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The U.S. Geological Survey (USGS), at the request of the U.S. Army Environmental Command (USAEC), evaluated the capabilities of two borehole technologies to measure horizontal groundwater velocity and direction of flow in a parallel-plate fractured-rock simulator. A colloidal borescope flowmeter (HB) and a heat-pulse flowmeter (HH) were deployed in 4-inch and 6-inch inner-diameter simulated uncased wells that spanned 0.39- and 1.0-inch apertures with simulated groundwater velocities ranging from 2 to 958 feet per day. Measurements were made at the USGS Hydrologic Instrumentation Facility in the Hydraulics Laboratory and the Indianapolis office of the USGS Ohio-Kentucky-Indiana Water Science Center. Ten measurements...
The U.S. Geological Survey, in cooperation with the Lewis and Clark, Lower Elkhorn, Lower Loup, Lower Platte North, Lower Niobrara, Middle Niobrara, Upper Elkhorn, and the Upper Loup Natural Resources Districts, designed a study to refine the spatial and temporal discretization of a previously modeled area. This updated study focused on a 30,000-square-mile area of the High Plains aquifer and constructed regional groundwater-flow models to evaluate the effects of groundwater withdrawal on stream base flow in the Elkhorn and Loup River Basins, Nebraska. The model was calibrated to match groundwater-level and base-flow data from the stream-aquifer system from pre-1940 through 2010 (including predevelopment [pre-1895],...
The heat-pulse flowmeter (HH) used in this testing is a KVA Model 200 system. The instrument computes groundwater vectors from heat arrival and decay in an array of four thermistors that surround a single heat source. An external compass attached to the top of the deployment system is used to orient the flowmeter in the borehole. The HH measured groundwater velocity and flow in the x-y plane. Fuzzy packers were filled with 0.08-inch diameter glass beads for all tests. The HH thermistors were centered over the simulated fracture during measurements. One to four measurements were made with the HH for each simulated flow.
The colloidal borescope flowmeter (HB) used in this testing was developed by AquaVISION, Llc. The instrument employs a charge-coupled device camera, an optical magnification lens (140x), and a light-emitting diode (LED) illumination source to visually track neutrally buoyant colloids (approximately 1-5 microns) moving horizontally through the borehole. The device measured groundwater velocity and flow direction in the x-y (horizontal) plane. The HB magnetometer was checked with a compass to assure proper instrument orientation before deployment into the simulators. Borescope data were collected for each flow condition for a period of at least 30 minutes. After data collection, borescope data were inspected for anomalous...
The effects of vertical flowmeter placement relative to the vertical fracture opening were examined using the colloidal borescope flowmeter (HB). For these measurements, the HB measurement interval was located at a depth equal to 0.5-inch above and below the top and bottom edges of the fracture, respectively; at upper and lower edge of the fracture; at the center of the fracture; and 0.25-inch above and below the center of the fracture. The HB measurement interval was radially centered in the borehole. For those tests, the simulated flow direction was 180, aperture was 1.0-inch and the velocity was held steady at 297 ft/d. This sub-study was intended to identify potential influence of turbulent eddies on measured...
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