# Trees and bats stall fix for faulty rain radar in Gelderland

> A row of poplars next to the KNMI radar in Herwijnen distorts rain forecasts for part of Gelderland, and protected bats may stop the municipality from pruning them for now.

News · published 2026-10-31 12:47 · https://nlnow.nl/a/trees-and-bats-stall-fix-for-faulty-rain-radar-in-gelderland/

Rain forecasts in apps such as Buienradar are not always right for a strip of Gelderland, because poplars are blocking the signal of the KNMI radar in Herwijnen. The municipality of West Betuwe cannot yet allow anyone to prune or fell the trees, because bats may use them.

The strip runs from Herwijnen eastwards, between Arnhem and Nijmegen, across Doetinchem and into Germany. There, far more or far less rain can fall than the radar shows.

“We can't step in straight away,” a West Betuwe spokesperson said, pointing to wildlife protection law. The poplars may be part of a hunting ground or flight route for bats. “These areas and routes are protected.”

The municipality has commissioned ecological research into the role of the trees for bats and the effects of any intervention. The results are expected soon, and the municipality will decide on next steps based on them. The KNMI asked West Betuwe for permission to prune the trees at the end of 2025.

Meanwhile the KNMI is correcting the picture with higher-altitude radar scans, which pass over the trees, and with data from other radars in the Netherlands, Belgium and Germany. The forecasts leave out scans of the area behind the row of trees.

“But it remains desirable to have as few disturbances as possible,” a KNMI spokesperson said. The radar in Herwijnen was put into use in 2016.

## Background

- **KNMI (Koninklijk Nederlands Meteorologisch Instituut)**: The Royal Netherlands Meteorological Institute is the Dutch national weather and climate service. It makes weather forecasts and issues warnings for the Netherlands, keeps climate records, and runs the country's weather radars and measuring stations. Its radar data is what the rain forecasts in the Netherlands are based on.

From NLnow, news from the Netherlands in English. How stories are made: https://nlnow.nl/about/