Final Project I. Calibration II.Drawdown Prediction III.Particle Tracking IV.Presentation of Results

Final Project - Conceptual Model From USGS Ground Water Atlas (HA 730)

Great Basin

Our basin belongs to this type

Playa Recharge Conceptual model of the flow system for our basin

Recharge along the sides of the valley from mountain runnoff Recharge is zero elsewhere Rabbit Brush Valley

Playa Playa fringe

MODEL DESIGN

Layer 3 – variable bottom Layer 2 Layer 1 50 ft gap represents confining bed 3 model layers in our basin; the confining bed is included indirectly using MODFLOWs quasi 3D option Datum The problem of dry cells and re-saturation

DATUM Layer 3 has a variable bottom elevation 50 ft gap between layers 2 & 3 represents the confining bed

from GWV Layer 1 = type 1 Layer 2, 3 = type 3

Leakance between layers where each Layer belongs to a different hydrogeologic unit See A&W, p. 81 Layer 1 Leakance (i.e., leakance between layers 1 & 2)

Leakance “Quasi 3D” model See A&W, p. 81 Layer 2 Leakance (i.e., leakance between layers 2 &3

from GWV

Choose Kz of aquitard

You input Kz of the aquitard in the leakance array in the properties menu.

Properties>top elevation (layer 1) (We will need these top elevations For the ET Package.)

Playa Recharge Conceptual Model of the flow system ET

The EVT package (for evapotranspiration) represents a head dependent boundary condition. (In GwVistas, however, ET is entered under the properties menu and not under the BC menu. Other head dependent boundary conditions are entered under the BC menu.) Review: The general expression for head dependent boundary conditions is: q = -K b (h b – h)/b For the EVT package, this expression is written: q ET = R ETM [h - (h s -d)] / d

h Q ET = R ETM  x  y [h - (h s -d)] / d ET d hshs extinction depth R ETM is the maximum ET rate, which occurs when h = h s. for h  h s -d and h < h s MODFLOW’s EVT Package

Q ET = 0 below the extinction depth. Q ET = Q ETM at the land surface.

Properties>top elevation (layer 1)

Properties>Evapotranspiration (layer 1)

Final Project I. Calibration II.Drawdown Prediction III.Particle Tracking IV.Presentation of Results

You will be given a set of head and ET targets for Rabbit Brush Valley. Please see the instructions for the Final Project on the course web page. You should also download a gwv file from the course web page. This gwv file contains an initial parameter set and the head targets, i.e, the “observed head values”.