Crystalline Rock Aquifer
Aquifer characteristics: Water levels in six wells were measured in crystalline-rock aquifers in the Piedmont and Blue Ridge Physiographic Provinces of Georgia. In this area, water is present in discontinuous joints and fractures and may be confined (under pressure by overlying sediments) or unconfined (in contact with the atmosphere). In general, crystalline-rock aquifers are local in extent and can be greatly affected by localized water use and climate. During 2015, about 100.5 million gallons per day (Mgal/d) were withdrawn from the crystalline-rock aquifers in Georgia, primarily for domestic use (Painter, 2019). Hydrographs for selected wells (below) illustrate monthly mean water levels for the period of record. The hydrographs show periodic upward or downward trends that reflect changes in precipitation and pumping.
Well Locations with Ten Year Trend Icons
Arrow icons represent upward or downward water-level trend. Water-level trend calculations based on last 10 years of data.
Circle icon represents slope of trend line with an absolute value that is less than 0.01 feet per year (ft/yr), and/or less than 100 monthly-mean water levels from the last 10 years of data.
Split color icons represent wells with graphs.
Light blue square indicates nearby precipitation gage.
(Click or hover over map icons for more information.)
Water-level Trends: The table below shows the period of record (POR) and most recent ten-year trends of monthly mean water levels for the crystalline-rock aquifer wells. The data used in the trend analyses are pulled from the USGS National Water Information System: Web Interface (NWISweb), and the trends are calculated in feet per year (ft/yr). The check boxes on the left side of the table allow the reader to compare only those wells of interest by selecting them on or off to appear on the Monthly Mean Composite Graph.
Below the table and composite graphs are trend analysis graphs for four selected wells. The trend analyses show mostly seasonal variations, with periodic upward or downward trends that respectively reflect surpluses or deficits in rainfall. A simple regression line may be placed on the graph by selecting the Simple Regression button, and the slope of the line is calculated. To clear the regression line, select the Clear Regression Line button. Like the composite graph, the user can click and drag the mouse vertically or horizontally to change the scale and zoom in to the time-period of interest. Any changes to the time scale will require the user to clear and recreate a regression line for the new time scale. Double click on the graph and it will return to the period of record.
2022 conditions for select wells: The POR mean of monthly water levels for well 12JJ04 ranged from 26.2 to 28.8 ft below land surface. During 2022, monthly mean water levels ranged from 26.1 to 29.9 ft below land surface. The POR mean of monthly water levels for well 10DD02 ranged from 5.2 to 7.5 ft below land surface. During 2022, monthly mean water levels ranged from 3.2-6.3 ft below land surface. The POR mean of monthly water levels for well 11FF04 ranged from 6.9 to 7.6 ft below land surface. During 2022, monthly mean water levels ranged from 7.3 to 8.5 ft below land surface. The POR mean of monthly water levels for well 16MM03 ranged from 3.9 to 4.8 ft below land surface. During 2022, monthly mean water levels ranged from 3.9 to 5.6 ft below land surface.
Period of Record (POR) and 2022 Summary Table
| Well | Period of Record | 2022 |
|---|---|---|
| Mean of monthly water levels in feet below land surface | Monthly mean water levels in feet below land surface | |
| 12JJ04 | 26.2-28.8 | 26.1-29.9 |
| 11FF04 | 6.9-7.6 | 7.3-8.5 |
| 10DD02 | 5.2-7.5 | 3.2-6.3 |
| 16MM03 | 3.9-4.8 | 3.9-5.6 |
Period of Record (POR) and 2022 Summary Table and above text, updated June 2023. Monthly Mean Composite graph updated weekly, all other graphs and tables continuously updated.
Slope of trend line for Period of Record (POR) and previous Ten Years
Station Name Data Link |
County |
POR First Month/Year |
POR slope (ft/yr) |
Ten Year slope (ft/yr) |
|---|---|---|---|---|
| Dawson | xx | xx | yy | |
| DeKalb | xx | xx | yy | |
| Fulton | xx | xx | yy | |
| Greene | xx | xx | yy | |
| Madison | xx | xx | yy | |
| White | xx | xx | yy |
Slope of 0.00 represents no trend.
Monthly Mean Composite Graph
To change the graph scale, click and drag mouse vertically or horizontally.
To reset the graph scale, double click on the graph.
(mouse over graph for date and depth)
Select Monthly Mean Data Graphs with Trend Analysis
To change the graph scale, click and drag mouse vertically or horizontally. To reset graph scale, double click on the graph.