Rivers Alliance
of Connecticut
Connecticut's United Voice for River Conservation


Connecticut Streamflow Overview

Connecticut Streamflow Overview

Know The Flow!

May 2, 2014, 2014 Summary: According to The Advanced Hydrological Prediction Service of the National Weather Service, Connecticut rainfall during the last 30 days (as of May 1 ) was well above average for this time of year for all of the state except for a small area of average precipitation around Bolton  Connecticut rainfall during the last 60 days finally shows almost all of the state firmly above average with only a few areas in the western half of the state still at or a little below average. Whether or not the recent above average rainfall was enough to compensate for the longer term below average will determine if our streams keep normal flow between rain events.

The US Geological Service Streamflow Map of Connecticut (on Fri May 2) shows all streams above average or even near flooding. How quickly the flow drops after each rainstorm is unique for that stream because it depends on how much water soaked in to increase the groundwater baseflow. Watersheds with lots of impervious roads, roofs, parking lot, patios, and compacted soil in lawns typically cause a lot of the rain to flow over the surface or through storm drains directly into the streams, leading to flooding problems far more often than natural surfaced watersheds. Their streamflow then drops quickly after the storm ends and the flow levels off far lower than streams with more natural surfaces in their waterheds.

Watch for Flooding!
The short and long range forecasts that show a lot of rainfall for the next two weeks and this should keep all of the streams in CT at or above average, or even frequent flooding. Remember if water is across the road, Turn Around Don't Drown! Only crazy people attempt to canoe or kayak on floodwaters, but apparently there are enough of them to cause one or two fatalities per year. Our Connecticut Water Trails website, and the webpages of the many paddler groups in the state all have good safety procedures. 

When floodwaters return to use that part of the stream channel that is called a floodplain, the water may find that someone has built a building or two in the channel. The water then saturates and fills any leach fields, often flushing untreated sewage out into the flow. The floodwaters also find these really nice holes in the ground called wells to flow down into. All kinds of interesting things can be delivered to the bottom of the well, such as the aforementioned sewage, and soil, bugs, leaves, pesticides such as weed killer and insect poison, even the dog droppings from the back yard. It is very important that any well that was flooded be pumped and flushed out thoroughly and the system sanitized or "shocked".  The Connecticut State Department of Health website has a good guide called: Flooding: Information for Homeowners About Private Wells, Sewage and Clean-Up

Also, there are places in Connecticut where the storm drains and the sewage pipes are combined into one system. With high rainfall, many of these combined pipes are designed to overflow into rivers and streams so the wastewater treatment plants are not overwhelmed. You really do not want to be downstream when raw untreated human sewage is entering the water. The DEEP has a map of Combined Sewer Overflows that shows the six urban areas where these can occur. Zoom in to any of them to see exactly where the combined flow may enter streams and rivers. Not every rain event is enough to cause these overflows, but its a good idea to avoid contact with the water downstream from them after significant rain.

Link to NWS graphic page
Graphic courtesy NOAA NWS showing CT area watches and warnings if any.

The State of CT Drought Preparedness and Response Plan authorizes the state to issue a Drought Advisory if the majority of the following criteria are met:

Criteria to Declare Drought Advisory
Precipitation: Two months cumulative below 65% of normal
CT State Water Status
Ground Water: Three consecutive months below normal,
USGS Groundwater
Streamflow: Two out of three months below normal,
Burlington Brook Streamflow
Reservoirs: Average levels less than 80% of normal..
CT State Water Status
Palmer Drought Severity Index::
 -2.0 to -2.99 (moderate drought)
Palmer Drought Index
Crop Moisture Index: range of
 -1.0 to –1.99 (Abnormally Dry)
Daily(ish) Forest Fire Danger Report
Click on any graphic below for more informationion
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High Flow    Low Flow
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CT Current Streamflow. Click to go to source page.
Streamflow in CT (click to go to the data page)
Current US Drought Conditions. Click to open source page.
Link to US Drought Monitor
Link to CT drought map


More Links:

State of CT - Drought (Search)

USGS Connecticut DroughtWatch

Water Conservation tips

Water Conservation is not just for droughts; it is important because:

  • It saves money and energy

  • It insures the reliability of your water supply

  • It protects our natural resources

What Can I Do?

  • Set a voluntary water use reduction goal of 10% (whether served by public water systems or private wells)

  • Cut back on unnecessary water use, such as watering lawns or washing cars

  • Cooperate with your local water utility and follow their plans

Model Water Use Restriction Ordinance (PDF, 28KB)

Rivers Alliance of Connecticut
PO Box 1797
7 West Street, 3rd Floor
Litchfield, CT 06759