When I model groundwater this message appear me
There are no reaches linked to this aquifer. Therefore groundwater/ surface water interaction can't be calculated

This error message appears because you have not linked your groundwater aquifer with your river object. To do this, you must click on one of your river reaches in the Data Tree, then under Inflows and Outflows, you must select your aquifer under the "from Groundwater" entry for one of the groundwater inflow or outflow parameters.

Apologies for the delayed response.