Nick Johnson
Nicholas Johnson, Ph.D., P.G., C.Hg.
Senior Managing Scientist
Environmental & Earth Sciences

Dr. Johnson is an applied physical hydrogeologist with more than 35 years of professional experience working at the intersection of earth sciences, hydrology, remedial and water-resources engineering, and water and environmental planning in California and other western states. He has conducted field studies and developed flow and transport models for the investigation, remediation, and management of alluvial basins, bedrock aquifers, and contaminant sites. He has addressed water-supply sustainability and protection, groundwater-surface water interactions, disputed water rights, and impacts associated with groundwater overdraft (e.g., land subsidence), saltwater intrusion, wastewater disposal, landfills, and the release of industrial chemicals and wastes, including under fractured-rock, volcanic, and karst conditions. His clients have included public and private water users and purveyors; regulatory, planning, and resource agencies; public and private developers; private industry; and professional firms and attorneys. He has taught university hydrogeology, served on regional technical committees, and presented expert testimony for USEPA.

Dr. Johnson is skilled at developing and conveying a conceptual understanding of groundwater flow systems through analysis of a wide variety of hard and soft data. The resulting conceptual models guide and provide input for subsequent numerical modeling, as needed.

He has prepared various water resource management, protection, and remediation plans, including a Groundwater Sustainability Plan (compliant with the California 2014 Sustainable Groundwater Management Act, SGMA), an Urban Water Management Plan, water supply master plans, environmental impact studies and reports, Drinking Water Source Assessment and Protection plans, and remedial investigations and feasibility studies under both CERCLA and RCRA.

Dr. Johnson is recognized for innovating geostatistical techniques to evaluate the spatial continuity of interbedded geologic materials. His work evaluating the spatial continuity of alluvial sediments beneath clusters of Silicon Valley Superfund sites has been regularly cited since it was published in Water Resources Research.

For an investigation of legacy contamination from rocket testing at a facility underlain by fractured sandstone, he investigated the influence of faults on site groundwater and received an Engineers’ Council Outstanding Engineering Achievement Merit Award for his work.

Dr. Johnson has conducted aquifer tests up to one-month long in a wide variety of hydrogeologic environments, including alluvium, sandstone, volcanic rock, fractured rock, and karst. He has performed streamflow measurements and stormflow-baseflow separation to formulate hydrologic budgets for the evaluation of surface water-groundwater conjunctive use and managed aquifer recharge.

Dr. Johnson has developed and applied three-dimensional and physically representative groundwater flow and solute transport models of various scales, primarily using the MODFLOW, MT3D, and PEST codes. Ranging from well-site to basin-wide scales, modeled conditions have included various alluvial and sandstone aquifers within the coastal ranges, valleys, and plains of central and southern California. Site models have addressed waste-unit closure and remediation at petroleum facilities and the migration and hydraulic control of dissolved solvents, hexavalent chromium, and other heavy metals. Basin-wide models have included ones for Santa Clara and San Fernando valleys. For the US Army Corps of Engineers, he developed and applied a groundwater model to evaluate the influence and effectiveness of a subsurface flow barrier beneath the ring levee surrounding the City of Marysville on the eastern edge of the Sacramento Valley.


  • Ph.D., Earth Sciences, University of California, Santa Cruz, 1994
  • M.S., Hydrology, University of Arizona, 1980
  • B.A., Earth Sciences, Environmental Studies, University of California, Santa Cruz, 1977


Professional Geologist (P.G.), California, #4344 1987-2017

Certified Hydrogeologist (C.Hg.), California, #661 1999-2017


Journal Articles

Cilona A, Aydin A, Johnson NM. Permeability of a fault zone crosscutting a sequence of sandstones and shales and its influence on hydraulic head distribution in the Chatsworth Formation, California, USA. Hydrogeology Journal 2015; 23(2):405-419.

Johnson NM. Characterization of alluvial hydrostratigraphy with indicator semivariograms. Water Resources Research 1995; 31(12):3217-3227.

Johnson NM. Dreiss SJ. Hydrostratigraphic interpretation using indicator geostatistics. Water Resources Research 1989; 25(12):2501-2510.

