Lesson 7: Finding the water table

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  • #61733
    Tyler Hogan

    If you’re curious to learn how far down you’d have to dig before you hit water, wonder no more! The United States Geological Survey (USGS) provides detailed hydrology data for the whole country on their website.

    For example, I live in Kent County, Delaware. Here’s a link to one of their well sites in my country showing the distance between the surface and the water table. Take a look: http://nwis.waterdata.usgs.gov/usa/nwis/gwlevels/?site_no=390935075320001

    Notice the graph shows a variation between 100–130′ over a 4-year period. This data is from the 1970’s, so things might have changed quite a bit since then, but some of the data points will be much more recent.

    You can find your own data by going to http://nwis.waterdata.usgs.gov/nwis/gwlevels?search_criteria=state_cd&submitted_form=introduction and selecting your state from the menu. Choose “Show sites on a map” under “Choose Output Format” then, click “submit”. It will generate a map showing you their data points. You can zoom in to find the closest data point to your home. Click on the data point and click “Access data.” Then click “Field groundwater-level measurements” to see the details.

    If you get an error saying there are too many data points (which happens in larger states), click here: http://nwis.waterdata.usgs.gov/nwis/gwlevels?search_criteria=state_cd&search_criteria=lat_long_bounding_box&submitted_form=introduction. From this link you can select BOTH the state, and a latitude/longitude bounding box. Since you know your own coordinates (from unit 1) you can set a bounding box. For instance, if your coordinates are 38.7° N, 77.2° W, you could type in NORTH: 39°, SOUTH: 38°, EAST: 77°, WEST 78°. That would give you a 1° x 1° box around your location, and narrow down the number of data points the map has to render considerably. (If you don’t remember your location, just Google search “CITY STATE coordinates”

    It may sound complicated, but once you get into it it’s not that hard.

    So, following that procedure, what’s the water table depth from the surface near you?

    OR, if you find an easier way to locate the data, let me know!

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