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

Intermittent 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 spatial drying patterns and temperature, precipitation, streamflow, and drought conditions. These models explained 85% of year-to-year variation in the total length of wet reaches, and 63 and 55% of year-to-year variation in habitat connectivity for large and small fish, respectively. With the US Southwest shifting to an even more arid climate, our results suggest that this may reduce habitat connectivity of fish populations in this region.

[1]  M. Delibes,et al.  Historical citizen science to understand and predict climate-driven trout decline , 2017, Proceedings of the Royal Society B: Biological Sciences.

[2]  David A. Lytle,et al.  Flow intermittency alters longitudinal patterns of invertebrate diversity and assemblage composition in an arid-land stream network , 2013 .

[3]  K. Gido,et al.  Fragmentation and dewatering transform Great Plains stream fish communities , 2015 .

[4]  D. Brookshire,et al.  Projecting avian response to linked changes in groundwater and riparian floodplain vegetation along a dryland river: a scenario analysis , 2011 .

[5]  G. Holland,et al.  Running dry: The U.S. Southwest's drift into a drier climate state , 2016 .

[6]  E. Stanley,et al.  Ecosystem Expansion and Contraction in Streams Desert streams vary in both space and time and fluctuate dramatically in size , 1997 .

[7]  Daniel C. Allen,et al.  Water as a trophic currency in dryland food webs , 2014 .

[8]  D. Turner,et al.  Wet/Dry Mapping: Using Citizen Scientists to Monitor the Extent of Perennial Surface Flow in Dryland Regions , 2011, Environmental management.

[9]  Olga Lyandres,et al.  Citizen science datasets reveal drivers of spatial and temporal variation for anthropogenic litter on Great Lakes beaches. , 2017, The Science of the total environment.

[10]  J. Olden,et al.  Climate change poised to threaten hydrologic connectivity and endemic fishes in dryland streams , 2014, Proceedings of the National Academy of Sciences.

[11]  P. Charles Goebel,et al.  Understanding controls on flow permanence in intermittent rivers to aid ecological research: integrating meteorology, geology and land cover , 2016 .

[12]  A. Cattaneo,et al.  In the eye of the beholder: Assessing the water quality of shoreline parks around the Island of Montreal through citizen science. , 2017, The Science of the total environment.

[13]  D. Lytle,et al.  Resistance and resilience of invertebrate communities to seasonal and supraseasonal drought in arid‐land headwater streams , 2015 .

[14]  J. M. Watts,et al.  Status of the Riparian Ecosystem in the Upper San Pedro River, Arizona: Application of an Assessment Model , 2006, Environmental monitoring and assessment.

[15]  Klement Tockner,et al.  Emerging concepts in temporary‐river ecology , 2010 .

[16]  D. Merritt,et al.  Linking stream flow and groundwater to avian habitat in a desert riparian system. , 2012, Ecological applications : a publication of the Ecological Society of America.

[17]  Claire Goulsbra,et al.  Temporary streams in a peatland catchment: pattern, timing, and controls on stream network expansion and contraction , 2014 .

[18]  A. Boulton.  Conservation of ephemeral streams and their ecosystem services: what are we missing? , 2014 .

[19]  David G. Tarboton,et al.  Potential Effects of Climate Change on Ecologically Relevant Streamflow Regimes , 2016 .

[20]  Nancy B. Grimm,et al.  TEMPORAL SUCCESSION IN A DESERT STREAM ECOSYSTEM FOLLOWING FLASH FLOODING , 1982 .

[21]  J. Olden,et al.  Declining streamflow induces collapse and replacement of native fish in the American Southwest , 2016 .

[22]  K. Tockner,et al.  Intermittent Rivers: A Challenge for Freshwater Ecology , 2014 .

[23]  James B. Grace,et al.  Structural Equation Modeling and Natural Systems , 2006 .

[24]  D. Turner,et al.  Application of hydrologic tools and monitoring to support managed aquifer recharge decision making in the Upper San Pedro River, Arizona, USA , 2014 .

[25]  H. Bateman,et al.  Novel water sources restore plant and animal communities along an urban river , 2015 .

[26]  K. Costigan,et al.  Fragmentation and drying ratchet down Great Plains stream fish diversity , 2015 .

[27]  C. Daly,et al.  Physiographically sensitive mapping of climatological temperature and precipitation across the conterminous United States , 2008 .

[28]  Matthew Rodell,et al.  Groundwater depletion during drought threatens future water security of the Colorado River Basin , 2014, Geophysical research letters.

[29]  C. Braak,et al.  Toward Ecologically Scaled Landscape Indices , 2001, The American Naturalist.

[30]  C. K. Minns.  Allometry of home range size in lake and river fishes , 1995 .

[31]  D. Turner,et al.  Development of a Shared Vision for Groundwater Management to Protect and Sustain Baseflows of the Upper San Pedro River, Arizona, USA , 2014 .

[32]  C. Konrad.  Location and timing of river-aquifer exchanges in six tributaries to the Columbia River in the Pacific Northwest of the United States , 2006 .

[33]  Mark Cable Rains,et al.  Hydrological Connectivity Between Headwater Streams and Downstream Waters: How Science Can Inform Policy 1 , 2007 .

[34]  B. Noon,et al.  Avian Density and Nest Survival on the San Pedro River: Importance of Vegetation Type and Hydrologic Regime , 2010 .

[35]  David P. Braun,et al.  A Method for Assessing Hydrologic Alteration within Ecosystems , 1996 .

[36]  J. Sabo,et al.  Anomalous droughts, not invasion, decrease persistence of native fishes in a desert river , 2015, Global change biology.

[37]  C. Wolter,et al.  Patterns and predictors of fish dispersal in rivers , 2014 .

[38]  Shinichi Nakagawa,et al.  A general and simple method for obtaining R2 from generalized linear mixed‐effects models , 2013 .