Other Publications

Cooper C, Shannon H, Johnson N, Altare C. Sustainable management of groundwater resources in the North Westside Basin, San Francisco City and County, California Through Implementation of the 2014 California Sustainable Groundwater Management Act. Poster abstract, American Water Resources Association, Water for Urban Areas: Managing Risks and Building Resiliency, Los Angeles, March 2015.

Johnson NM. Pumping-test evaluation of fault-zone hydraulic properties in a fractured sandstone. American Geophysical Union Fall Meeting poster abstract H53D-0878, San Francisco, CA, December 2014.

Aydin A, Cilona A, Johnson N, Eichhubl P. Shales in shear zones and their effect on cross-fault fluid flow. AAPG International Conference & Exhibition abstract, Istanbul, September 2014.

Johnson NM. Drought of 2012-14(?)—Testing the limits of conjunctive use, Santa Cruz Mountains, California. 14th Biennial Symposium on Managed Aquifer Recharge presentation abstract, Orange, July 2014.

Bower MO, Taege D, Pierce AA, Johnson NM. Case study for controlling chlorinated ethenes discharging at seeps in a fractured sandstone aquifer. Battelle Conference poster abstract, Monterey, May 2012. 

Johnson NM. Hydrogeology of coastal watersheds: Southern Santa Cruz and Northern Monterey Counties in Peninsula. Geological Society Spring Field Trip Guidebook, pp. 51-91, 2000.

Johnson NM. Hydrostratigraphic interpretation using indicator profiles. Geological Society of America Annual Meeting, Abstracts with Programs 30(7): A-104, Toronto, October 1998.

Johnson NM. Basinwide approach to the San Fernando Valley Superfund Site. Transactions American Geophysical Union Fall Meeting, 47(46):239-240, San Francisco, CA, December 1996.

Williams D, Johnson NM, Fowler AC. Conceptual modeling of a well-developed alluvial basin. In: Subsurface Fluid Flow Modeling, Ritchey, J.D. and Rumbaugh, J.O. (eds.) American Society for Testing and Materials, ASTM STP 1288, pp. 81-96, 1996.

Johnson NM. Deterministic and stochastic approaches for evaluating multiple scales of Santa Clara Valley Hydrostratigraphy. In: Recent Geological Studies in the San Francisco Bay Area, Pacific Section SEPM v. 76, p. 193-208, 1995.

Creasy CL, Johnson NM, Dreiss SJ. Geostatistical analysis of hydrostratigraphic units in alluvial aquifers. Transactions American Geophysical Union Fall Meeting, 74(17), San Francisco, CA, December 1993.

Johnson NM, Dreiss SJ. Characterization of hydrostratigraphic architecture with indicator variograms. Transactions American Geophysical Union Fall Meeting, 71(17): 518, San Francisco, CA, December 1990.

Johnson NM, Dreiss SJ. An indicator geostatistics approach to hydrostratigraphic interpretation. Transactions American Geophysical Union Spring Meeting, 68(16):299, Baltimore, MD, May 1987.

Johnson NM, Dreiss SJ. Geostatistical characterization of alluvial stratigraphy from borehole data at groundwater contamination sites, Geological Society of America Annual Meeting Abstracts with Programs,18(6): 648, San Antonio, TX, October 1986.

Johnson NM. Groundwater recharge and erosion induced by earth fissuring, South-central Arizona, Geological Society of America Abstracts with Programs, 13(2): 63, Cordilleran section meeting, Hermosillo, Sonora, Mexico, March 1981.

Theses and Dissertation

Analysis of Alluvial Hydrostratigraphy Using Indicator Geostatistics, with Examples from Santa Clara Valley, California, Ph.D. dissertation, Earth Sciences, University of California, Santa Cruz, CA, 1994 (committee: S.J. Dreiss, A. Journel [Stanford], R.S. Anderson, P. Gooveraerts [Stanford], and G.B. Griggs).

The Relation Between Ephemeral Stream Regime and Earth Fissuring in South-Central Arizona, M.S. thesis, Hydrology, University of Arizona, Tucson, AZ, 1980 (committee: S.N. Davis, W.B. Bull, and S.Ince).

