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USGS Mendenhall Postdoctoral Research Fellowship Program

17-25. The power of headwaters: forecasting effects of human alterations on constituent delivery, downstream water quality, and best management practices

The expanding footprint of human disturbance and fragmentation of aquatic systems by infrastructure has led to widespread degradation of the functions and services of the nation’s rivers (U.S. Environmental Protection Agency, 2017; Michalak et al., 2013; Poff et al. 2015). The role of headwaters is paramount to the integrity of river systems, with headwaters comprising approximately 89% of the total river network length globally (Allen et al., 2018) that are thought to be the source of 75% or more of all water and chemicals flowing through the larger network of streams and rivers to the coastal ocean (Alexander et al., 2007).

Headwaters tend to be one of the most poorly specified aspects of regional water-quality models. Despite decades of investigation, the downstream consequences of hydrochemical alterations in headwaters remain poorly understood in terms of water quality and aquatic health. Yet, small-scale studies suggest that headwater streams, ponds, and wetlands can retain a large fraction of the nutrients and sediment delivered from the land surface. The lack of validation of headwater conditions in larger scale models leaves unclear the relative roles of hydrologic alteration (McManamay et al., 2017), channel geomorphic change (Quinton et al., 2010, Konrad and Gellis, 2018), and land conversion from forested to agricultural and urban use (Alexander et al., 2007) in controlling the degree of retention of nutrients and sediments.

Recent advancements in data synthesis and integrated modeling present new approaches for investigating the hydrochemical alteration of headwaters (Harvey and Gooseff, 2015). Past work was limited by a coarse geospatial framework (RF1 network with 68 thousand river reaches in the conterminous U.S.) where most headwaters were not represented. At present there are 2.6 million river reaches in the updated USGS NHDPlus V2 network, and finer-scale characterization of headwaters is fast becoming a reality. New physical and chemical data sets are being synthesized and linked to the NHD network (Gomez-Velez and Harvey, 2014). For perhaps the first time it may be possible to specify dynamic controls of constituent loading at large spatial scales, including factors such as alteration of runoff, water transit times, flowpath reactivity, floodplain activation, and other factors that govern downstream outcomes for water resources.

The overarching theme for this Mendenhall postdoctoral opportunity is identifying the impacts of human alterations of headwaters to downstream water quantity and quality. We seek a postdoctoral fellow who will make fundamental contributions to the integration of data and models to understand and predict the role of headwaters in water quality outcomes in large river basins. The successful candidate will develop model and nonlinear statistics-based approaches to unite spatially-extensive observations of headwater conditions with flow and water-quality outcomes across large river basins. The Fellow will work with the Research Advisors to advance river science through important scientific discoveries, and also will improve the scientific basis for management actions, with examples such as allocating total maximum daily load (TMDL) reductions and evaluating specific contributions of best management practices, such as riparian setbacks, stormwater retention structures, in-stream restoration, and related strategies in headwaters.


Alexander, R. B., Boyer, E. W., Smith, R. A., Schwarz, G. E., & Moore, R. B. (2007). The Role of Headwater Streams in Downstream Water Quality. Journal of the American Water Resources Association, 43(1), 41–59. DOI: 10.1111/j.1752-1688.2007.00005.x

Allen, G. H., Pavelsky, T. M., Barefoot, E. A., Lamb, M. P., Butman, D., Tashie, A., & Gleason, C. J. (2018). Similarity of stream width distributions across headwater systems. Nature Communications, 9(1), 610.  DOI: 10.1038/s41467-018-02991-w

Gomez-Velez, J.D., & Harvey, J.W. (2014). A hydrogeomorphic river network model predicts where and why hyporheic exchange is important in large basins. Geophysical Research Letters, DOI 10.1002/2014GL061099.

Harvey, J., & Gooseff, M. (2015). River corridor science: hydrologic exchange and ecological consequences from bedforms to basins. Water Resources Research, 51(9), 6893–6922. DOI: 10.1002/2015WR017617

Konrad, C., and Gellis, A. (2018). Factors Influencing Fine Sediment on Stream Beds in the Midwestern United States. Journal of Environmental Quality, DOI: 10.2134/jeq2018.02.0060

McManamay, R. A., Surendran Nair, S., DeRolph, C. R., Ruddell, B. L., Morton, A. M., Stewart, R. N., et al. (2017). US cities can manage national hydrology and biodiversity using local infrastructure policy. Proceedings of the National Academy of Sciences, 114(36), 9581–9586. DOI: 10.1073/pnas.1706201114

Michalak, A. M., Anderson, E. J., Beletsky, D., Boland, S., Bosch, N. S., Bridgeman, T. B., et al. (2013). Record-setting algal bloom in Lake Erie caused by agricultural and meteorological trends consistent with expected future conditions. Proceedings of the National Academy of Sciences of the United States of America, 110(16), 6448–52. DOI:10.1073/pnas.1216006110

Poff, N. L., Brown, C. M., Grantham, T. E., Matthews, J. H., Palmer, M. A., Spence, C. M., et al. (2015). Sustainable water management under future uncertainty with eco-engineering decision scaling. Nature Climate Change, 6, 25. DOI: 10.1038/nclimate2765

Quinton, J. N., Govers, G., Van Oost, K., & Bardgett, R. D. (2010). The impact of agricultural soil erosion on biogeochemical cycling. Nature Geoscience, 3, 311.. DOI: 10.1038/ngeo838

Environmental Protection Agency (2017). National water quality inventory: report to Congress. EPA Report EPA 841-R-16-011.

Proposed Duty Station: Reston, VA

Areas of Ph.D.: Hydrology, environmental sciences, geosciences, civil and environmental engineering, biological resource engineering, and related disciplines (candidates holding a Ph.D. in other disciplines, but with extensive knowledge and skills relevant to the Research Opportunity may be considered).

Qualifications: Research Hydrologist, Research Physical Scientist, Research Environmental Engineer, Research Ecologist, Research Civil Engineer/Civil Engineer, Research Geophysicist, Research Statistician, Research Geographer. (This type of research is performed by those who have backgrounds for the occupations stated above. However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Human Resources specialist.)

Research Advisor(s): Jud Harvey, (703) 648-5876,; Chris Konrad, (253) 552-1634,; Greg Schwarz, (703) 648-5718,; Neil Dubrovsky, (916) 278-3078,

Human Resources Office Contact: Nina Ngo,, 703-648-7431

Go back to Summary of Opportunities

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