GRADUATE PROGRAM of HYDROLOGIC SCIENCES

Academic & Research Interest

Capsule summary of qualifications. 
 
My research (currently 38%) supports exposure assessment as a part of risk assessment associated with human health protection. I have conducted studies of exposure and potential for exposure to:
  • Arsenic in private water supplies,
  • E. coli, as an indicator of fecal contamination in water,
  • Leptospira, as a result of changes in land use in Hawaii, and  
  • Cryptosporidium.
My extension work (currently 50%) provides technical support and information through:
  • Water supply operators throughout Nevada, using an innovative partnership and distance learning technologies,
  • Web sites that help interpret water quality and have served as models for at least two national efforts,
  • Peer-reviewed fact sheets and special publications,
  • Newsletters, and
  • Small grants programs for Extension Educators.
My teaching (currently 12%) includes:
  • A course (NRES 304—Principles of Hydrology) formerly required or recommended for 4 different B.S. programs, including 2 outside the department,
  • A seminar series (NRES 790—Environmental Sciences) offered each semester, featuring prominent speakers, and
  • A course (NRES 295—Ecohydrology), which is the cornerstone for the recently established Ecohydrology major.
My service includes:
  • Current director of the Environmental Sciences Interdisciplinary Graduate Program for the University
  • Former director of the Graduate Program, Natural Resources and Environmental Sciences Department
  • Departmental, college and university committees, including NRES Departmental Chair Evaluation (ad hoc), Peer-review, Ecohydrology, Geographic Information Systems and Executive Committees (NRES Department), Research Committee (College of Agriculture, Biotechnology and Natural Resources), Extension Governing Board and International Affairs Committee (University)
  • Chair and principal author: committee to establish the Ecohydrology B.S. major in the NRES Department
  • Co-chair of Coalition for Water and Wastewater Management (a statewide advisory committee)
  • Reviewer—competitive grants programs (NRI/CSREES/Government of Ireland/USGS-NWRI/Nevada Agricultural Experiment Station Hatch program), journal articles and books, Extension materials, and
  • Numerous outreach presentations and educational activities for community groups. 
 
EDUCATION
English and Journalism, S.U.N.Y Binghamton
University of Arizona
Cornell University, 1998

Areas of Study

Environmental science,   Geochemistry,   Risk assessment,  

Past Students:

Allison Fennema (MS)
Scott Fennema (MS)
Paul Garvin (MS)
Michael Meinert (MS)
David Moeser (MS)

Representative Publications

Journals
Walker, R. F., Swim, S. L., Fecko, R. M., Johnson, D. W., Miller, W. W. 2015, Bark beetle demography in Sierra Nevada mixed conifer: Variability and influencing factors., Journal of Forest Research, 4(3), 147.  
Walker, R. F., Swim, S. L., Fecko, R. M., Johnson, D. W., Miller, W. W. 2015, Long-term growth of Sierra Nevada mixed conifer in response to mechanized thinning, slash mastication, and prescribed fire., Journal of Forest Research, 4(4), 159.  
Walker, M. J., Pritsos, C., Seiler, R. 2012, Review of the Churchill County, NV ALL cluster, 1997–2004, Chemico-Biological Interactions, Vol 196, Issue 3, pg 52-58   Read More...
Dunkell, D., Bruland, G., Evensen, C., Walker, M. J. 2011, Effects of Feral Pig (Sus scrofa) Exclusion on Enterococci in Runoff from the Forested Headwaters of a Hawaiian Watershed, Water Air and Soil Pollution, 221(1-4), 313-326  
Ragosta, G., Evensen, C., Atwill, E., Walker, M. J., Ticktin, T., Asquith, A., Tate, K. 2011, Risk factors for elevated Enterococcus concentrations in a rural tropical island watershed, Journal of Environmental Management, 92(8), 1910-1915  
Ragosta, G., Evensen, C., Atwill, E. R., Walker, M. J. 2010, Causal Connections between Water Quality and Land Use in a Rural Tropical Island Watershed., J. Ecohealth. 7:105–113   Read More...
Newman, J., Walker, M. J. 2010, Short-term releases of arsenic, lead and uranium following oxidation by shock chlorination., Journal of Water and Health/International Water Association.  
Walker, M. J., Fosbury, D. 2009, Exposure to Arsenic, As(III) and Tungsten through private domestic water supplies., Journal of Water and Health, 7(2), 293-301.  
Abstract:
In some parts of the nation, particularly the arid west, groundwater used for drinking water contains arsenic high concentrations and other substances such as tungsten, which has unknown potential for morbidity and mortality. In a Nevada county, we collected tap water samples from private domestic wells to measure concentrations of arsenic and tungsten and the proportion of arsenic occurring in trivalent form (As(III)). The valence form of inorganic arsenic in groundwater has important implications for treatment efficiency. 
Jakus, P., Shaw, D., To, N., Walker, M. J. 2009, Risk Perceptions of Arsenic in Tap Water and Consumption of Bottled Water., Water Resources Research, 45; doi:10.1029/2008WR007427.  
Abstract:

The demand for bottled water has increased rapidly over the past decade, but bottled water is extremely costly compared to tap water. The convenience of bottled water surely matters to consumers, but are others factors at work? This manuscript examines whether purchases of bottled water are associated with the perceived risk of tap water. All of the past studies on bottled water consumption have used simple scale measures of perceived risk that do not correspond to risk measures used by risk analysts. We elicit a probability-based measure of risk and find that as perceived risks rise, expenditures for bottled water rise.