Potential Hydrologic Impacts of Quarrying in the Felton-Scotts Valley Area, Santa Cruz County, California, B.A. thesis, Earth Sciences, Environmental Studies (double major), University of California, Santa Cruz, CA, 1977.

Short Courses and Selected Conferences

Groundwater Law Workshop, Groundwater Resources Association of California, October, 2017.

Advanced PEST Course, S.S. Papadopoulos & Associates, Dr. John Doherty instructor, April. 2014.

Managed Aquifer Recharge, 14th Biennial Symposium, Groundwater Resources Association of California and Arizona Hydrological Society, Orange, California, July (presenter). 2014.

Water Technology for Emerging Regions, International WaTER Conference, University of Oklahoma, October. 2011.

Artificial Recharge of Ground Water, National Ground Water Association, Dr. Herman Bower and David Pyne instructors, March.

Prior Experience

MWH, now a part of Stantec, Principal Hydrogeologist, 2008-2017

Nicholas M. Johnson, Water Resources Consultant, 1999-2014

Geomatrix Consultants, Senior Hydrogeologist, 1996-1999

CH2M HILL, Hydrogeologist and Project Manager, 1991-1996

Nicholas M. Johnson, Consulting Hydrologist and Hydrogeologist, 1985-1990

J.H. Kleinfelder & Associates, Hydrogeologist, 1982-1985

H. Esmaili & Associates, Hydrologist/Hydrogeologist, 1980-1982

Santa Cruz County Watershed Management Office, Hydrologist Intern, 1976-1977

Professional Affiliations

American Geophysical Union 1983-2017

National Ground Water Association 1983-2017

Geological Society of America 1983-2017

Groundwater Resources Association of California 1999-2017

Project Experience

Contaminated Groundwater Investigation and Remediation

Investigated legacy contamination from rocket engine testing, experimental reactors, and other research activities at a hilltop facility underlain by fractured and faulted sandstone. Contributed to the refinement of the hydrogeologic conceptual model and helped guide the refinement and use of a sitewide numerical groundwater flow model (FEFLOW). Presented investigation results to the California Department of Toxic Substances Control (DTSC), with particular focus on the influence of faults on site groundwater. Received consulting firm’s President’s Award for directing the three-dimensional visualization of the site’s contaminant plumes, and the Engineers’ Council Outstanding Engineering Achievement Merit Award for evaluating the site’s faults.

Developed and applied three-dimensional and physically representative groundwater flow and solute transport models, primarily using the MODFLOW, MT3D, and PEST codes, for contaminant sites occurring under a wide range of hydrogeologic conditions. Models have addressed waste-unit closure and remediation, and the migration and hydraulic control of dissolved solvents, hexavalent chromium, and other heavy metals.

For attachment to an environmental impact report, evaluated the influence of quarry operations and proposed expansion on a coastal karst spring used as a water source by the City of Santa Cruz, California. Developed hydrogeologic conceptual model consistent with boring logs; a stable-isotope survey of springs, streams, and wells; a year-long multiple-tracer test; more than 40 years of groundwater, rainfall, streamflow, and spring monitoring records; and seven years of continuous data-logger records of spring discharge, temperature, and electrical conductivity.

Evaluated potential impacts on vineyard, winery, and residential groundwater use from recycled water use for irrigation in Sonoma County, California.

Developed a compressive hydrogeologic conceptual model of an MTBE-impacted groundwater sub-basin within the Los Angeles coastal plain. Used geostatistical methods and GIS spatial analysis to construct a three-dimensional hydrostratigraphic model of the complex alluvial hydrostratigraphy. Interpreted historical pumping, recharge, water levels, water quality, and changes in storage since 1930. 

