Rethinking the water cycle

How moving to a circular economy can preserve our most vital resource.

Three billion people will join the global consumer class over the next two decades, accelerating the degradation of natural resources and escalating competition for them. Nowhere is this growing imbalance playing out more acutely than the water sector. Already, scarcity is so pronounced that we cannot reach many of our desired economic, social, and environmental goals. If we continue business as usual, global demand for water will exceed viable resources by 40 percent by 2030.

Many experts have claimed that wasteful treatment of water results from dysfunctional political or economic systems and ill-defined markets. But the real issue is that water has been pushed into a linear model in which it becomes successively more polluted as it travels through the system, rendering future use impossible. This practice transforms our most valuable and universal resource into a worthless trickle, creating high costs for subsequent users and society at large. Since the linear model is economically and environmentally unsustainable, we must instead view water as part of a circular economy, where it retains full value after each use and eventually returns to the system. And rather than focus solely on purification, we should attempt to prevent contamination or create a system in which water circulates in closed loops, allowing repeated use. These shifts will require radical solutions grounded in a complete mind-set change, but they must happen immediately, given the urgency of the situation.

A new, ‘circular’ perspective on water management

The global water crisis is real and graphically manifest. It’s apparent in rivers that no longer reach the sea, such as the Colorado; exhausted aquifers in the Arabian Peninsula and elsewhere; and polluted water sources like Lake Tai, one of the largest freshwater reserves in China. The root of this challenge is the violation of the zero-waste imperative—the principle that lies at the heart of any circular economy. It rests on these three basic beliefs:

• All durables, which are products with a long or infinite life span, must retain their value and be reused but never discarded or down cycled (broken down into parts and repurposed into new products of lesser value).
• All consumables, which are products with a short life span, should be used as often as possible before safely returning to the biosphere.
• Natural resources may only be used to the extent that they can be regenerated.

Even countries with advanced water-management systems violate these fundamental rules. They often fail to purify water before discharging it back into the environment because cleanup costs are high or prohibitive, even when energy or valuable chemicals could be extracted. The substances contained in the water then become pollutants. Equally troubling, any volume of water removed from the system is seldom replaced with return flow of the same quality.

When considering a redesign that will create a new, circular water system, we can take three different views:

• the product perspective, which calls for a strict distinction between water as a consumable and water as a durable, since there are different strategies for reducing waste in each category
• the resource perspective, which calls for a balance between withdrawals and return flows
• the utility perspective, which focuses on maximizing the value of our existing water infrastructure by increasing utilization and ensuring better recovery and refurbishment of assets

Further reading: https://www.mckinsey.com/business-functions/sustainability/our-insights/rethinking-the-water-cycle