Anne J. Jefferson

Present-day and future contributions of glacier runoff to summertime flows in a Pacific Northwest watershed: implications for water resources.

[1]xa0While the impacts of long-term climate change trends on glacier hydrology have received much attention, little has been done to quantify direct glacier runoff contributions to streamflow. This paper presents an approach for determining glacier runoff contributions to streamflow and estimating the effects of increased temperature and decreased glacier area on future runoff. We focus on late summer streamflow (when flow is lowest and nonglacier contributions to flow are minimal) of a small glacierized watershed on the flanks of Mount Hood, Oregon, United States. Field and lab measurements and satellite imagery were used in conjunction with a temperature-index model of glacier runoff to simulate potential effects of increased temperature and reduction in glacier area on late summer runoff in the watershed. Discharge and stable isotope data show that 41–73% of late summer streamflow is presently derived directly from glacier melt. Model simulations indicate that while increased temperature leads to rapid glacier melt and therefore increased streamflow, the consequences of glacier recession overcomes this effect, ultimately leading to substantial declines in streamflow. Model sensitivity analyses show that simulation results are most sensitive to degree day factor and less sensitive to uncertainties in debris-covered area and accumulation area ratio. This case study demonstrates that the effects of glacier recession on streamflow are a concern for water resource management at the local scale. This approach could also be extended to larger scales such as the upper Columbia River basin where glacier contributions to late summer flows are also thought to be substantial.

Influence of volcanic history on groundwater patterns on the west slope of the Oregon High Cascades

[1]xa0Spring systems on the west slope of the Oregon High Cascades exhibit complex relationships among modern topography, lava flow geometries, and groundwater flow patterns. Seven cold springs were continuously monitored for discharge and temperature in the 2004 water year, and they were periodically sampled for δ18O, δD, tritium, and dissolved noble gases. Anomalously high unit discharges suggest that topographically defined watersheds may not correspond to aquifer boundaries, and oxygen isotope data reveal that mean recharge elevations for the springs are coincident with extensive Holocene lava fields. The 3He/4He ratios in most of the springs are close to atmospheric, implying shallow flow paths, and aquifer thicknesses are estimated to be 30–140 m. Estimates using 3H/3He data with exponential and gamma distributions yield mean transit times of ∼3–14 years. Recharge areas and flow paths are likely controlled by the geographic extent of lava flows, and some groundwater may cross the Cascade crest.

Seasonal versus transient snow and the elevation dependence of climate sensitivity in maritime mountainous regions

[1]xa0In maritime mountainous regions, the phase of winter precipitation is elevation dependent, and in watersheds receiving both rain and snow, hydrologic impacts of climate change are less straightforward than in snowmelt-dominated systems. Here, 29 Pacific Northwest watersheds illustrate how distribution of seasonal snow, transient snow, and winter rain mediates sensitivity to 20th century warming. Watersheds with >50% of their area in the seasonal snow zone had significant (α ≤ 0.1) trends towards greater winter and lower summer discharge, while lower elevations had no consistent trends. In seasonal snow-dominated watersheds, runoff occurs 22–27 days earlier and minimum flows are 5–9% lower than in 1962, based on Sens slope over the period. Trends in peak streamflow depend on whether watershed area susceptible to rain-on-snow events is increasing or decreasing. Delineation of elevation-dependent snow zones identifies climate sensitivity of maritime mountainous watersheds and enables planning for water and ecosystem impacts of climate change.

Simulation of the cumulative hydrological response to green infrastructure

In this study, we evaluated the cumulative hydrologic performance of green infrastructure in a residential area of the city of Parma, Ohio, draining to a tributary of the Cuyahoga River. Green infrastructure included the following spatially distributed devices: 16 street-side bioretention cells, 7 rain gardens, and 37 rain barrels. Data consisted of rainfall and outfall flow records for a wide range of storm events, including pretreatment and treatment periods. The Stormwater Management Model was calibrated and validated to predict the hydrologic response of green infrastructure. The calibrated model was used to quantify annual water budget alterations and discharge frequency over a 6 year simulation period. For the study catchment, we observed a treatment effect with increases of 1.4% in evaporation, 7.6% in infiltration, and a 9.0% reduction in surface runoff. The hydrologic performance of green infrastructure was evaluated by comparing the flow duration curve for pretreatment and treatment outfall flow scenarios. The flow duration curve shifted downward for the green infrastructure scenario. Discharges with a 0.5, 1, 2, and 5 year return period were reduced by an average of 29%. Parameter and predictive uncertainties were inspected by implementing a Bayesian statistical approach.

