Streamflow, water quality, and constituent loads and yields, Scituate Reservoir drainage area, Rhode Island, water year 2009

Open-File Report 2010-1275
Prepared in cooperation with the Providence Water Supply Board
By:  and 



Streamflow and water-quality data were collected by the U.S. Geological Survey (USGS) or the Providence Water Supply Board (PWSB), Rhode Island's largest drinking-water supplier. Streamflow was measured or estimated by the USGS following standard methods at 23 streamgage stations; 13 of these stations were also equipped with instrumentation capable of continuously monitoring specific conductance and water temperature. Streamflow and concentrations of sodium and chloride estimated from records of specific conductance were used to calculate loads of sodium and chloride during water year (WY) 2009 (October 1, 2008, to September 30, 2009). Water-quality samples also were collected at 37 sampling stations by the PWSB and at 14 monitoring stations by the USGS during WY 2009 as part of a long-term sampling program; all stations are in the Scituate Reservoir drainage area. Water-quality data collected by PWSB are summarized by using values of central tendency and are used, in combination with measured (or estimated) streamflows, to calculate loads and yields (loads per unit area) of selected water-quality constituents for WY 2009. The largest tributary to the reservoir (the Ponaganset River, which was monitored by the USGS) contributed a mean streamflow of about 27 cubic feet per second (ft3/s) to the reservoir during WY 2009. For the same time period, annual mean1 streamflows measured (or estimated) for the other monitoring stations in this study ranged from about 0.50 to 17 ft3/s. Together, tributary streams (equipped with instrumentation capable of continuously monitoring specific conductance) transported about 1,400,000 kilograms (kg) of sodium and 2,200,000 kg of chloride to the Scituate Reservoir during WY 2009; sodium and chloride yields for the tributaries ranged from 10,000 to 64,000 kilograms per square mile (kg/mi2) and from 15,000 to 110,000 kg/mi2, respectively. At the stations where water-quality samples were collected by the PWSB, the median of the median chloride concentrations was 21.7 milligrams per liter (mg/L), median nitrite concentration was 0.001 mg/L as N, median nitrate concentration was 0.02 mg/L as N, median orthophosphate concentration was 0.09 mg/L as P, and median concentrations of total coliform and Escherichia coli (E. coli) bacteria were 61 and 16 colony forming units per 100 milliliters (CFU/100 mL), respectively. The medians of the median daily loads (and yields) of chloride, nitrite, nitrate, orthophosphate, and total coliform and E. coli bacteria were 190 kg/d (61 kg/d/mi2), 12 g/d (4.5 g/d/mi2), 93 g/d (32 g/d/mi2), 420 g/d (290 g/d/mi2), 6,200 million colony forming units per day (CFU?106/d) (2,600 CFU?106/d/mi2), and 1,100 CFU?106/d (340 CFU?106/d/mi2), respectively. 1The arithmetic mean of the individual daily mean discharges for the year noted or for the designated period.

Study Area

Publication type Report
Publication Subtype USGS Numbered Series
Title Streamflow, water quality, and constituent loads and yields, Scituate Reservoir drainage area, Rhode Island, water year 2009
Series title Open-File Report
Series number 2010-1275
DOI 10.3133/ofr20101275
Edition -
Year Published 2010
Language ENGLISH
Publisher U.S. Geological Survey
Contributing office(s) Rhode Island Water Science Center
Description iv, 24 p.
Time Range Start 2008-10-01
Time Range End 2009-09-30
Online Only (Y/N) N
Additional Online Files (Y/N) N
Google Analytic Metrics Metrics page
Additional publication details