%0 Conference Proceedings %B Abstracts with Programs - Geological Society of America %D 2006 %T Implications of diurnal river fluctuations on mass transport in a valley-fill aquifer %A Brandon J Fleming %A David F Boutt %A Stephen B Mabee %K #StaffPubs %K aquifers %K BEDROCK %K clastic sediments %K controls %K diffusion %K diurnal variations %K drainage %K drift %K Eastern U.S. %K Environmental geology 22 %K floods %K fluctuations %K geochemical cycle %K geologic hazards %K ground water %K measurement %K mixing %K models %K Northeastern U.S. %K numerical models %K nutrients %K pollution %K processes %K pumping %K quantitative analysis %K residence time %K sediments %K shallow aquifers %K surface water %K three-dimensional models %K tracers %K transport %K United States %K valleys %K water pollution %K water resources %K water wells %X Aquifers located in isolated stratified drift deposits in the northeastern portion of the US are extremely fragile and important groundwater resources. These aquifers, when restricted to bedrock valleys, are often strongly coupled to significant surface water drainage systems. In northwestern Massachusetts, surface water associated with the Deerfield River watershed is highly regulated by dams to protect against flooding and to generate hydroelectric power. Regular releases of water from these dams cause diurnal fluctuations in river stage. In a previous study performed by the USGS, measurements from two clusters of wells show a significant response to river stage fluctuations in the aquifer. Fluctuations in river stage and resulting changes in head levels in the aquifer cause a switch from a losing to a gaining stream. The flow reversals have implications for mass transport and nutrient cycling within the hyporheic zone. In this paper we investigate the physical hydrologic controls on mass transport in the shallow aquifer. Using a coupled groundwater flow and transport code, we built a quasi three dimensional transient numerical model to approximate the head changes in the aquifer caused by the stage fluctuations in the river. Flow velocities and residence times were estimated in the aquifer for a variety of flow conditions. The mixing process driven by the aquifer head changes were quantified in the proximity of the hyporheic zone and shown to significantly influence both vertical and horizontal flow velocities in a region close to the stream-aquifer boundary. The diurnal river stage changes also appear to influence farfield hydrologic conditions and potentially hydrologically isolate the river and hyporheic zone. To further investigate these mixing processes we applied a mass transport code with conservative tracers to the aquifer. Fluctuation of the river stage combined with the heterogeneous nature of the aquifer creates a pumping mechanism that creates excess mixing within shallow portions of the aquifer. Aquifer dispersivity and molecular diffusion both contribute to the anomalous mixing modeled in the shallow aquifer. Mixing driven by stream stage changes has important implications for nutrient cycling as well as contaminant transport in the shallow aquifer. %B Abstracts with Programs - Geological Society of America %I Geological Society of America (GSA) : Boulder, CO, United States %C United States %V 38 %P 468 - 468 %8 2006/10/01/ %@ 00167592 %G eng %U https://gsa.confex.com/gsa/2006AM/finalprogram/abstract_115285.htm %N 77 %! Abstracts with Programs - Geological Society of America %0 Journal Article %J International Journal of Rock Mechanics and Mining Sciences [1997] %D 2010 %T Comparison of three fracture sampling methods for layered rocks %A Alex K Manda %A Stephen B Mabee %K #StaffPubs %K Big Quarry %K carbonates %K case studies %K data acquisition %K data processing %K dolomite %K Door Peninsula %K fractures %K geographic information systems %K ground water %K information systems %K joints %K layered materials %K mapping %K methods %K movement %K multiple scanline method %K northeastern Wisconsin %K numerical models %K permeability %K sampling %K selection method %K simulation %K single scanline method %K statistical analysis %K Structural geology 16 %K style %K three-dimensional models %K United States %K Wisconsin %X Three methods of fracture data collection are tested against each other in layered dolomitic rocks to evaluate the effectiveness of each method in sampling fracture properties. The methods tested are the single scanline method (SSM), selection method (SM), and multiple scanline method (MSM). Finite element techniques were first used to build a base model with the exact locations, sizes and orientations of each fracture observed in the natural fracture network. Then, a second set of models were stochastically generated using statistics from each sampling technique. For each network, the overall fracture intensity was used to assess the effectiveness of each sampling technique in capturing the real fracture properties. Fracture network permeability was also calculated for each of two directions to evaluate the transmissive properties of the networks. Although all three methods produced good matches of relative intensity and permeability between natural and synthetic fractures, the results reveal that a well-placed scanline performed the best at recreating natural fractures. However, the results from one variation of the SSM were only slightly