Stormwater management network effectiveness and implications for urban watershed function: A critical review

Deleterious effects of urban stormwater are widely recognized. In several countries, regulations have been put into place to improve the conditions of receiving water bodies, but planning and engineering of stormwater control is typically carried out at smaller scales. Quantifying cumulative effectiveness of many stormwater control measures on a watershed scale is critical to understanding how small-scale practices translate to urban river health. We review 100 empirical and modelling studies of stormwater management effectiveness at the watershed scale in diverse physiographic settings. Effects of networks with stormwater control measures (SCMs) that promote infiltration and harvest have been more intensively studied than have detention-based SCM networks. Studies of peak flows and flow volumes are common, whereas baseflow, groundwater recharge, and evapotranspiration have received comparatively little attention. Export of nutrients and suspended sediments have been the primary water quality focus in the United States, whereas metals, particularly those associated with sediments, have received greater attention in Europe and Australia. Often, quantifying cumulative effects of stormwater management is complicated by needing to separate its signal from the signal of urbanization itself, innate watershed characteristics that lead to a range of hydrologic and water quality responses, and the varying functions of multiple types of SCMs. Biases in geographic distribution of study areas, and size and impervious surface cover of watersheds studied also limit our understanding of responses. We propose hysteretic trajectories for how watershed function responds to increasing imperviousness and stormwater management. Even where impervious area is treated with SCMs, watershed function may not be restored to its predevelopment condition because of the lack of treatment of all stormwater generated from impervious surfaces; non-additive effects of individual SCMs; and persistence of urban effects beyond impervious surfaces. In most cases, pollutant load decreases largely result from run-off reductions rather than lowered solute or particulate concentrations. Understanding interactions between natural and built landscapes, including stormwater management strategies, is critical for successfully managing detrimental impacts of stormwater at the watershed scale.

Identification of local groundwater pollution in northeastern Pennsylvania: Marcellus flowback or not?

Northeastern Pennsylvania has rapidly changed over the past 5xa0years from an area with no unconventional natural gas drilling, to the most productive shale gas region within the Marcellus shale play, causing concerns about environmental safety. One issue that has caught the attention of homeowners and media is the possibility that flow-back fluids from drilling and fracturing processes have contaminated private water wells. Major and trace ion water chemistry was analyzed from 21 groundwater wells suspected by homeowners to be contaminated by flow-back fluids. These data, collected in 2012–2013, were compared to historical groundwater data, Marcellus flow-back fluid, and other sources of common groundwater contamination in rural areas (agricultural waste, septic waste, and road salt). Results from graphical and statistical tests indicate that flow-back fluids have not impacted these wells. However, some of the 2012–2013 wells do plot graphically within zones identified as waters that have been influenced by animal waste, septic, or road salt. The remaining 2012–2013 wells are geochemically similar to historical groundwater wells. These findings suggest that the major and trace element geochemistry of local groundwater in the northeastern Pennsylvania study area has not been detectably influenced by flow-back fluid spills.

