Current Water Levels for Chester County
The graphs and tables below present current conditions for precipitation, groundwater, and streamflow conditions for sites in Chester County.
Summary reports for 2021, 2020, 2019, and 2018 are available on the CCWRA Water Conditions and Water Quality Reports web page.
CCWRA also prepares a Weekly Summary of Hydrologic Conditions at the end of each week with basic information on precipitation, groundwater and reservoir levels, and stream flows.
For the fifth year in a row, precipitation levels in Chester County were above the average of 47.1 inches.
|Year||Total Precipitation for Year||Compared to Long-Term Average of 47.1 inches|
|2022||53.4 inches||6.3 inch surplus|
|2021||51.2 inches||4.1 inch surplus|
|2020||55.2 inches||8.1 inch surplus|
|2019||54.9 inches||7.8 inch surplus|
|2018||69.8 inches||22.7 inch surplus|
|2017||42.7 inches||4.4 inch deficit|
90-Day Precipitation Indicator Graph
A useful metric for the amount and timing of precipitation is the 90-Day Precipitation Indicator Graph (shown above). The rainfall data is collected by the National Weather Service (NWS) and published by the U.S. Geological Survey and provide a reference for whether or not recent precipitation amounts are within normal levels, or if the region is entering a drought watch, warning, or emergency.
For 2022 and 2023, the graph illustrates that for most of the past year, Chester County had normal or above normal rainfall as indicated by the black line, which is the measured 90-day cumulative rainfall, being in or above the green band. There was a period in the winter and early spring of 2022 when the rainfall dropped below the historic average. When the black line in the graph above is in the green band, it means that rainfall over the past 90-days is considered "normal" from 25% above to 25% below the historic average. The yellow band indicates drought watch (from 25% to 35% below average), the orange is drought warning (from 35% to 45% below average), and the red is drought emergency (greater than 45% below average).
90-Day Precipitation Total and Departure from Average
The National Weather Service's Middle Atlantic River Forecast Center publishes updates on total rainfall (in inches) as well as the surplus or deficit for each county across the state.
The illustration above is for the past 90 days. Counties shaded blue or green have a rainfall surplus and counties shaded yellow, orange, or red have a rainfall deficit.
Groundwater is water located beneath the ground’s surface that occupies the pore spaces and fractures between soil particles and rocks. Depth to groundwater can vary significantly based on slope, geology, elevation, and location on the landscape. Long-term monitoring of groundwater levels provides information on normal conditions and typical annual variations. Deviations from normal levels may indicate that less groundwater is available to sustain stream flows and groundwater-based drinking water supplies.
High groundwater levels can result in the emergence of new springs and seeps on valley walls and in low-lying areas or areas along the base of slopes. These springs and seeps can impact agricultural production by reducing suitable cropland areas or delaying harvests, interfere with septic fields or spray application of wastewater disposal, and present difficulties in mowing or maintaining residential areas.
30-Day Moving Average for Groundwater
With precipitation surpluses in 2022, groundwater levels have generally remained in the "normal" range throughout 2022. While not reflected in the graph above for Well 10, groundwater levels in some areas of the County have dipped below the normal range in the summer and fall of 2022; monthly recorded water levels for other wells in the County is available on the CCWRA Observation Well Network web page.
One of the wells monitored by the U.S. Geological Survey is located in central Chester County (West Marlborough Township). The USGS plots the 30-day moving average of the water level compared to normal and drought indicators. When the black line is in the green band, groundwater levels at that location are "normal" or between 25% above and 25% below the historic average.
USGS Observation Well Network in Chester County
There are 22 observation wells measured by the USGS, with one well outfitted with a data logger to monitor the water level hourly and the other 21 wells measured once per month.
The well with hourly data is Well CH 10 (link to USGS web page)
Wells Measured Monthly around the 20th of each month
(Most Recent Published Information)
Chester County has over 2,300 miles of streams across 21 watersheds. Water flowing in these streams originates from the precipitation that falls upon the landscape, which makes its way to streams either from overland runoff (after rainfall events) or from groundwater contributing to the streams‘ base flow (between rainfall events). Water quality is closely linked to stream flow; higher flows from storm runoff can result in increased instream sediment loads (by generating greater streambank erosion and bed scour) and other pollutants. When the stream flows are not a result of storm runoff, the water quality in the stream is more representative of groundwater conditions, as groundwater infiltration replenishes baseflows in our streams.
Stream flows are monitored at 32 USGS continuous-record gaging stations in and around Chester County. These stations provide hourly updates, which can be found on the USGS stream flow website for Pennsylvania.
30-Day Moving Average for Stream Flow
Stream flows are a combination of groundwater flowing to streams and runoff from rain events. In 2022, stream flows in Chester County were typically within the 'normal' range (the green band in the above graph). The graph shown above is for the Brandywine Creek at Chadds Ford which is one of the larger creeks in Chester County.
The U.S. Geological Survey plots the 30-day moving average of the water level compared to normal and drought indicators. Sharp increases in the black line are following significant storms that raise the water levels well above normal levels.
7-Day Average Stream Flow
The U.S. Geological Survey provides a map of the status of stream flows across the state compared to historic stream flow levels. Locations that are green are at normal levels, locations in blue are above normal and locations that are orange or red are below normal.
Source: USGS WaterWatch web page
Additional Information & Resources from CCWRA
- Drought Conditions/Hydrology
- Chester County Volunteer Rainfall Observer Network
- Groundwater Observation Network
- USGS Precipitation Monitoring Network
- USGS Streamflow Measurement Network