“Smart tanks” are increasingly used in rainwater harvesting systems to address water shortages and urban flooding. They can use a range of digital information (e.g. rainfall forecast) to make optimal decisions to release some tank water before heavy rain in order to reduce flood risk while still supply water to households. Globally, most uses of this technology use 1-day forecasts of rainfall.
To understand the effect of longer prediction window, Xu et al.  compared four strategies using either 1-day or 7-day rainfall forecast and modeled their performance using specialized computer code. They found that smart tanks using 7-day rainfall forecasts are superior in reducing urban flood risks and restoring baseflows to streams. More importantly, they can release the tank water in a pattern that is similar to natural streamflow, thus helping to restore and sustain healthy waterway habitats.
The study is the first reported application of 7-day forecast information in smart control rainwater tanks. It opens up a new opportunity in managing urban water in a range of contexts and for a range of stream health objectives.
Citation: Xu, W. D., Fletcher, T. D., Burns, M. J., & Cherqui, F. . Real time control of rainwater harvesting systems: The benefits of increasing rainfall forecast window. Water Resources Research, 56, e2020WR027856. https://doi.org/10.1029/2020WR027856
—Jim Hall, Editor, Water Resources Research