[Bold terms are FEQ or FEQUTL output that are not echoed from input terms.]
AL : Cross-sectional area of flow in the steady-flow computations at the station. The steady-flow computations proceed from downstream to upstream and are printed in that order.
AREA : Cross-sectional area of flow in the unsteady-flow computations. The unsteady- flow results are printed from upstream to downstream in the output.
BACKWATER (4): Water surface of stream raised above its normal level by a natural or artificial obstruction.
BC : Balance computation summary label. A system-wide water-volume balance is maintained by tracking the inflows and outflows at the boundaries of the system and comparing the sum to the change in storage within the system. If the relative error in the balance, R, is larger than a fraction of 1 percent, then an error is likely.
BOTM ELEV: Bottom elevation for free nodes and level-pool reservoirs in the summary of extremes at the end of a simulated event. The elevation may be an actual bottom elevation or it may be the datum for the depth variable associated with the free node or level-pool reservoir. In most cases, it is convenient to make the elevation and depth the same value for the free and level-pool reservoir nodes; thus, the bottom elevation is zero.
BOUNDARY CONDITIONS: The stage, discharge, or rating curve data needed at one or more terminating branches of an unsteady-flow model in order to solve the equations of flow for the system.
BRANCH: The FEQ representation of a reach of a channel or other watercourse between hydraulic features that cannot be represented by the governing equations for gradually varied flow.
BRA (iteration log): The branch number in which the maximum relative correction RCORECT occurred. If the branch number is zero, then the node number in the NODE column is an exterior node number or name; otherwise, the node number is the number of the node on the branch.
BRANCH NUMBER : Branch number of the output of detailed results for each time step.
BRANCH PONDING VOLUME: Volume of water ponded above a branch if the storm-sewer option is invoked by inputting CF and YC to represent the path for inflow and outflow of water from a storm sewer in the branch.
CHANNEL: A natural or artificial waterway that periodically or continuously contains moving water.
COMPUTATION TIME : Computer processing time spent to complete unsteady-flow computations including function table lookup, network matrix content, solving network matrix, updating variables, output of results, and so forth. Excludes the input processing and the initialization time.
CONVEYANCE : A measure of the flow carrying capacity of a channel section.
CROSS SECTION : A series of coordinates representing the elevations and distances of points across a stream channel, perpendicular to the direction of flow.
CSUR: The maximum relative change in storm-sewer surcharge storage for the system. See BRANCH PONDING VOLUME.
D (end of time step output) : Balance error in cubic feet or cubic meters. The balance error is computed by the equation D = S2 + Q - S1 - I , where S2 is the water volume in the system at the current time; Q is the sum of the outflows from the start of the event to the current time; S1 is the water volume in the system at the start of the event; and I is the sum of the inflows from the start of the simulated event to the current time.
DEPTH (each time step): Maximum water depth for the time step. The water depth is the difference between the water-surface elevation and the minimum elevation point in the cross section.
DT/ITER (each time step): Number of seconds of simulation time per iteration since the start of the computations for the simulated event.
DX : Length of each computational element in a branch in the steady-flow computations.
DZ : Change in elevation across each computational element in a branch in the steady-flow computations. A negative value indicates a drop in the downstream direction.
ELEV : Water-surface elevation in both the steady-flow computations and in the detailed output for a time step.
FLOW (each time step): Flow rate in cubic feet per second. A negative value indicates that the flow is moving from downstream to upstream at a node.
FR : Square of the Froude number in both the steady-flow computations and in the output for each time step.
FROUDE NUMBER : Dimensionless parameter that is the ratio of inertial to gravitational force. The Froude number value is one for critical flow, where the specific energy is minimum for a given depth.
I : The sum of the inflows to the system, used in the water-balance computation. See also BC, Q, D, S1, S2, and R.
