Connecticut Streamflow and Groundwater Overview
Know Your Flow!
CT Conditions At A Glance(Click on any graphic below for more information)
Streamflow in CT Now
(click map to go to the data page)
High Flow Low Flow Not Ranked
US Drought Monitor Map of CT
(click map for details)
The U.S. Drought Monitor is jointly produced by the National Drought Mitigation Center at the University of Nebraska-Lincoln, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration. Map courtesy of NDMC-UNL.
Map of Below Normal 28-Day Average Streamflow
Recent Flow At a Typical CT Stream
(click graph for details)
(click graph to see more well data)
Check your forecast here
(click map to go to state weather page)
Graphic courtesy NOAA NWS showing CT area watches and warnings if any.
January 19, 2017 Update
(See also climate news: Climate Change Threat to Both the Natural World and to Human Civilization)
Summary (details below)
For the tenth week, the U.S. Drought Monitor rates
41% or more of Connecticut as Extreme Drought. Last week the area rated Severe
Drought dropped a little to 37% where it remained this week. 22% is
Moderate Drought. Between storms, streamflow drops
to unusually low levels for about a third of our rivers and streams but not as far below
normal as in previous months. Most rivers and streams are showing near-normal
flow patterns. Some groundwater levels
have recovered, but for about half the state, they are not anywhere near normal yet.
The worst drought since the historic
drought of the 1960s continues.
Watch continues for six CT counties; Drought Advisory
continues for the eastern two counties. The state also
requests all residents to reduce their water use by 15%. The Interagency Drought Workgroup (IDW) may meet soon to decide on any changes to the state's drought alert level.
Water utilities statewide are still calling for conservation, but their reporting of reservoir levels shows much improvement (for details, see Utility Alerts below). The U.S. Department of Agriculture declared Hartford, Litchfield, Tolland, and Windham Counties natural disaster areas. There are numerous reports of private wells low or dry.
44% of CT rivers and streams measured by the US Geological Service (USGS) were experiencing low flows this week (alphabetical list is below). Last week there were 56%. This continues the clear improvement that should continue if normal precipitation continues.
For the first time since last Spring, most river and stream
gages' graphs are showing the normal pattern of about equal areas of
above-average flow when it rains, then below-average between storms. About a
third continue to show streams rising to or above average during storms, then
rapidly dropping to well below average. A few do not come close to
average even during rain. See Streamflow Graphs and Storms below for
Dry conditions that cause flow to be below
average more often than it is above average is affecting stream life
throughout the state. Fishermen are reporting long stretches of
rivers with no catch at all. Whatever dormant life is left on our
stream bottoms will be lost if flow remains too low to prevent the
stream from freezing solid. This is different than the common winter fish kills explained in fact
sheets from DEEP.
Your water utility and town web
pages are the best sources of information on water use
restrictions that apply specifically to you. The Department of Public Health's (DPH) Reservoir
Data monthly web page dated Jan 9 stated that capacity was at 77% of
normal (note that "normal" for December is 88% of capacity), the percentage reported on their
Monthly Reservoir Status Summary for December.
That percent of normal is based on reports from 34 large water
systems that use reservoirs. That percentage means those
reservoirs averaged 69% of capacity. Most of those water
utility companies had issued water use restrictions. The
DPH also has a separate list of
Public Water Systems with water use restrictions, last update Dec 12.
Waterbury may lift its ban on outdoor watering at the end of January. In October, DPH allowed the City of Waterbury to reduce the amount of water discharged to the Shepaug River from their reservoirs in Warren, Morris, and Litchfield. Normally, Waterbury is required to release 6 million gallons per day (mgd) in October, but the DPH order allowed the city to lower that to the 1.5 mgd required level from November through February. The Shepaug River gaging station recorded flows around 2.6 mgd for the rest of October, though the rate very briefly dropped to 1.23 mgd. In order to move to the lower level, the city instituted mandatory water conservation measures and was required to demonstrate to DPH that it was maximizing the use of all current water sources. Click here for Waterbury's Warning page. They were also required to publish weekly reports.
