Optimising production and distribution operations in large water supply networks: A piecewise linear optimisation approach

Optimal planning of water production and distribution operations in large pressurised water supply networks is one of the most challenging problems in production planning. Its underlying optimisation model is typically formulated as a mixed-integer nonlinear programme (MINLP) involving a large number of nonconvex hydraulic constraints. This makes the optimisation task in an actual water supply network particularly complex. After a brief overview of the existing literature on water supply optimisation, we highlight the major similarities and differences between the water production and distribution operations planning problem and the common production planning problems, and discuss its specific challenges. We then present a complete and sufficiently accurate optimisation model to generate feasible operating plans for water production and distribution in a typical large-scale network. Next, we propose a heuristic method, based on piecewise linearisation, to determine close to optimal solutions in reasonable computational time. Results obtained for some instances generated from an actual drinking water network operated by De Watergroep in Flanders, Belgium, are reported and discussed. Finally, some concluding remarks on the computational difficulties to solve practical water supply optimisation instances in large-scale networks are presented.