Linear reservoir groundwater method

In the linear reservoir method, the entire catchment is subdivided into a num­ber of subcatchments and within each subcatchment the saturated zone is represented by a series of interdependent, shallow interflow reservoirs, plus a number of separate, deep groundwater reservoirs that contribute to stream baseflow.

The lateral flows to the river (i.e. interflow and baseflow) are by default routed to the river links that neighbour the model cells in the lowest topographical zone in each subcatchment.

Interflow will be added as lateral flow to river links located in the lowest inter­flow storage in each catchment. Similarly, baseflow is added to river links located within the baseflow storage area

Three Integer Grid Code maps are required for setting up the framework for the reservoirs,

·         a map with the division of the model area into Subcatchments,

·         a map of Interflow Reservoirs, and

·         a map of Baseflow Reservoirs.

The division of the model area into subcatchments can be made arbitrarily. However, the Interflow Reservoirs must be numbered in a more restricted manner. Within each subcatchment, all water flows from the reservoir with the highest grid code number to the reservoir with the next lower grid code num­ber, until the reservoir with the lowest grid code number within the subcatch­ment is reached. The reservoir with the lowest grid code number will then drain to the river links located in the reservoir.

For baseflow, the model area is subdivided into one or more Baseflow Reser­voirs, which are not interconnected. However, each Baseflow Reservoir is fur­ther subdivided into two parallel reservoirs. The parallel reservoirs can be used to differentiate between fast and slow components of baseflow dis­charge and storage.

For more detailed information, see the section Linear Reservoir Method (V1 p. 613).