The Metropolitan District Commission (MDC) issued a Drought Advisory because their reservoirs dropped to 75% of capacity. Aquarion
Water Company asked its customers to cut indoor
water use by 20 percent. DPH issued a rare Declaration of a Public Water Supply Emergency
for Greenwich, Stamford, New Canaan, and Darien, which was later amended to allow Aquarion to build a 1.5-mile
temporary pipeline. As part of this declaration, Aquarion maintains a weekly updated water usage
report on their website that includes customer usage trends,
system transfers, system capacities, days usable storage
remaining, and precipitation. Their graphs and charts on Jan. 4
indicated conditions were near or even above their trigger levels for
water usage alerts.
New Britain Water is proposing to buy 5 million to 7 million gallons of water a day from MDC. New Britain has not had to buy water for decades. The South Central Regional Water Authority is asking customers to reduce water use by 15%. Bristol issued new mandatory water restrictions. On Nov. 16, UConn lowered its alert level to a Stage III Water Emergency. A mandatory water use ban introduced by Norwalk on Oct. 6 affects two systems with the unusual addition of how it will be enforced by police. On Oct. 25, the DPH commissioner declared a Public Water Supply Emergency for the City of Danbury, also affecting Ridgefield and Bethel.
MDC suspended releases from their hydroelectric facility at Goodwin Dam. This dam forms the West Branch Reservoir (sometimes called Hogback Lake) on the Farmington River West Branch in Hartland just below the Colebrook River Reservoir. Citing the ongoing drought, MDC is recommending a change to its policy of selling water at a reduced price to high-volume consumers.
Earlier in the year, fishing was banned in some areas of the Farmington River due to low water levels.
One sign of improving conditions last week (1/12) was that two of the
real-time monitoring wells run by the USGS
with multi-year records were reporting the water table had returned to the
average level recorded by those stations for the date. Over the last week, the
water level in one of those wells continued to rise, but the water table has
started to fall at the other.
On Jan 19, three wells reported levels lower than ANY of those station's records for the date. Two stations are lower than 75% of records for the date. Before this week groundwater levels at all eight live-data stations had been recovering steadily from the previous months when more stations were breaking low-water-level records than those that were merely very low. Over the past week however, the groundwater level in three of the eight stations leveled off.
The USGS Connecticut office has two new live-data wells in Clinton and Salisbury. These show data going back to August of this year, so comparisons to previous years cannot be made, but groundwater trends for this year can be observed. Another of their live-data wells is down for repair.
The water level in streams and rivers between storms depends on the flow of water out of the ground into the stream channel. The higher the water table, the more water is available to keep streams flowing. During a drought, smaller upland streams dry up faster than the larger rivers (details below). An occasional brief, powerful rainstorm does not do much to help groundwater levels rise. The rain falls faster than the ground can absorb, and thus much of it becomes stormwater runoff. In that situation, public water supply systems that depend on reservoirs are affected less than those with wells because the runoff is collected by the reservoirs. How much groundwater is contributed by snow depends on several factors including slope, rate of snow melt, and whether the ground beneath the snow is frozen or saturated.
There has been an apparent pattern for the last five years in which normal groundwater levels in winter and spring have alternated with well-below-average in summer and fall. Click the graph to the right for a larger version in a new tab of a modified USGS graph. What is most worrisome, however, is that the below-normal levels got worse in each of those years. Five years is not long enough to make any statistically valid conclusions about climate, however, and those station records only go back seven to 14 years. Click here to see all the USGS graphs for their real-time groundwater measurements that compare levels from the last four years to the median level for each day of the year (lots of data, so it takes a long time to load). USGS manually measures other wells once a month or so, and a quick look at those records verified the possibility that this pattern may apply to all our groundwater.
Why is Connecticut still rated Extreme and Severe Drought even though we have received near-average precipitation recently? The U.S. Drought Monitor's narrative summary for the Northeast for Jan 10 said:
"Generally light precipitation ... fell on most of the Northeast, maintaining the long-term drought as enough precipitation fell to prevent deterioration but wasn’t heavy enough to warrant improvement...Since late fall, precipitation has been on the increase in New England, but not great enough to put a major dent in the long-term deficits. " (click here for their latest narrative)
According to the National Weather Service Advanced Hydrologic Prediction Service, precipitation since the middle of December was near average for two-thirds of the state and under 90% of average for the other third. Small areas were under 75% of average. The near-average precipitation is gradually improving long-term streamflow and groundwater levels, but in the areas where rain and snow in the last couple weeks has dropped below normal for this time of year, streamflow is slow in getting back to normal. Go to this link for detailed maps and data.
