Reservoir Basics

Flow includes a reservoir model based very closely on the ResSIM model developed by the USACE. The purpose of this model is to represent, to the greatest extent possible, ResSIM within the Envision framework.  It is built around two central concepts - defining individual reservoirs in the system, and defining control points, points in the stream network reporeseting points whose flow rates influence  reservoir operations.

document describing the technical details of the ResSIM model employed in Envision is provided here

Like other aspects of Flow, reservoirs are specified in the Flow Xml input file, as well as additional external reservoir files, defined within the <reservoirs> tag. Within this tag, individual reserrvoirs are defined with <reservoir> tags, one for each reservoir defined in the system, and individual control points are defined with <control_point> tags. Attributes for the <reservoir> and <control_point> tags are defined below.  In general, the Xml for specifying reservoirs uses the following general form:

 

Within {myflowmodel}.xml

<flow_model>
    ...
    <reservoirs col="ResIDCol" >
      <reservoir name="Res1" ... />
        ...
      <reservoir name="ResN" ... />
        
      <controlPoint name="CP for Res1" ... />
        ...
      <controlPoint name="CO for ResN" ... />
    </reservoirs>
    ...
</flow_model>

Specifying Reservoirs in the Flow Xml Input file

Tags used to define reservoirs and control points for Flow are defined below. The tags include:

• reservoirs
• reservoir
• controlPoint

<reservoirs>

Attribute	Description	Default Value	Required	Example Usage
col	column in the Streams coverage containing the reservoir ID for each stream reach that contains a reservoir		Yes	RES_ID

 

<reservoir>

Attribute	Description	Default Value	Required	Example Usage
name	Reservoir name		Yes	My Reservoir
id	Unique Reservoir ID		Yes	any integer
path	Path of reservoirs main directory, where reservoir input files are stored.
initVolume	Initial volume, set to lower value of flood control pool, m3
area_vol_curve	Filename of text file with area, volume and pool elevation relationships
av_dir	Directory containing area volume curves
rule_curve	Filename of text file with rule curve information
rc_dir	Directory containing rule curves
buffer_zone	Filename of text file containing the buffer zone curve values
composite_rc	Filename of text file with release capacity information
re_dir	Directory containing release capacity curves
rp_dir	Directory containing rule priority file
rule_priorities	Filename of text file with rule priority information, by zone (e.g. flood control, conservation, buffer)
cp_dir	Directory containing text files with control point constraints (accessed by multiple reservoirs)
minOutflow	Minimum outflow (cms)
maxVolume	Maximum reservoir volume (m3)
td_elev	Top of dam elevation (m)
inactive_elev	Inactive elevation (m)
fc1_elev	Flood control elev (m) – only if more than 1 flood control zone exists
fc2_elev	Flood control elev (m) – only if more than 2 flood control zones exist
fc3_elev	Flood control elev (m) – only if more than 3 flood control zones exist
maxPowerFlow	Physical maximum flow that can be passed through the powerhouse
ro_rc	Filename of text file containing capacity information for regulating outlets (typically dependent on pool elevation).
spillway_rc	Filename of text file containing capacity information for spillway outlets (typically dependent on pool elevation).
tailwater_elev	Elevation of tailwater (m). Used in hydropower calculations.
turbine efficiency	Reported turbine efficiency (values taken directly from ResSIM). Used in hydropower calculations.
p_maintainence	Probability of maintenanceename
ressim_output_f	Filename of file containing flow output from ResSIM model (used for model comparison purposes)
ressim_output_r	Filename of file containing rule output from ResSIM model (used for model comparison purposes)

<controlPoint>

Attribute	Description	Default Value	Required	Example Usage
name	Name of control point (names used directly from ResSIM)
Id	Unique numerical ID
Dir	Directory where the text file describing constraints at the control point is located
Control_point	Name of the text file describing constraints
Location	COMID of the reach within which the control point is located
Reservoirs	A list of all the reservoir that this particular control point influences

Defining Reservoir Operations in Flow/RESSIM-Lite

Operating parameters for RESSIM-Lite are defined using a set of CSV files. The operating parameters are organized using four files:

• Area Capacity Curves
• Reservoir Rule Curve
• Release Capacity Curve
• Rule Priority Table

Rule Priority Table

The rule priority table contains a list of constraints, from lowest priority on top to highest priority on the bottom, for each operation zone within the reservoir. The zones are organized as follows:

Zone 0	Top of Dam
Zone 1	Flood Control
Zone 2	Conservation Zone
Zone 3	Buffer Zone
Zone 4	Alternative Flood Control 1
Zone 5	Alternative Flood Control 2

Below is an example rule priority file (CSV format): Min_Daily_MaxD_BiOp.csv Min_Foster_min_for_Buffer_Zone.csvPow_Max_FOS_power_release.csv     

0	1	2	3	4
Max_Drafting.csv	Min_Daily_MaxD_BiOp.csv	cp_Max_bf_Jefferson_23780423.csv	MaxD_Decreasing_Rate_of_Change.csv
MaxD_FloodDcrsRate_Fostr.csv	MaxI_Increasing_Rate_of_Change.csv	cp_Max_bf_Waterloo_23785687.csv	MaxI_Increasing_Rate_of_Change.csv
MaxI_FloodIncrsRate_Fostr.csv	Max_Winter_and_Con.csv	cp_Max_bf_Salem_23791083.csv	Release_10000cfs.csv
Pow_Max_FOS_power_release.csv	Spill_Min_Fish_Weir.csv	Min_Daily_MaxD_BiOp.csv	Spill_Min_Fish_Weir.csv
	Pow_Max_FOS_power_release.csv	MaxI_IncrseRampingRate_Fostr.csv	Pow_Max_FOS_power_release.csv
		Min_ConservFlow_Fostr.csv
		Max_Winter_and_Con.csv
		Spill_Min_Fish_Weir.csv
		Pow_Max_FOS_power_release.csv

The zone number is in the first row, and the names of the text files corresponding to each constraint are located in a list below. Each column in the table above is stored as an array of objects called ResConstraints within an object called a ZoneInfo. A ZoneInfoArray for each reservoir stores the array of ZoneInfo objects (5 in the example above). Each ResConstraint is a text file with allowable reservoir release values given 1 or 2 variables. There are 8 types of constraints described in the table below:

Rule type	File header	Constraint Type
Minimum	Min_	1
Maximum	Max_	2
Increasing Rate	MaxI_	3
Decreasing Rate	MaxD_	4
Control Point	cp_	5
Power Plant rule (gate specific)	Pow_	6
Regulating Outlet rule (gate specific)	RO_	7
Spillway Rule (gate specific)	Spill_	8

Defining Reservoir Operations in Flow/RESSIM-Lite

Operating parameters for RESSIM-Lite are defined using a set of CSV files. The operating parameters are organized using four files:

• Area Capacity Curves
• Reservoir Rule Curve
• Release Capacity Curve
• Rule Priority Table

These files are defined below.

Rule Priority File

The Rule Priority File