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[Fwd: [Fwd: Re: Fw; A follow-up note ... Re: Low -flow characteristics
Subject: [Fwd: [Fwd: Re: Fw: A follow-up note ... Re: Low -flow characteristics at Lock 1...]]
From: Alan Clark <[e-mail]>
Date: Wed, 12 Dec 2007 08:26:40 -0500
To: Planning Section - DWQ <[e-mail]>
FYI. Attached is an email thread between USGS, DWR and a past director of the Lower Cape
Fear Water and Sewer Authority. This thread is interesting at several levels as it
addresses
1) Impacts of drought on 7Q10 levels across the state
2) Interactions/roles of USGS and DWR in water supply planning
3) Identification of a potential shortfall in water supply to lower Cape Fear River water
users
4) Long-range water supply planning for the Cape Fear and other river basins.
Alan
------- - Original Message --------
Subject: [Fwd: Re: Fw: A follow-up note ... Re:
Date: Tue, 11 Dec 2007 18:24:32 -0500
From: Paul Rawls <[e-mail]>
To: Belinda Henson <[e-mail]>
Alan Clark <alan. clark@ncmail. net>
fyi
Low -flow characteristics at Lock 1...1
Gil Vinzani <[e-mail]>,
Subject: Re: Fw: A follow-up note ... Re: Low -flow characteristics at Lock 1...
From: Coleen Sullins <[e-mail]>
Date: Tue,11 Dec 2007 13:27:08 -0500
To: John C Weaver <[e-mail]>
CC: Jerad D Bales <[e-mail]>, Jeanne C Robbins <[e-mail]>, Paul Rawls
<[e-mail]>, Matt Matthews <[e-mail]>
Curtis - I would suggest that you send this kind of information to Paul Rawls (paul.rawls(ancmail.net) and
Matt Matthews (matt.matthews(a-),ncmail.net). Thanks Coleen
John C Weaver wrote:
Coleen,
Forwarded below is an email concerning some low -flow issues (both general and specific to Cape Fear
River at Lock 1) sent to several personnel at the N.C. Division of Water Resources.
Would you please advise me who within the Division of Water Quality needs to receive this email?
Thanks for your assistance on this and for your support of hydrologic data collection and programs within
the USGS North Carolina Water Science Center.
Curtis Weaver
1 of 9 12/12/2007 11:39 AM
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[Fwd: [Fwd: Re: Fw: A follow-up note ... Re: Low -flow characteristics ...
***********************************************************************
J. Curtis Weaver, Hydrologist, PE
USGS North Carolina Water Science Center
3916 Sunset Ridge Road
Raleigh, NC 27607
Telephone: [phone] // Fax: [phone]
E-mail address -- jcweaver _usgs.gov
Internet address -- http://nc.water.usgs.gov/
---- Forwarded by John C Weaver/WRD/USGS/DOI on 12/10/2007 02:12 PM -----
John C Weaver/WRD/USGS/DOI To Tom Fransen <Tom.Fransen(aD_ncmail.net>, Kurt Taube
<ktaube(c)_ec.rr.com>, phil.fragapane(o)ncmail.net,
12/10/2007 02:11 PM Woody.Yonts(aD_ncmai[.net
cc Jerad D Bales/WRD/USGS/DOI@USGS, Jeanne C
Robbins/WRD/USGS/DOI@USGS, John C
W eaver/W RD/USGS/DOI@USGS
Subject A follow-up note ... Re: Low -flow characteristics at Lock 1... Link
All,
I would like to provide some response from the USGS perspective to Mr. Taube's questions and comments.
(1) The 7Q10 statistic does change overtime as additional streamflow records are collected. One would
expect that with a sufficiently long period of record, the statistic would show decreasing inter -annual
variability as each new additional year of data is added to the record. To illustrate this, I have attached a
.BMP file that shows the observed annual minimum 7-day flows at the Lock 1 gage (station id 02105769,
drainage area 5,255 sqmi). After 10 years of data were collected, the 7-day, 10-year low -flow discharge
(7Q10) is plotted to show how this statistic changes with the addition of another year of data. Both pre- and
post -regulated conditions are depicted, but it is not appropriate to combine these records when computing
the 7Q10. This plot was prepared in early 2006 in response to some questions from the Corps about
low -flow characteristics in the Cape Fear River downstream of Jordan Lake.
