TL;DR: water from beaver ponds is spread around the landscape in little channels the beavers dig. The pond water slowly seeps into the soil. When droughts happen, there is enough water stored in the soil around beaver ponds to keep plants green without rain. Beavers = Irrigation Managers.
Publication: Fairfax, E, Small, EE. Using remote sensing to assess the impact of beaver damming on riparian evapotranspiration in an arid landscape. Ecohydrology. 2018; 11:e1993. https://doi.org/10.1002/eco.1993
Beavers and Drought: The Conceptual Model
Beavers build dams, dig channels, and change small streams into broad wetland areas. Their ponds and channels in particular slow down water and spread it out in the landscape. This gives that water more time to soak into the soil, which ultimately keeps plants green and lush even during periods of drought. The channels the beavers dig almost act like a little drip irrigation system running throughout the entire riparian zone.
Beavers and Drought: The Cool, Green Oasis
Whether it’s just the usual hot dry summers we experience here in the American West, or if its a prolonged multi-year drought – the beavers have it covered. Their activity keeps riparian plants green through both by maintaining access to water in the root zone.
Beavers and Drought: The Results
In my study in Nevada, we saw beaver ponds stay green throughout normal summertime droughts as well a prolonged 3-year drought. The vegetation in places with beavers had annual patterns in NDVI (plant greenness) and ET (plant water use) that mirrored the nearby human-irrigated alfalfa fields. Meanwhile, vegetation on the same creeks in sections without beavers quickly wilted each summer, and behaved more like the hillside vegetation (i.e. hydrologically disconnected from the stream system).