Plenary Session: \u3cem\u3eWater Research Needs in Kentucky\u3c/em\u3e

Four panelists were invited to present their visions/predictions of current and future water research needs in Kentucky in an opening plenary session at the 2012 Kentucky Water Resources Annual Symposium. The requested overall general focus was ground water research needs

Spatial and Temporal Variability in Seepage between a Contaminated Aquifer and Tributaries to the Ohio River

Because interactions between ground water and tributaries may influence contaminant loading to rivers, we delineated seepage along Little Bayou and Bayou Creeks in McCracken County, Kentucky, during a two-year period. From the Paducah Gaseous Diffusion Plant, on the divide between the creeks, trichloroethene and technetium-99 plumes extend several km toward the Ohio River. Gaining conditions occur where the creeks are incised into coarse sediments in the river\u27s flood plain. Such conditions were marked by upward hydraulic gradients within the bed; maximum specific discharge (q) \u3e 0.24 m d-1; relatively narrow ranges of stream, piezometer, and bed temperatures; relatively cool bed and bank temperatures in summer and early autumn; detections of trace solutes in stream water; and observations of springs, boils, and seeps. Evidence of losing or no-net-discharge conditions included downward or lateral hydraulic gradients; minimal q values (indicative of stream-water flow through the bed); and relatively broad annual ranges of stream and piezometer temperatures. Mixing calculations using δ18O and Cl- support inferences about gaining and losing reaches. Seepage rates and directions changed during dry periods in summer and early autumn and following Ohio River flooding in spring. Discharge of uncontaminated ground water dilutes contaminants in Little Bayou Creek

Modeling of Groundwater Potential Using Cloud Computing Platform: A Case Study from Nineveh Plain, Northern Iraq

Knowledge of the groundwater potential, especially in an arid region, can play a major role in planning the sustainable management of groundwater resources. In this study, nine machine learning (ML) algorithms—namely, Artificial Neural Network (ANN), Decision Jungle (DJ), Averaged Perceptron (AP), Bayes Point Machine (BPM), Decision Forest (DF), Locally-Deep Support Vector Machine (LD-SVM), Boosted Decision Tree (BDT), Logistic Regression (LG), and Support Vector Machine (SVM)—were run on the Microsoft Azure cloud computing platform to model the groundwater potential. We investigated the relationship between 512 operating boreholes with a specified specific capacity and 14 groundwater-influencing occurrence factors. The unconfined aquifer in the Nineveh plain, Mosul Governorate, northern Iraq, was used as a case study. The groundwater-influencing factors used included elevation, slope, curvature, topographic wetness index, stream power index, soil, land use/land cover (LULC), geology, drainage density, aquifer saturated thickness, aquifer hydraulic conductivity, aquifer specific yield, depth to groundwater, distance to faults, and fault density. Analysis of the contribution of these factors in groundwater potential using information gain ratio indicated that aquifer saturated thickness, rainfall, hydraulic conductivity, depth to groundwater, specific yield, and elevation were the most important factors (average merit \u3e 0.1), followed by geology, fault density, drainage density, soil, LULC, and distance to faults (average merit \u3c 0.1). The average merits for the remaining factors were zero, and thus, these factors were removed from the analysis. When the selected ML classifiers were used to estimate groundwater potential in the Azure cloud computing environment, the DJ and BDT models performed the best in terms of all statistical error measures used (accuracy, precision, recall, F-score, and area under the receiver operating characteristics curve), followed by DF and LD-SVM. The probability of groundwater potential from these algorithms was mapped and visualized into five groundwater potential zones: very low, low, moderate, high, and very high, which correspond to the northern (very low to low), southern (moderate), and middle (high to very high) portions of the study area. Using a cloud computing service provides an improved platform for quickly and cheaply running and testing different algorithms for predicting groundwater potential

Trichloroethene Biodegradation Potential in Wetland Soils and Paleowetland Sediments