(2) The USGS has been responding to low -flow requests for decades. The USGS is not a part of the
regulatory process that uses the 7Q10 statistic for decision -making, so our calculations are independent
from, but support, the process. I am not aware of any kind of formal agreement that designates the USGS
as the "official" provider of low -flow information, but we continue to act in that role.
(3) When responding to low -flow requests, I generally use all of the streamflow information available to
compute a 7Q10, particularly for continuous -record gaging stations in order to provide the most up-to-date
information. There are published low -flow statistics for many sites in the state, but in some cases these
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statistics may have been computed 10 or more years ago. Hence, when I provide an updated statistic, it will
likely be different from the published value, perhaps leading to some confusion because the new statistic is
documented only in our files and in the files of the requesting agency (usually DWQ or DWR).
(4) The occurrence of the recent droughts (1998-2002, 2006-07) has changed the low -flow characteristics at
some of our gaging stations. For example, at the long-term gaging station on South Yadkin River near
Mocksville (station id 02118000, drainage area 306 sgmi), the pre- and post -drought (1998-2002) 7Q10
discharges are 60 and 45 cfs, respectively. This is a substantial change at this particular site. A quick
check of pre- and post -drought 7Q10 discharges at selected sites across the state gives varying percentage
changes in the values, but 10 to 25 percent is a good characterization of the range in percentage change.
There is a growing need to re -assess the low -flow characteristics at many of our gaging stations.
With the recent droughts (2002 and 2007), we may indeed need to reassess low -flow statistics across the
state. We should also consider development of a web -based tool that would allow documentation of our
response to individual requests so that water -resources managers and the public can have ready access to
the most up-to-date information.
Hope this information is helpful for the moment.
Thank you.
Curtis Weaver
J. Curtis Weaver, Hydrologist, PE
USGS North Carolina Water Science Center
3916 Sunset Ridge Road
Raleigh, NC 27607
Telephone: [phone] H Fax: [phone]
E-mail address -- icweaverRusgs.gov
Internet address -- http://nc.water.usgs.gov/
Tom Fransen <Tom.Fransen(a)_ncmail.net> To Kurt Taube <ktaube(a_ec.rr.com>
cc Woody.Yonts(a.ncmail.net, phil.fragapane(d)_ncmail.net, John C
12/05/2007 08:48 AM Weaver <icweaverCa.usgs.gov>
Subject Re: Low -flow characteristics at Lock 1...
See my responses after each question.
Kurt Taube wrote:
Gentlemen,
3 of 9 12/12/2007 11:39 AM
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[Fwd: [Fwd: Re: Fw: A follow-up note ... Re: Low -flow characteristics ...
Thank you for everyone's response regarding questions about the 7Q10 at Lock and Dam No. 1
in Bladen County. Based on Mr. Weaver's response below to Phil and Woody, I have a couple of
more questions as there are three (3) major state and federal agencies that maintain and/or promote
the 7Q10 data on their websites. This includes DWR, USGS, and the U.S. Army Corps of Engineers.
The questions are as follows:
1. Which organization is the official designator of which 7Q10 is to be used upon the appropriate
designated period of time at any given station? I only ask because of Mr. Weavers comments
in his (2) notes.
If there is a question or concern DWR defaults to USGS.
2. I understand that water supply planners typically use 20% of the 7Q 10 to determine the safe yield
of the run of the river at a given intake point.
We do not consider 20% of the 7Q10 a safe yield. It is a screening criteria to determine if site specific
instreamflow studies are needed.
How much emphasis or creedance will be given to
this data criteria for approving future withdrawal capacities by water supply providers?
To look at the accumulative effect of existing and future withdrawals is why we are developing basin
water supply models for the all the river basins.
An important
consideration for this criteria is to help preserve water quality standards down stream from the
intake. Thus, which agencies are responsible for regulating this matter? Is it DWR and DWQ
together, or either or neither one? Is there an answer?
