HomeMy WebLinkAboutAgenda 03-15-22; 12-3 - Information Item - Memorandum – Update - Groundwater Observation Well Network 1
Department of Environment,
Agriculture, Parrs &R.ecreation
MEMORANDUM
TO: Board of Orange County Commissioners
CC: Bonnie Hammersley, County Manager
FROM: David Stancil, Environment, Agriculture, Parks and Recreation Director
Wesley Poole, Water Resources Coordinator
DATE: February 25, 2022
RE: Update - Groundwater Observation Well Network
The purpose of this memorandum is to provide an update on the progress and activities
of Orange County's Groundwater Observation Well Network. This network is known
informally as the Orange Well Net (OWN) and was created in 2005 to monitor local
groundwater conditions from several different types of subsurface conditions. OWN is
designed to provide important information regarding the quantity of groundwater
available to the citizens of the County, especially during times of drought.
Background
Groundwater is the sole source of water for approximately 40 percent of the residents of
Orange County. The County has a history of proactive measures regarding the
investigation and protection of surface water and groundwater resources. From 1992-
2001, the County's Water Resources Initiative engaged in three examinations of local
groundwater resources and conditions with the U.S. Geological Survey. In May 2005,
the Initiative proposed the creation of OWN in Orange County to continue the work of
the previous decade of groundwater research, and provide a long-term database and
network for the collection of information on local groundwater quality and quantity. The
goals of the network include the collection of groundwater level data from a combination
of bedrock and regolith wells spread across the nine main types of generalized bedrock
geology present in the County. Regolith wells, which exist in the layer of
Orange County Department of Environment, Agriculture, Parks & Recreation
PO Box 8181
Hillsborough, NC 27278
Phone: (919) 245-2510
Fax: (919) 644-3351
2
unconsolidated rocky material which lies above bedrock, are designed to monitor
natural stresses on the quantity of groundwater available in storage that are caused by
variations in climatic conditions. Bedrock wells are utilized to monitor changes in
groundwater levels in the bedrock across the County. Taken together, OWN is
designed to collect information concerning the amount of groundwater available locally
in Orange County. The network concept is a long-term project designed to collect and
analyze data over periods of time to examine trends and conditions.
Current Status
Currently, groundwater level data collection is underway at a total of 13 wells - six
bedrock wells and seven regolith wells. Attachment A is a map showing the locations of
the wells that are currently in use along with the underlying geology. Groundwater level
data collected from the OWN wells is automatically uploaded to the North Carolina
Division of Water Resources (DWR) website to add to the statewide well database:
https://www.ncwater.org/?page=537&tl=1&net=orange&inactive
The DWR website includes maps of well locations, geologic information, and statistical
curves that provide monthly minimum, mean, and maximum groundwater level
information for each well in OWN. This information can be used to compare recent
groundwater levels with historical values. Attachment B (Blackwood Farm Bedrock) and
Attachment C (Blackwood Farm Regolith) represent sample data available to the public
from two of the wells in the network.
What Does the Data Tell Us?
To date, the OWN data has confirmed many of the long-known factors about
groundwater in Piedmont North Carolina. The lack of extended droughts during the
period since the OWN began has not shown the fluctuations that would be expected (on
a delayed basis) that might result from drought.
Groundwater levels typically fall during the months of the growing season, due to a
reduction in groundwater recharge. Groundwater recharge, the replenishment of
supplies of groundwater through precipitation and other sources, including surface
water systems, is reduced in part during this time of year due to increased evaporation
as a result of higher ambient temperatures and through the increased use of water by
plants during the growing season (transpiration). These factors normally result in
significantly lower groundwater levels during the summer months in North Carolina. The
Orange County Department of Environment, Agriculture, Parks & Recreation
PO Box 8181
Hillsborough, NC 27278
Phone: (919) 245-2510
Fax: (919) 644-3351
3
non-growing season, November through March, is the period during which most
significant groundwater recharge occurs. Most recharge takes place when precipitation
infiltrates into the ground and reaches the water table, rather than evaporating, being
used by plants, or exiting the system as runoff. Recharge also occurs from surface
water streams, especially during the drier months of the year. Infiltration increases the
amount of groundwater held in storage, raising groundwater levels in the regolith
(upper) aquifer and then the underlying bedrock aquifer. Typically this recharge is then
available for use during the subsequent growing season. Periods of drought or dry
weather can, of course, reduce recharge which could then impact the amount of
groundwater available during the growing season. As noted above, the surface water
and groundwater systems are linked and interdependent, with changes to one system
affecting the other.