Prepared a basin-wide groundwater remediation feasibility study for the San Fernando Valley Superfund Site, a 15-mile long co-mingled contaminant plume derived from multiple sources. Established a comprehensive basin-wide conceptual model and developed both basin-wide and local MODFLOW models that projected groundwater extraction and replenishment by the cities of Los Angeles, Burbank, and Glendale through 2020. With revisions, model used by EPA for more than a decade. Established relationships with local water managers and presented expert testimony at a pre-trial hearing regarding cost recovery from a potentially responsible party. Evaluated potential for ongoing contamination from vadose zone sources and the associated implications for achieving long-term cleanup. 

Groundwater Supply and Management

Prepared the Groundwater Sustainability Plan (GSP) for the westside groundwater basin of San Francisco in compliance with the 2014 California’s Sustainable Groundwater Management Act (SGMA). The plan guides implementation of the city’s Groundwater Supply Project, which will supplement the municipal water supply with groundwater pumped from the westside basin. The plan establishes measurable objectives for avoiding saltwater intrusion, land subsidence, and potential impacts to surface water, while protecting groundwater quality and recharge. The plan’s development included a stakeholder process of inter-agency cooperation, coordination with neighboring water purveyors, and public outreach. 

For the US Army Corps of Engineers, developed and applied a groundwater model to evaluate the influence and effectiveness of a subsurface flow barrier beneath the ring levee surrounding the City of Marysville on the eastern edge of the Sacramento Valley. 

Served as the primary hydrologic and hydrogeologic consultant for a water district in the Santa Cruz Mountains of Central California for greater than two decades. Water district serves thousands of residential connections through the conjunctive use of diverted streamflow and pumped groundwater. Work for district has included stream and groundwater gaging and sampling; multi-well long-term aquifer tests; regional isohyetal maps and precipitation-runoff relations; calibrated sub-regional and wellfield MODFLOW models; comprehensive planning studies, including a 2009 Water Supply Master Plan; State-required documentation of water supply dependability and protection, including a 2010 Urban Water Management Plan; and emergency drought planning. The Urban Water Management Plan assessed water demand and supply; determined base per capita use and use targets mandated by the California Urban Water Planning Act and Water Conservation Bill; evaluated water supply reliability; and described water shortage contingency plans, demand management measures, and potential effects of climate change. 

Evaluated sustainable groundwater yields of the Purisima and Aromas aquifers in coastal Santa Cruz County, California, in light of potential streamflow depletion and saltwater intrusion. Assessed potential conjunctive use and supplemental supply alternatives. 

Retained by the California Attorney General's Office on behalf of the California Department of Parks and Recreation to develop expert opinion for presentation to the California Energy Commission (CEC) regarding the proposed use of groundwater for power-generation cooling in Shasta County, California and its potential impact on spring-fed Burney Falls. 

Analyzed river-groundwater interactions relevant to adjudicated water rights for a consortium of water purveyors in the upper Mojave groundwater basin of southern California. Served on the Mojave Water Agency "scalping" committee to determine annual river baseflows. Developed a procedure for separating stormflow and baseflow hydrographs supported by monitoring data. 

Developed conceptual designs for four facilities to artificially recharge local runoff and help offset basin overdraft and salt water intrusion. Facilities included seasonal surface storage, dual purpose injection-extraction wells, sand dune percolation ponds, and riverside spreading basins. Estimated the quantity and quality of divertible stream flows; directed environmental and water rights assessments and the design of sedimentation facilities; and assisted with pilot injection well. A completed dune recharge facility won the 2001 National Ground Water Association Ground Water Protection Award. 

Developed a hydrogeologic conceptual model of the Santa Clara Valley groundwater basin relying on 80 years of historical data and information from more than 1,000 wells and a dozen recharge facilities. Layered basin based on statistical distribution of well perforations, and zoned aquifer properties from interpretation of ancient depositional environments. The resulting MODFLOW model simulated the basin’s steep, vertical gradients, and was used by the Santa Clara Valley Water District for more than a decade. 



  • Ph.D., Earth Sciences, University of California, Santa Cruz, 1994
  • M.S., Hydrology, University of Arizona, 1980
  • B.A., Earth Sciences, Environmental Studies, University of California, Santa Cruz, 1977


Professional Geologist (P.G.), California, #4344 1987-2017

Certified Hydrogeologist (C.Hg.), California, #661 1999-2017