| Abstract: | This report describes the results of a study by
the U.S. Geological Survey, in cooperation with the
Delaware River Basin Commission, to develop a
regional ground-water-flow model of the French
Creek Basin in Chester County, Pa. The model was
used to assist water-resource managers by illustrating
the interconnection between ground-water
and surface-water systems. The 70.7-mi2 (square
mile) French Creek Basin is in the Piedmont Physiographic
Province and is underlain by crystalline
and sedimentary fractured-rock aquifers. Annual
water budgets were calculated for 1969-2001 for
the French Creek Basin upstream of streamflow measurement
station French Creek near Phoenixville
(01472157). Average annual precipitation was
46.28 in. (inches), average annual streamflow was
20.29 in., average annual base flow determined by
hydrograph separation was 12.42 in., and estimated
average annual ET (evapotranspiration) was
26.10 in. Estimated average annual recharge was
14.32 in. and is equal to 31 percent of the average
annual precipitation. Base flow made up an average
of 61 percent of streamflow.
Ground-water flow in the French Creek Basin
was simulated using the finite-difference
MODFLOW-96 computer program. The model
structure is based on a simplified two-dimensional
conceptualization of the ground-water-flow system.
The modeled area was extended outside the
French Creek Basin to natural hydrologic boundaries;
the modeled area includes 40 mi2 of adjacent
areas outside the basin. The hydraulic
conductivity for each geologic unit was calculated
from reported specific-capacity data determined
from aquifer tests and was adjusted during model
calibration. The model was calibrated for aboveaverage
conditions by simulating base-flow and water-level measurements made on May 1, 2001, using a recharge rate of 20 in/yr (inches per year). The model was calibrated for below-average conditions by simulating base-flow and water-level measurements made on September 11 and 17, 2001,
using a recharge rate of 6.2 in/yr. Average conditions
were simulated by adjusting the recharge rate
until simulated streamflow at streamflow-measurement
station 01472157 matched the long-term
(1968-2001) average base flow of 54.1 cubic feet
per second. The recharge rate used for average
conditions was 15.7 in/yr.
The effect of drought in the French Creek
Basin was simulated using a drought year recharge
rate of 8 in/yr for 3 months. After 3 months of
drought, the simulated streamflow of French Creek
at streamflow-measurement station 01472157
decreased 34 percent. The simulations show that
after 6 months of average recharge (15.7 in/yr) following
drought, streamflow and water levels recovered
almost to pre-drought conditions.
The effect of increased ground-water withdrawals
on stream base flow in the South Branch
French Creek Subbasin was simulated under average
and drought conditions with pumping rates
equal to 50, 75, and 100 percent of the Delaware
River Basin Commission Ground Water Protected
Area (GWPA) withdrawal limit (1,393 million gallons
per year) with all pumped water removed from
the basin. For average recharge conditions, the
simulated streamflow of South Branch French
Creek at the mouth decreased 18, 28, and 37 percent
at a withdrawal rate equal to 50, 75, and
100 percent of the GWPA limit, respectively. After
3 months of drought recharge conditions, the simulated
streamflow of South Branch French Creek at
the mouth decreased 27, 40, and 52 percent at a
withdrawal rate equal to 50, 75, and 100 percent of
the GWPA limit, respectively.
The effect of well location on base flow, water
levels, and the sources of water to the well was
simulated by locating a hypothetical well pumping
200 gallons per minute in different places in the
Beaver Run Subbasin with all pumped water
removed from the basin. The smallest reduction in
the base flow of Beaver Run was from a well on the
drainage divide |
| Genre: | USGS Numbered Series |
| ProdID: | 53972 |
| Citation Author: | Sloto, Ronald A. |
| Citation Contributing Office: | |
| Citation Datum: | |
| Citation Day: | |
| Citation Edition: | - |
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| Citation Keywords: | |
| Citation Language: | ENGLISH |
| Citation Larger Work Title: | |
| Citation LatN: | 0402500 |
| Citation LatS: | 0397500 |
| Citation LonE: | -0752500 |
| Citation LonW: | -0760000 |
| Citation Month: | |
| Citation No Pagination: | |
| Citation Number Of Pages: | |
| Citation Online Only Flag: | |
| Citation Phsyical Description: | viii, 82 p. : ill., maps ; 28 cm. |
| Citation Projection: | |
| Citation Public Comments: | |
| Citation Publisher: | |
| Citation Series: | Water-Resources Investigations Report |
| Citation Series Code: | WRI |
| Citation Series Number: | 2003-4263 |
| Citation Search Results Text: | Geohydrology of the French Creek basin and simulated effects of droughtand ground-water withdrawals, Chester County, Pennsylvania; 2004; WRI; 2003-4263; Sloto, Ronald A. |
| Citation Start Page: | |
| Citation Volume: | |
| Citation Year: | 2004 |
| Type: | citation/reference |
| Text: | Geohydrology of the French Creek basin and simulated effects of droughtand ground-water withdrawals, Chester County, Pennsylvania; 2004; WRI; 2003-4263; Sloto, Ronald A. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/usgs_thumb.jpg |
| URL (INDEX PAGE): | http://pubs.usgs.gov/wri/wri034263/ |
| Date Other: | Sat, 1 Jan 1994 00:00 -0600 |
| Publisher: | |
