The problem
The courtyard sits between two 60 m towers with an open north face. Anemometers we left on site for eleven weeks recorded a mean of 4.1 m/s and gusts over 9 m/s on a third of days. The competition-winning image showed a 6 m plume. A 6 m plume in 9 m/s lands on the paving twelve metres downwind, which means a wet entrance, a slip claim, and a fountain the facilities team switches off in March and never switches back on.
What we changed
We took the height out and put the length in. The scheme became a 34 m rill, 380 mm wide and 60 mm deep, cut into the granite and running the full courtyard before turning under the building line. Eighty-four smooth-bore jets sit along it at 2.4 m maximum — low enough that the drift envelope stays inside the coping at 9 m/s, which we verified on the rig rather than in a spreadsheet.
An ultrasonic anemometer on the west tower feeds the controller. Above 6 m/s the jets drop to 1.2 m; above 8.5 m/s they stop and the rill runs alone. The rill is legible in any weather, so the courtyard never looks broken — which is the actual brief that nobody writes down.
What it costs to run
Two 4 kW variable-speed pumps, typically at 55 per cent. Measured consumption over the first full year was 21,400 kWh and 340 m³ of make-up water, most of it evaporation in July and August. Filtration is a 40 µm bag set changed monthly by the building team; we train them and they send us the log.
