Assessment of Water Quality Sampling Sites by a Dynamic Programming Approach

Abstract

Water quality monitoring network design is an iterative procedure, where an existing network should be reassessed from time to time on the basis of changing environmental demands and objectives in water quality management. In recent years, the economic and financial constraints faced by monitoring agencies have led to the initiation of network reduction procedures in the space domain (i.e., the reduction of the number of stations within a network). In this regard, the dynamic programming approach (DPA) can be effectively used to determine which monitoring sites are to be preserved when the network is consolidated for a fixed number of stations. However, previous studies on the use of the DPA methodology in network redesign have not yet resolved two basic questions: (1) what is the required (optimum) number of stations to be retained in the network to best represent the basin? and (2) how many subbasins should be selected when segregating the basin into smaller units as foreseen by DPA? Accordingly, the primary objective of this paper is to modify the DPA approach to determine the optimum number of stations to be retained when consolidating a monitoring network. In previous studies, the selection of subbasins in DPA was realized basically by subjective approaches based on general experiences of the designers so that the secondary objective of the study is to expand the capabilities of DPA by utilizing a more systematic approach to subbasin identification. The previously mentioned modifications to the DPA methodology are demonstrated in the case of a water quality monitoring network in Gediz River basin along the Aegean coast of Turkey. The results obtained indicate that DPA can also be an effective tool in optimizing the number of stations to be retained in a monitoring network.