When Trees Are Thirsty, Data Can Help

Current temperatures clearly illustrate what urban climate adaptation is really all about: 35 to 40 degrees, hot streets, dry ground, and urban trees that come under increasing stress during heat waves. For Jena, therefore, urban greenery is much more than just a pretty sight. Trees provide shade, cool their surroundings, filter the air, and trap dust, thereby significantly improving the quality of life on streets, squares, and paths on hot days.

But it is precisely this urban greenery that is coming under increasing pressure. Prolonged dry spells, high temperatures, compacted soil, and impervious surfaces make it difficult to provide trees with sufficient water. Watering in urban areas is therefore an enormous task. In Jena, Kommunalservice Jena (KSJ) is responsible for the maintenance and irrigation of public green spaces. During heat waves, however, this becomes increasingly challenging: Many locations require attention at the same time, traditional watering routes reach their limits, and water should be used as precisely as possible where it is actually needed.

Sensors measure where water is needed

This is precisely where the “Sensor-Based Urban Green Space Maintenance” initiative in the Jena Smart City Project comes in. Soil moisture sensors are installed at selected tree locations. They measure, at various depths, how much water is actually available in the soil. This provides a more accurate picture of how soil moisture changes over time and when a location is truly dry.

“Especially during prolonged periods of heat and drought, any reliable information from the soil helps us. In the future, the sensors can help us plan irrigation even more precisely and reduce the workload for our colleagues in urban green space maintenance. After all, it makes a big difference whether we water according to fixed routes or whether we need to water based on actual needs,” says Olivia Busch, Smart City subproject manager.

Not every tree in the city can or should be equipped with sensors. That’s why the city works with so-called reference areas. This means that tree locations in similar settings, with similar conditions, are grouped together. Up to five sensors are installed at various depths per reference area. The measurement data can then be used to draw conclusions about comparable locations. This way, even with a limited number of sensors, we can still obtain the most informative picture possible.

Data for More Targeted Watering

The sensors transmit their data via the city’s LoRaWAN network. LoRaWAN is a wireless technology that is particularly well-suited for transmitting small amounts of data over long distances in an energy-efficient manner. The measured soil moisture data is stored in municipal databases and analyzed and visualized on a dashboard for KSJ staff.

The data is intended to provide an additional basis for decision-making to plan watering routes more efficiently and in line with actual needs. Water is to be used more strategically, and routes better coordinated. The information is also intended to become more visible to citizens. In the future, the sensor data will be retrieved via the urban data platform and made available for analysis through a visual user interface. 

Smart City with Tangible Benefits

This initiative demonstrates what “Smart City” means in concrete terms in Jena: digitalization is not an end in itself. It is intended to provide support where real challenges arise. The project focuses on improving the vitality of urban trees, developing sensor-based planning frameworks, and easing the burden on the people who care for the city’s green spaces on a daily basis.

Especially now, with temperatures reaching up to 40 degrees, it’s clear: urban green spaces need attention, care, and new solutions. Soil moisture sensors can help us take a closer look, make better decisions, and make Jena more climate-resilient step by step.