The Farm Dam Observation Point node has been included in Source to enable backwards compatibility with older Source models built using the original Farm Dams plugin developed by SKM (Jacobs since 2013). This node is not required in later versions of Source where the Farm Dam node has been integrated into Source catchment model functionality.
The Observation Point node is most often used in the a Source model in conjunction with the node including (but not limited to the farm dam ) a Farm Dam node.
The functionality of Farm Dams the Observation Point (FDOP) node now can be accessed from CORE Source without the ObservationPointNodeModel plugin now.
Similar to the farm dam node, the Observation Point Node can be created by dragging the FDOP Observation Point icon 
from the Node Palette in a Source schematic model or changing an existing node to the the Observation Point node type of FDOPin a Source catchment model.
Right-clicking on a node of FDOP can an Observation Point node will open the Feature Editor to configure this node (Figure 1).
The inflows into a Farm Dams an Observation Point (FDOP) node come from two alternative Sources: (i) overflows from the upstream dam(s)/FDOP Observation Point node(s)/subcatchment(s) . (ii) local inflow generated by the interstation area between the upstream dam(s)/FDOP Observation Point node(s)/subcatchment(s) and this the downstream observation point. These interstation inflows are calculated on the basis of a reference timeseries that has been (i.e. at a gauge) that can be scaled down/up. The scaling will reflect (a) the interstation catchment area relative to the reference catchment area and (b) the non-linearity of the relationship between the catchment area and flow.
The parameters include the Scaling factor Factor and a 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 flowwhich can be configured as a Value, a Data Source or a Function.
The interstation inflows from an Observation Point node and its upstream flow will be summed and added together to the network flows.
Figure 1 Farm Dams Observation Point editor