For most of 2016, storm tracks brought precipitation out to sea or north of us because a persistent high-pressure system called a blocking pattern was diverting weather fronts and storms. It was only when that blocking pattern moved away for short periods that some weather systems came over Connecticut, creating temporary returns to more normal rainfall. That normal precipitation did not end the drought due to the serious long-term rain deficit, but it kept it from getting worse for a while. Streamflow between storms continued to drop to low levels, however.
This is the same bad situation that we had in 2015 (see below), caused not only by less total rainfall than normal over a long period of time but also by the intensity of the rain we did get. As our climate changes, heavy precipitation events are becoming more frequent. Heavy rain does not recharge groundwater aquifers as much as an equal amount of rain over longer periods would.
Rain? The National Weather Service's one-week forecasts and their long-range computer models are predicting a little below to near-normal precipitation for us, with heavier precipitation tracking out to sea. While normal rain and snow is certainly good news for our rivers and streams, it would not be enough to alleviate all drought conditions. If the storms actually track our way instead of out to sea, we could get enough rain to significantly ease the drought. If the blocking pattern has returned, the drought conditions will probably worsen.
Each month the NWS Climate Prediction Center issues analyses of global atmospheric conditions that could influence general temperature and precipitation patterns. Their Jan 19 analysis for trends through May 2017 show equal chances for above-normal or for normal or for below-normal precipitation. Above-normal temperatures are a little more likely than normal temperatures. This is pretty much the same four-month forecast we have seen for the past year, but actual precipitation was much lower than normal. Their prognostications for next Summer, however, give a 40% chance for above-normal rainfall, 33% chance of normal and 27% chance for below-normal. This prediction has not been seen in several years. Summer temperatures are also predicted to be above normal.
27 out of 62 rivers and streams measured by the USGS in CT were experiencing low flows* on Tuesday, Jan. 17. A week earlier there were 35. On December 23, there were 53. On Jan. 19, the 5 streams and rivers in bold red below were lower than any record for the date. There were also 5 record breakers on Jan 10th, there were 7 on Jan 3rd, 15 on Dec. 23rd. To see the status of any them right now, click the station's URL.
|Station Name||Station Website|
|BUNNELL BROOK NEAR BURLINGTON, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01188000|
|FARMINGTON RIVER AT TARIFFVILLE, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01189995|
|FARMINGTON RIVER AT UNIONVILLE, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01188090|
|FENTON RIVER AT MANSFIELD, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01121330|
|FIVEMILE RIVER NEAR NEW CANAAN, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01209761|
|HOCKANUM RIVER NEAR EAST HARTFORD, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01192500|
|HOUSATONIC RIVER AT STEVENSON, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01205500|
|MILL RIVER NEAR HAMDEN, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01196620|
|MUDDY RIVER NEAR EAST WALLINGFORD, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01196561|
|NONEWAUG RIVER AT MINORTOWN, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01203600|
|POOTATUCK RIVER AT BERKSHIRE||https://waterdata.usgs.gov/ct/nwis/uv?site_no=012035055|
|POOTATUCK RIVER AT SANDY HOOK, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01203510|
|QUINNIPIAC RIVER AT SOUTHINGTON, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01195490|
|QUINNIPIAC RIVER AT WALLINGFORD, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01196500|
|RIPPOWAM RIVER AT STAMFORD, CT.||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01209901|
|SALMON CREEK AT LIME ROCK, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01199050|
|SALMON RIVER NEAR EAST HAMPTON, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01193500|
|SAUGATUCK R BELOW SAUGATUCK RES NR LYONS PLAIN, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01209005|
|SAUGATUCK RIVER NEAR WESTPORT, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01209500|
|SHEPAUG RIVER AT PETERS DAM AT WOODVILLE, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01202501|
|STILL RIVER AT ROUTE 7 AT BROOKFIELD CENTER, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01201487|
|STONY BROOK NEAR WEST SUFFIELD, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01184100|
|WEEKEEPEEMEE RIVER AT HOTCHKISSVILLE, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01203805|
|WEST BRANCH FARMINGTON RIVER AT RIVERTON, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01186000|
|WILLIMANTIC RIVER AT MERROW RD. NEAR MERROW, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01119382|
|WILLIMANTIC RIVER NEAR COVENTRY, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01119500|
|YANTIC RIVER AT YANTIC, CT||https://waterdata.usgs.gov/ct/nwis/uv?site_no=01127500|
*We are defining low flow as below the 25th percentile for that stream, OR below 25% of the mean OR below 25% of the median flow for that stream for the date. Data source: http://waterwatch.usgs.gov/webservices/realtime?region=ct&format=xml on Tuesday, Jan. 17, 2017. Click here for a list of all CT stream gages comparing their flow right now to their mean and median flows for today's date.
