Detecting drawdowns masked by environmental stresses with water-level models.
Bottom Line: Pumping signals are generated with Theis models, where the pumping schedule is translated into water-level change with the Theis solution.This approach closely matched drawdowns simulated with a complex three-dimensional, hypothetical model and reasonably estimated drawdowns from an aquifer test conducted in a complex hydrogeologic system.Pumping-induced changes generated with a numerical model and analytical Theis model agreed (RMS as low as 0.007 m) in cases where pumping signals traveled more than 1 km across confining units and fault structures.
Affiliation: US Geological Survey, 2730 N Deer Run Rd, Carson City, NV 89701, USA.Show MeSH
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Mentions: where t is the time since pumping commenced, Q is the pumping rate [L3/T], T is the transmissivity [L2/T], W(u) is the exponential integral solution, u is dimensionless time, r is the radial distance from the pumping well [L], and S is the storage coefficient [dimensionless]. Variable-rate pumping schedules (Figure 2) and multiple pumping wells can be simulated by superimposing multiple Theis solutions in time and space, respectively (Halford et al. 2012). Similar to the amplitude and phase shift of a moving average, a pumping signal generated with the Theis solution is adjusted by changing transmissivity (T) and storage coefficient (S) in Equation 3.
Affiliation: US Geological Survey, 2730 N Deer Run Rd, Carson City, NV 89701, USA.