Characterizing the Effects of Stormwater Mitigation on Nutrient Export and Stream Concentrations

Urbanization increases nutrient loading and lowers residence times for processing of reactive solutes, including nitrate, total dissolved nitrogen, orthophosphate, and dissolved organic carbon), which leads to increased stream concentrations and mass export. Stormwater control measures mitigate the impacts of urbanization, and have the potential to improve stream water quality, however the net effect instream is not well understood. We monitored two urban and two suburban watersheds in Charlotte, NC to determine if mitigation controlled the fraction of total mass export during storm, if development classification as either urban or suburban (defined by the age, density and distribution of urban development) controlled storm nutrient and carbon dynamics, and if stormwater control measures were able to change stream water chemistry. While average concentrations during stormflow were generally greater than baseflow, indicating that storms are important times of solute export, the fraction of storm-derived export was unrelated to mitigation by stormwater control measures. Development classification was generally not an important control on export of N and dissolved organic carbon. However, event mean concentrations of orthophosphate were higher at the suburban sites, possibly from greater fertilizer application. Stormwater control measures influenced instream water chemistry at only one site, which also had the greatest mitigated area, but differences between stormwater control measure outflow and stream water suggest the potential for water quality improvements. Together, results suggest stormwater control measures have the potential to decrease solute concentrations from urban runoff, but the type, location, and extent of urban development in the watershed may influence the magnitude of this effect.

The Expanding Utility of Laser Spectroscopy

Laser spectroscopy for analysis of stable isotopes is a rapidly emerging technology with the potential to enable new scientific investigations in hydrology and biogeochemistry. The two basic advantages of laser spectroscopy over mass spectrometry—lower instrument cost and ease of use—mean more laboratories can obtain the capability. Portability of instruments allows field deployment with online analysis of large numbers of samples outside the laboratory. However, the novelty of laser spectroscopy for isotope applications means there is little collective experience, so its strengths and limitations are not as well understood as those of mass spectrometry.

Efforts large and small speed science reform

The Working Life article “Instagram wont solve inequality” (M. Wright, 16 March, p. [1294][1]) asserts that science outreach efforts by individual women cannot counteract structural inequities and that women are doing outreach at a cost to their own careers. We concur that collective action and

Call for new AAAS harassment policy

![Figure][1] nnAAAS Leshner Leadership Institute fellows are calling on AAAS to instate a harassment policy that rescinds honors in the case of misconduct.nnILLUSTRATION: ADAPTED BY C. AYCOCK/ SCIENCE FROM ISTOCK.COM/SORBETTO AND ISTOCK.COM/PURUANnnAs fellows of the AAAS Leshner Leadership Institute for Public Engagement with Science (“Public engagement helps scientists tackle global challenges,” A. Q. Hoy, Association Affairs, 27 July, p. [372][2]), we are writing to express concern that AAAS (the publisher of Science ) continues to honor scientists who have engaged in harassment. Harassment, including sexual and gender harassment, is scientific misconduct, and its effects influence the daily lives of scientists, especially those who are from underrepresented populations. Honoring harassers sends a message to the entire scientific community that a harassers individual scientific achievements are considered more valuable than their victims as well as more valuable than the severe, widespread effects of a culture of harassment on the careers, livelihoods, and scientific potential of a much broader population.nnCurrently, no clear mechanism exists for preventing individuals who have damaged science by engaging in harassment from receiving and retaining awards, titles, and honors from AAAS. We urge AAAS to adopt a strong, enforceable policy to address harassment and discrimination, along with other types of scientific misconduct, among honorees (including elected fellows and award recipients). A meaningful policy would be applied prospectively and retroactively, require disclosure of institutional findings of professional misconduct, establish transparent and accountable procedures to report incidents, and make recommendations for appropriate responses, including revoking honors. Such an awards and honors policy would send a message that behavior that harms, degrades, and discriminates is incompatible with attaining the highest levels of scientific recognition. We would welcome its application to our own and future Leshner cohorts.nnWe were selected as Leshner fellows for our commitment to public engagement and institutional change. An inclusive scientific community is necessary for fulfilling these goals. By taking a leadership role on this important issue, we believe that AAAS can serve as a model for other institutions and professional societies.nn1. An expanded version of our letter and a list of signatories is available at [https://sites.google.com/view/timesupaaas][3].nn [1]: pending:yesn [2]: /lookup/doi/10.1126/science.361.6400.372n [3]: http://sites.google.com/view/timesupaaas