The system present below is evaluated to determine the potential impact of proposed wells in both the shallow and deep aquifers. Stakeholders want to know the drawdowns and depletion of river discharge. Heads and stream discharge data are available to calibrate average annual steady conditions. Heterogeneities are likely to exist in such a setting, complicating the model, but a simple setting is used here to demonstrate modeling principles, while allowing the modeler to easily understand how the system works.

INITIAL ESTIMATES OF PARAMETER VALUES



USE CELLS THAT ARE 1000m x 1000m

K in layer 2 approximately = K2base * (1+ x (8/18000))
where x is the distance from the river, but this increase occurs in roughly a step-wise fashion every 2000 m due to the fact that layer 2 is 100% low K facies (we will call it the base K) beneath the river with gradually increasing K toward the hillside in approximately step wise fashion each 2000 meters.
e.g. >>>> K= 4x10-5 m2/s * 1 for first 2000m, 8x10-5 m2/s for next 2000 m, 36x10-5 m2/s for the 2000m section nearest the hillside

The basic parameter values for the system are as follows:
Recharge on the hillside is insignificant
VARIABLE VALUE DESCRIPTION
K1 3 x 10-4 m/s hydraulic conductivity of layer 1
K2base 4 x 10-5 m/s hydraulic conductivity of layer 2 below the river
KnearHill 3.6 x 10-4 m/s hydraulic conductivity of layer 2 near the hillside
KVtards 1 x 10-7 m/s hydraulic conductivity of the aquitard
KRB 1.2 x 10-3 m/s vertical hydraulic conductivity of the river bed
KHILL 2 x 10-9 m/s hydraulic conductivity of the hillside material
RCH1 2 x 10-8 m/s recharge near the river
RCH2 1 x 10-8 m/s recharge near the hillside
S1 1.3 x10-3 storage coefficient of layer 1
S2 2 x10-4 storage coefficient of layer 2
b1 50 m thickness of layer 1
b2 50 m thickness of layer 2
bz 10 m thickness of confining layer
bRB 10 m thickness of riverbed
LHILL HEAD 1500 m distance to observation in hill
LCELL = LRB 1000 m length of cell parallel to river
WRB 10 m equivalent width of river
not applicable 100 m river stage
not applicable 90 m equivalent river bottom
not applicable 350 m hillside head