466
Upper Mississippi River Adaptive Environmental Assessment
erate with a user-friendly graphical interface, and
require a Pentium computer using a Windows 95
or NT operating system.
31.4.1 River System Model
The river system model simulates the movement of
water and sediment between navigation pools, incorporating the operating constraints of dams, natural seasonal and interannual variability in discharge, and sediment loads delivered from major
tributaries. The model was designed to operate over
pools 2 through 26.
However, due to constraints of time, data, and
budget during development, the initial model operates only on pools 2 through 10, the pools within
the Corps of Engineers' St. Paul District. Key elements of this model evaluate the movement of water, including stage and discharge, and calculate
sediment dynamics. Current and planned model
outputs include changes in stage, sediment storage
and outflow, area of different habitat types, tonnage of barge traffic, an indicator of recreational
uses, dredging requirements, and an indicator of riparian zone area flooded. Issues raised by workshop participants that are currently outside the
scope of this model include exotic species, water
quality, and contaminants. The model does not attempt to quantify in monetary terms the public costs
and benefits provided by the environment.
The model operates on a daily time step and is
driven by historical data on discharge and sediment
input from 1959 to 1995. Calculation of sediment
input from tributaries is based on tributary discharge
and pool water levels. The model allows the user
to set a stage height policy on a monthly basis over
the year for one or more pools. For each day in
each pool, the model calculates the daily inflow,
adds that value to the current water volume of the
pool, and then calculates a new water elevation for
the pool. The water elevation is compared to a userdefined target elevation and water is released as
needed, within the operational constraints of the
dam, to reach the target level. The amount of sediment exported from a pool is based primarily on
water velocity in the main channel, which is a function of discharge and water depth. The model assumes that the channel depth will be maintained at
12 feet; thus all new sediment stored in the channel is assumed to be dredged annually. A navigation-economic component predicts shipping potential in each pool on a monthly time step based
on the average channel depth over the month and
operating constraints of the lock and dam system.
31.4.2 Pool Model
The pool model covers the area between two successive dams, commonly referred to as a pool, with
a spatial grid using lOO-meter cells. The model
evaluates changes in timing and duration of water
levels, flows, and sediment deposition and resuspension among cells, which are then linked to distribution of floodplain topography and vegetation
communities. Currently, the model simulates pool
8, for which the 100-meter grid results in about
30,000 cells. A vegetation module models changes
in vegetation types, ranging from open water to upland forest. Plant growth and mortality are linked
to water depth, turbidity, and duration of flooding.
Regeneration and establishment of plants are related to available seed sources, soil saturation, and
number of years of dry or wet stress. A stand-alone
submodel was also developed that models relative
abundance of various fish species based on different combinations of water depth and current velocity as determined by the pool model.
The user can modify information on land and
water elevations within a pool (e.g., to incorporate
levees or deep holes) by changing values on maps
representing initial conditions. Water flows from
upstream and tributaries can be modeled as historical flows (from 1959 to 1995), as a specific scenario defined by the user, or as natural system flows
that operate as if no dams were present. The user
can also modify any parameters for flow and sediment dynamics, as well as parameters for vegetation and fish response.
31.5 Assessing the Model:
Workshop 2
The first-cut simulation model was developed
based on the December 1995 workshop, with data
provided by a variety of government agencies and
guidance from the UMR AEA steering committee.
The steering committee held a small technical review session in August 1996, at which an initial
version of the model was assessed and the modeling team was asked to make some relatively modest modifications. A second workshop was then
held on January 15-17, 1997. Approximately 45
participants, representing a wide range of organizations, disciplines, and experiences, were asked to
review the first-cut simulation model, recommend
refinements, and consider how they would like to
use the model to explore various management scenarios. A user's guide describing the first-cut sim-
Upper Mississippi River Adaptive Environmental Assessment
erate with a user-friendly graphical interface, and
require a Pentium computer using a Windows 95
or NT operating system.
31.4.1 River System Model
The river system model simulates the movement of
water and sediment between navigation pools, incorporating the operating constraints of dams, natural seasonal and interannual variability in discharge, and sediment loads delivered from major
tributaries. The model was designed to operate over
pools 2 through 26.
However, due to constraints of time, data, and
budget during development, the initial model operates only on pools 2 through 10, the pools within
the Corps of Engineers' St. Paul District. Key elements of this model evaluate the movement of water, including stage and discharge, and calculate
sediment dynamics. Current and planned model
outputs include changes in stage, sediment storage
and outflow, area of different habitat types, tonnage of barge traffic, an indicator of recreational
uses, dredging requirements, and an indicator of riparian zone area flooded. Issues raised by workshop participants that are currently outside the
scope of this model include exotic species, water
quality, and contaminants. The model does not attempt to quantify in monetary terms the public costs
and benefits provided by the environment.
The model operates on a daily time step and is
driven by historical data on discharge and sediment
input from 1959 to 1995. Calculation of sediment
input from tributaries is based on tributary discharge
and pool water levels. The model allows the user
to set a stage height policy on a monthly basis over
the year for one or more pools. For each day in
each pool, the model calculates the daily inflow,
adds that value to the current water volume of the
pool, and then calculates a new water elevation for
the pool. The water elevation is compared to a userdefined target elevation and water is released as
needed, within the operational constraints of the
dam, to reach the target level. The amount of sediment exported from a pool is based primarily on
water velocity in the main channel, which is a function of discharge and water depth. The model assumes that the channel depth will be maintained at
12 feet; thus all new sediment stored in the channel is assumed to be dredged annually. A navigation-economic component predicts shipping potential in each pool on a monthly time step based
on the average channel depth over the month and
operating constraints of the lock and dam system.
31.4.2 Pool Model
The pool model covers the area between two successive dams, commonly referred to as a pool, with
a spatial grid using lOO-meter cells. The model
evaluates changes in timing and duration of water
levels, flows, and sediment deposition and resuspension among cells, which are then linked to distribution of floodplain topography and vegetation
communities. Currently, the model simulates pool
8, for which the 100-meter grid results in about
30,000 cells. A vegetation module models changes
in vegetation types, ranging from open water to upland forest. Plant growth and mortality are linked
to water depth, turbidity, and duration of flooding.
Regeneration and establishment of plants are related to available seed sources, soil saturation, and
number of years of dry or wet stress. A stand-alone
submodel was also developed that models relative
abundance of various fish species based on different combinations of water depth and current velocity as determined by the pool model.
The user can modify information on land and
water elevations within a pool (e.g., to incorporate
levees or deep holes) by changing values on maps
representing initial conditions. Water flows from
upstream and tributaries can be modeled as historical flows (from 1959 to 1995), as a specific scenario defined by the user, or as natural system flows
that operate as if no dams were present. The user
can also modify any parameters for flow and sediment dynamics, as well as parameters for vegetation and fish response.
31.5 Assessing the Model:
Workshop 2
The first-cut simulation model was developed
based on the December 1995 workshop, with data
provided by a variety of government agencies and
guidance from the UMR AEA steering committee.
The steering committee held a small technical review session in August 1996, at which an initial
version of the model was assessed and the modeling team was asked to make some relatively modest modifications. A second workshop was then
held on January 15-17, 1997. Approximately 45
participants, representing a wide range of organizations, disciplines, and experiences, were asked to
review the first-cut simulation model, recommend
refinements, and consider how they would like to
use the model to explore various management scenarios. A user's guide describing the first-cut sim-