Monday, May 23, 2016
13:30 - 15:00

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13:30 - 13:45: / 307 ESTIMATING UNIMPAIRED STREAMFLOWS AS A BASELINE FOR ASSESSMENT OF CLIMATE CHANGE AND ANTHROPOGENIC MODIFICATION

5/23/2016  |   13:30 - 13:45   |  307

ESTIMATING UNIMPAIRED STREAMFLOWS AS A BASELINE FOR ASSESSMENT OF CLIMATE CHANGE AND ANTHROPOGENIC MODIFICATION We developed empirical models that predict natural monthly flows in streams and rivers from 1950 onward across all stream segments in California, USA. These models provide a baseline for assessments of change in stream hydrology due to climate change or anthropogenic modifications. For model development, we screened 1800 gage sites statewide to select sites that had a minimum of 10 years of streamflow data and minimal land use and hydrologic infrastructure. Our final data set consisted of 250 least-impacted sites to construct our reference hydrology models, including 75 in the Sierra Nevada Region. Model performance was comparable to published models, suggesting our models can be used to estimate natural monthly flows in most California streams. Empirical models were developed to predict flow modification using basin-scale geospatial indicators of human influences and proved to be suitable tools for identifying streams experiencing flow modification via hydrologic infrastructure and land use. We believe a similar approach would be useful in estimating the effects of climate change on Sierra Nevada streams.

Jason May (Primary Presenter/Author), U.S. Geological Survey, California Water Science Center, jasonmay@usgs.gov;


Daren Carlisle ( Co-Presenter/Co-Author), U.S. Geological Survey, dcarlisle@usgs.gov;


David Wolock ( Co-Presenter/Co-Author), U.S. Geological Survey, dwolock@usgs.gov;


Jeanette Howard ( Co-Presenter/Co-Author), The Nature Conservancy, jeanette_howard@tnc.org;


Larry Brown ( Co-Presenter/Co-Author), U.S. Geological Survey, lrbrown@usgs.gov;


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13:45 - 14:00: / 307 SENSITIVITY OF RIVER FLOWS TO CLIMATE CHANGE IN CALIFORNIA

5/23/2016  |   13:45 - 14:00   |  307

SENSITIVITY OF RIVER FLOWS TO CLIMATE CHANGE IN CALIFORNIA Trends of decreasing snowpack and increasing risk of drought threaten California’s economic vitality and the health of its freshwater ecosystems. Despite growing awareness of climate change impacts, robust management adaptation has been hindered by uncertainty in future climate predictions for the region. Global climate model (GCM) projections uniformly suggest future warming, but projections are highly variable with respect to the direction and magnitude of change in precipitation. Here we examine the sensitivity of California river flows to climate variation independently of GCMs. We use a statistical approach to construct predictive models of monthly discharge based on climate and natural river basin characteristics. We then propagate an ensemble of synthetic climate simulations through the models to assess potential flow responses to changes in temperature and precipitation in different months and regions of the state. By quantifying the sensitivity of river flow to climate change, rather than attempting to predict future hydrology based on uncertain GCM projections, our results should be more informative to managers seeking to assess and reduce the vulnerability of California’s freshwater ecosystems to climate change.

Ted Grantham (Primary Presenter/Author), University of California, Berkeley, tgrantham@berkeley.edu;


Daren Carlisle ( Co-Presenter/Co-Author), U.S. Geological Survey, dcarlisle@usgs.gov;


David Wolock ( Co-Presenter/Co-Author), U.S. Geological Survey, dwolock@usgs.gov;


Greg McCabe ( Co-Presenter/Co-Author), U.S. Geological Survey, gmccabe@usgs.gov;


Mike Wieczorek ( Co-Presenter/Co-Author), U.S. Geological Survey, mewieczo@usgs.gov;


Jeanette Howard ( Co-Presenter/Co-Author), The Nature Conservancy, jeanette_howard@tnc.org;


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14:00 - 14:15: / 307 TEMPORAL FLOW FLUCTUATION EFFECTS ON MOUNTAIN STREAM ECOSYSTEMS

5/23/2016  |   14:00 - 14:15   |  307

TEMPORAL FLOW FLUCTUATION EFFECTS ON MOUNTAIN STREAM ECOSYSTEMS Glacier-fed streams display very specific flow regime characterized by a strong temporal variability at various temporal scales due to the complexity of the water storages and releases by glaciers. However, the acceleration of glacier shrinkage under the ongoing climate change results in a strong alteration of glacier runoff. In particular, we expect an increase in both low and high extreme flow events. In a tropical glacierized catchment, we examine the relationship between flow fluctuation and aquatic community composition from the diurnal to the inter-annual time scales to identify the mechanisms driving the community structure and predict the aquatic biodiversity response to potential changes in flow regime under global warming. Based on observational and experimental studies, we show that the benthic fauna is highly adapted to the natural flow fluctuation and display both resistance and resilience to high and low flow events. However, our studies suggest that an increase in frequency of those extreme flow events might prevent communities to fully recover leading to irreversible shifts; and that reduction in glacier runoff would strongly affect the remarkable mountain stream biodiversity.

