Potentiometric surface

Fig. 1. Aquifers and monitoring wells where denotes the well screen and Hthe water-filled space in the monitoring well. (—) denotes the water table level, (—), the potentiometric surface, and ( ) the ground surface. Terms are discussed in text.

Baildown testing is a widely used field method to evaluate the actual thickness of LNAPL product in a monitoring well. Baildown testing involves the rapid removal of fluids from the well, and subsequent monitoring of fluid levels, both the water level or potentiometric surface (oil-water interface) and NAPL level (oil-air interface), with time. Such testing was originally used as a preliminary field method to evaluate recoverability of NAPLs and thus to determine potential locations for recovery wells. All monitoring wells at a site that exhibited a measurable thickness of LNAPL were typically tested. Whether or not all the LNAPL product could be... 

The recharge test has the advantage of yielding results regardless of the location of the mobile LNAPL-water interface in relation to the potentiometric surface. Although more accurate than a baildown test, it is also more complicated to conduct. 

Cherkauer (1980) monitored groundwater near a fly ash site, operating 8 years for the Port Washington Power Plant in southeastern Wisconsin, USA. The maps in Fig. 16.16 show the potentiometric surface contours and direction of flow, TDS, S04, Ca, and HC03, along with the positions of the monitoring piezometers. The ash leachate contained various metals that were not observed in the monitoring wells, except some iron. 

Figure 4 Map showing the prepumping potentiometric surface of the Floridan aquifer and locations of wells shown...

Regionally confined aquifer Shape and position of groundwater potentiometric surface are independent of configuration shown portion of basin s ground surface... 

Figure 8.5 Relation between hypsographic curve of the ground surface and that of the groundwater potentiometric surface of regionally confined and unconfined aquifers (after Tdth, 1978, Water Resources Research, Vol. 14, no. 5, Fig. 7, p. 813. Copyright ( ) 1978 by the American Geophysical Union).

A regional picture of changes in groundwater pressure with depth and groundwater potential with depth in combination with potentiometric surfaces constructed for different hydrogeological units permit the delineation of the vertical and lateral extent of the shallow, intermediate and deep subsystems of burial-induced flow in the studied area. 

Because residential wells are often open to both the St. Peter aquifer and the overlying confining unit, water levels do not provide an accurate measurement of hydraulic head in the aquifer. Therefore, the water levels measured in residential wells are termed static water levels . This is distinguished from the potentiometric surface , defined by water levels in wells open only to the confined St. Peter and deep sandstone aquifers. 

The major source of recharge of the Cambro-Ordovician aquifer is the area around the Ozark Mountains of southwestern Missouri. The generalized potentiometric surface for the Cambro-Ordovician aquifer is shown in Fig. 

Because of the paucity of wells in the more saline area, the configuration of the potentiometric surface presently is not well defined, although there is some evidence for a very gentle southward to southwestward plunging... 

Fig. 2. The potentiometric surface of the Cambro-Ordovician aquifer in the Tri-State region with sample locations. (Potentiometric data provided by the Kansas Geological Survey.)...

The hydraulic-head distributions are determined mainly from extrapolated drill-stem pressure data (Earlougher, 1977). In all cases, test results have been rejected if the initial and final maximum reservoir pressures differed by more than 5%. Pressure determinations are expressed as equivalent freshwater hydraulic head in meters above sea level at 15.6°C. Maps of the potentiometric surfaces for eight major geological units have been prepared from this data set (Fig. 4). Because potentials may have been influenced by gas and oil production (or groundwater in the case of the Milk River aquifer), the location of major fields is indicated on the figure. 

A preliminary map of departure from equilibrium with respect to dolomite is also shown in Figure 2. The area of undersaturation is larger for dolomite than for calcite. Because the dolomite value is exactly one half that of calcite, it follows that in order for a water that is in equilibrium with calcite to become saturated with respect to dolomite, it is only necessary for the magnesium concentration to equal the calcium concentration (12, 13, 14). The area of recharge and the area of highest potentiometric surface show that the water is undersaturated with respect to dolomite downgradient, it progressively attains equilibrium with dolomite and eventually becomes supersaturated. 

The results of calculating entropy production from head values ranging between elevations of 40 meters to about sea level are shown on Figure 4. Note that the high point on the potentiometric surface is designated as having a zero entropy level. This is the input boundary of the system, and by our definition, the entropy of the water attributed to position is zero at this point. Therefore in order to depict the entropy increase attributed to downgradient flow, the equation was modified to... 

As the water flows down the potentiometric surface, entropy is progressively produced by this physical process to about 300 mcal/kg/°K. 

Figure 1.4-3 Potentiometric Surface and Groundwater Flow Directions...

Lefebvre J (1957) Potentiometric surface method. Ill Application to the study of compounds of malic and citric acids with copper. J Chim Phys PCB 54 581-600 Ekstrom LG, Olin A (1979) On the complex formation between lead(II) and citrate ions in acid, neutral and weakly alkaline solution. Chemica Scripta 13 10-15 Heinz E (1951) Investigations on complex compounds of calcium. Biochem Z 321 314-342... 

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