Low-flow characteristics of selected streams in northern Rhode Island

Low-flow characteristics were estimated for selected streams in northern Rhode Island. Streamflow was measured at 18 low-flow partial-record gaging stations on rivers and brooks including those contributing to the two largest water supplies in Rhode Island, the Scituate Reservoir and the Pawtucket Reservoir system. Relations were developed between streamflows at the partial-record stations and flows at five continuous-record gaging stations based on the maintenance of variance extension type 1 method and the logistic regression method. Based on these relations, the 7-day, 10-year low flow (7Q10), selected flow durations, and selected monthly mean daily flows for the partial-record stations were estimated. Low flows of the different streams varied considerably. The 7Q10 ranged from a high of 4.0 cubic feet per second (ft3/s) at the Chepachet River to a low 7Q10 of 0 ft3/s at Huntinghouse, Winsor, and Catamint Brooks, and Moosup Riven The 99-percent flow duration ranged from a high of 4.3 ft3/s to a low of 0 ft3/s on the same streams. The largest tributary to the Scituate Reservoir at low flow is the Ponaganset River with a 7Q10 of 0.56 ft3/s and a 99-percent flow duration of 0.64 ft3/s. The next largest tributaries at low flow are the Hemlock Brook with a 7Q10 of 0.36 ft3/s and the Peeptoad Brook with a 7Q10 of 0.29 ft3/s. The largest tributary to the Pawtucket Reservoir system at low flow was Ash Swamp Brook with a 7Q 10 of 0.31 ft3/s, the next largest tributary at low flow was Burnt Swamp Brook with a 7Q10 of only 0.006 ft3/s. The mean daily flow for August was never more than 30 percent different from the 85 percent flow-duration value.