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Connecticut Streamflow Overview and Drought Conditions

Connecticut Streamflow and Groundwater Overview

Know Your Flow!
We update this webpage with the latest information weekly.

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)

 [color code for]  color code for  color code for color code for  color code for  color code for  color code for               [color code for]         
   High Flow     Low Flow        Not Ranked
CT Current Streamflow. 
Click to go to source page.
US Drought Monitor Map of CT
(click map for details)
Current US Drought Conditions. 
Click to open source page.
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)

Link to Burlington Brook flow data
Groundwater Level
(click graph to see more well data)
USGS monitoring well. Click to see more.
Check your forecast here
(click map to go to state weather page)
Link to NWS graphic 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 rated 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.

The Drought 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 more explanation.

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.

Click here for the USGS Connecticut stream gage web page with graphs of flow from every gage for the past 30 days compared to their daily average flows.

Public Water Supply Information

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 six 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.

Precipitation Patterns

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.

Driest Streams and Rivers in Connecticut

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.

Streamflow Graphs and Storms

Click to enlarge. Streamflow graphics courtesy USGS 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.

How does the current drought compare to historic droughts in Connecticut? The graph to the right is from NOAA's National Environmental Satellite, Data, and Information Service (NESDIS), displaying the Palmer Hydrologic Drought Index (PHDI) for our state for the past century (click on it for a larger view in a new tab). If groundwater and streamflow did not fully recover from the annual return of drought conditions of the past few years, we can consider our current drought as starting in 2010 or 2012. The overall length of time we have had these intermittent drought conditions is becoming comparable to the continuous drought of the 1960s. The severity of the current drought is approaching the average severity of the 1960s. It is therefore fair to say the current drought is one of the worst in 100 years. Area weather forcasters have been reporting that the current drought is the worst since the 1960s.  


Dire situation last year....

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...
Click to enlarge

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.
Coppermine Brook, Bristol CT, Friday, Dec. 11, 2015; photo by Tony Mitchell


This graph plots the rate of flow on September 4, 2015 as a percentage of the median for each stream gage. For example, a dot at the 40% line means that stream that day was flowing at 40% of what could be considered normal for that date. The few rivers and streams flowing at or above 100% of their median rate are mostly those with flows managed by dam releases.

Click here for a search of news articles about the drought

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 


NASA's climate monitoring programs to be axed?

Rivers Alliance of Connecticut
PO Box 1797, 7 West Street 3rd Floor, Litchfield, CT 06759-1797
rivers@riversalliance.org, www.riversalliance.org