Singapore's Protected Water Catchments — Avoided-Cost Alternative to Desalination & Import

Singapore, a small water-scarce city-state, treats rainfall catchment as core water-security infrastructure. About two-thirds of the island's land drains into 17 reservoirs, with roughly half of Singapore's land legally gazetted as protected or partially protected water catchment where PUB restricts polluting activities. At the system's centre is the 2,880-hectare Central Catchment Nature Reserve, co-managed by NParks and PUB, which surrounds reservoirs supplying the city since the 1860s and retains secondary lowland rainforest with fragments of primary forest.

In a normal rainfall year, local catchment yield meets up to 40% of daily demand — water that would otherwise have to come from Singapore's two most expensive sources, desalination and imported water. This is government land-use zoning and direct management rather than a cash-payment PES scheme, so it sits at the infrastructure/avoided-cost end of the spectrum; no independently monetized estimate of the cost avoided was found, and catchment areas outside the nature reserves still require ongoing engineered stormwater treatment.