IFRZ: The number of frozen time steps not yet completed. A frozen time step is a time step where the time is held constant while the time step is greater than zero. It is used to reduce the small differences between the initial condition as given by the steady-flow computations and the steady flow that would result if the unsteady-flow computations were continued with the boundary conditions held fixed. Freezing the time step results in fixed boundary conditions.
INITIALIZATION TIME: The computer time spent processing the input to FEQ and computing the initial conditions.
IT: The number of iterations required to reach convergence in the steady-flow computations.
JTIME: The time in Julian time as defined in FEQ. FEQ takes the beginning of January 1, 1901 as Julian time 15385.0. Thus, JTIME=15385.5 is the same as noon on January 1, 1901. The relations used to compute JTIME and also to invert JTIME (compute the year, month, day, and hour from a given JTIME) are valid from November 17, 1858 through December 31, 25000. JTIME is used to create a strictly increasing and uniform index for time. All the dates given in FEQ are converted to Julian time to make comparisons both easier and faster. JTIME is based on modified Julian time (as defined astronomically) but with changes for convenient use in FEQ.
LAT IN: This column gives the lateral inflows when DIFFUS=YES. These flows are averaged over the time step.
LEVEL-POOL RESERVOIR: A body of water with a water surface that has no slope and no momentum.
LOC: The location of the maximum residual given in the column headed by MXRES. The location is the equation number in either the exterior or interior system. A negative number denotes an equation in the exterior system and a positive number an equation in the interior system. This is sometimes useful in diagnosing problems with the solution when debugging the software.
MANNING'S n: The roughness coefficient used in Manning's formula for computing conveyance in an open channel.
MAX DEPTH: Appears in the extreme value summary at the end of the event and given the maximum depth reached during the event.
MAX ELEV: Appears in the extreme value summary at the end of the event and gives the maximum depth reached during the event.
MAX VELOC: Appears in the extreme value summary at the end of the event and gives the maximum velocity reached during the event. This is the absolute value of the velocity so that high-velocity flows that are reversing also are included as a positive velocity.
MXRES: Appears in the iteration log and gives the maximum absolute value of the residual in solving the network matrix. MXRES will be small relative to the other terms in the equation.
ND: Used with CSUR and RLTQ to denote the branch and node location. It consists of two numbers: the first is the branch number and the second, following the colon, is the node number on the branch.
NETWORK PONDING VOLUME: Appears after the branch results in the detailed output at a time step and is the ponding volume above storm sewers for the entire network.
NODE: Labels the column of node numbers on a branch in the branch output and the column of exterior node numbers in the exterior node output. Note that the exterior nodes in the new input style are names for nodes and not numbers.
NODEID: Labels the column of the alphanumeric string giving the node identification taken from the input.
NUMGT: If the user has given a value to NUMGT in the input in the Run Control Block, the NUMGT is the number of nodes that fall outside the primary tolerance for convergence but meet the secondary tolerance for convergence. The values given under this column in the iteration log will never exceed the input value of NUMGT.
Q: The sum of outflows from the system in the balance computations from the beginning of the event to the current time. See BC.
QE1: The flow at the exterior node in the output of the detailed exterior node information given at a time step.
QL: Appears in the steady-flow profile output and is the flow at the node.
QMAX: Appears in the summary of extremes output and is the maximum flow rate. This is the true maximum with regard to sign. That is, negative flows are considered to be smaller than any positive flow.
QMIN: Appears in the summary of exter me output and is the minimum flow rate. This is the true minimum with regard to sign. Any negative flow is considered to be smaller than any positive flow.
RATING CURVE: The plot representing the relation of stage or elevation and discharge at a particular structure or point in a stream.
R: Appears in the balance check output and gives the error in balance relative to the sum of the current storage and the cumulative outflow of water from the hydraulic system (S2 +Q).
RCORECT: The maximum relative correction in the iteration log for the entire stream system. Used for applying the primary convergence criterion that the maximum relative correction in absolute value must be less than the tolerance specified by the user.
