𝐀𝐥𝐦𝐨𝐬𝐭 𝐚 𝐦𝐢𝐥𝐥𝐢𝐨𝐧 𝐜𝐮𝐛𝐢𝐜 𝐦𝐞𝐭𝐫𝐞𝐬. That’s roughly the amount of water stored by the 200 beaver ponds scattered throughout Poland’s Białowieża Forest.
This year, my colleagues and I traversed every river in the forest. For months, we donned wellies to trapse through peatbogs and reedbeds, recording every sign of beaver activity we could find. We even plunged—sometimes knee-deep, once waist-deep—into ice-cold beaver dens and meandering rivers. Yes, it was frigid, and yes, I had to rush home to warm up!
By the end of our survey, we had documented thousands of beaver constructions: dams, canals, lodges, and burrows. Among these were 140 active dams and 20 older, poorly maintained ones. Conservatively, we estimate about 200 active and old dams in the forest—a lot of engineering feats holding a lot of water.
Water is the lifeblood of the forest. This year, Poland is experiencing one of its driest spells on record. In such times, water is wet gold: trees become stressed, animals grow thirsty, and beavers are vulnerable. Many ponds I visited this winter were dry. Lodge entrances, usually submerged to deter predators, were exposed, leaving beavers at risk from wolves.
Yet many ponds still hold water. The empty ones will refill when heavy rains arrive. Let’s do some “back-of-the-handkerchief” math:
- Each pond stores ~3,000 m³ of water. Multiply by 200 ponds → ~600,000 m³ of surface water.
- Beavers also raise local water tables by 0.3–1 meter over 0.5–2 hectares per dam. That’s an additional ~1,250 m³ of groundwater per pond.
𝐓𝐨𝐭𝐚𝐥: Beavers may retain around 850,000 m³ of water across the forest.
This number fluctuates with rainfall: heavy rain fills ponds and raises water tables; prolonged drought reduces storage. Luckily, recent rains have boosted water levels, and beavers are now storing this liquid sunshine in their natural reservoirs. Over the coming weeks, it will slowly feed rivers, sustaining the ecosystem long after the rain has passed.
Beavers, in many ways, are wonderful creatures—true architects of water and guardians of forest life