An approach for modeling a natural dam-river network systems is proposed in this paper. Generally, the relationship among the variables of a natural dam-river network system are complex and difficult to describe. In this paper, some simple relationships among the water levels measured at a limited number of points of the network system are presented in such a way that a simple model is achieved. The model is identified and validated with the real time operational data. An example is given and the modelling methodology. It is believed that the proposed approach can be used in the operation of natural dam-river or river network systems.