Trichloroethene (TCE) plumes extend north-northeast toward the Ohio River from the Paducah Gaseous Diffusion Plant (PGDP), a Superfund site in the Gulf Coastal Plain of western Kentucky. Wetlands in the floodplain are in the paths of these plumes, and on-site contamination has migrated downward from the Regional Gravel Aquifer (RGA) into the upper McNairy Formation, which overlies a bedrock aquifer. Intrinsic biodegradation in these two environments at the margins of the RGA could limit further contaminant migration and ecosystem or water-quality degradation. To assess cometabolic biodegradation potential in these uncontaminated environments, we attempted to culture and enumerate methanogens, sulfate- and Fe(III)-reducers, and methanotrophs, which have been implicated elsewhere as TCE degraders. Soil samples were collected at three wetland sites in the floodplain. McNairy sediments were collected beneath one of the suspected source areas at PGDP. Methanogens, sulfate reducers, and methanotrophs were abundant in wetland soils, with populations generally decreasing with depth. Methanogens were the only group cultured from McNairy sediments, and they showed little activity compared with wetland methanogen cultures. TCE loss in methanogenic batch cultures by chemoautotrophic and acetoclastic methanogens was monitored, but no significant degradation was observed

Variable responses of karst springs to recharge in the Middle Atlas region of Morocco

Springs in the Middle Atlas region of Morocco are important public water supplies, but their responses to storm-event and seasonal forcings have received only limited study. From March 2014 to May 2015, water temperature was measured hourly at three springs (Ribaa, Sidi Rached, and Zerouka); water level (stage) was measured hourly at Sidi Rached and Zerouka; and maximum daily turbidity was recorded at Ribaa. From March 2014 to March 2015, daily water samples were taken at Zerouka for analyses of deuterium and oxygen-18. Hourly weather data (precipitation and air temperature) were available from March 2014 to May 2015 from Ifrane, near Zerouka. Temperature responses varied between the springs, showing a time-lagged seasonal signal at Sidi Rached, near-constant values at Zerouka, and relatively stable dry-season values followed by flashy wet-season behavior at Ribaa. Stage at Sidi Rached and Zerouka tracked together, with a broad minimum in late summer and responses to individual storms superposed on the signal. Stable isotopes fluctuated daily but were frequently out of phase with each other. Autocorrelation analyses of spring parameters indicate that Sidi Rached and Zerouka have greater inertia than Ribaa. Cross-correlation analyses show characteristic time lags between (1) precipitation and stage, (2) air temperature and water isotopes, and (3) air and water temperatures. However, as shown in previous work, there is a broad range of time lags between precipitation and turbidity. The variety of spring behaviors is consistent with differences in hydraulic connectivity within each spring basin

Plate tectonics influence on geogenic arsenic cycling: from primary sources to global groundwater enrichment

More than 100 million people around the world are endangered by geogenic arsenic (As)in groundwater, residing in sedimentary aquifers. However, not all sedimentary aquifers are groundwater As enriched, and the ultimate source of As in enriched aquifer sediments is yet-unknown, globally. A reconnaissance of the major aquifers suggests that major As enriched aquifers are predictably systematic on a global scale, existing in sedimentary foreland basins in the vicinity of modern or ancient orogenic systems. In conformity with the Principle of Uniformitarianism, we demonstrate that the groundwater As comes from magmatic arcs (primary source)in present (e.g. Andes)or ancient (e.g. Himalaya)continental convergent margins of some of the most prominent orogenic systems across the globe, and ends up in sediments (secondary source)in adjoining foreland or related basins that eventually act as aquifers. These arc magmas scavenge As while rising through the deep continental crust. Erosion of such orogens ultimately increases the bulk As content in sediments of adjoining basins, leading to groundwater As enrichment in downstream aquifers. Such As-polluted aquifers are eventually extensively used for groundwater exploitation, for drinking and other human purposes. Surface geological and biogeochemical processes, like redox reactions, are conducive to such groundwater As enrichment. We suggest this model by integrating our study of long-time observations in Himalayan and Andean basin aquifers, and generalizing 63 major aquifers across the globe, to demonstrate the source-to-sink transport of As, thereby delineating it's geogenic cycling in the subsurface. This work outlines the specifics of the mechanisms that would drive the processes of groundwater As enrichment across spatio-temporal scales, i.e. tectonic-scale taking place over millions of years on continental-scale and groundwater pollution taking place at human time-scales on village to household scale. Thus, in this work, we demonstrate a direct evidence of connectivity between global geological processes and individual human health

