Using remote sensing to assess the impact of beaver damming on riparian evapotranspiration in an arid landscape

Beaver damming creates and maintains riparian ecosystems in arid regions, which are often afflicted by seasonal and multi-year droughts. We hypothesize that beaver ponds act as buffers against the effects of drought on nearby riparian vegetation via the following mechanism: Beaver ponds formed upstream of each dam retain water during wetter parts of the year, then during drier parts of the year, they gradually release that water into nearby soil where it is accessible to the roots of riparian vegetation. We calculated the evapotranspiration (ET) and normalized difference vegetation index (NDVI) of riparian vegetation on Susie and Maggie Creeks in north-eastern Nevada from 2013 to 2016 and then compared the ET and NDVI to the location and intensity of beaver damming on the creeks. We found that the ET of riparian areas with beaver damming was 50-150% higher than the ET in riparian areas without beaver damming and that NDVI in dammed riparian areas was 6-88% higher than that in undammed areas. These differences peaked in mid-summer when the landscape is at its hottest and driest state. There was no apparent loss of beaver pond drought buffering as a multi-year drought (2013-2015) progressed. Our results indicate that riparian areas with beaver damming in arid landscapes are better able to maintain vegetation productivity than areas without beaver damming during both short and extended periods of drought.