Estimating water availability and demand for urban green with a minimal model

Urban green infrastructure (UGI) is key in retaining stormwater and mitigating the urban heat island effect, thus complementing efforts in climate change adaptation. However, UGI itself is vulnerable to climate change, particularly in the form of heatwaves and droughts. This study introduces a freely available coupled modelling approach consisting of a library for quantifying evapotranspiration, a continuous water balance model, and an approach to estimate minimum water requirements. This approach is applied to 21 cities (stations) in Germany for street trees over a period of 29 years. The study discusses spatio-temporal variations in water availability and demand across Germany. According to the model, water demand became relevant from 2015 onwards for most stations, reaching magnitudes of up to 150 mm per season, especially during the multi-year drought period between 2018–2022. Data and model codes are publicly available and might help to inform stakeholders about estimates of irrigation needs.