Farm Dams Observation Point node is often used in the Source model with the node including but not limited to the farm dam node.
The functionality of Farm Dams Observation Point (FDOP) node can be accessed from CORE without ObservationPointNodeModel plugin now.
Similar to the farm dam node, the Observation Point Node can be created by dragging the FDOP icon 
from Node Palette or changing an existing node to the node type of FDOP.
Right-clicking on a node of FDOP can open the Editor to configure this node (Figure 1).
The inflows into a Farm Dams Observation Point (FDOP) come from two alternative Sources: (i) overflows from the upstream dam(s)/FDOP node(s)/subcatchment(s). (ii) local inflow generated by the interstation area between the upstream dam(s)/FDOP node(s)/subcatchment(s) and this observation point. These interstation inflows are calculated on the basis of reference timeseries that has been scaled down/up.
The parameters include Scaling factor and Reference Timeseries in the format of Value, Data Source, and Function Editor. The user can select the option Value for the constant value, or Data Source for a timeseries defined in Data Sources; or define it by a function.
The inflow from a FDOP node will be added to the network along with its upstream flow.
Figure 1 Farm Dams Observation Point editor