Assignment of Water Allocation Costs of Network Flow Model

Abstract

Network flow programming (NFP) can effectively simulate water allocation due to its computational efficiency and structural flexibility. One of the key issues while using such a model is to mimic the complexity of water allocation rules by properly assigning a set of cost coefficients to every arc in the water supply network. Similar to the concept of Israel and Lund (1999), this study proposed a procedure to determine the cost coefficients of a pure NFP-based simulation model. It can correctly preserve the water allocation priorities which were originated from allocation rules of water rights, reservoir operating rule curves, water convey preferences and multi-reservoir storage allocations, etc. Water allocation rules were converted into linear inequalities composed of arc cost coefficients through path enumeration analysis. These linear inequalities are then solved to obtain a set of cost coefficients which conform to the allocation priorities. I. Foreword Simulation is the major approach used by Taiwanese water resources planning and management institutes for assessing the water supply situations of water resources systems. It entails constructing computer models to imitate the allocation of water in a water resources system. A major complexity of the model is the need to find the best way of regulating flows to supply demands in a sense that following the priority requirements and minimizing unregulated residual flow into the final water receiving body to elevate water utilization efficiency. Among the various applications of water allocation simulations, network flow programming (NFP) has been extensively used to develop general models (Yeh, 1985; Wurbs, 1993; Labadie, 2004). NFP possesses advantages of computational efficiency and structural flexibility. The physical water resources system is conceptualized by a flow network of nodes and arcs in a NFP model. A cost coefficient which denotes cost per unit flow is assigned to every arc to guide the water allocation mechanism. NFPbased simulation models appeared in the literatures include SIMYLD (Evenson and Moseley, 1970), ARSP (Sigvaldason, 1976), SIM-V (Martin, 1987), MODSIM (Labadie et al., 1986; Fredericks et al., 1998; Dai & Labadie, 2001), WASP (Kuczera & Diment, 1988), WRAP (Yerrameddy & Wurbs, 1996), DWRSIM (Chung et al., 1989), CRAM