Utilization of Tryptophan-like Fluorescence as a Proxy for <i>E. coli</i> Contamination in a Mixed-Land-Use Karst Basin

Karst aquifers are susceptible to contamination by pathogenic microorganisms, such as those found in human and animal waste, because the surface and subsurface drainage are well integrated through dissolution features. Fecal contamination of water is commonly assessed by the concentration of thermotolerant coliform bacteria, especially E. coli. This method is time-consuming, taking ≥18 h between the start of incubation and subsequent enumeration, as well as the time required to collect and transport samples. We examined the utility of continuous monitoring of tryptophan-like fluorescence (TLF) as a real-time proxy for E. coli in a mixed-land-use karst basin in the Inner Bluegrass region of central Kentucky (USA). Two logging fluorometers were sequentially deployed at the outlet spring. During storm flow, TLF typically peaked after discharge, which suggests that TLF transport in the phreatic conduit is likely related to sediment transport. The ability of TLF and other parameters (48 h antecedent precipitation, turbidity, and air temperature) to predict E. coli concentrations was assessed using the Akaike information criterion (AIC) applied to linear regression models. Because both the models and baseline concentrations of TLF differed between fluorometers, TLF and instrument interaction were accounted for in the AIC. TLF was positively correlated with E. coli and, in conjunction with antecedent precipitation, was the best predictor of E. coli. However, a model that included air temperature and antecedent precipitation but not TLF predicted E. coli concentrations similarly well. Given the expense of the fluorometers and the performance of the alternate model, TLF may not be a cost-effective proxy for E. coli in this karst basin

Contrasting controls on hydrogeochemistry of arsenic-enriched groundwater in the homologous tectonic settings of Andean and Himalayan basin aquifers, Latin America and South Asia

High groundwater arsenic (As) across the globe has been one of the most well researched environmental concerns during the last two decades. Consequently, a large scientific knowledge-base has been developed on As distributions from local to global scales. However, differences in bulk sediment As concentrations cannot account for the As concentration variability in groundwater. Instead, in general, only aquifers in sedimentary basins adjacent to mountain chains (orogenic foreland basins) along continental convergent tectonic margins are found to be As-enriched. We illustrate this association by integrating observations from long-term studies of two of the largest orogenic systems (i.e., As sources) and the aquifers in their associated foreland basins (As sinks), which are located in opposite hemispheres and experience distinct differences in climate and land-use patterns. The Andean orogenic system of South America (AB), an active continental margin, is in principle a modern analogue of the Himalayan orogenic system associated with the Indus-Ganges-Brahmaputra river systems in South Asia (HB). In general, the differences in hydrogeochemistry between AB and HB groundwaters are conspicuous. Major-solute composition of the arid, oxic AB groundwater exhibits a mixed-ion hydrochemical facies dominated by Na-Ca-Cl-SO4-HCO3. Molar calculations and thermodynamic modeling show that although groundwater of AB is influenced by cation exchange, its hydrochemical evolution is predominated by feldspar dissolution and relationships with secondary clays. In contrast, humid, strongly reducing groundwater of HB is dominated by Ca-HCO3 facies, suggestive of calcite dissolution, along with some weathering of silicates (monosiallitization). This work demonstrates that although hydrogeochemical evolutionary trends may vary with local climate and lithology, the fundamental similarities in global tectonic settings can still lead to the elevated concentrations of groundwater As