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Groundwater Awareness Week is March 6-12

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Groundwater is not a single vast pool of underground water; rather, it is contained within a variety of aquifer systems. Each of these aquifers has its own set of questions and challenges. From large drawdowns in the Great Plains aquifer to arsenic in some wells in New England, this episode of CoreCast highlights six different USGS groundwater studies all across the United States.




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Groundwater Awareness Week is March 6-12


Kara Capelli: Hello and welcome to USGS CoreCast. I'm your host, Kara Capelli. Groundwater is one of the nation's most important natural resources. In fact, groundwater is the primary source of drinking water for approximately half the nation. And it provides about 40 percent of irrigation water for agriculture. Groundwater is hidden from view so we often take it for granted.

The USGS studies the quantity and quality of groundwater all across the nation. When it comes to groundwater, each area has its own of questions and challenges. For this episode of CoreCast, I spoke with USGS scientists from all over the country who study groundwater. We'll start in the middle of the country. The High Plains Aquifer in the Midwest is one of the world's largest aquifers. It's also one of the most used for drinking water and agriculture.


Jenny McGuire: My name is Jenny McGuire. I'm a hydrologist working at the USGS Nebraska Water Science Center. My job is to study water level changes in the High Plains Aquifer. The reason the water levels need to be monitored is to assess the extent of declines in the aquifer. When water levels decline, the irrigation pumps become less efficient. So, it's more costly to pump the water out or if the water levels can decline so much that the pumps don't work anymore.

Kara Capelli: Even further west, in San Diego, California, scientists are just beginning to understand how much groundwater is available.

Wes Danskin: My name is Wes Danskin. I'm the research hydrologist in charge at the San Diego Hydrogeology Project. So, San Diego is an area of very little water. And that has always been true. It survived off of its local surfacing groundwater resources up until about World War II. And since that time, it has been surviving on imported water from the Colorado River in the San Francisco Bay Delta. So, the local groundwater resources have not really been investigated because of the imported water. So, now with those resources, being both environmentally and politically less reliable, they're interested locally in identifying what groundwater resources are available.


So, the USGS has been involved for almost a period of 10 years in mapping the geology, the subsurface structure of the groundwater basins, identifying the groundwater flow paths, identifying how much water recharges in the mountains, how it flows to the coasts and then putting in deep monitoring wells 1500 feet, 2000 feet deep monitoring wells, to help identify the geologic structure, map the groundwater and then be able to monitor if additional groundwater has extracted potential adverse effects.

Kara Capelli: Groundwater drawdowns and quality issues are not unique to the western half of the country. As recently as last year, some residence of Raleigh, North Carolina, faced empty wells.

Melinda Chapman: I'm Melinda Chapman and I'm the groundwater specialist for the USGS in the North Carolina Water Science Center in Raleigh. An issue of interfering groundwater use has occurred in the Piedmont region in North Raleigh in Wake County since 2005. And the county has a large number of private homeowner wells and hundreds of community wells.


The community wells pump much larger volumes of groundwater compared to an individual private well. As recently as September and October 2010, groundwater levels in some private wells in the North Raleigh neighborhood declined below 300 feet, resulting in dry wells and a temporary loss of water for supply.

Kara Capelli: Groundwater quality can be an issue in parts of the East Coast as well, like Maine, where recently USGS scientists have been studying arsenic levels.

Joe Ayotte: My name is Joe Ayotte and I'm a USGS hydrologist studying arsenic and groundwater in New England and throughout the US. Arsenic is a known carcinogen but also affects other aspects of human health, including cardiovascular and possibly immune system response functions.


We have identified large areas in New England where high concentrations of arsenic are common and where a large percentage of the population uses private wells. The evidence suggests that the arsenic we see in groundwater originates from rocks and minerals in the region. These findings have led to New England states and US EPA to recommend testing for arsenic in all private wells in the region in order to better protect human health.

Kara Capelli: Further south, in Florida, quality can be affected when saline coastal waters mix with freshwater aquifers.

Chris Langevin: My name is Chris Langevin. I'm a research hydrologist with the USGS. Saltwater intrusion is what happens in many coastal areas when too much water is withdrawn from an aquifer and saltwater in any aquifer is drawn inland. And this can be a big problem for local residents and municipalities because much of the freshwater that is provided to cities comes from the shallow aquifers.


So, the USGS is actively involved in this on several different fronts. One would be providing the data, showing where saltwater intrusion has occurred. But there are also studies that use computer simulations to predict what might happen in the future if pumping rates were to increase or sea level were to rise. And so, this is important to many of the cities in coastal areas as a way to manage the resources.

Kara Capelli: Even in areas where it seems like there is an abundance of water, like the Great Lakes Basin, it may not always be available when and where it's needed. Scientists in this area are working to understand how groundwater and surface water interact and how different uses impact one another.

Howard Reeves: My name is Howard Reeves. I'm a research hydrologist at the USGS Michigan Water Science Center. Groundwater is very important in the Great Lakes system. In a recent study, USGS estimated that the amount of groundwater in storage is equal to about another Lake Huron worth of water.


Groundwater is also used extensively around the basin by many different users from individual homes to industries and agriculture. One of the big questions that we're looking at now is the interaction between groundwater and surface water. There is a lot of interest for people in knowing is there an impact of a well on a nearby stream. And USGS is working on different methods to quantify that interaction.

Kara Capelli: Groundwater is not a single vast pool of underground water. It's contained within a variety of aquifer systems, like the ones you heard about today. Many aquifers cross political boundaries, including counties, states and international boundaries. The USGS provides impartial groundwater data and information and develops new methods for studying and protecting groundwater.


Robert Schreiber: My name is Robert Schreiber. I'm serving as the non-federal co-chair of the Subcommittee on Groundwater. I also serve on the board of directors of the National Groundwater Association. Groundwater is a widely used resource that is not easily seen. It's under the ground. And so, you can't see what's happening to it. And it can be threatened very easily and damaged very easily. We need to protect it and we also need to understand how to keep it sustainable. The USGS provides extremely important data for characterizing groundwater. And we use that information all the time on our projects.

Kara Capelli: For information about the studies mentioned on this episode of CoreCast and for information on groundwater in your area, visit the USGS Groundwater Information website at And don't forget to follow the USGS on Twitter at or visit our other social media channels at I'm Kara Capelli and CoreCast is a product of the US Geological Survey, Department of the Interior.

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