Showing papers on "Groundwater flow published in 1969"

A possible way of tracing groundwater flows in karst

Abstract: In designing as well as in the construction of hydro-electric power plants and water-supply projects in karst, the knowledge of the location of groundwater flows is invaluable. Attempts made so far in this direction have not produced the desired results and all the methods known so far have shown to be more or less ineffective, especially with respect to deep-seated underground flows. An interesting suggestion on the possible determination of the groundwater flow location by using a specific geophysical prospecting procedure is based on the studies and knowledge of groundwater flows in the karstland of Yugoslavia. The procedure is as follows: a time-bomb thrown down a swallow-hole travels down to the groundwater flow and explodes at a predetermined moment. Elastic waves generated by the explosion propagate reaching the surface, where they are detected by properly arranged geophones that are connected with a standard seismic apparatus. By a specific graphical or arithmetical method the coordinates of the epicentre and hypocentre of the underground explosion can be worked out, and thus the location of the groundwater flow determined. By successive repetition of the experiment, i.e. by different time activation of underground explosion of the time-bomb, the location of the groundwater flow can be defined over longer paths. The success of the experiment depends upon a number of factors all of which must be met. If only one of them is overlooked, the experiment will not succeed. All this calls for great care both in preliminary work and in the course of the experiment. Substantial funds invested in and considerable time required in executing the experiment are multiply recompensed by the success of the experiment. The information obtained about the location of groundwater flows will directly affect the maximum operating pool adopted for hydro-electric power projects and the most favourable point in cutting off groundwater flows and bringing them to the surface for water-supply purposes.

Flow Rates in Two-Dimensional, Unsteady, Confined Groundwater Flow

Abstract: The theory of two-dimensional, unsteady, confined groundwater flow is first reviewed and then extended to allow unsteady flow rates to be computed from steady-state solutions. The difference between the steady and unsteady solutions is examined, and it is shown that the steady-state solution can be used to approximate the unsteady solution under certain special conditions.

Borehole logs from the Precambrian basement on Bornholm, eastern Denmark: geology and groundwater flow

Abstract: Bornholm is situated in the Sorgenfrei–Tornquist Zone that separates the North-West European Craton from the Baltic Shield and the East European Platform (Fig.1). The Precambrian basement of northern and eastern Bornholm consists of different granitic and gneissic Mesoproterozoic rocks that are dated to c. 1455 Ma (Waight et al. 2012). It appears from the age data that granitic magmatism, deformation and metamorphism occurred over a relatively short time period. The rocks contain abundant pegmatite and aplite bodies. More than 250 mafic dykes occur. The dykes were intruded during three Precambrian events at c. 1326 Ma, 1220 Ma, 950 Ma and during a Permian event at c. 300 Ma (Holm et al. 2010). The present study focuses on the Østermarie–Paradisbakke area north of Paradisbakkerne and deals with the Paradisbakke migmatite and part of the Bornholm gneiss. The aim of the study was to map the distribution of fractures in the rocks and determine the groundwater flow in these low-permeability rocks using outcrop data and borehole logs. The survey was part of an investigation of potential areas for disposal of radioactive waste from the Research Centre Risø area (Gravesen et al. 2011a, b, 2012, 2013).

Influence of Mountain Groundwater on Streamflow

Abstract: This investigation has determined the quantities of water stored as groundwater in the three watersheds in Utah, Logan River upstream from State Dam, South Fork Ogden River upstream from Huntsville, and Weber River upstream from Oakley. The proportion of the total streamflow contributed from this groundwater storage has been determined from past streamflow records, and the knowledge obtained from the analysis of groundwater contribution to streamflow has been utilized in developing water .supply forecasting techniques and pro.cedures. The first phase of the study dealt with theory and methods for separating the groundwater component from the total streamflow hydrograph. The method used for this separation is based upon the justified assumption that the effluent from groundwater is proportional to the volume of groundwater in storage at anytime and is a modification of the procedure applied by Troxell and others (1954) in a study of Mill Creek watershed in California. An equation giving the component of groundwater flow with parameters whose magnitudes are determined from past flow records results from this separation technique. By utilizing this equation to forecast the groundwater contribution on a continuous basis and for forecasting the surface runoff and interflow components by regression equations similar in form to those presently adopted by The Water Supply Forecast Division, Weather Bureau, ESSA, a forecasting procedure has been developed. This procedure's forecasting accuracy has been studied by examining how good past forecasts might have been and how the accuracy of these forecasts compares with those obtained by the currently used procedure. A considerable improvement in the accuracy of past forecasts was made possible by this technique. Consequently a third forecasting procedure (referred to in the discussions as Method 3) was developed by using the equation for the groundwater cbntribution and regression equations for the remaining portion of the streamflow. The latter regression equations were based on data from high watershed snow courses instead of the valley stations used in the presently adopted ESSA method. By separating the groundwater component of flow from the remaining flow in a forecasting procedure, approximately an additional 30 percent of the unexplained squared deviations between observed and forecasted volume of streamflow can be accounted for.