In January, Brian Richter, director of freshwater strategies at The Nature Conservancy, spelled out four water resolutions through a thought-provoking series of blog posts. One of those resolutions was to better understand and communicate the differences between water use and water consumption. This is a particularly important issue, as there has been a lot of discussion lately about water scarcity, water stress, and the risks associated with them.
So what do ”water use” and “water consumption” mean?
“Water use” describes the total amount of water withdrawn from its source to be used. Measures of water usage help evaluate the level of demand from industrial, agricultural, and domestic users. For example, a manufacturing plant might require 10,000 gallons of freshwater a day for cooling, running, or cleaning its equipment. Even if the plant returns 95 percent of that water to the watershed, the plant needs all 10,000 gallons to operate.
“Water consumption” is the portion of water use that is not returned to the original water source after being withdrawn. Consumption occurs when water is lost into the atmosphere through evaporation or incorporated into a product or plant (such as a corn stalk) and is no longer available for reuse. Water consumption is particularly relevant when analyzing water scarcity and the impact of human activities on water availability. For example, irrigated agriculture accounts for 70 percent of water use worldwide and almost 50 percent of that is lost, either evaporated into the atmosphere or transpired through plant leaves.