Multicompartment Depletion Factors for Water Consumption on a Global Scale

Balancing human communities’ and ecosystems’
need
for freshwater is one of the major challenges of the 21st century as population growth and improved living conditions put
increasing pressure on freshwater resources. While frameworks to assess
the environmental impacts of freshwater consumption have been proposed
at the regional scale, an operational method to evaluate the consequences
of consumption on different compartments of the water system and account
for their interdependence is missing at the global scale. Here, we
develop depletion factors that simultaneously quantify the effects
of water consumption on streamflow, groundwater storage, soil moisture,
and evapotranspiration globally. We estimate freshwater availability
and water consumption using the output of a global-scale surface water–groundwater
model for the period 1960–2000. The resulting depletion factors
are provided for 8,664 river basins, representing 93% of the landmass
with significant water consumption, i.e., excluding Greenland, Antarctica,
deserts, and permanently frozen areas. Our findings show that water
consumption leads to the largest water loss in rivers, followed by
aquifers and soil, while simultaneously increasing evapotranspiration.
Depletion factors vary regionally with ranges of up to four orders
of magnitude depending on the annual consumption level, the type of
water used, aridity, and water transfers between compartments. Our
depletion factors provide valuable insights into the intertwined
effects of surface and groundwater consumption on several hydrological
variables over a specified period. The developed depletion factors
can be integrated into sustainability assessment tools to quantify
the ecological impacts of water consumption and help guide sustainable
water management strategies, while accounting for the performance
limitations of the underlying model.