On Modeling Philosophies

Capture-Rates and Directions of Groundwater Flow Don't Matter!

“…Durbin et al (2008) show how to represent nonlinear head‐dependent boundaries in numerical‐superposition models. For a perspective on groundwater modeling using flow and superposition modes, see Bredehoeft (2006). The disadvantage in using complex flow models is that pumping‐induced changes Δ R and Δ D must be determined by subtracting computed budget quantities that commonly are many orders of magnitude larger than the rate of capture for any given time.…”

Groundwater: Recharge is Not the Whole Story

“…Groundwater systems, because they both store and transmit water, behave with a diffusive response (Bredehoeft 2006). The differential equations that describe groundwater flow are similar to equations for heat and electricity, and in simple situations can be solved by classical methods.…”

Application of Superposition with Nonlinear Head‐Dependent Fluxes

“…The principle of superposition is a simple concept that is used routinely to solve ground water problems (Longenbaugh 1967; Pinder and Bredehoeft 1968; Walton 1970; Young and Bredehoeft 1972; Reilly et al 1987; Hubbell et al 1997; Batu 1998; Kendy and Bredehoeft 2006; Bredehoeft 2006). Based on this principle, a complex problem can be separated into parts, individual solutions can be derived for the respective parts, and the solution to the original complex problem is simply the combination of the solutions for the parts.…”

“…The management of capture typically is the essential component for the overall management of the ground water system. As described by Bredehoeft (2006), capture can be quantified by two modeling approaches. The first approach is to use a model of the overall ground water system.…”

“…The second approach is to use superposition to simulate capture directly, which does not require domain‐wide knowledge of the steady‐state heads or the recharge and pumping producing those heads. While the examples cited by Bredehoeft (2006) represent linear ground water systems, capture of nonlinear head‐dependent fluxes can also be simulated using superposition.…”