Browsing by Author "Ward, Adam S."

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    Assessing placement bias of the global river gauge network
    Krabbenhoft, Corey A.; Allen, George H.; Lin, Peirong; Godsey, Sarah E.; Allen, Daniel C.; Burrows, Ryan M.; DelVecchia, Amanda G.; Fritz, Ken M.; Shanafield, Margaret; Burgin, Amy J.; Zimmer, Margaret A.; Datry, Thibault; Dodds, Walter K.; Jones, C. Nathan; Mims, Meryl C.; Franklin, Catherin; Hammond, John C.; Zipper, Sam; Ward, Adam S.; Costigan, Katie H.; Beck, Hylke E.; Olden, Julian D. (Nature Portfolio, 2022-07)
    Hydrologic data collected from river gauges inform critical decisions for allocating water resources, conserving ecosystems and predicting the occurrence of droughts and floods. The current global river gauge network is biased towards large, perennial rivers, and strategic adaptations are needed to capture the full scope of rivers on Earth. Knowing where and when rivers flow is paramount to managing freshwater ecosystems. Yet stream gauging stations are distributed sparsely across rivers globally and may not capture the diversity of fluvial network properties and anthropogenic influences. Here we evaluate the placement bias of a global stream gauge dataset on its representation of socioecological, hydrologic, climatic and physiographic diversity of rivers. We find that gauges are located disproportionally in large, perennial rivers draining more human-occupied watersheds. Gauges are sparsely distributed in protected areas and rivers characterized by non-perennial flow regimes, both of which are critical to freshwater conservation and water security concerns. Disparities between the geography of the global gauging network and the broad diversity of streams and rivers weakens our ability to understand critical hydrologic processes and make informed water-management and policy decisions. Our findings underscore the need to address current gauge placement biases by investing in and prioritizing the installation of new gauging stations, embracing alternative water-monitoring strategies, advancing innovation in hydrologic modelling, and increasing accessibility of local and regional gauging data to support human responses to water challenges, both today and in the future.
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    Co-located contemporaneous mapping of morphological, hydrological, chemical, and biological conditions in a 5th-order mountain stream network, Oregon, USA
    Ward, Adam S.; Zarnetske, Jay P.; Baranov, Viktor; Blaen, Phillip J.; Brekenfeld, Nicolai; Chu, Rosalie; Derelle, Romain; Drummond, Jennifer D.; Fleckenstein, Jan H.; Garayburu-Caruso, Vanessa; Graham, Emily B.; Hannah, David; Harman, Ciaran J.; Herzog, Skuyler; Hixson, Jase; Knapp, Julia L. A.; Krause, Stefan; Kurz, Marie J.; Lewandowski, Joerg; Li, Angang; Marti, Eugenia; Miller, Melinda C.; Milner, Alexander M.; Neil, Kerry; Orsini, Luisa; Packman, Aaron I.; Plont, Stephen; Renteria, Lupita; Roche, Kevin; Royer, Todd; Schmadel, Noah M.; Segura, Catalina; Stegen, James; Toyoda, Jason; Wells, Jacqueline; Wisnoski, Nathan I.; Wondzell, Steven M. (2019-10-22)
    A comprehensive set of measurements and calculated metrics describing physical, chemical, and biological conditions in the river corridor is presented. These data were collected in a catchment-wide, synoptic campaign in the H. J. Andrews Experimental Forest (Cascade Mountains, Oregon, USA) in summer 2016 during low-discharge conditions. Extensive characterization of 62 sites including surface water, hyporheic water, and streambed sediment was conducted spanning 1st- through 5th-order reaches in the river network. The objective of the sample design and data acquisition was to generate a novel data set to support scaling of river corridor processes across varying flows and morphologic forms present in a river network. The data are available at https://doi.org/10.4211/hs.f4484e0703f743c696c2e1f209abb842 (Ward, 2019).