As the graphic to the right illustrates, where a storm moves
across the state, the streams show flows that peak above their
averages for this time of year but then quickly drop. The streams
that maintain healthy flows between storms are those draining the
parts of the state where there has been decent rainfall or those
controlled by managed dams.
How quickly the flow drops after each rainstorm is unique for each stream, because it depends on how much water soaked in to increase the groundwater baseflow. In watersheds with lots of impervious roads, roofs, parking lots, patios, and compacted soil in lawns, a lot of the rain typically flows over the surface or through storm drains directly into the streams, leading to flooding problems far more often than in watersheds with mostly natural surfaces. Their streamflow then drops quickly after the storm ends, and the flow levels off far lower than in streams whose watersheds have more natural surfaces.
The U.S. Drought Monitor publishes a weekly analysis of drought conditions across the entire nation based on a variety of types of data that include streamflow. The report comes out every Thursday based on data from that Tuesday. Since the Drought Monitor began in 2000, the only time any part of Connecticut was as dry as it is now was 2002 when around 16% of the state was in the Extreme category for three weeks. This means this is the worst drought so far this century. The U.S. Drought Monitor is produced by the National Drought Mitigation Center, which is also on Facebook.
Connecticut now has the dubious distinction of the highest percentage of area rated Extreme of all fifty states. We are sixth in actual square miles. Although some areas that had been rated Extreme and Severe Drought in New York State and Massachusetts have been downgraded to lower levels, Connecticut precipitation has not been enough to reverse drought effects. In the surrounding states, the Drought Monitor cautions: "it should be noted that stream flows and ground water levels there remain much lower than normal and conditions will be closely monitored for possible re-intensification".
As the below graph shows, Connecticut has been labeled Abnormally Dry, Moderate Drought, or worse pretty often over the last few years. This graph was made before any of the state was rated as Extreme.
For a good analysis of last year's stream problems across the state, see this press release from Pomperaug River Watershed Coalition (PRWC). Here is a key quote:
The September and October low river flows demonstrate that rivers were not supporting the critical flows needed for a healthy river habitat. In fact, sections of the Weekeepeemee River had dry river beds and the Pomperaug River was flowing only at a rate of 15% of the critical flow requirement. DEEP officials confirmed that they would expect fish mortality to increase significantly during such conditions...
Photo from PRWC.
Meanwhile, parts of Coppermine Brook in
Bristol were drawn down to rocks and dirt, as shown in the photo
below taken Dec. 11, 2015, in Bristol. The sandy ditch in the
foreground is the stream channel. Bristol Water Company and New
Britain Water Company have eight registered diversions near
Coppermine or its tributaries with a combined registered water
withdrawal of 36.6 million gallons per day (source: CT DEEP). Company
representatives report they do not withraw anywhere near that much
water. Bristol Water says they stopped pumping from their well
near this photo for a day but with no apparent effect on the
stream. This is a perennial stream with a state Trout Management
Area below where this picture was taken. Click on the photo for a
full-screen version in a new tab.
Coppermine Brook, Bristol CT, Friday, Dec. 11, 2015; photo by Tony Mitchell
Some archived Know Your Flow pages
http://www.riversalliance.org/drought/droughtarchive.cfm?filename=droughtbefore20150925.htm http://www.riversalliance.org/drought/droughtarchive/droughtbefore20150903.htm http://www.riversalliance.org/drought/droughtarchive/droughtbefore20160316.htm