I've been intrigued for many years by the things one can learn from the concepts underlying hydraulics. It is an axiom of highway planning, for example, that engineering hydraulics predict much of the phenomena experienced in traffic flow. Hydraulics explains, for example, why it takes so much longer to clear a traffic backup after an accident than it does for the backup to develop. And it explains how a single driver can trigger those infuriating "no cause" stoppages.
But engineering aside, much of public management rests on virtual "plumbing." As in preventing a household plumbing emergency, careful attention to throughput capacities, sticky valves, identification of blockages and plugging of leaks is essential. Otherwise, speculation of causes or cures can result in misleading metrics, lost resources and frustrated citizens.