In this paper, a preliminary study is made of the dynamic optimization problem for a river with many polluters using a recently developed model of a section of the river Cam near Cambridge in England. Because of the high dimensionality of the system it is computationally prohibitive to obtain optimal solutions. However, the system has a fairly simple structure which could be utilized to alleviate the computational burden. A simple hierarchical structure is proposed for the river pollution control and the strategy is demonstrated on a digital simulation. For the practical implementation of the strategy, it is necessary, however, to have available the state vector of the system. In practice, only certain corrupted measurements of the outputs are available. It is therefore necessary to construct a state estimator. Like the optimal controller, the optimal estimator also requires prohibitive amounts of computation. However, a hierarchical strategy similar to the control strategy could be used to alleviate the computational burden. Such an estimator is also demonstrated on a digital simulation of the river.