Subsurface Flow Patterns Research Articles

Linking Sediment Biofilms, Hydrodynamics, and River Bed Clogging: Evidence from a Large River.

> Abstract We investigated possible effects of the hydrodynamics at the water/sediment interface on river bed biofilms within the reservoir Freudenau (Vienna, Austria) of the Danube River during the period 1996/97. Two study sites (OBB and SSF) that differed in the magnitude of surface/subsurface water exchange were selected and intersite comparisons revealed higher organic matter, bacterial cell numbers, and esterase activity in SSF with lower horizontal outflow. Concentrations of colloidal carbohydrates and uronic acids were unaffected by hydrodynamics. The relative contribution of uronic acids to bulk colloidal carbohydrates was higher in the low-flow site SSF. The distribution patterns of this relative contribution generally matched the subsurface flow pattern. Shortly after impoundment in March 1996 and along with decreased surface flow velocity, maximal biofilm carbohydrate exopolymers concurred with minimal esterase activity in OBB. We hypothesize that this inverse relationship is due to increased diffusional resistance within the exopolymer biofilm matrix that reduces mass transfer and hydrolytic activity. These results, to our knowledge, are the first evidence for microbial participation in the clogging of a large river bed. Biofilm-associated organic carbon increased significantly by a factor of approximately 3.3 to 4.4 with progressive clogging as determined by the sediment leakage coefficient, which increased approximately 3.8 times. Concomitantly, with ongoing clogging, esterase activity exhibited increasingly higher values at the interface relatively to deeper sediment layers, which translates into steeper depth gradients. Furthermore, minimal inflow from the surface water into the river bed along with steepest esterase gradients concurred with a senescent benthic algal bloom. This suggests an important role for algae in clogging. Either algae obstruct voids mechanically, or their exudates fuel heterotrophic bacteria that in turn are involved in clogging processes. However, our data do not allow unequivocal differentiation between biogenic and physical clogging mechanisms.

Using ground-penetrating radar to investigate a subsurface karst landscape in north-central Florida

Doline formation in karst areas has been a major concern in Florida. Recently, there has been increased interest in investigating the subsurface conditions that influences preferential flow in these karst landscapes. This information is necessary to improve transport and fate models of contaminants. In addition, there is interest in knowing if the formation and expansion of dolines can be predicted by studying subsurface conditions and flow patterns. The soils on the Newberry Limestone Plain are typically sandy above a thin or absent phosphatic, clayey Hawthorne Formation. Underlying this formation is the Crystal River Limestone. A field survey with ground-penetrating radar (GPR) was conducted on the Newberry Limestone Plain at a site with recently formed dolines. The objectives were (i) to investigate the subsurface materials, (ii) to ascertain subsurface landscape variability, (iii) to relate the subsurface landscapes to subsurface flow patterns, and (iv) to predict doline growth and formation in the study area. The results of this study indicated that the subsurface features; presence of clay over limestone, location of solution pipes and paleo-dolines are variable. In general, the subsurface landscape does not follow the surface topography. Subsurface solute movement can be estimated in these landscapes assuming the clay layer that drapes the limestone acts as an aquatarde. Thus, subsurface modeling of flow at the study site is improved. Locations of paleo-dolines and solution pipes were obvious in the radar data. Predictions, though, of future doline formation and growth at the study site were difficult with GPR. Fracture patterns, e.g. dips in the limestone, can be evaluated and weak zones where paleo-dolines have formed can be identified. This study would not have been possible without the use of the GPR. The radar was able to obtain continuous information on 16% of the site to a depth of 3 m. A highly detailed soil survey using conventional methods would have provided only 0.8% coverage of the site.

Subsurface Flow Patterns in a Riparian Buffer System

Matric potential was measured in a grass and forest riparian buffer system adjacent to a cropped field in the Georgia Coastal Plain. The soil in the adjacent cropped field is a Tifton loamy sand, containing an argillic subsurface horizon with plinthite at approximately 1 m which has been shown to restrict vertical infiltration and induce lateral flow. Two years of matric potential data and measurements of soil hydraulic characteristics were examined to evaluate and quantify unsaturated water flow in the riparian buffer. The lowest soil matric potential occurred at the grass/forest interface, and the greatest surface infiltration occurred within 10 m downslope of the same interface. The area of low matric potential was likely due to water uptake by trees. Water flowed laterally through the unsaturated soil into the riparian area from the upland field, apparently induced by low vertical conductivity in the subsurface and driven by the high water demand of the forest.