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    Pervasive changes in stream intermittency across the United States
    Zipper, Samuel C.; Hammond, John C.; Shanafield, Margaret; Zimmer, Margaret; Datry, Thibault; Jones, C. Nathan; Kaiser, Kendra E.; Godsey, Sarah E.; Burrows, Ryan M.; Blaszczak, Joanna R.; Busch, Michelle H.; Price, Adam N.; Boersma, Kate S.; Ward, Adam S.; Costigan, Katie; Allen, George H.; Krabbenhoft, Corey A.; Dodds, Walter K.; Mims, Meryl C.; Olden, Julian D.; Kampf, Stephanie K.; Burgin, Amy J.; Allen, Daniel C. (2021-08)
    Non-perennial streams are widespread, critical to ecosystems and society, and the subject of ongoing policy debate. Prior large-scale research on stream intermittency has been based on long-term averages, generally using annually aggregated data to characterize a highly variable process. As a result, it is not well understood if, how, or why the hydrology of non-perennial streams is changing. Here, we investigate trends and drivers of three intermittency signatures that describe the duration, timing, and dry-down period of stream intermittency across the continental United States (CONUS). Half of gages exhibited a significant trend through time in at least one of the three intermittency signatures, and changes in no-flow duration were most pervasive (41% of gages). Changes in intermittency were substantial for many streams, and 7% of gages exhibited changes in annual no-flow duration exceeding 100 days during the study period. Distinct regional patterns of change were evident, with widespread drying in southern CONUS and wetting in northern CONUS. These patterns are correlated with changes in aridity, though drivers of spatiotemporal variability were diverse across the three intermittency signatures. While the no-flow timing and duration were strongly related to climate, dry-down period was most strongly related to watershed land use and physiography. Our results indicate that non-perennial conditions are increasing in prevalence over much of CONUS and binary classifications of 'perennial' and 'non-perennial' are not an accurate reflection of this change. Water management and policy should reflect the changing nature and diverse drivers of changing intermittency both today and in the future.
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    Solute Transport and Transformation in an Intermittent, Headwater Mountain Stream with Diurnal Discharge Fluctuations
    Ward, Adam S.; Kurz, Marie J.; Schmadel, Noah M.; Knapp, Julia L. A.; Blaen, Phillip J.; Harman, Ciaran J.; Drummond, Jennifer D.; Hannah, David M.; Krause, Stefan; Li, Angang; Marti, Eugenia; Milner, Alexander M.; Miller, Melinda C.; Neil, Kerry; Plont, Stephen; Packman, Aaron I.; Wisnoski, Nathan I.; Wondzell, Steven M.; Zarnetske, Jay P. (MDPI, 2019-10-23)
    Time-variable discharge is known to control both transport and transformation of solutes in the river corridor. Still, few studies consider the interactions of transport and transformation together. Here, we consider how diurnal discharge fluctuations in an intermittent, headwater stream control reach-scale solute transport and transformation as measured with conservative and reactive tracers during a period of no precipitation. One common conceptual model is that extended contact times with hyporheic zones during low discharge conditions allows for increased transformation of reactive solutes. Instead, we found tracer timescales within the reach were related to discharge, described by a single discharge-variable StorAge Selection function. We found that Resazurin to Resorufin (Raz-to-Rru) transformation is static in time, and apparent differences in reactive tracer were due to interactions with different ages of storage, not with time-variable reactivity. Overall we found reactivity was highest in youngest storage locations, with minimal Raz-to-Rru conversion in waters older than about 20 h of storage in our study reach. Therefore, not all storage in the study reach has the same potential biogeochemical function and increasing residence time of solute storage does not necessarily increase reaction potential of that solute, contrary to prevailing expectations.
