Consumptive Use of Water

Consumptive use of water is the fraction of withdrawn water that does not return to the same basin in a quantity and quality suitable for reuse. It includes water that evaporates or transpires, water that becomes part of a product, and water that is transferred to another basin. The remainder, often called return flow, can in principle be treated and reused downstream.

The distinction matters because only consumptive use permanently removes water from a basin. A facility may withdraw large volumes but return most of them; what determines its real contribution to water stress is how much it actually consumes.

How it is calculated

Consumptive use = total withdrawal minus return flow to the local water body.

Why it matters

• Real water stress: only consumptive use reduces the water available to others, since treated return flows can be reused.
• Blue water scarcity: it is calculated on the basis of water consumed, not merely withdrawn.
• Scarcity weighting: consumptive use is the basis for scarcity-weighted indicators such as the AWARE factor used in water footprinting.

Typical patterns by sector

Consumptive use varies widely between activities. Irrigated agriculture tends to have a very high consumptive share because most of the water evaporates or is transpired by crops. Many industrial processes that use water mainly for cooling return a large part of it, so their consumptive share is lower, although this depends heavily on the cooling technology and on local conditions. For accurate figures, consumption should be measured at the specific site rather than assumed from generic averages.

Reduction strategies

• Efficient irrigation: drip and deficit irrigation and covering open channels reduce evaporation losses.
• Closed-loop industrial cooling: recirculating systems sharply cut the volume consumed compared with once-through cooling.
• Managed aquifer recharge: capturing stormwater to replenish groundwater.
• Reuse of treated water: returning water to productive use instead of losing it.

Relationship with water neutrality

Corporate water neutrality requires offsetting consumptive use, weighted by local scarcity, to keep water-stressed basins in balance. Quantifying consumptive use is therefore essential for prioritising efficiency investments and setting credible water targets.

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