Controls on two-phase fluid flow in heterogeneous sandstones

Abstract The effective flow behaviour of two immiscible fluids in a permeable medium is a function of fluid/fluid as well as fluid/matrix interactions. These are described by relative permeability functions, which are strongly influenced by the spatial distribution of permeability in sedimentary media, given specified fluid and pore surface properties. For typical subsurface flow rates and patterns of rock heterogeneity in hydrocarbon reservoirs, capillary forces can result in significant amounts of trapping and bypassing of the non-wetting phase. Different types of sedimentary media (e.g. laminated, crossbedded and pervasively faulted strata) result in different, quantifiable, degrees of trapping. Examples of typical water-wet oil/water systems illustrate how the amount of trapped oil can vary between around 40% and 65% depending on the type of heterogeneity. Furthermore, the layered nature of most sedimentary strata means that the relative permeability of two immiscible phases is highly anisotropic. These findings have important implications for reservoir engineering and studies of oil migration.

Modeling of streaming potential responses caused by oil well pumping

The occurrence of streaming potentials is directly related to movement of fluids in the subsurface. To investigate whether streaming potential measurements in boreholes and at the surface can be used to monitor subsurface flow and detect subsurface flow patterns in oil reservoirs, we model streaming potential responses caused by oil well pumping in monitoring wells and at the earth's surface. Since the model parameters: permeabilities, cross‐coupling properties, and electric conductivities depend on a few basic rock‐physics parameters such as brine conductivity, amount of water saturation, and porosity, the model parameters are evaluated self‐consistently using rock‐physics models. Using a threedimensional, (3-D) finite‐difference algorithm, the governing differential equations that are drawn from nonequilibrium thermodynamics are solved numerically in three self‐consistent steps: solution of the hydraulic problem, computation of the streaming current sources based on the principle of conservation of charge, and solution of the resistivity problem. For simple models of oil reservoirs at shallow depth between 325 m and 500 m, we assume a total production rate of 500 bbl/day for all phases (gas/water or oil/water), a porosity of 0.2 in the reservoir, brine conductivities in the range of 0.3 S/m to 1.0 S/m, and water saturations in the range of 0.7 to 1.0. Maximum values of the computed streaming potential response are less than 0.6 mV at the surface and less than 9 mV in the monitoring wells. The streaming potential response depends on brine conductivity, conductivity structure, well casing, and reservoir dimensions and decreases rapidly with distance from the production well. The parameterization of the models establishes bounds for the expected streaming potential response that varies by approximately one order of magnitude. Because of the ac nature of pumping processes, signal stacking could perhaps be used to make the expected small signals discernible. Our models are mainly limited by poor knowledge of in‐situ, cross‐coupling properties.

Modelling of flow pattern in a shallow aquifer affected by reservoirs

A process for identifying and quantifying a spatial subsurface flow pattern in a shallow semi-confined aquifer is presented. The conceptual model is aimed at describing the hydraulic effects of surface reservoirs on a shallow semi-confined conducting layer that results in salinization of the top soil. A qualitative study of the relationship between water load in reservoirs, the artesian conducting layer, and water in the top soil was based on chemical and isotopic characteristics. Results indicate limited infiltration from reservoirs into the top soil layers and probably no penetration of water into the conducting layer. Results were then used to establish the regional flow pattern emphasizing the role of surface reservoirs on the build up of artesian pressure in the shallow conducting layer. The flow system was formulated using a compartmental approach in which the unknown parameters are the various sources of recharge and the physical parameters of the aquifer. A complete mathematical setup and suggested solution for the mathematical algorithm are presented in a second paper.

