A linear cost minimization model for water supply system with constrained sources

Abstract

Municipal water supply systems primarily depend on surface and groundwater sources to meet the demand. Water quantity and quality limitations of the sources often impose economic constraints on system operation requiring additional treatment cost including more expensive alternative sources in the system. It increases the cost of water production. Selection of the appropriate water-sources to minimize production cost is a challenging task when the system depends on multiple sources having different attributes and cost coefficients. This paper presents a linear cost minimization model for such a multiple-source groundwater-based water supply system. The model decides on the optimum production amount from each source with the objective of cost minimization for a specified set of demand and source constraints. The model would be useful for system analysis, planning and management purposes such as, analyzing water production at various levels of system loss or unaccounted-for water (UFW), or determining optimal production schedule under different system operation scenarios. The model is applied to simulate a groundwater-based sub-network of Dhaka city water supply system where seasonal demand from the system is the highest, when the groundwater level is relatively low, and water production cost varies with the operation mode of the deep tube wells (DTWs). Model results show that significant cost reduction would be possible in different operational scenarios through optimal production scheduling at various UFW levels while ensuring a minimum supply to the local coverage areas of the DTWs