k. 1 Avai labil ity of data 



Measurements of streamflow have been made on many streams within 

 or adjacent to the Long Island Sound Region since the early 1900's. These 

 records have been published in U.S. Geological Survey Water-Supply Papers 

 and in the annual series entitled Water Resources Data for Connecticut, Part 

 1 {kV) , and Water Resources Data for New York, Part 1 (kl) . Flow records of 

 selected streams are published on a monthly basis in Water Resources Condi- 

 tions in Connecticut (43) and Water Resources Summary, Long Island (kk) . 

 Short-term forecasts of streamflow are published monthly by the National 

 Weather Service in Water Supply Outlook for the northeastern United States 

 (19). 



Twelve continuous-record stream gaging stations in Connecticut 

 and one in New York having periods of record in water years 19^1-70 were used 

 as the primary surface-water data for the mainland part of the study area. 

 Four of these stations, located outside the region boundary, measure inflow 

 to the area. Ten continuous-record stations within the region have periods 

 of record for water years 1961-70. The records of five of these stations 

 were adjusted to the reference period 19^1-70, while the other five stations 

 were used for low-flow values only. 



Forty-two low-flow partial -record sites, in and near the mainland 

 part of the region, at which discharge measurements were made in water years 

 1961-70 were selected to study the range and variability of low flows. The 

 values of the 7-day, 10-year recurrence interval low flow for these sites 

 were estimated through relation curves of discharge, with the long-term 

 records. Drainage areas of the low-flow partial -record sites range from 1 

 to 29 square miles but are generally between k and 15 square miles. 



The primary surface-water data for Long Island consists of 19 

 continuous-record stream gaging stations having periods of record in water 

 years 19^0-65. Four of these stations are on streams that discharge into 

 Long Island Sound whereas the others drain south into the Atlantic Ocean or 

 into Great Peconic Bay. Surface drainage areas of these streams range from 

 k to 75 square miles. 



The information on average annual, and.average monthly runoff 

 and the 7-day, 10-year low flows has been prepared in map format (see 

 Appendix C) . The streamflow information for the continuous record gaging 

 stations on the mainland is summarized in Appendix E. 



4.2 Fresh water inflow to the Sound 



The three principal streams flowing into Long Island Sound--the 

 Thames, Connecticut, and Housatonic Rivers — have a combined drainage area of 

 14,700 square miles, 91 percent of the 16,200 square mile mainland drainage 

 area. Annual runoff to the Sound averages 26,200 cubic feet per second (cfs) ^ 



1 - One cubic foot per second (cfs) is equivalent to 646,317 gallons per day 

 to approximately 0.65 million gallons per day (mgd), and to 0.24 billion 

 gallons a year (bgy) . 



19 