better than the results from both versions of the SM. In general, the SSM provides the best results but possibly at heavy costs in time and labor, whereas the SM gives comparable results with less expenditure of energy and time. Thus, the SM is an adequate technique and recommended for use at large outcrops or where time, access or budget constraints are a concern. %B International Journal of Rock Mechanics and Mining Sciences [1997] %I Elsevier : Oxford-New York, International %C International %V 47 %P 218 - 226 %8 2010/02/01/ %@ 13651609 %G eng %U http://www.sciencedirect.com/science/article/pii/S1365160909001804 %N 22 %! International Journal of Rock Mechanics and Mining Sciences [1997] %0 Journal Article %J Water Resources Research %D 2009 %T Implications of anthropogenic river stage fluctuations on mass transport in a valley fill aquifer %A David F Boutt %A Brandon J Fleming %K #Hydro %K #WaterResources %K aquifers %K boundary conditions %K Charlemont %K Deerfield River basin %K fluctuations %K fluvial features %K Franklin County Massachusetts %K ground water %K human activity %K Hydrogeology 21 %K hydrology %K massachusetts %K numerical models %K preferential flow %K rivers %K shallow aquifers %K streams %K surface water %K transport %K two-dimensional models %K United States %K valleys %X In humid regions a strong coupling between surface water features and groundwater systems may exist. In these environments the exchange of water and solute depends primarily on the hydraulic gradient between the reservoirs. We hypothesize that daily changes in river stage associated with anthropogenic water releases (such as those from a hydroelectric dam) cause anomalous mixing in the near-stream environment by creating large hydraulic head gradients between the stream and adjacent aquifer. We present field observations of hydraulic gradient reversals in a shallow aquifer. Important physical processes observed in the field are explicitly reproduced in a physically based two-dimensional numerical model of groundwater flow coupled to a simplistic surface water boundary condition. Mass transport simulations of a conservative solute introduced into the surface water are performed and examined relative to a stream condition without stage fluctuations. Simulations of 20 d for both fluctuating river stage and fixed high river stage show that more mass is introduced into the aquifer from the stream in the oscillating case even though the net water flux is zero. Enhanced transport by mechanical dispersion leads to mass being driven away from the hydraulic zone of influence of the river. The modification of local hydraulic gradients is likely to be important for understanding dissolved mass transport in near-stream aquifer environments and can influence exchange zone processes under conditions of high-frequency stream stage changes. %B Water Resources Research %I American Geophysical Union : Washington, DC, United States %V 45 %P @CitationW04427 - @CitationW04427 %8 2009/01/01/ %@ 0043139719447973 %G eng %U http://onlinelibrary.wiley.com/doi/10.1029/2007WR006526/full %N 44 %! Water Resources Research %0 Journal Article %J Hydrogeology Journal %D 2013 %T A method of estimating bulk potential permeability in fractured-rock aquifers using field-derived fracture data and type curves %A Alex K Manda %A Stephen B Mabee %A David F Boutt %A Cooke, Michele L. %K #StaffPubs %K aquifers %K boundary conditions %K eastern Massachusetts %K fractured materials %K fractures %K ground water %K Hydrogeology 21 %K massachusetts %K Nashoba terrane %K naturally fractured reservoirs %K numerical models %K permeability %K prediction %K pump tests %K simulation %K two-dimensional models %K United States %X A method is devised for estimating the potential permeability of fracture networks from attributes of fractures observed in outcrop. The technique, which is intended as a complement to traditional approaches, is based on type curves that represent various combinations of fracture lengths, fracture orientations and proportions (i.e., intensities) of fractures that participate in flow. Numerical models are used to derive the type curves. To account for variations in fracture aperture, a permeability ratio (R) defined as the permeability of a fracture network in a domain divided by the permeability of a single fracture with identical fracture apertures, is used as a dependent variable to derive the type curves. The technique works by determining the point on the type curve that represents the fracture characteristics collected in the field. To test the performance of the technique, permeabilities that were derived from fractured-rock aquifers of eastern Massachusetts (USA) are compared to permeabilities predicted by the technique. Results indicate that permeabilities estimated from type curves are within an order of magnitude of permeabilities derived from field tests. First-order estimates of fracture-network permeability can, therefore, be easily and quickly acquired with this technique before more robust and expensive methods are utilized in the field. Copyright 2012 Springer-Verlag Berlin Heidelberg %B Hydrogeology Journal %I Springer : Berlin - Heidelberg, Germany %C Federal Republic of Germany %V 21 %P 357 - 369 %8 2013/03/01/ %@ 1431217414350157 %G eng %U http://link.springer.com/article/10.1007%2Fs10040-012-0919-2 %N 22 %! Hydrogeology Journal