Implications of perennial saline springs for abnormally high fluid pressures and active thrusting in western California

Research Article| May 01, 1992 Implications of perennial saline springs for abnormally high fluid pressures and active thrusting in western California J. R. Unruh; J. R. Unruh 1Department of Geology, University of California, Davis, California 95616 Search for other works by this author on: GSW Google Scholar M. L. Davisson; M. L. Davisson 1Department of Geology, University of California, Davis, California 95616 Search for other works by this author on: GSW Google Scholar R. E. Criss; R. E. Criss 1Department of Geology, University of California, Davis, California 95616 Search for other works by this author on: GSW Google Scholar E. M. Moores E. M. Moores 1Department of Geology, University of California, Davis, California 95616 Search for other works by this author on: GSW Google Scholar Geology (1992) 20 (5): 431–434. https://doi.org/10.1130/0091-7613(1992)020<0431:IOPSSF>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation J. R. Unruh, M. L. Davisson, R. E. Criss, E. M. Moores; Implications of perennial saline springs for abnormally high fluid pressures and active thrusting in western California. Geology 1992;; 20 (5): 431–434. doi: https://doi.org/10.1130/0091-7613(1992)020<0431:IOPSSF>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Perennial saline springs in the Rumsey Hills area, southwestern Sacramento Valley, California, locally discharge at high elevations and near ridgetops. The springs are cold, are commonly associated with natural gas seeps, and typically emerge along west-vergent thrust faults. Stable isotope analyses indicate that the spring waters are similar to oil-field formation fluids and that they have had a significant residence time in the subsurface at moderate temperatures. The non-meteoric character of the springs demonstrates that they are not being fed by perched water tables. We propose that these subsurface formation waters are being forced to the surface by anomalously high pore-fluid pressures. The Rumsey Hills area is one of Quaternary uplift, thrusting, and crustal shortening, and prospect wells drilled there have encountered anomalously high fluid pressures at shallow depths. We attribute these high fluid pressures to active tectonic compression and shortening of Cretaceous marine sedimentary rocks. The widespread occurrence of anomalously high pore-fluid pressures and perennial saline springs in the Coast Ranges and western Great Valley suggests that much of western California may be characterized as a seismically active, overpressured thrust belt. The emergence of formation waters along thrust faults further suggests that patterns of subsurface fluid flow in western California may be similar to those in overpressured accretionary prisms, and that excess fluid pressures may also play a role in the distribution of seismicity. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Runoff process on a steep forested slope

Three slope units are defined by combining nine basic slope types. A convergent slope unit is called a zero-order basin, because it combines a slope and a stream. Field measurements of the runoff process of stormflow on Pliocene slopes are presented. Pipe flow and saturated overland flow play an important part on convergent colluvial slope units. Surface soils significantly influence saturated throughflow on creeping middle slopes. The depth of weathering has a major effect on initial moisture storage for residual and creeping slopes. A subsurface storm flow pattern on a typical Pliocene slope is reconstructed based on the field measurements.

Sea surface flow estimation from advanced very high resolution radiometer and coastal zone color scanner satellite imagery: A verification study

A refined technique for estimating surface currents from the displacement of features in sequential advanced very high resolution radiometer (AVHRR) and coastal zone color scanner (CZCS) images is presented. It is used to calculate flow fields in two regions along the California coast, and the results are compared to concurrent drifter drogue observations. There is overall agreement to within approximately 6 cm/s, with somewhat better agreement at velocities less than 40 cm/s. The poorer performance of the technique at high velocities was due to difficulties in identifying and tracking features in areas of rapid flow. The accuracy of the measurements is primarily affected by the analyst's precision in tracking each feature which, in turn, depends on how well the 2‐ to 6‐km features preserve their identity from one image to the next. A 12‐ to 24‐hour interval yielded the best results in this study. The directional component of the satellite‐derived flow field was representative of subsurface flow patterns down to at least 100 m. Although velocities obtained from AVHRR infrared and CZCS visible images may not always represent flow at the same depth, the measurements were practically identical with the data used.

未固結地山中のトンネル周辺における地下水挙動 ＩＩ

During tunnel-excavation in unconsolidated ground, it is necessary to pay attention to erosion or collapse caused by groundwater flow.So an observation of groundwater has been made around a tunnel in Neogene Pliocenean sandstone.By investigating the relation between groundwater behavior and factors concerned with the erosion or collapse of the face of an inclined shaft, it was showed that the occurrence of erosion is mainly influenced by groundwater flow, degree of consolidation and grading composition.The concentration and its variation with time of radio-isotope in groundwater leads an estimation of the subsurface flow pattern when the erosion or collapse is accompanied with the mixing flow of groundwater clustered by those duration time in each porous geological basins.