Urban Water Storage Capacity Inferred From Observed Evapotranspiration Recession.

Area of Science:

• Environmental Science
• Urban Hydrology
• Evapotranspiration Studies

Background:

• Urban water storage is crucial for mitigating urban heat and flooding.
• Assessing urban water storage capacity is complex due to surface heterogeneity.
• Traditional methods rely on runoff, which may not fully capture storage dynamics.

Purpose of the Study:

• To develop and test a novel approach for estimating effective urban water storage capacity.
• To quantify urban water storage using evaporation recession rates.
• To compare urban water storage capacity with natural ecosystems.

Main Methods:

• Utilized eddy-covariance measurements of latent heat flux.
• Analyzed 583 precipitation-free periods (drydowns) across 14 urban sites.
• Calculated storage capacity from the recession rates of observed evaporation.

Main Results:

• Estimated urban storage capacities ranged from 1.3 to 28.4 mm.
• Derived e-folding timescales for evaporation varied from 1.8 to 20.1 days.
• Urban storage capacity was found to be at least five times smaller than in natural ecosystems.

Conclusions:

• The novel evaporation-based method provides a new way to assess urban water storage.
• Urban areas exhibit significantly limited water storage, leading to water-limited evaporation regimes.
• Findings highlight the vulnerability of urban environments to water availability and extreme events.