricultural and roadway runoff, mine drainage, or coalbed natural gas (CBNG)-produced water, potentially can be of environmental concern. In order to mitigate potential environmental effects, it may be important to be able to trace water discharged to the surface as it infiltrates and interacts with near-surface aquifers. We have chosen to study water withdrawn during CBNG production for isotope tracing in the hyporheic zone because it poses a variety of economic, environmental, and policy issues in the Rocky Mountain states. Ground water quality must be protected as CBNG water is added to semiarid ecosystems. Strontium (Sr) isotopes are effective fingerprints of the...
The relationship between local ground water flows and NO(3)(-) transport to the channel was examined in three well transects from a natural, wooded riparian zone adjacent to the Shingobee River, MN. The hillslope ground water originated as recharge from intermittently grazed pasture up slope of the site. In the hillslope transect perpendicular to the stream, ground water NO(3)(-) concentrations decreased from approximately 3 mg N L(-1) beneath the ridge (80 m from the channel) to 0.01 to 1.0 mg N L(-1) at wells 1 to 3 m from the channel. The Cl(-) concentrations and NO(3)/Cl ratios decreased toward the channel indicating NO(3)(-) dilution and biotic retention. In the bankside well transect parallel to the stream,...
A study using multiple techniques provided insight into tectonic influences on ground water systems; the results can help to understand ground water systems in the tectonically active western United States and other parts of the world. Ground water in the San Bernardino Valley (Arizona, United States and Sonora, Mexico) is the main source of water for domestic use, cattle ranching (the primary industry), and the preservation of threatened and endangered species. To improve the understanding of ground water occurrence, movement, and sustainability, an investigation was conducted using a number of complementary methods, including major ion geochemistry, isotope hydrology, analysis of gases dissolved in ground water,...
The relationship between local ground water flows and NO(3)(-) transport to the channel was examined in three well transects from a natural, wooded riparian zone adjacent to the Shingobee River, MN. The hillslope ground water originated as recharge from intermittently grazed pasture up slope of the site. In the hillslope transect perpendicular to the stream, ground water NO(3)(-) concentrations decreased from approximately 3 mg N L(-1) beneath the ridge (80 m from the channel) to 0.01 to 1.0 mg N L(-1) at wells 1 to 3 m from the channel. The Cl(-) concentrations and NO(3)/Cl ratios decreased toward the channel indicating NO(3)(-) dilution and biotic retention. In the bankside well transect parallel to the stream,...
Concern has been raised that selenium contamination may be adversely affecting endangered fish in the upper Colorado River basin. The objective of the study was to determine if operation of a water control structure (opened in December 1996) that allowed the Colorado River to flow through a channel area at Walter Walker State Wildlife Area (WWSWA) would reduce selenium and other inorganic elements in water, sediment, aquatic invertebrates, and forage fish. Endangered Colorado pikeminnow were collected and muscle plug samples taken for selenium analysis. Selenium concentrations in filtered water were 21.0 microg/L in 1995, 23.5 microg/L in 1996, 2.1 microg/L in 1997, and 2.1 microg/L in 1998. Selenium concentrations...
Stable isotope values of hydrogen and oxygen from precipitation and ground water samples were compared by using a volumetrically based mixing equation and stable isotope gradient to estimate the season and location of recharge in four basins. Stable isotopes were sampled at 11 precipitation sites of differing elevation during a 2-year period to quantify seasonal stable isotope contributions as a function of elevation. Supplemental stable isotope data collected by the International Atomic Energy Association during a 14-year period were used to reduce annual variability of the mean seasonal stable isotope data. The stable isotope elevation relationships and local precipitation elevation relationships were combined...
A recent article in Environmental Management by All argued that flood flows in North America's Colorado River do not reach the Gulf of California because they are captured and evaporated in Laguna Salada, a below sea-level lakebed near the mouth of the river. We refute this hypothesis by showing that (1) due to its limited area, the Laguna Salada could have evaporated less than 10% of the flood flows that have occurred since 1989; (2) low flow volumes preferentially flow to the Gulf rather than Laguna Salada; (3) All's method for detecting water surface area in the Laguna Salada appears to be flawed because Landsat Thematic Mapper images of the lakebed show it to be dry when All's analyses said it was flooded; (4)...
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Analysis of a typical semiarid mountain system recharge (MSR) setting demonstrates that geochemical tracers help resolve the location, rate, and seasonality of recharge as well as ground water flowpaths and residence times. MSR is defined as the recharge at the mountain front that dominates many semiarid basins plus the often-overlooked recharge through the mountain block that may be a significant ground water resource; thus, geochemical measurements that integrate signals from all flowpaths are advantageous. Ground water fluxes determined from carbon-14 ((14)C) age gradients imply MSR rates between 2 x 10(6) and 9 x 10(6) m(3)/year in the Upper San Pedro Basin, Arizona, USA. This estimated range is within an order...
Intermontane basins in the Trans-Pecos region of westernmost Texas and northern Chihuahua, Mexico, are target areas for disposal of interstate municipal sludge and have been identified as possible disposal sites for low-level radioactive waste. Understanding ground water movement within and between these basins is needed to assess potential contaminant fate and movement. Four associated basin aquifers are evaluated and classified; the Red Light Draw Aquifer, the Northwest Eagle Flat Aquifer, the Southeast Eagle Flat Aquifer, and the El Cuervo Aquifer. Encompassed on all but one side by mountains and local divides, the Red Light Draw Aquifer has the Rio Grande as an outlet for both surface drainage and ground water...
Initial river rehabilitation efforts along the North Fork Gunnison River in Colorado focused on the use of in-stream structures and channel stabilization to create a single-thread channel with pools along a braided river. These efforts were based on the assumption that the river's braided planform results primarily from land use during the past century. In order to establish a context for further rehabilitation, we evaluated the possibility that the river might be braided as a result of processes independent of land use. We estimated volume, grain-size distribution, and lithology of sediment sources along the river corridor and evaluated the planform stability of the river during the past century using historical...
We examined the effects of the Zemko Dam removal on the Eightmile River system in Salem, Connecticut, USA. The objective of this research was to quantify spatiotemporal variation in fish community composition in response to small dam removal. We sampled fish abundance over a 6-year period (2005-2010) to quantify changes in fish assemblages prior to dam removal, during drawdown, and for three years following dam removal. Fish population dynamics were examined above the dam, below the dam, and at two reference sites by indicator species analysis, mixed models, non-metric multidimensional scaling, and analysis of similarity. We observed significant shifts in fish relative abundance over time in response to dam removal....
    map background search result map search result map Geochemical quantification of semiarid mountain recharge. Ground water recharge and flow characterization using multiple isotopes. Geochemical quantification of semiarid mountain recharge. Ground water recharge and flow characterization using multiple isotopes.