RES: Appears in the output for the steady-flow profiles and is the residual in the function used to define the root of the equation being solved. A large residual at convergence may indicate some problem in the steady-flow computations.
RESULTS AT TIME: Appears in the detailed output for a time step. The elapsed time since the beginning of the event in seconds.
RLTQ: The maximum relative lateral inflow for the system. Computed as the ratio of the current rate of lateral inflow to the current average flow in the element receiving the lateral inflow. Large values often indicate computational problems where any value greater than one can be considered.
S1: The initial storage in the stream system at the beginning of the event used in the balance check. This storage includes the water in the branches and in reservoirs.
S2: The current storage in the stream system used in the balance check. This storage includes the water in the branches, reservoirs, and in storm-sewer surcharge storage.
SIMULATION COMPLETE: Message given when the simulation of an event has been completed. The final time point in the simulation is printed in detail to show the final state of the stream system.
SIMULATION ENDING AT: The time in terms of year, month, day, and hour and fraction of an hour at the end of the current time step. The length of the current time step is given in seconds.
STAT: The station of each node on a branch in the detailed output for a time step.
STATION: The station of each node on a branch in the steady-state profile computation output.
STORAGE: The amount of water stored in each level-pool reservoir. Two numbers are given: the first is the storage in internal units, cubic feet or cubic meters, and the second is the storage in acre-feet in English units and thousands of cubic meters in metric units. In the output of extreme values, only the values in units or acre-feet or thousands of cubic meters are given.
SUBCRITICAL FLOW: The flow condition at which gravitational acceleration is the dominant governing force. The Froude number is less than 1.0.
SUPERCRITICAL FLOW: The flow condition for which inertia is the dominant governing force. The Froude number is greater than 1.0.
SURF AREA: The surface area of each reservoir corresponding to the maximum water-surface elevation in the output of extreme values. Acres in English units and square kilometers in metric units.
SUMSQR: Appears in the iteration log and is the sum of the squared residuals of all the equations in both the interior and exterior system. Used internally for controlling the size of the correction used in the iterative solution.
TIME IN COMPUTING NETWORK MATRIX: The elapsed time in computing the contents of the network matrix. This may be an underestimate for small networks because the timing software resolution is sometimes too coarse for accurate timing.
TIME IN SOLVING NETWORK MATRIX: The elapsed time in solving the network matrix. This may be an underestimate for small networks because the timing software resolution is sometimes too coarse for accurate timing.
TIME OF MAX Q: Heading for the column of the times of maximum flows in the summary of extremes. The time is given in year (first two digits dropped to save space), month, day, and hour in fractional form.
TIME OF MAX Z: Heading for the column of the times of maximum elevations in the summary of extremes. The time is given in year (first two digits dropped to save space), month, day, and hour in fractional form.
TIME OF MIN Q: Heading of the column of times of the minimum flows in the summary of extremes. The time is given in year (first two digits dropped to save space), month, day, and hour in fractional form. The minimum flow is defined algebraically considering the sign of the flow. Thus, the minimum flow could be the maximum flow if the absolute value is considered.
TIME STEP RESET IN MANTIM TO: The ending time specified by the user in the Run Control Block is used in FEQ. However, there is no guarantee that the sequence of time steps selected by FEQ will exactly match the ending time. The subroutine used to manage the time step, MANTIM, resets the final time step to match the ending time specified by the user.
TL: The top width of the wetted cross section in the steady-flow profile output.
TOP: The top width of the wetted cross section in the detailed output for the time step.
VEL: The average velocity for the flow in the cross section in the detailed output for a time step.
WT: The current value of the time integration weight factor. When WT=0.5, the trapezoidal rule is used to approximate the integrals with respect to time. Values of WT>0.5 reduce the accuracy of the approximate integration but reduce the effect of non-linear oscillations that sometimes distort the numerical solution.
YE1: The depth at each exterior node in the detailed output for exterior nodes at a time step.
YL: The depth at each node on a branch
in the steady-flow computation.