NC0090000_More Information (Received)_20210813

Supplemental Attachment for
NPDES Individual Permit Application
USGS Low Flow Determination

Brian Garner
From: Weaver,John C <[e-mail]>
Sent: Tuesday,June 15, 2021 4:04 PM
To: Brian Garner
Cc: Hill, David A; [e-mail]; Montebello, Michael J;Albertin, Klaus P;Weaver,John C
Subject: [EXT] USGS response to DWR USGS Low Flows request#2021-125 (dated 2021/06/11)for NP Clarke
Creek Mecklenburg County...RE: [EXTERNAL] Low-flow request approval
CAUTION
Mr.Garner,
In response to your inquiry about the low-flow characteristics for the North Prong Clarke Creek just upstream from
Huntersville-Concord Road (Secondary Road 2442) near Huntersville in northern Mecklenburg County,the following
information is provided:
A check of the low-flow files here at the USGS South Atlantic Water Science Center(Raleigh office)does not indicate a
previous low-flow determination for the point of interest, identified by the lat/long coordinates (35.420289,-80.799470)
associated with the email dated 06/11/2021 from the DWR USGS Low Flow portal following your request submission.
No USGS discharge records are known to exist for the point of interest.
In the absence of site-specific discharge records sufficient for a low-flow analysis,estimates of low-flow characteristics at
ungaged locations are determined by assessing a range in the low-flow yields(expressed as flow per square mile
drainage area, or cfsm)at nearby sites where estimates have been determined.
A basin delineation completed using the online USGS StreamStats application for North Carolina
(https://streamstats.usgs.gov/ss/) indicates the drainage area for the point of interest(StreamStats adjusted
coordinates 35.42054,-80.79948 NAD83)is 3.5 sqmi,which confirms the drainage area submitted as part of the request
information.
For streams in northern Mecklenburg County,low-flow characteristics published by the USGS are provided in the
following reports:
(1)The first is a statewide report completed in the early 1990's. It is USGS Water-Supply Paper 2403, "Low-flow
characteristics of streams in North Carolina" (Giese and Mason, 1993). An online version of the report is available at
http://pubs.usgs.gov/wsp/2403/report.pdf. The report provides the low-flow characteristics(based on data through
1988)via regional relations and at-site values for sites with drainage basins between 1 and 400 sqmi and not considered
or known to be affected by regulation and/or diversions.
(2)The second is a basin-wide report for the Rocky River basin published in 2003. It is USGS Water-Resources
Investigations Report 03-4147, "Low-Flow Characteristics and Profiles for the Rocky River in the Yadkin-Pee Dee River
Basin, North Carolina,through 2002" (Weaver and Fine,2003). An online version of the report is available through
http://pubs.usgs.gov/wri/wri034147/. The report provides the low-flow characteristics(based on data through 2002)
for continuous-record gaging stations and partial-record sites within the Rocky River basin. The report also provides
low-flow discharge profiles(7010, 30Q2,winter 7010,and 7Q2)for the Rocky River from its headwaters in Mecklenburg
County to its mouth.
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(3)The third is a statewide report published in March 2015. It is USGS Scientific Investigations Report 2015-5001, "Low-
flow characteristics and flow-duration statistics for selected USGS continuous-record streamgaging stations in North
Carolina through 2012" (Weaver, 2015). The report is available online at http://pubs.usgs.gov/sir/2015/5001/. The
report provides updated low-flow characteristics and flow-duration statistics for 266 active(as of 2012 water year)and
discontinued streamgages across the state where a minimum of 10 climatic years discharge records were available for
flow analyses.
Low-flow characteristics estimated for point of interest:
Inspection of the latter two reports indicates the presence of eight (8) selected nearby USGS partial-record sites (6) and
continuous-record streamgages(2) in the general vicinity of the point of interest where low-flow characteristics were
published. Among these 8 sites,the low-flow discharge yields for the indicated flow statistics are as follows:
Annual 7Q10 low-flow yields ==>from 0 to 0.16 cfsm (average about 0.071 cfsm, median about 0.075 cfsm) (zero flow at
1 of 6 index sites)
Annual 30Q2 low-flow yields ==>from 0.015 to 0.28 cfsm (average about 0.17 cfsm, median about 0.16 cfsm)
Winter 7Q10 low-flow yields==>from 0.0045 to 0.24 cfsm (both average and median about 0.12 cfsm)
Annual 7Q2 low-flow yields==>from 0.0045 to 0.23 cfsm (average about 0.12 cfsm, median about 0.11 cfsm)
Average annual discharge yields==>from 0.98 to 1.1 cfsm (both average and median about 1.1 cfsm)
Application of the above range in yields to the drainage area (3.5 sqmi)for the point of interest results in the following
estimated low-flow discharges:
Annual 7Q10 low-flow discharges==>from 0 to 0.56 cfs (average about 0.25 cfs, median about 0.26 cfs)
Annual 30Q2 low-flow discharges==>from 0.053 to 0.98 cfs(average about 0.6 cfs, median about 0.56 cfs)
Winter 7Q10 low-flow discharges==>from 0.016 to 0.84 cfs(both average and median about 0.42 cfs)
Annual 7Q2 low-flow discharges==>from 0.016 to 0.81 cfs (average about 0.42 cfs, median about 0.39 cfs)
Average annual discharge discharges ==>from 3.4 to 3.9 cfs(both average and median about 3.9 cfs)
Please note:
(1)The estimated flows are provided in units of cubic feet per second (cfs).
(2)The low-flow yields provided above are rounded to 2 significant figures. Estimated low-flow discharges less than 1
cfs are rounded to 2 significant figures. If between 1 and 100 cfs,then rounded to 1 decimal place; if greater than 100,
then rounded to the nearest whole number(zero decimal places).
(3)The information provided in this message is based on a preliminary assessment and considered provisional, subject
to revision pending collection of future data and further analyses.
These provisional streamflow statistics are provided via the DWR USGS Low Flows cooperative agreement between the
USGS and the N.C. Department of Environmental Quality, Division of Water Resources.
Hope this information is helpful.
Thank you.
Curtis Weaver
J. Curtis Weaver, Hydrologist, PE Email: icweaver(a�usgs.gov
USGS South Atlantic Water Science Center Online:https://www.usgs.gov/centers/sa-water
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North Carolina-South Carolina-Georgia
3916 Sunset Ridge Road
Raleigh,NC 27607
Phone:[phone] // Fax:[phone]
From:Albertin, Klaus P<[e-mail]>
Sent: Friday,June 11,2021 11:37 AM
To: [e-mail]
Cc:Albertin, Klaus P<[e-mail]>; Hill, David A<[e-mail]>; [e-mail];
Weaver,John C<[e-mail]>; Montebello, Michael J<[e-mail]>
Subject: [EXTERNAL] Low-flow request approval
This email has been received from outside of DOI-Use caution before clicking on links,opening attachments,or responding.
Your request has been approved and will be forwarded to USGS.A response from USGS usuallytakes 7- 10 business
q PP P
days.
Request Flow Statistic Approval
Request ID: 125
Requestor: Brian Garner
Requestor e-mail: [e-mail]
Requestor Phone: [phone]
Local Government:
Public Water Supply:
Consultant:Apex Companies
Contact: Brian Garner
Reason: Permit
River/Stream: North Prong Clarke Creek
Drainage Area (sq. mi.):3.5
Latitude: 35.420289
Longitude:-80.799470
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Other Information:
Statististics: ["7010","3002"]
Approved by:Albertin, Klaus P
This email originated from outside of the organization.Do not click links or open attachments unless you recognize the sender and
know the content is safe.
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