What 40 years of data reveal about America’s rivers and aquifersA new USGS study finds that across much of the United States, streamflow has b...
Published by Water Network Research, Official research team of The Water Network
What 40 years of data reveal about America’s rivers and aquifers
A new USGS study finds that across much of the United States, streamflow has been rising while groundwater levels keep falling, and only one way of slicing the map can make sense of why.
For decades, hydrologists have treated groundwater and surface water as two faces of the same resource: water that seeps into the ground eventually feeds the streams above it, and water drawn from streams can recharge the aquifers below. Groundwater discharge is estimated to account for roughly half of all streamflow in the United States. In theory, when one rises, the other should follow.
A new study by USGS researchers Zachary C. Johnson, of the Washington Water Science Center, and Michelle A. Walvoord, of the Water Resources Mission Area, put that assumption to a national-scale test and found that the two systems are, more often than not, moving in opposite directions.
Published in the journal Environmental Research: Water under the title “As above, so below? Trends in groundwater and streamflow across the United States 1980–2020,” the study is the first to attempt a systematic, coupled trend analysis of groundwater and streamflow data at the scale of the entire country.
A dataset four decades deep
The analysis draws on two of USGS’s largest hydrologic data releases: streamflow trend data from 4,992 monitoring sites and groundwater trend data from 19,304 wells screened in unconfined aquifers, the type most likely to respond to changes at the surface. Rather than settle on a single time frame, the authors examined three overlapping windows, 1980–2020, 1990–2020, and 2000–2020, to see whether the length of record changed the story.
A new USGS study finds that across much of the United States, streamflow has been rising while groundwater levels keep falling, and only one way of slicing the map can make sense of why.
For decades, hydrologists have treated groundwater and surface water as two faces of the same resource: water that seeps into the ground eventually feeds the streams above it, and water drawn from streams can recharge the aquifers below. Groundwater discharge is estimated to account for roughly half of all streamflow in the United States. In theory, when one rises, the other should follow.
A new study by USGS researchers Zachary C. Johnson, of the Washington Water Science Center, and Michelle A. Walvoord, of the Water Resources Mission Area, put that assumption to a national-scale test and found that the two systems are, more often than not, moving in opposite directions.
Published in the journal Environmental Research: Water under the title “As above, so below? Trends in groundwater and streamflow across the United States 1980–2020,” the study is the first to attempt a systematic, coupled trend analysis of groundwater and streamflow data at the scale of the entire country.
A dataset four decades deep
The analysis draws on two of USGS’s largest hydrologic data releases: streamflow trend data from 4,992 monitoring sites and groundwater trend data from 19,304 wells screened in unconfined aquifers, the type most likely to respond to changes at the surface. Rather than settle on a single time frame, the authors examined three overlapping windows, 1980–2020, 1990–2020, and 2000–2020, to see whether the length of record changed the story.
Tags
- Research
- Groundwater
- Water Resources
- Groundwater Recharge
- Groundwater Mapping
- Groundwater Data Scientist
- United States