But interventions tend to solve water scarcity problems at a local level, while aggravating water scarcity downstream.
In a new study published in the journal Nature Communications, researchers have now assessed the impacts of human interventions on water scarcity at a global scale.
"It’s common sense that taking water out of a river will leave less for those people downstream.
But it’s not so straightforward," says Ted Veldkamp, researcher at Vrije Universiteit Amsterdam and guest researcher at IIASA, who led the study.
Seasonal changes in precipitation and water storage make it difficult for modelers to estimate water availability and impacts of interventions, and the effects of climate change can be difficult to tease out from other impacts like human activities.
This systematic approach allowed the researchers to come up with an estimate that is more realistic than previous approaches — and which also shows greater water scarcity than previous estimates.
From 1971 to 2010, the study found, human impacts have drastically reshuffled water scarcity hotspots, with impacts on approximately one-third of the global population.
On average, approximately 20% of the global population has experienced a significant increase in water availability due to human interventions, such as building water storage, alleviating water scarcity experienced by 8% of the population.
As climate change and population place further pressure on tight water resources, the researchers found that policymakers and water managers need to take a regional and global perspective on local decisions.
This is especially important for transboundary river basins, where policy development in one country may have consequences on different countries downstream.