Groundwater flow direction

Groundwater table gradient (natural flow direction). 

Fig. 16.28 Dissolved-phase concentration plumes showing 0.5, 0.15, and 0.015 (and 0.0015 for last four TCM dates) contours. The inner, darkest shade contour is the maximum concentration. The source is 1 m upgradient of the 1 X 1.5 m areal faces shown here, and groundwater flow directions relative to north (normal to source face) are also shown. Reprinted with permission from Rivett MO, Feenstra S (2005) Dissolution of an emplaced source of DNAPL in a natural aquifer setting. Environ Sci Technol 39 447 55. Copyright 2005 American Chemical Society...

Aldstadt et al. described the determination of U in groundwater using a FI system with a TRU-Resin column coupled on-line to an ICP-MS. The system used three 2-position valves and a flow-reversal scheme to load the sample in one direction and elute in the reverse direction. The system provided an enrichment factor on the order of 30-fold compared to direct groundwater analysis. Separate elution of Pu and Th in a group prior to eluting U was also discussed. 

The level of the water in a well is measured to provide data for groundwater flow direction calculations and to calculate purge volumes required for a particular well. If a low-flow sampling protocol is used, the water level is also measured during pumping to ensure that there is minimal drawdown of the stagnant water column. 

Automated water-level measurement can be achieved by deploying pressure transducers that can be set to log data as frequently as every second if required. Loggers also record temperature and are able to compensate for altitude, water density, temperature and barometric pressure. These are routinely used when undertaking hydraulic tests on a well but are also useful to provide accurate, regular, longterm water level data and are invaluable for groundwater flow direction calculations. 

Advection is the transport of dissolved contaminant mass due to the bulk flow of groundwater, and is by far the most dominant mass transport process [2]. Thus, if one understands the groundwater flow system, one can predict how advection will transport dissolved contaminant mass. The speed and direction of groundwater flow may be characterized by the average linear velocity vector (v). The average linear velocity of a fluid flowing in a porous medium is determined using Darcy s Law [2] ... 

Fig. 2.19 A more detailed cross-section of the U-shape model area shown in Fig. 2.18 (condensing several figures of Toth, 1963, 1995). Groundwater flow paths deduced by the U-shape flow paths model are marked with arrows denoting flow directions. Three flow zones have been concluded local, intermediate, and regional, with alternating points of discharge (e.g., points A, B, D, F) and points of recharge (points C, E, G, H). The symmetry of the suggested flow lines, centered in the modeled box, reveals that they are a direct outcome of the assumption of the three impermeable flow planes.

Fig. 3.3 Factors controlling the flow direction of groundwater. (I) porous rock water direction is determined by topographic gradients alone (II) a tilted impervious rock bed deviates direction of water flow.

In the saturated zone the chloride concentration stays constant unless mixing of different water types occurs. A chloride concentration that decreases along a suggested groundwater flow direction indicates the suggested flow path model is not valid, as there is no process that can reduce... 

This system has been studied by Geyh and Wirth (1980). Figure 11.28 depicts the outcrop areas and the suggested groundwater flow direction. The 14C data reveal a sharp discontinuity of waters, with 32-70 pmc near the outcrops (A) and 2-7 pmc in the downflow section of the confined aquifer (B)—another example of lack of hydraulic communication between adjacent phreatic and confined systems. 

Fig. 11.28 14C values (pmc) in wells of the Sokoto basin, northern Nigeria. The arrow denotes the orginally suggested groundwater flow direction. The phreatic aquifer (A) coincides with the rock outcrops (stippled) and has high 14C values. An abrupt drop in 14C values is observed in the adjacent confined section of the system (B). (Data from Geyh and Wirth, 1980.)... 

Discussion. Looking at the water table elevations (Fig. 16.18) and the analytical results (Table 16.4), which wells may be regarded as representing uncontaminated groundwater Well 401 is upstream (Fig. 16.18), and on this basis alone should be uncontaminated. This is confirmed by the observation that the water in this well is lowest in Cl, NH4, COD, and TDS. Wells 404, 405, 406, 415, 416, and 417 are closest to the landfill and in the groundwater flow direction (Fig. 16.18). Therefore, they should to be suspected of contamination. The data reveal that these wells, and additional wells that are located downflow, are indeed contaminated. 

The sources of water and solutes for saline lake brines are mainly direct precipitation, associated surface flow, or groundwater (Figures 2 and 3). Groundwater can be derived from the local or regional meteoric system, interstitial water of sediments, or deep basinal or hydrothermal... 

Figure 14 The conceptual hydrogeological model of the Palmottu, Finland research site. The arrows indicate the measured flow directions, the distribution of groundwater types is shown, and some of the measured and inferred geochemical processes are also indicated (Blomqvist et al., 2000) (reproduced by permission of European Commission from The Palmottu Natural Analogue Project, Phase II Transport of Radionuclides in a Natural Flow...

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