Piezometric surface

A water table piezometric surface contour map is presented in Figure 12.18. The elevation of this surface varies from 10 to 40 ft below sea level across the facility. Groundwater occurring under water table conditions is first encountered between 30 and 60 ft in depth. The regional direction of flow of shallow groundwater is toward a depression in the piezometric surface of the Gage aquifer located about... 

Figure 15.4 Morphology of the piezometric surface obtained from both surface and deep boreholes piezometers.

The oxidation of sulfide minerals appears to have been promoted by groundwater abstraction which has led to the lowering of the piezometric surface at a rate of —0.6 m yr since the 1950s, leading to partial dewatering of the confined aquifer. The high arsenic concentrations occur where the piezometric surface intersects, or lies close to, the sulfide cement horizon (Schreiber et al., 2000). 

The upper part of the Flowerpot contains as much as 60 m of interbedded salt and shale in the subsurface several kilometers to the south, but in the vicinity of the salt plains most of the salt is missing. The top of the Flowerpot salt is 10—15 m below the surface of the salt plains, and the depth, thickness and distribution of salt here are erratic. The salt beds contain some natural dissolution cavities that generally are less than 1 m high. The cavities contain brine under artesian conditions with a piezometric surface that locally is as much as several meters above the salt plains in the canyon floors. The Flowerpot Shale in the base of the canyons is fractured and acts as an aquitard that permits slow, upward flow of brine along joints and fracture planes. 

In all cases cited above, the energy needed to cause flow of the water is the hydrostatic head created in the recharge areas, with brine moving laterally and upward toward the piezometric surface. 

The piezometric surface described by Equation 7 can be discretised into a series of triangular facets as shown in Figure 1. The triangular facet E F G can be described by the equation... 

The equation of the block surface EFG acted on by this piece of the piezometric surface is... 

Figure 2a. Three-block rock slope system and piezometric surface.

Figure 2b. 3-D DDA results for three-block slope without piezometric surface.

Another case of sliding on a circular surface is considered. The block system in this case is shown in Figure 3a along with the piezometric surface. The bottom and left boundaries of the slope shown are fixed in their respective normal directions, and the other boundaries are free. The material constants for all the blocks are Young s modulus E... 

Figure 3a. Rock slope model with circular sliding surface and piezometric surface.

Anonymous (1971). C.V. Theis. Journal of the American Water Works Association 63(4) 32. Anonymous (1984). 1984 Robert E. Horton Medal to Charles V. Theis. Eos 65(28) 436-437. P Back, W., Herman, J.S. (1997). American hydrogeology at the millennium An annotated chronology of 100 most influential papers. Hydrogeology Journal 5(4) 37-50. P Theis, C.V. (1935). The relation between the lowering of the piezometric surface and the rate... 

However, In confined aquifers, water Is not yielded simply by gravity drainage from the pore space because there is no falling water table and the material remains saturated. Hence, other factors are involved regarding yield, such as consolidation of the aquifer and expansion of groundwater consequent upon lowering of the piezometric surface. Therefore, much less water is yielded by confined than unconfined aquifers. 

Table 2. Piezometric surfaces in the existing and designed slopes. 

Note Slope A—the existing slope, slope B— the designed slope, X, y—the coordinates on the piezometric surface. 

The natural piezometric surface of Kotlin aquifer changes due to groundwater consumption for industry and domestic use, which started at the end of 19th century. In 1941-1945 the active... 

---