Most maps or cross sections show a number of flow tubes to represent general groundwater flow conditions (Figure 77a). Potentiometric maps can have an infinite number of flow tubes as there are as many tubes as there are pairs of flow lines. Conceptually, the discharge through flow tubes is constant under steady state conditions. As presented in the previous sub sections, a set of parallel flow lines encompasses a flow tube. However, it may be referred to as a potentiometric map, water table map or a flow net. When flow lines are added to sets of equipotential lines the potentiometric map becomes a flow net (Figure 77). Strictly speaking, a potentiometric map or cross section is a representation of the distribution of head (head values and equipotential lines). Potentiometric Maps, Cross Sections and Flow Nets Challenges to presenting, developing and interpreting potentiometric information are included in this section. Interpretation of the mapped gradients and behavior of groundwater flow can shed light on the aquifer conditions including changes in hydraulic conductivity, aquifer thickness, and can be used to identify the location of recharge and discharge areas. Head measurements obtained from field investigations are used to interpret horizontal and vertical groundwater flow directions and rates, and the potential for exchange between aquifers and aquitards. Developing Potentiometric Maps and Cross SectionsĪ key component of evaluating groundwater flow conditions is the construction of potentiometric maps of unconfined and confined aquifers and, in complex groundwater systems, representations of multiple aquifers and aquitards. In most cases, it is necessary to determine the groundwater flow system behavior under both steady-state and transient conditions, and to prepare a water budget. Meeting these goals requires an understanding of the geologic framework forming the aquifer system, physical and hydraulic boundary conditions, as well as the locations, rates and timing of groundwater sources (e.g., recharge, stream leakage) and sinks (e.g., pumping, evapotranspiration). Hydrogeologic investigations have specific goals defined to answer questions related to applied groundwater projects or to meet research objectives.
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