Citizen scientists document long-term streamflow declines in intermittent rivers of the desert southwest, USA

AbstractIntermittent rivers are spatially dynamic, expanding and contracting in response to changes in water availability, but studies that explicitly examine spatial drying patterns are scarce. We used long-term data produced by citizen scientists to map wet and dry reaches of 3 different river systems to investigate mechanisms producing temporal variation in drying patterns. We quantified the total wetted river length in each survey, and calculated ecologically scaled landscape indices that indicate the carrying capacity (population size) and habitat connectivity of large and small fish metapopulations in these systems. We found that the spatial extent of perennial water decreased over the study period in 2 of the 3 study rivers: ∼26% in the Agua Fria River from 2008 to 2016, and ∼14% in Cienega Creek from 2006 to 2016. We also observed an ∼8% decline in habitat connectivity for large fish in the Agua Fria River. We used multivariate structural equation models to infer causal relationships between spati...