Analysis of hydraulic capture zones and efficiency under time-varying flow and pumping conditions

Abstract

The capture zone of a groundwater extraction well can be defined as the portion of the aquifer from which the well draws its water. The accurate delineation of the capture zone is important in many groundwater remediation applications and in defining wellhead protection zones. Hydrologists often simplify the mathematical delineation of the capture zone by assuming the flow field is steady state and by using time-weighted average pumping rates and background gradients. However, this approach may not be adequate under actual transient flow conditions. A new approach to the estimation of the capture zone under time-varying flow is developed. Using the concept of capture efficiency, capture zones under time-varying flow conditions are compared to those computed using steady state averages. This thesis investigates the impact on the capture zone of intermittent pumping, time-varying background hydraulic gradients, and nearby wells pumping at both intermittent and constant rates.