                               Readme.txt

This file describes the updated Salt Rive Valley groundwater flow model input files.
The Name File is used to run the SRV model and contains the input and output files 
used in the model simulation. The Name file is copied below.

Name File:

#  MODFLOW 2000 Name file for the
#  SRV transient model 1983 - 2002
#
#  Output Files
GLOBAL          5   srv83_02.GLO 
LIST            6   srv83_02.lst
DATA           30   srv83_02heds.out
DATA(binary)   39   srv83_02bud.out
#
# Observation Files
#
OBS     3   srv02.obs
HOB     4   srv02.hob
#
#  Data Input Files
#
DIS     7   srv83_02.dis
BAS6   10   srv83_02.ba6
BCF6   11   srv83_02.bc6
WEL    12   srv83_02.wel
EVT    15   srv83_02.evt
RCH    18   srv83_02.rch
PCG    19   srv83_02.pcg
OC     22   srv83_02.oc
STR    23   srv83_02.str

The data output file srv83-02heds.out contain the head output from the model
The data output file srv83-02bud.out contain the budget output from the model

The observation file, srv02.obs, contains the 2002 observed water levels (heads)
used as calibration targets for the model.  MODFLOW uses the observed heads and 
their weighting values to analyze the model residuals and generate a report that
describing the results of the model calibration.

A brief description of each model input file is provided below.

Discretization File (srv83_02.dis):
Defines the number of model layers, rows, and columns (3 layers, 62 rows, 90 columns),
the model length unites (feet), the model time unites (days), the number and length of
stress periods (20 years and 365 days).  It also assigns the thickness of model layers
by defining the model surface elevation, bottom of layer 1 (Upper Alluvial Unit), 
bottom of layer 2 (Middle Alluvial Unit), and bottom of layer 3 (Lower Alluvial Unit)
for every active cell.

Basic File (srv83_02.ba6):
Defines the active model array and the starting heads.  




Block-Centered Flow File (BCF) (srv83_02.bc6):
Defines the model layer type, turns on the rewetting capability, and assigns
hydraulic properties to each active model cell.  The layer type flag in the 
BCF package defines how the transmissivity for each model cell is calculated.  
The hydraulic conductivity, primary and secondary storage (when applicable), 
and the vertical hydraulic conductivity (Vcont) are assigned using the BCF package.  
Layer 1 is simulated as an unconfined (Ltype 1) layer with transmissivity values 
that are calculated using the saturated thickness and hydraulic conductivity.  
The storage value, specific yield, is assigned to each cell.  Layer 2 and 3 are 
defined as confined/unconfined (Ltype 3) layers.  Transmissivity values are calculated
from saturated thickness and hydraulic conductivity and the storage value may 
alternate between confined (storage coefficient) and unconfined (specific yield) 
values.  The rewetting capability of the BCF6 package is set active.    

Well File (srv83_02.wel):
Simulates pumpage, recharge, and groundwater flux into and out of the model for
each stress period. Pumpage values are annualized (365 day stress periods) and 
have units of cubic feet per day (model time units are days and length units are
feet).  Negative values represent well pumpage that is distributed by cell and 
layer or estimated groundwater underflow out of the model along selected 
model boundaries.  Positive pumpage values represent specified mountain front
recharge, ephemeral stream recharge, and underflow into the model along some of 
the model boundaries.  

Recharge File (srv83_02.rch):
The Recharge file applies areal recharge to cells within the model.  The source 
of areal recharge includes natural recharge (mountain-front and stream infiltration)
and incidental recharge (agricultural, artificial, and urban).  Stream infiltration
includes flood recharge on the Salt, Gila, and Agua Fria Rivers and Cave and Queen 
Creeks.  Incidental recharge source include agricultural recharge, groundwater 
recharge facilities such as GRUSP, urban and lake recharge, and canal seepage.  
Recharge values are assigned for each stress period using an array and are distributed 
to the highest active cell in each vertical column.  The individual cell values 
represent annual recharge volumes and are multiplied by a constant (4.2810E-06) 
within MODFLOW to convert the annual volume to a daily rate.  

Evapotranspiration File (srv83_02.evt):
 The Evapotranspiration file simulated evapotranspiration from plants that have 
their roots in the water table and surface evaporation.  The same file used in 
the initial SRV model simulation.

Stream File (srv83_02.str):
The Stream-Flow Routing (STR) file replaces the River (RIV) file used in earlier
versions of the SRV model.  The entire length of the Salt and Gila Rivers within 
the model boundaries is now simulated.  Also simulated are the Agua Fria, Hassayampa, 
and Santa Cruz Rivers, and the Buckeye Irrigation Canal.  The latter is simulated 
as a diversion that receives its flow from the Gila River.  The starting base flows 
on all the rivers are set to zero from 1983-2002.  Discharges from the 23rd and 91st 
avenue Waste Water Treatment Plants are simulated as assigned tributary flow into 
the Salt River.