Sophie Cauvy-Fraunié (Primary Presenter/Author), IRSTEA Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture, sophie.cauvy@gmail.com;


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14:15 - 14:30: / 307 VARIABILITY IN HYDROLOGY, WATER CHEMISTRY, AND SEDIMENT LOADS FOR HEADWATERS OF THE SOUTHERN SIERRA NEVADA

5/23/2016  |   14:15 - 14:30   |  307

VARIABILITY IN HYDROLOGY, WATER CHEMISTRY, AND SEDIMENT LOADS FOR HEADWATERS OF THE SOUTHERN SIERRA NEVADA The Kings River Experimental Watersheds study has documented the variability in conditions during the past 12 years at 10 perennial, headwater streams. For precipitation during this time, two years are considered average, four above average, and six below average. While historic precipitation in some years has been as low or lower in the southern Sierra Nevada, the very low values for several consecutive years has never been recorded before. The study provides insight into climate change since five of the catchments are snow dominated and five are at the rain-snow transition zone. The patterns seen in physical and chemical stream conditions during this time period show differences among seemingly similar catchments of the mixed-conifer forest. Conductivity is higher during low flow and at the low elevation catchments (40-75 µS), while pH is lowest during high spring flows and is acidic at the high elevation catchments (sometimes <6.5). Nutrient concentrations in stream water are higher during storm events rather than being diluted. Sediment loads are highly variable, but correlate with annual precipitation amounts.

Carolyn Hunsaker (Primary Presenter/Author), Pacific Southwest Research Station, USDA Forest Service, chunsaker@fs.fed.us;


Dave Herbst ( Co-Presenter/Co-Author), Sierra Nevada Aquatic Research Laboratory, University of California Santa Barbara, david.herbst@lifesci.ucsb.edu;


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14:30 - 14:45: / 307 BENTHIC MACROINVERTEBRATE COMMUNITIES IN RIFFLE AND POOL HABITATS IN FORESTED STREAMS OF THE SIERRA NEVADA OF CALIFORNIA DURING DROUGHT

5/23/2016  |   14:30 - 14:45   |  307

BENTHIC MACROINVERTEBRATE COMMUNITIES IN RIFFLE AND POOL HABITATS IN FORESTED STREAMS OF THE SIERRA NEVADA OF CALIFORNIA DURING DROUGHT Variation in flow across habitats, seasons, and years is a key driver of the composition of benthic invertebrate communities in mountain streams. We monitored invertebrate communities in the pools and riffles of 12 headwater streams in the central Sierra Nevada over seven separate years from 2002 to 2015. Invertebrate communities in riffle and pool habitats were strikingly, consistently different in composition and in the abundances of different taxa and trait groups. Greater biomass turnover in pools than riffles was indicated by higher densities of small, multivoltine, collector-gatherer taxa in pools and higher densities of slower-growing, medium to large, grazing, filtering, and predatory taxa in riffles. Community structure shifted with flow regime, and spring communities under drought flows resembled those found during fall base flows, reflecting changes in the availability of pool versus riffle habitat with discharge. Nearly all taxa and trait groups were more abundant during low than high flow periods, but comprised of greater proportions of small, multivoltine chironomids with higher stress and thermal tolerances. Different chironomid species, however, showed different responses to temporal changes in flow.

Bruce Medhurst (Primary Presenter/Author), Sierra Nevada Aquatic Research Laboratory, University of California Santa Barbara, rbmedhurst@ucsb.edu;


Dave Herbst ( Co-Presenter/Co-Author), Sierra Nevada Aquatic Research Laboratory, University of California Santa Barbara, david.herbst@lifesci.ucsb.edu;


Scott Cooper ( Co-Presenter/Co-Author), University of California Santa Barbara, scott.cooper@lifesci.ucsb.edu;


Sheila Wiseman ( Co-Presenter/Co-Author), University of California Santa Barbara, wiseman9@cox.net;


Carolyn Hunsaker ( Co-Presenter/Co-Author), Pacific Southwest Research Station, USDA Forest Service, chunsaker@fs.fed.us;


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14:45 - 15:00: / 307 OBSERVATIONS OF CHANGING HABITAT AND BENTHIC INVERTEBRATE COMMUNITIES FROM THE SIERRA NEVADA SENTINEL STREAM NETWORK DURING EXTENDED DROUGHT

5/23/2016  |   14:45 - 15:00   |  307

OBSERVATIONS OF CHANGING HABITAT AND BENTHIC INVERTEBRATE COMMUNITIES FROM THE SIERRA NEVADA SENTINEL STREAM NETWORK DURING EXTENDED DROUGHT Prolonged drought of four years (2012-2015) depleted snowmelt stream flows in the Sierra Nevada mountains. During this time, and in preceding normal and high runoff years, we monitored conditions in a sentinel stream network covering the extent of the Sierra Nevada, at elevations from 1200 to 3500 meters, in granitic and volcanic terrain. Data from the network will elucidate effects of hydroclimatic change and drought. We found that as flows dwindled, so too did stream area, with the proportion of pool cover increasing at the expense of biologically diverse riffles. Flow intermittency increased as drought continued and average water temperatures rose from 8-9 °C prior to the drought to 12-13 °C during the drought. Algae and fine organic matter also accumulated. Benthic macroinvertebrates were more diverse in northern regions with more groundwater inputs than in the south where snowmelt was the major source of flow. As flows diminished, and in some sites became intermittent, there were substantial losses of diversity and change in community composition. These observations portend dramatic alterations of stream ecosystems in mountain regions subject to persistent drought.

Dave Herbst (Primary Presenter/Author), Sierra Nevada Aquatic Research Laboratory, University of California Santa Barbara, david.herbst@lifesci.ucsb.edu;


Bruce Medhurst ( Co-Presenter/Co-Author), Sierra Nevada Aquatic Research Laboratory, University of California Santa Barbara, rbmedhurst@ucsb.edu;


Ian Bell ( Co-Presenter/Co-Author), Sierra Nevada Aquatic Research Laboratory, ian.douglas.bell@gmail.com;


Michael Bogan ( Co-Presenter/Co-Author), School of Natural Resources and the Environment, The University of Arizona, mbogan@email.arizona.edu;


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