Difference between revisions of "Module Reservoirs"

Revision as of 13:46, 2 November 2015

Overview

Module Reservoirs allows to compute reservois dynamic that change river flows and concentrations. Module Reservoirs recieves flows and concentrations from Module Drainage Network and gives flows and concentrations to the same module.

Main Processes

The reservoirs do not have a explicit geometry and are located in a given Drainage Network node (that will interact flows and concetrations with it.

Hydrology

The reservoirs minimum parameter is maximum volume (keyword MAX_VOLUME) and optionally minimum volume (keyword MIN_VOLUME, default is 0.0). Below minimum volume the reservoir does not discharge and above maximum volume the reservoir discharges the remainder so that volume does not get higher than maximum.

Inflows

The inflows are imposed by Drainage Network at the nodes where the reservoir are located.

Discharges

Via Module Discharges any discharge can be imposed (positive e.g. WWTP, or negative e.g. water abstraction for irigation).

Surface Fluxes

Surface fluxes as precipitation and evaporation are not computed yet but routines already exist for that purpose

Outflows

The outflows can be computed by defining several options:

Outflow Unmanaged Reservoir 1) If the maximum volume is the only information available, the reservoir will not discharge untill complete full and there after will discharge the volume above maximum divided by time step.

2) There is the option to define unmanaged reservoir as a weir (by keyword IS_WEIR : 1) and the reservoir outflow is defined by the weir equation (also defined in ModuleDischarges). Then the crest elevation and widht need to be defined.

Outflow Managed Reservoirs 1) If beside the maximum volume only an environmental flow (keyword MIN_OUTFLOW) is defined, then above minimum volume the environmental flow will be discharged until it reaches the maximum volume and there after will discharge the volume above maximum divided by time step.

2) If an operation curve is given (keyword OPERATION_TYPE), on the form of:

1. level - outflow - OPERATION_TYPE : 1
2. level - outflow = percentage of inflow - OPERATION_TYPE : 2
3. percentage of res volume - outflow - OPERATION_TYPE : 3
4. percentage of res volume - outflow = percentage of inflow - OPERATION_TYPE : 4

then the curve is read and the outflow computed based on actual reservoir volume or level. The outflow can be given directly from volume or level or the curve can define a percentage of inflow, where the outflow will be a percentage of the inflow at that instant.

The curves are given by <<beginoperation>> <<endoperation>> block wher first column is level (elevation) or percentage of reservoir volume and second column is outflow (m3/s) or percentage of inflow (0-1) and between defined points the model linearly interpolates.

If at any given instant the volume/level of the reservoir is below the lowest point of curves, it will impose environmental flow if available or zero. If at any given instant the volume/level of the reservoir is above the highest point of curves, it will impose the last point outflow.

Reminder: if level is used an accumulated volumes curve is required (volume - elevation)) through a <<beginaccvolumecurve>> <<endaccvolumecurve>> block where first column is reservoir volume and second is elevation.

3) There is also the option to impose the outflow (e.g. from measured data) where this is done via Module Discharges but the discharge needs to be negative and a keyword in discharge present (IS_OUTFLOW)

This management option will be given priority and will be used even that environmental flow or operation curves are defined.