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    Spatial and temporal variation in river corridor exchange across a 5th-order mountain stream network
    Ward, Adam S.; Wondzell, Steven M.; Schmadel, Noah M.; Herzog, Skuyler; Zarnetske, Jay P.; Baranov, Viktor; Blaen, Phillip J.; Brekenfeld, Nicolai; Chu, Rosalie; Derelle, Romain; Drummond, Jennifer D.; Fleckenstein, Jan H.; Garayburu-Caruso, Vanessa; Graham, Emily B.; Hannah, David; Harman, Ciaran J.; Hixson, Jase; Knapp, Julia L. A.; Krause, Stefan; Kurz, Marie J.; Lewandowski, Joerg; Li, Angang; Marti, Eugenia; Miller, Melinda C.; Milner, Alexander M.; Neil, Kerry; Orsini, Luisa; Packman, Aaron I.; Plont, Stephen; Renteria, Lupita; Roche, Kevin; Royer, Todd; Segura, Catalina; Stegen, James; Toyoda, Jason; Wells, Jacqueline; Wisnoski, Nathan I. (2019-12-20)
    Although most field and modeling studies of river corridor exchange have been conducted at scales ranging from tens to hundreds of meters, results of these studies are used to predict their ecological and hydrological influences at the scale of river networks. Further complicating prediction, exchanges are expected to vary with hydrologic forcing and the local geomorphic setting. While we desire predictive power, we lack a complete spatiotemporal relationship relating discharge to the variation in geologic setting and hydrologic forcing that is expected across a river basin. Indeed, the conceptual model of Wondzell (2011) predicts systematic variation in river corridor exchange as a function of (1) variation in baseflow over time at a fixed location, (2) variation in discharge with location in the river network, and (3) local geomorphic setting. To test this conceptual model we conducted more than 60 solute tracer studies including a synoptic campaign in the 5th-order river network of the H. J. Andrews Experimental Forest (Oregon, USA) and replicate-intime experiments in four watersheds. We interpret the data using a series of metrics describing river corridor exchange and solute transport, testing for consistent direction and magnitude of relationships relating these metrics to discharge and local geomorphic setting. We confirmed systematic decrease in river corridor exchange space through the river networks, from headwaters to the larger main stem. However, we did not find systematic variation with changes in discharge through time or with local geomorphic setting. While interpretation of our results is complicated by problems with the analytical methods, the results are sufficiently robust for us to conclude that space-for-time and time-for-space substitutions are not appropriate in our study system. Finally, we suggest two strategies that will improve the interpretability of tracer test results and help the hyporheic community develop robust datasets that will enable comparisons across multiple sites and/or discharge conditions.
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    Spatial Patterns and Drivers of Nonperennial Flow Regimes in the Contiguous United States
    Hammond, John C.; Zimmer, Margaret A.; Shanafield, Margaret; Kaiser, Kendra E.; Godsey, Sarah E.; Mims, Meryl C.; Zipper, Samuel C.; Burrows, Ryan M.; Kampf, Stephanie K.; Dodds, Walter K.; Jones, C. Nathan; Krabbenhoft, Corey A.; Boersma, Kate S.; Datry, Thibault; Olden, Julian D.; Allen, George H.; Price, Adam N.; Costigan, Katie H.; Hale, Rebecca; Ward, Adam S.; Allen, Daniel C. (2021-01-28)
    Over half of global rivers and streams lack perennial flow, and understanding the distribution and drivers of their flow regimes is critical for understanding their hydrologic, biogeochemical, and ecological functions. We analyzed nonperennial flow regimes using 540 U.S. Geological Survey watersheds across the contiguous United States from 1979 to 2018. Multivariate analyses revealed regional differences in no-flow fraction, date of first no flow, and duration of the dry-down period, with further divergence between natural and human-altered watersheds. Aridity was a primary driver of no-flow metrics at the continental scale, while unique combinations of climatic, physiographic and anthropogenic drivers emerged at regional scales. Dry-down duration showed stronger associations with nonclimate drivers compared to no-flow fraction and timing. Although the sparse distribution of nonperennial gages limits our understanding of such streams, the watersheds examined here suggest the important role of aridity and land cover change in modulating future stream drying. Plain Language Summary A majority of global streams are nonperennial, flowing only part of the year, and are critical for sustaining flow downstream, providing habitat for many organisms, and regulating chemical and biological processes. Using long-term U.S. Geological Survey measurements for 540 watersheds across the contiguous United States, we mapped patterns and examined the causes of no-flow fraction, the fraction of each climate year with no flow, no-flow timing, the date of the climate year on which the first recorded no flow takes place, and length of the dry-down period, the average number of days from a local peak in daily flow to the first occurrence of no flow. We found differences in patterns of no-flow characteristics between regions, with higher no-flow fraction, earlier timing, and shorter dry-down