Cost minimisation for multiple-source water supply systems

Management of municipal water supply systems having multiple groundwater sources constrained by water availability is often challenging. Water quantity limitations of the sources cause economic constraints on system operation, requiring more expensive alternative sources. This paper presents a linear cost minimisation model for such a groundwater-based multiple-source water supply system where water demand is relatively high and groundwater availability is limited, while a minimum supply is to be ensured to the local coverage area of each well. The model decides on the optimum production amount from each source with the objective of cost minimisation for a specified set of demand and source constraints. The model would be useful for system analysis, planning and management purposes, such as analysing water production at various levels of system loss or unaccounted-for water (UFW), or determining optimal production schedules 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. Model results show that significant cost reduction would be possible under different operational scenarios through optimal production scheduling at various UFW levels.