Walker, M. J., Seiler, R., Meinert, M. 2008, Effectiveness of household reverse osmosis systems in a Western U.S. region with high arsenic in groundwater., Science of the Total Environment, 389(2-3), 245-252.  
Garfield, L. M., Walker, M. J. 2008, Water Potential Changes in Fecal Matter & E. coli Survival., Journal of Applied Microbiology, 105, 1009-1016.  
Book or Chapter(s) in Books
Walker, M. J., Wilcox, B., Wong, M. 2008, Waterborne Zoonoses and Changes in Hydrologic Response Due to Watershed Development., In Fares, A.; Elkadi., A.I. (Ed.), Coastal Watershed Management (pp. 349-359). Wessex: WIT Press.  
Fact Sheets
Walker, M. J., Skelly, J., Mcadoo, J. K. 2009, Can arsenic in soil and water contaminate homegrown vegetables?, University of Nevada Cooperative Extension (ed., pp. 4)  
Abstract:
This Fact Sheet summarizes the results of research about the possibility that home-grown vegetables will be unsafe to eat when irrigated with water that contains high concentrations of arsenic. Although some research has shown that arsenic can accumulate in plants, the research indicates that even if arsenic concentrations in soils and water are high, arsenic in roots, leaves and fruits will likely be less than the concentrations that the U.S. Food and Drug Administration has determined to be safe for consumption. Research also indicates that plants will likely be damaged, with reduced yields, if concentrations of arsenic are high. When concentrations of arsenic are high enough in soils and water to potentially lead to accumulations, the plants are unlikely to produce edible roots, leaves and fruits. 
Walker, M. J., Newman, J. 2009, Shock Chlorination: How to tell when water is safe to drink after treatment, University of Nevada Cooperative Extension (ed., pp. 4)  
Abstract:

Shock chlorination can release metals from aquifer rocks and soils that can combine with dissolved substances to create chemicals that may be harmful to health. Researchers have shown that purging a well after treatment returns the water to its pre-treatment chemical state, but it is difficult to tell when a well has been pumped enough. This fact sheet explains how to use chlorine test kits to determine when enough water has been pumped to eliminate the side effects of shock chlorination. This is a supplement to the series on shock chlorination that explains the principles and practices of shock chlorination for home well disinfection

Bulletin/Reports
Fosbury, D., Walker, M. J., Stillings, L. 2008, Chemical Analyses of Ground Water in the Carson Desert near Stillwater, Churchill County, Nevada, 2005, Washington, D.C./U.S. Geological Survey: Open File Report/U.S. Geological Survey, (pp. 17 pages).  
Professional Papers
Walker, M. J. 2008, ). Method Development and Preliminary Applications for Leptospira Spirochetes in Water Samples: EPA/600/R 08/17., Cincinnati, OH: U.S. Environmental Protection Agency’s National Homeland Security Research Center, Cincinnati, OH.  
Curriculum Development
Walker, M. J. 2009, Water Treatment Plant Operators’ Instructional Video: Review, Examples and Practice Problems, University of Nevada Cooperative Extension. (ed., pp. 50).  
Abstract:
This curriculum is a companion to the DVD “Water Treatment Plant Operation.” It contains examples of calculations to illustrate the principles presented in the video. The DVD is designed to prepare water treatment plant operators for certification examinations, especially for Treatment Levels I and II. The curriculum was developed to provide a technical resource for self-instruction for water treatment plant operators in Nevada. The DVD and workbook have been revised and published in print and digital form at the request of the Nevada Water and Wastewater Training Coalition and water treatment plant operators throughout Nevada.
Audio/Visual
Parker, J., Walker, M. J. (2009). 2009, Water Treatment Plant Operators' Instructional Video., University of Nevada Cooperative Extension.  
Abstract:

The DVD “Water Treatment Plant Operation” contains problems and step-by-step examples of calculations to illustrate the principles presented in the accompanying workbook. The DVD is designed to prepare water treatment plant operators for certification examinations, especially for Treatment Levels I and II.

Research Reports
Walker, R. F., Johnson, D. W., Miller, W. W. 2015, Termination Report: Long-term influences of adaptive management practices on an eastern Sierran pine forest., U.S. Department of Agriculture.  
 
Photo of Mark Walker

Contact Info

1664 North Virginia Street
Reno,  Nevada   89557
Office: (775) 784-1938
Fax: 784-4789

Cell: 313-2614