DWQ is responsible for the administration of the State's water quality regulations.
3. Has the most up to date Cape Fear River Basin Model been used yet to simulate worst case flow
scenarios at Lock and Dam No. 1 that factors in projected drought conditions in 2008 and/or
beyond as well use water use demands by all upstream water providers? If so, can you share the
results of this data, and if not can such a scenario be run?
We are working on an updated set of simulations with a 50 year planning horizon. We had hoped to have
the work done by December, but drought activities and interbasin transfer litigation has slowed our
progress. The results should be available early next year. These simulations will include the full 75 years
of records, so a worse case drought will be part of the analysis and do include information at Lock &
Dam No. 1. This work is a long-range planning effort. If your question is more related to the weekly
forecasting we are doing, you can find the results of those simulations at
http•//www ncwater orgIData and Modeling/Cape Fear River Basin Model/ForecastArchives/. The
output from the forecast runs are focused on Jordan Lake operations. However, the simulations do
include Lock & Dam No. 1, no has requested to see the output for that node. However, anyone with
account on the modeling server has access to those runs and can look at any of the output that is of
interest to them.
I would appreciate someone taking the time to answer each of the above posed questions. The surface
water supply to Southeastern North Carolina is vitally important to our region's future. At the bottom of
the largest river basin in the State, we are impacted by upstream user demands, interbasin transfers
(current and future), and climatic situations as we now have experienced twice since the completion of
Jordan Lake in 1982.
Bottom Line: The Lower Cape Fear Water and Sewer Authority has published in its literature that it is
counting on a water pumping capacity of 110 MGD as its utltimate future capacity. Current upgrades will
provide a capacity of 55 to 60 MGD. Customer use projections at 2030 demands 96 MGD. The current
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[Fwd: [Fwd: Re: Fw: A follow-up note ... Re: Low -flow characteristics ...
safe yield or 20%of 7Q10 for the period 1982 through November 2007 is 73 MGD. The numbers dont
mesh!!
What needs to happen?
Thank you for your assistance and response.
Regards,
Kurt Taube
----- Original Message ----- From: <Wood y.Yonts(a,ncmail.net>
To: <ktaube(a,ec.rr.com>
Cc: <phil.fragapane(a,ncmail.net>; "John C Weaver" <[e-mail]>; <tom. fransenpncmail. net>
Sent: Friday, November 30, 2007 3:51 PM
Subject: Fw: Low -flow characteristics at Lock 1...
The 20% of 7Q10 value estimated for water supply planning in the 2002
LWSP was based on available Cape Fear low -flow characteristics (since
Jordan Lake) when you prepared the LCFWASA 2002 LWSP.
Woody Yonts
NC Division of Water Resources
919-715-5453
----Original Message ----
From: jcweaverAusgs.gov
Date: Nov 30, 2007 12:17
To: "Wood [e-mail]"<Woody.Yonts a,ncmail.net>, <phil.
fragapaneAncmail.net>
Cc: "John C Weaver"_<lcweaver(a),usgs.gov>, "Jeanne C Robbins"
<j robb ins(ausgs. gov>
Subj: Low -flow characteristics at Lock 1... Re: Fw: DELIVERY FAILURE:
User curtis.weaver (curtis.weaver(a),usgs.gov) not listed in Domino
Directory
Woody, Phil...
A quick response...
The most recent published 7Q 10 for Cape Fear River at Lock 1 near
Kelly
(station id 02105769) is listed at 825 cfs, based on an analysis of
records during 1982-97 climatic years (ending March 31, 1998),
reflective
of regulated flow releases from Jordan Lake.
A couple of notes:
5 of 9 12/12/2007 11:39 AM
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[Fwd: [Fwd: Re: Fw: A follow-up note ... Re: Low -flow characteristics ...
(1) The estimate of 538 cfs that was referenced from the WRISARS
database
is based on an analysis for full period of record dating back to
1969,
including the 13 years prior to start of regulation from Jordan Lake.
The
full period of record should not be used in generating the low -flow
estimates at this gage.
