This volume describes the Water Distribution Model (DM), the central model in PAWN's analysis methodology. The DM is a computer simulation of the water distribution system in the Netherlands. It determines water demands over time, allocates water resources to help meet the demands, calculates the concentrations of several water pollutants throughout the distribution system, calculates losses to agriculture and shipping due to water shortages and water salinity, and provides output from which the costs of meeting water thermal standards can be determined for the electrical power industry. The DM was used in the screening stage of the PAWN analysis to estimate the expected monetary benefits (or disbenefits) to agriculture and shipping from implementation of the technical and managerial tactics being evaluated. In the impact assessment stage of the analysis, the DM was used to determine the monetary benefits (or disbenefits) of promising water management policies to agriculture, shipping, and the electrical power generating industry, and to determine any effects of these policies on pollutant concentrations throughout the country.