Going Forward
Orange County's Groundwater Observation Well Network has been a beneficial project
from the beginning. While its findings and data over the last 17 years have not resulted
in many dramatic results or trends, this is in fact good news. The County's groundwater
resources have remained stable and for the most part predictable during the period of
collection, which admittedly has not seen a severe drought or extended duration.
Findings from the OWN are used to inform the public and officials about groundwater
supply issues including the impact of natural phenomena on groundwater in Orange
County. This collection of data allows the public to have no-cost access to the
groundwater level information collected here in the County at any time. The nominal
annual operating cost of this network (—$1,600 per year) compared to the long-term
groundwater trend information it provides, is highly useful to water resource
professionals, hydrogeologists and other scientists.
The OWN has proven to be a low-cost data collection system that is providing important
contextual long-term data, which to date has not generated short-term time-critical
policy information, but very well may someday prove to be of vital and timely importance
when the next inevitable wave of drought or excessive precipitation occurs.
Orange County Department of Environment, Agriculture, Parks & Recreation
PO Box 8181
Hillsborough, NC 27278
Phone: (919) 245-2510
Fax: (919) 644-3351
Attachment A
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Attachment 6
Blackwood Farm Bedrock
Groundwater Level Database Detail
Field cuts Orange County Monitoring Database Detail for H44P1
county Orange Show Map--Monthly Statistics Plot
Quad H 44R1
Local Well ID Blackwood Form Bedrock 548 H441`1 water levels
Latitude36-018709 546 .................................................................. ............................... ...... _ ...
Longitude -79.080016 5" .................................................................... ..... ...... .... ...... ..
General Rock l)nit 4 m 542 ........i........................i........... ...............
w
-- 541 .........:...........:............:... .. ...
..................
Geology Felsic laws and tuffs(Dacite) 0
g .. ......:...........:...........: .... .... ... ... ... :...... ...t ....... _
Land Elevation }
556 w 536 ... ........ .. .... .
NED elevation=55531 feel
534 .......... .............. ......................... ...: .........:....... .. ..........._........ ..
TotoIDepth302 532 ........:...... ........................<.......................<............;......... ..... ...... ...... ......
Casing Depth 100 5W
01110 i)V11 i)V12 i)V13 i)V14 1)1115 01116 i)V17 i)V15 i)V19 010) i)V21 i)l22
Number of Water Levels 4.347 water levels +
{dote'feet below land wrfooe` 999..99 feet below land surface value 02-25-2022 NC-DWR daily water levels
elevatianj indioates dry well
-22222 feet above land surface value /�y
2010-03-25 to 202112-15 indicates o flawing well 0 q + D o x W
output fie(s)is(am)tob-delimited text 546
NED-Nolimol Elevation Dutoset.1/3 oro second value r
(-10 X 10 meter grid)
542
return to well table 54D
53s
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s3s
534
Oct 200i Jan 2021 Apr 2027 Jd 2021 Oct 2021
6
Attachment C
Blackwood Farm Regolith
Groundwater Level Database Detail
Field Cato Orange County Monitoring Database Detail for H44P3
County Orange Show Mop--Mmthka Stotisfi s Plot
Quad H 44R3
Local Well ID Blackwood Form Regolith 550 H44P3water levels
Latitude36018506 541 ......................................................................................... ....... ............ ........
Longitude -79.079923 ...................................:..................:...................................: . ...............................# .............
Geology Felsic lavas and tuffs(Dacite) m 54d .................................. ............................................ ..... .... .....
w
Geneml Rock Unit 4 0
54p ............................. .:......... .. ..:.... .......:..... ......... V
...... .........
Land Elevation
556 w 53S ......... .... .... ... .. . ....
NED elevation=556.42 feet
_ 536 ..............:.......... ................................... ....... ........................ ...... ............................. ....
TotalDepth 45 534 ....................................................................<. ..............<.......... ..................................
Casing Depth 15 532
i)V14 i)V15 i)V16 i)V17 i)V15 i)V19 010) 01l21 01l22
Number of Water Levels Z water levels +
{dote'feet below land wrfooe` 999..99 feet below land surface value 02-25-2M NC-DWR daily water levels
elevation} indicates dry vrell
-22222 feet above land surface value
?OM-11--to 211-12.15 indicates o flawing vreN r-.[ + Q
output file(s)is(are)tab-delimited text
NED-Notirnal Elevation Daa et,V3 arc second value #
(-10 X 10 meter grid) - 545
retum to well table
541)
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535
Oct 2020 Jan 2021 Apr 2021 Jul 2021 Oct 2021