Hank Johnson



Hank Johnson is a hydrologist with the U.S. Geological Survey at the Oregon Water Science Center in Portland, Oregon. His research interests include arid-system hydrology, groundwater and spring systems, and environmental tracers.


Active Studies


Understanding changes in spring discharge to short- and long-term climatic changes in southeastern Oregon

Springs are an important resource for grazing animals and wildlife in southeastern Oregon, where precipitation is seasonal and spatially heterogeneous. This study seeks to identify common causes of interannual spring variability on lands managed by the U.S. Bureau of Land Management and U.S. Fish and Wildlife Service to help them prioritize individual springs and regions for long-term conservation.


Recharge dynamics of basalt aquifers in northeastern Oregon

Recharge of the basalt aquifers underlying the Blue Mountains and adjacent lowlands in northeastern Oregon is not well understood. Recent studies have demonstrated that much of the recharge occurring in the Blue Mountains emerges as streamflow and only a fraction of that initial recharge infiltrates into the deep basalt aquifers of the region. Ongoing water budget and geochemical studies are providing new insights into the sources and timing of recharge to these regional aquifers used for drinking and irrigation.


Groundwater resources of the Walla Walla Basin, Oregon-Washington

Surface water in the Walla Walla Basin is overappropriated and groundwater levels are declining rapidly in portions of the underlying basalt aquifer system. The rivers in the basin support several species of threatened fish and other culturally important fish species. Demands for groundwater and surface water for irrigation, drinking water, and other uses are often at odds with the needs of the aquatic ecosystem. Competing interests, coupled with differing legal structures for water management in the two states, has led to ongoing conflicts in recent years. To provide a scientific framework for managing competing interests for the finite water resources of the basin, the states of Oregon and Washington engaged USGS to begin a comprehensive assessment of the groundwater resources of the Walla Walla Basin starting in 2020. The study will be the first  basin-wide assessment of groundwater since the 1970s. It will incorporate and synthesize the enormous amount of data and understanding that have accumulated in the intervening years, and will collect new information to fill in gaps in understanding.



Groundwater resources of the Harney Basin, Oregon

Groundwater levels have been in decline in many areas of the Harney Basin since the 1970s. In the last decade, new withdrawals for irrigation have sharply increased the rate of decline in portions of the basin. Substantial uncertainty exists regarding the extent to which the newest groundwater development will impact surface-water resources and holders of senior surface-water rights throughout the basin. To provide a modern, scientific framework to address these concerns, USGS began an evaluation of the Harney Basin groundwater flow system in cooperation with the Oregon Water Resources Department in 2016. The study builds on the only comprehensive study of the groundwater flow system published in the 1930s. Modern analytical methods, such as remote sensing to quantify evapotranspiration and geochemical tracers to quantify groundwater recharge source and residence time are advancing our understanding of the groundwater flow system and water budget. New reports describing the hydrogeology and water budget are in preparation, and will provide stakeholders and water resource managers with information to make informed groundwater-resource decisions. A numerical model is currently being developed and will provide additional tools for understanding and planning the impacts of water development in the basin.



Characterizing the timing, stability, and sources of water to the Willamette River using stable isotopes

Climate of the Willamette River Basin is characterized by warm, dry summers and wet, cool winters; 75% of the annual precipitation falls between October and March. During the wet season, rain is the dominate form of precipitation below about 1,000 m and snow dominates above about 1,500 m. Late summer flow in the Willamette River and its tributaries is dominated by precipitation that fell at least 6 months prior. The timing, stability, and sources of water to the Willamette River and its tributaries during summer low-flow periods is the primary question being investigated in this study.




M.S., Environmental Science and Engineering, 1996
Oregon Graduate Institute of Science & Technology
Hillsboro, Oregon

B.S., Geological Sciences, 1992
Virginia Polytechnic Institute & State University
Blacksburg, Virginia