Folders: ROOT > ScienceBase Catalog > USGS National Research Program > USGS National Research Program Projects > Borehole Geophysics as Applied to Geohydrology ( Show all descendants )
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Categories: Publication;
Types: Citation
Cross-borehole flowmeter pulse tests define subsurface connections between discrete fractures using short stress periods to monitor the propagation of the pulse through the flow system. This technique is an improvement over other cross-borehole techniques because measurements can be made in open boreholes without packers or previous identification of water-producing intervals. The method is based on the concept of monitoring the propagation of pulses rather than steady flow through the fracture network. In this method, a hydraulic stress is applied to a borehole connected to a single, permeable fracture, and the distribution of flow induced by that stress monitored in adjacent boreholes. The transient flow responses...
Categories: Publication;
Types: Citation;
Tags: Borehole flow modeling,
Flowmeter logging,
Fractured
A new computer program, FLASH (Flow-Log Analysis of Single Holes), is presented for the analysis of borehole vertical flow logs. The code is based on an analytical solution for steady-state multilayer radial flow to a borehole. The code includes options for (1) discrete fractures and (2) multilayer aquifers. Given vertical flow profiles collected under both ambient and stressed (pumping or injection) conditions, the user can estimate fracture (or layer) transmissivities and far-field hydraulic heads. FLASH is coded in Microsoft Excel5 with Visual Basic for Applications routines. The code supports manual and automated model calibration.
Categories: Publication;
Types: Citation
Continuous, high-resolution d18O records from cored sediments of Pyramid Lake, Nevada, indicate that oscillations in the hydrologic balance occurred, on average, about every 150 years (yr) during the past 7630 calendar years (calyr). The records are not stationary; during the past 2740 yr, drought durations ranged from 20 to 100 yr and intervals between droughts ranged from 80 to 230 yr. Comparison of tree-ring-based reconstructions of climate change for the past 1200 yr from the Sierra Nevada and the El Malpais region of northwest New Mexico indicates that severe droughts associated with Anasazi withdrawal from Chaco Canyon at 820 calyrBP (calendar years before present) and final abandonment of Chaco Canyon, Mesa...
Categories: Publication;
Types: Citation
Deep observation boreholes in the vicinity of active production wells in Honolulu, Hawaii, exhibit the anomalous condition that fluid-column electrical conductivity logs and apparent profiles of pore-water electrical conductivity derived from induction conductivity logs are nearly identical if a formation factor of 12.5 is assumed. This condition is documented in three boreholes where fluid-column logs clearly indicate the presence of strong borehole flow induced by withdrawal from partially penetrating water-supply wells. This result appears to contradict the basic principles of conductivity-log interpretation. Flow conditions in one of these boreholes was investigated in detail by obtaining flow profiles under...
Categories: Publication;
Types: Citation
Categories: Publication;
Types: Citation
A simple hydrologic-isotopic-balance (HIBAL) model for application to paleolake d18O records is presented. Inputs to the model include discharge, on-lake precipitation, evaporation, and the d18O values of these fluid fluxes. Monthly values of climatic parameters that govern the fractionation of 18O and 16O during evaporation have been extracted from historical data sets and held constant in the model. The ability of the model to simulate changes in the hydrologic balance and the d18O evolution of the mixed layer has been demonstrated using measured data from Pyramid Lake, Nevada. Simulations of the response in d18O to step- and periodic-function changes in fluid inputs indicate that the hydrologic balance and d18O...
Categories: Publication;
Types: Citation
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