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Estimating Surface-water Runoff to Narragansett Bay, Rhode Island and Massachusetts
| Content Provider | Semantic Scholar |
|---|---|
| Author | Ries, Kernell G. |
| Copyright Year | 1990 |
| Abstract | Monthly and annual estimates of mean freshwater inflow to the 143 square mile Narragansett Bay for water year 1987 (Oct. 1, 1986 through Sept. 30, 1987), and for long-term average conditions were required for use by other investigators. Fresh-water inflow consists of surface-water runoff from streams draining into the bay, and precipitation on the bay itself. About 63 percent of the land area within the 1,820 square mile drainage basin was monitored by streamflow-gaging stations prior to commencement of the study; the remainder was ungaged. Mean runoff to the basin, which includes the bay, during water year 1987 was estimated to be 4,860 ft3Is (cubic feet per second), with estimates of monthly mean runoff ranging from a low of 1,060 ft3Is in August, to a high of 14,400 ff Is in April. Long-term mean annual runoff to the basin was estimated to be 3,690 ft3/s, with long-term mean monthly estimates ranging from 1,820 ft3Is for July, to 6,540 ft3Is for March. The estimates were derived by summing the known runoff from gaged areas of the basin with estimates of runoff from ungaged land areas, diversions from gaged areas, and computed runoff equivalents of rainfall on the bay. The estimates of the 1987 water year and long-term mean annual runoff are both considered to be within 10 percent of actual. The estimates of the 1987 water year monthly mean and long-term mean monthly runoff are considered to be within 20 percent of actual and 15 percent of actual, respectively. The estimates of long-term runoff from ungaged areas of the basin were derived primarily by using multiple regression analyses. Long-term mean annual and mean monthly runoff data from 13 streamflowgaging stations located within or near the basin were used as the dependent variables in the analyses, which produced separate predictive equations for each month and for the mean annual runoff. Various physical characteristics of the drainage basins for the streamflow-gaging stations were used as the independent variables. Lengths of continuous records for the 13 stations ranged from 21 to 62 years, with a mean record length of 38 years. Techniques used to estimate runoff from ungaged areas of the basin for the 1987 water year include a previously unpublished method that uses linear regression to relate discharge measurements obtained monthly at an ungaged site to concurrent discharges at a nearby gaged site. Empirical tests of the method using data from gaging stations in the basin indicate that the average accuracy of the method is within 7 percent for annual estimates, and within 13 percent for monthly estimates. |
| File Format | PDF HTM / HTML |
| DOI | 10.3133/wri894164 |
| Alternate Webpage(s) | https://pubs.usgs.gov/wri/1989/4164/report.pdf |
| Alternate Webpage(s) | https://doi.org/10.3133/wri894164 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
