SPECIAL FLOOD REPORT FOR FLOOD OF JUNE 13-17, 1998 The following assessments of precipitation, streamflow, ground-water-level, and reservoir conditions are based on PROVISIONAL DATA and are subject to revi- sion. PRECIPITATION DATA.-- Late on June 12, 1998 an intense and prolonged rainfall event occurred in east- ern Massachusetts and Rhode Island. National Weather Service rainfall totals for the period June 12-15, 1998 ranged from about 2 inches on outer Cape Cod to greater than 10 inches near Brockton, MA. Most locations in Massachusetts and Rhode Island received 4-8 inches of rain during the 4-day period. The USGS rain gage located at the Shawsheen River at Hanscom Field near Bedford, MA, 01100568, recorded 8.56 inches of rain during the period June 12-18, with 5.75 inches recorded on June 13. STREAMFLOW DATA.-- The precipitation event during the period June 13-17, 1998 was a long-duration event that yielded large amounts of rain. Streamflows in Rhode Island and east- ern Massachusetts responded to the prolonged rainfall event by reaching record and near-record levels. At selected streams where flooding occurred, peak dis- charges (in cubic feet per second) and corresponding recurrence intervals (in years) for June 1998 are compared to those for the October 1996 event (the most recent flood event prior to June 1998). Recurrence interval, a measure of the magnitude of peak discharge, is presented in terms of years. A 50-year flood is one where the peak flow has a 1 in 50 chance of occurring in any given year. The following table lists USGS station number, stream name, October 1996 peak discharge and recurrence interval, and June 1998 peak discharge and recurrence interval. Oct.1996 Oct.1996 June 1998 June 1998 Peak Recurrence Peak Recurrence Station Discharge Interval Discharge Interval Number Stream Name (cfs) (yrs) (cfs) (yrs) 01096000 Squannacook R.-West Groton 3,330 20 1,880 3 01096500 Nashua R.-East Pepperell 5,790 7 4,300 3 01097000 Assabet R.-Maynard 1,590 4 1,480 3 01097300 Nashoba Br.-Acton 599 30 291 4 01100000 Merrimack R.-Lowell 47,900 3 52,800 5 01100600 Shawsheen R.-Wilmington 1,850 70 1,240 20 01101000 Parker R.-Byfield 883 150 302 5 01102000 Ipswich R.-Ipswich 3,030 50 1,950 10 01102500 Aberjona R.-Winchester 1,150 50 1,070 50 01103500 Charles R.-Dover 1,370 3 2.070 5 01104500 Charles R.-Waltham 2,990 20 2,230 13 01105000 Neponset R.-Norwood 710 10 1,100 50 011055566 Neponset R.-Milton Village --- -- 2,930 -- 01108000 Taunton R.-Bridgewater 3,710 12 2,850 4 01109000 Wading R.-Norton 410 2 1,220 50 Discharge hydrographs for selected rivers for the period June 12-19, 1998 are compared to recorded peak discharges during the October 1996 flood event. Com- posite discharge hydrographs for gaging stations in the Charles and Neponset River Basins are also included. A comparison of discharges during the October 1996 and June 1998 floods for the Aberjona River at Winchester are also included. Click on the indicated graph title to view the graph. GROUND-WATER-LEVEL DATA.-- For wells with 5 or more years of monthly measurements, five wells yielded new record high-water levels for period of well record: Chelmsford 384 (1987 - ); and Northbridge 54 (1984 - ); Plymouth 494 (1985 - ); Pawtucket 136 (1962 - ); and Richmond 785 (1989 - ). New high-water levels for June were measured in 59 of 131 wells with 5 or more years of monthly measurements. Of special note are Haverhill 23 (highest June since 1960), Sterling 1 (highest June since 1947), and Winchendon 13 (highest June since 1939). A composite hydrograph of ground-water levels for recording wells in eastern Massachusetts for the month of June 1998 are available. Click on the indicated graph title to view the graphs. RESERVOIR LEVEL DATA.-- Reservoir conditions (contents, in millions of cubic feet (mcf) and percent full) for three reservoirs in Massachusetts and Rhode Island are shown below and are compared to the previous month conditions for both the June 1998 and October 1996 flood events. May 1998 June 1998 Sept 1996 Oct 1996 (contents, %full) Borden Brook + Cobble Mountain 3137, 92 3232, 95 2842, 84 2962, 87 (western Mass.) Quabbin Reservoir 54081, 98 55232,100 53175, 96 53443, 97 (central Mass.) Scituate Reservoir 5079, 99 5155, 96 4051, 83 4402, 90 (central Rhode Island)