(2) An updated value is warranted given the recent drought conditions
that
have occurred since 1998. The most recent analyses completed for
this
site (based on data through 2004 climatic year, ending March 31,
2005)
indicate that 7Q10 has declined to about 600 cfs. Any further
updates
based on last few years' additional record will need to be completed.
JCWeaver
J. Curtis Weaver, Hydrologist, PE
USGS North Carolina Water Science Center
3916 Sunset Ridge Road
Raleigh, NC 27607
Telephone: [phone] // Fax: [phone]
E-mail address -- jcweaver(a.,usgs.gov
Internet address -- http://nc.water.usgs.gov/
"Woody.Yonts(a-),ncmail.net" <Woody.Yonts(a,ncmail.net>
11/30/2007 11:45 AM
Please respond to
"[e-mail]" <Woody.Yonts(q_),ncmail.net>
To
i cweaver(ausgs. gov
cc
Subject
Fw: DELIVERY FAILURE: User curtis.weaver (curtis.weaver(ausgs.gov) not
listed in Domino Directory
6 of 9 12/12/2007 11:39 AM
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[Fwd: [Fwd: Re: Fw: A follow-up note ... Re: Low -flow characteristics ...
hope this message gets to you
----Original Message ----
From: Postmaster crusgs.gov
Date: Nov 30, 2007 11:33
To: "Woody.Yonts(a-),ncmail.net"<Woody.Yonts(a),ncmail.net>
Subj: DELIVERY FAILURE: User curtis.weaver (curtis.weaver( )a,usgs.gov)
not listed in Domino Directory
Your message
Subject: Lock and Dam #1
was not delivered to:
curtis. weaver(ausgs. gov
because:
User curtis.weaver (curtis.weaver(a-,usgs.gov) not listed in Domino
Directory
Reporting-MTA: dns;gscodenhOl.cr.usgs.gov
Final -Recipient: rfc822;curtis.weaver(ausgs.gov
Action: failed
Status: 5.1.1
Diagnostic -Code: X-Notes; User curtis.weaver (curtis.weaverCa),usgs.gov)
n
of listed in Domino Directory
----- Message from "Woody.Yonts(a),ncmail.net" <Woody.Yonts(a,ncmail.net>
on
Fri, 30 Nov 2007 11:33:53 -0500 (EST) -----
To:
Phil. fragapane(-,ncmail. net
cc:
curtis. weaver(a,usgs. gov
Subject:
Lock and Dam # 1
Phil ---------------------- what's up on this one, thanks, woody
----Original Message----
7 of 9 12/12/2007 11:39 AM
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[Fwd: [Fwd: Re: Fw: A follow-up note ... Re: Low -flow characteristics ...
From: ktaube(aec.rr.com
Date: Nov 29, 2007 17:22
To: "W.L. Yonts Jr. PE"<woody.yonts(a,ncmail.net>
Subj: Fw:
Dear Woody,
I would like to talk to you tomorrow about what the 20 % of the 7Q 10
is behind Lock and Dam No. 1.
As you can see from the attached email from Phil, the safe yield is
about 69 MGD and not 100 MGD as
I reported in my last Water Supply Plan for the Lower Cape Fear Water
and Sewer Authority.
Could you please check my Water Supply Plan and see if you can
determine where I might have come
up with 100 MGD for my 20% of the 7Q 10. I need to know the right
answer for this important question.
Hope you are doing well.
Thanks,
Kurt Taube
----- Message from Phil Fragapane <phil.fragapane(&,ncmail.net> on Thu,
29
Nov 2007 16:41:03 -0500 -----
To:
Kurt Taube <ktaube(a,ec.rr.com>
Subject:
Lock and Dam #1
Kurt,
I just checked the 7Q10 at the Lock and Dam #1 gage. See this link:
http://www.ncwater.org/wrisars/ResultsTabJS.php?
line 1=dailyLine&submit=submit&02105769=on&curparam=DC&tab=stat&statType=dQr
It is estimated as about 538 cfs or 348 mgd. For water supplies, we
often talk about 20% of the 7Q10 as a rough estimate for safe yield
at
a run of river intake.
You were possibly referring to 20% of the 7Q10 on our phone call
which
is about 107 cfs or 69 mgd.
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Thanks for your call,
Phil
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