Nonsmooth Hydraulics, Smooth Control: System Theory Framework for Analyzing Water Networks

TL;DR

This paper develops a control-theoretic framework for water network hydraulics, analyzing nonlinear models, smoothing techniques, and stability, with validation against EPANET simulations.

Contribution

It introduces a systematic approach to analyze, regularize, and understand water network dynamics, including stability and controllability, using a novel DAE-based system theory.

Findings

Smoothed DAE models closely match EPANET simulations.

Energy dissipation is characterized by a weighted Laplacian.

Demand variation affects stability and controllability margins.

Abstract

This paper presents a comprehensive control-theoretic analysis of water distribution network (WDN) hydraulics. Starting from a general nonlinear differential algebraic equation (DAE) model of WDNs with arbitrary topology and network components (valves and pumps), we investigate three main questions. First, we study local well-posedness of the network dynamics and characterize the loss of differentiability introduced by pump and valve switching. Second, we introduce regularization methods that smooth flow and pressure trajectories under changing controls. Third, we establish error bounds for DAE linearization, local stability, and finite-horizon controllability, and quantify how network-induced parametric uncertainty impacts these properties. We demonstrate that the developed smoothed DAE models produce trajectories closely matching EPANET, a widely used WDN simulator, for various benchmark networks. The case studies also show that the WDN DAE exposes energy dissipation through a weighted Laplacian, ranks pipes by operating point sensitivity, and reveals that aggressive demand variation changes stability and controllability margins without eliminating local stability or pump authority. The developed theoretical foundations enable network analysis, mitigation strategies, and system design.