Controlling Reservoirs and Lakes

Reservoirs and lakes can be everywhere in the model domain - theoretically in an unlinited number. However, it is recommended to limit the number of reservoirs and lakes to one per subbasin. If there are more reservoirs than subbasins it may be a good idea to split the subbasin into even more subbasins - one for each reservoir. Or to put the reservoirs together as one large reservoir, if this is suitable. The reason for this recommendation is, that only from the very last reservoir of a subbasin abstractions can be taken out. If a sub-basin does have abstractions defined and there is also a reservoir, the abstractions are not taken from the river but from the reservoir. If that doesn't match the reality (because the abstraction is really taken from a river), the subbasin should be divided into two subbasins (the lower one gets the reservoir) and the abstraction should be defined for the first sub-basin (the one without reservoir).

Some aspects of modelling reservoirs are:

• filling up of the reservoirs takes place by inflow from upstream tributaries
• Reservoirs are always assumed to be at the subbasins lowest point, i.e. at the outlet.
• Reservoir cascades (multiple reservoirs in a line) can be used (However, abstractions for hydropower generation and irrigation can only be taken from the last reservoir).
• Reservoir outflow is defined by "abstruction_rules" (content-runoff-relations, time variable for seasons (months), week-days and hours of the day).
• Irrigation water can be taken from reservoirs.
• Interactions of the reservoir with soil and groundwater as well as evaporation from and precipitation into the reservoir will only be regarded if the lake module is switched on. Otherwise, reservoirs have no real location in the grid and are managed as virtual objects in the channel routing module only

Details on parameterization of reservoirs can be found in the explatantions on defining routing descriptions or in the WaSiM model documentation.

Time variant abstraction rules are available starting with WaSiM 8.0.10 (see also Lake module).

Details: Extended reservoir rules