duration in the western United States. No-flow fractions were greater and less variable in natural watersheds, while no-flow timing was earlier and dry-down duration was shorter in human-modified watersheds. Aridity had the greatest effect on intermittence across the United States, but unique combinations of climate, biophysical, and human impacts were important in different regions. The number of gages measuring streamflow in nonperennial streams is small compared to perennial streams, and increased monitoring is needed to better understand drying behavior. Key Points . Three metrics reveal regional and human-driven patterns of nonperennial flow: no-flow fraction, day of first no flow, and dry-down duration Streams with human modifications generally dry more quickly than unmodified streams, especially in California and the Southern Great Plains Climate strongly influences no-flow fraction and timing, but physiographic variables are more important for the duration of dry down
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    What’s in a Name? Patterns, Trends, and Suggestions for Defining Non-Perennial Rivers and Streams
    Busch, Michelle H.; Costigan, Katie H.; Fritz, Ken M.; Datry, Thibault; Krabbenhoft, Corey A.; Hammond, John C.; Zimmer, Margaret A.; Olden, Julian D.; Burrows, Ryan M.; Dodds, Walter K.; Boersma, Kate S.; Shanafield, Margaret; Kampf, Stephanie K.; Mims, Meryl C.; Bogan, Michael T.; Ward, Adam S.; Perez Rocha, Mariana; Godsey, Sarah E.; Allen, George H.; Blaszczak, Joanna R.; Jones, C. Nathan; Allen, Daniel C. (MDPI, 2020-07-13)
    Rivers that cease to flow are globally prevalent. Although many epithets have been used for these rivers, a consensus on terminology has not yet been reached. Doing so would facilitate a marked increase in interdisciplinary interest as well as critical need for clear regulations. Here we reviewed literature from Web of Science database searches of 12 epithets to learn (Objective 1—O1) if epithet topics are consistent across Web of Science categories using latent Dirichlet allocation topic modeling. We also analyzed publication rates and topics over time to (O2) assess changes in epithet use. We compiled literature definitions to (O3) identify how epithets have been delineated and, lastly, suggest universal terms and definitions. We found a lack of consensus in epithet use between and among various fields. We also found that epithet usage has changed over time, as research focus has shifted from description to modeling. We conclude that multiple epithets are redundant. We offer specific definitions for three epithets (non-perennial, intermittent, and ephemeral) to guide consensus on epithet use. Limiting the number of epithets used in non-perennial river research can facilitate more effective communication among research fields and provide clear guidelines for writing regulatory documents.
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    Zero or not? Causes and consequences of zero-flow stream gage readings
    Zimmer, Margaret A.; Kaiser, Kendra E.; Blaszczak, Joanna R.; Zipper, Samuel C.; Hammond, John C.; Fritz, Ken M.; Costigan, Katie H.; Hosen, Jacob; Godsey, Sarah E.; Allen, George H.; Kampf, Stephanie K.; Burrows, Ryan M.; Krabbenhoft, Corey A.; Dodds, Walter K.; Hale, Rebecca; Olden, Julian D.; Shanafield, Margaret; DelVecchia, Amanda G.; Ward, Adam S.; Mims, Meryl C.; Datry, Thibault; Bogan, Michael T.; Boersma, Kate S.; Busch, Michelle H.; Jones, C. Nathan; Burgin, Amy J.; Allen, Daniel C. (2020-05)
    Streamflow observations can be used to understand, predict, and contextualize hydrologic, ecological, and biogeochemical processes and conditions in streams. Stream gages are point measurements along rivers where streamflow is measured, and are often used to infer upstream watershed-scale processes. When stream gages read zero, this may indicate that the stream has dried at this location; however, zero-flow readings can also be caused by a wide range of other factors. Our ability to identify whether or not a zero-flow gage reading indicates a dry fluvial system has far reaching environmental implications. Incorrect identification and interpretation by the data user can lead to inaccurate hydrologic, ecological, and/or biogeochemical predictions from models and analyses. Here, we describe several causes of zero-flow gage readings: frozen surface water, flow reversals, instrument error, and natural or human-driven upstream source losses or bypass flow. For these examples, we discuss the implications of zero-flow interpretations. We also highlight additional methods for determining flow presence, including direct observations, statistical methods, and hydrologic models, which can be applied to interpret causes of zero-flow gage readings and implications for reach- and watershed-scale dynamics. Such efforts are necessary to improve our ability to understand and predict surface flow activation, cessation, and connectivity across river networks. Developing this integrated understanding of the wide range of possible meanings of zero-flows will only attain greater importance in a more variable and changing hydrologic climate. This article is categorized under: Science of Water > Methods Science of Water > Hydrological Processes Water and Life > Conservation, Management, and Awareness