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Internally, Source partitions the link into ndiv divisions (where ndiv is the lag measured in number of model timesteps). Water moves progressively through the link, one division at a time, without attenuation and ignoring any loss and gain fluxes and any dead storage, as follows:
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Storage Routing links can be configured to represent lagged flow without attenuation (equivalent to a Lagged Flow link) but with the capacity to include lateral fluxes. See the Links user guide for how to configure the Storage Routing link to achieve this, and the Storage Routing Link SRG for information on the solution procedure.