CHAPTER 3
ASR MODEL
This chapter focuses on two objectives. The first is to develop a quasi-analytical
model to predict the quality of water recovered during the operation of an ASR system.
The second objective is to validate the model by comparing simulation results of test
cases against a numerical simulation generated using MODFLOW-96 (Harbaugh and
McDonald, 1996a and 1996b) and MT3DMS (Zheng and Wang, 1999) packages.
Analytical Statement of Front Movement
The assumed conceptual model of an ASR system operating in homogeneous
confined aquifer is that of a fully screened well, uniformly recharging or extracting water
over the entire thickness of the aquifer, L. During extraction and recharge, stored water is
continuously under the influence of regional hydraulic gradient. It is conceptually
assumed that the regional aquifer flow is uniform and of a steady specific discharge q
that is proportional to the regional hydraulic gradient in an aquifer that is both
homogeneous and of constant thickness. Thus,
q= -Kd (3-1)
ds
in which K is the aquifer hydraulic conductivity [L/T]; (p is the hydraulic head [L], and s
is the primary direction of groundwater flow [L]. This natural gradient flow is considered
here to describe the horizontal displacement of water injected at the ASR well.