Prepared in Cooperation with the UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WATER-RESOURCES INVESTIGATIONS REPORT 00-4124 U.S. DEPARTMENT OF THE INTERIOR MASSACHUSETTS DEPARTMENT OF ENVIRONMENTAL MANAGEMENT Breault, R.F., Barlow, L.K., Reisig, K.D. and Parker, G.W. U.S. GEOLOGICAL SURVEY NEW ENGLAND INTERSTATE WATER POLLUTION CONTROL COMMISSION Spatial distribution, temporal variability, and chemistry of the salt wedge in the Lower Charles River, Massachusetts 226,000 228,000 230,000 232,000 234,000 236,000 250,000 50,000 150,000 EXPLANATION INDEX MAPS MASSACHUSETTS 220,000 900,000 BATHYMETRY 910,000 230,000 0 50 MILES 800,000 0 to 1.9 meters 0 50 KILOMETERS 900,000 2 to 3.9 meters 210,000 4 to 5.9 meters 890,000 200,000 GRIDS SHOWN ARE METRIC 6 to 7.9 meters 230,000 235,000 880,000 10.5-C 8 to 9.9 meters 900,000 So 870,000 ld 10 to 11.9 meters 10.9-B ie r s F Charlestown Bridge ii el Harvard University e Harvard University Eliot Bridge Eliot Bridge Herter East l LOWER CHARLES RIVER d 12 meters and over d CHARLES RIVER DRAINAGE BASIN STUDY AREA Park 1.5-B RR oa 1.9-B o Commuter Rail Draw Bridge 1.0-C a Old Charles River Dam 1.7-C 1.0-B 5.2-C d 2.0-B 0.0-C STATION AND IDENTIFIER 10.0-B 2.9-G 2.0-C 1.7-B 0.0-A 11.5-B 9.5-B Museum of Science 2.5-C 1.9-A 0.0-B 1.5-A 1.0-A1 8.9-B 2.5-B 2.0-A eeks Bridge 1.7-A 1.0-A Anderson Bridge 3.0-D 2.9-B 902,000 2.5-A 3.0-C New Charles River Dam Harvard Stadium Larz Anderson Bridge John WWeeks Bridge 3.0-B 2.9-A and Locks 3.2-A 3.0-A 3.5-C Watertown Dam Watertown Dam 3.5-B 3.7-C 3.5-A WWesternestern AAvenuevenue Bridge 3.7-B 3.7-A 3.9-C 3.9-B2 3.9-B 3.9-A Arsenal Street Bridge Longfellow Bridge 4.0-B Beacon Street Bridge River Street Bridge 4.1-B 4.1-A2 6.9-B Massachusetts Institute 4.2-A of TTechnologyechnology 4.2-A1 Community Daly Field Boating Community Riverside Rowing Center urnpike Memorial Drive 4.5-B Massachusetts TTurnpike Boat Club 4.8-C Hatch 4.5-A Shell Massachusetts Institute of TTechnologyechnology 4.5-A2 Sailing Pavilion 4.9-C 5.1-C 5.2-C Harvard Bridge 5.1-B2 4.8-B 4.6-A Magazine Beach 5.1-B 4.9-B Boston University 4.7-A Esplanade 6.2-B Boathouse 5.2-B PondsPonds 5.5-B 4.9-A 5.9-B Storrow Drive Massachusetts Avenue BostonBoston University University Bridge Bridge 900,000 A venue Massachusetts TTurnpikeurnpike Fenway Park Orthophoto map base by MassGIS, state plane coordinates, 2 km grid, NAD83 0 .5 1 1.5 2 MILES Figure 1. Water-quality sampling locations and bathymetry of the Lower Charles River, Massachusetts. 0 0.5 1 1.5 2 KILOMETERS INTRODUCTION Salinity values between water-quality sampling sites were The Charles River is of great recreational and ecological estimated using GRID commands (a module of ARC/INFO) June 19, 1998 June 24, 1998 July 1, 1998 July 15, 1998 August 19, 1998 October 7, 1998 value to the Boston metropolitan region and the within the AML. Volumes of the salt wedge and salt mass 235,000 236,000 235,000 236,000 235,000 236,000 235,000 236,000 234,000 235,000 236,000 234,000235,000 236,000 Commonwealth of Massachusetts. It is also the focus of the were calculated with the AML for 1-m depth intervals. Total U.S. Environmental Protection Agency (USEPA) Region I, volume of the salt wedge and mass of salt in the Basin were 902,000 902,000 Clean Charles 2005 Task Force. The main goal of the Task calculated as the sum of the volumes and salt mass calculated Force is to make the Charles River “fishable and swimmable” for each 1 m of the water column. by the year 2005. Achieving “fishable and swimmable” SPATIAL DISTRIBUTION AND TEMPORAL conditions will require continued progress in addressing a VARIABILITY OF THE SALT WEDGE 902,000 902,000 902,000 902,000 range of environmental conditions now degrading water quality, including the infiltration of saltwater from Boston Because the density of the harbor water causes it to sink to Harbor into the freshwater Charles River. the bottom of the channel, its spatial distribution is dependent 901,000 901,000 To better understand the pattern of saltwater intrusion, the not only on the amount of harbor water infiltrating into and U.S. Geological Survey (USGS), in cooperation with the U.S. discharging from the Basin, but also upon the channel Environmental Protection Agency (USEPA), Massachusetts morphology of the Basin. The present-day channel morphology of the Basin is similar to that of the original tidal Department of Environmental Management (MADEM), and 0 2,000 FEET 0 2,000 FEET 0 4,000 FEET channel and associated mudflats surveyed in detail prior to 0 2,000 FEET 0 2,000 FEET 0 4,000 FEET 0 500 METERS 0 New England Interstate Water Pollution Control Commission 0 500 METERS 0 500 METERS 0 500 METERS 0 1,000 METERS 1,000 METERS (NEIWPCC), collected data on the spatial distribution, construction of the old dam (Pritchett and others, 1901); however, the bathymetry of the Basin surveyed in 1901 has 0 0 0 0 0 0 temporal variability, and chemistry of the saltwater that Longfellow Longfellow Longfellow Longfellow Harvard Longfellow Museum of Harvard Longfellow Museum of New Charles 2 Museum of New Charles 2 Museum of New Charles 2 Museum of New Charles 2 Museum of New Charles 2 New Charles 2 Bridge Bridge Science been slightly modified by sediment accumulation and man- Bridge Science River Dam Bridge Bridge Bridge Bridge Bridge Science River Dam River Dam entered the lower Charles River from June 1998 to July 1999. 4 4 Science River Dam 4 Science River Dam 4 Science River Dam 4 4 The purpose of this investigation is to extend and comple- made holes dug during the last 97 years. The denser harbor 6 6 6 6 6 6 water that infiltrates the Basin generally collects in these 8 8 8 8 8 8 ment a regional-scale study of Charles River water quality 10 10 10 10 10 10 1,400 1,200 1,000 800 600 400 200 0 1,400 1,200 1,000 800 600 400 200 0 1,400 1,200 1,000 800 600 400 200 0 5,000 4,500 4,000 3,500 3,000 2,500 2,000 1,500 1,000 500 0 DEPTH, IN METERS DEPTH, IN METERS 1,400 1,200 1,000 800 600 400 200 0 DEPTH, IN METERS 5,000 4,500 4,000 3,500 3,000 2,500 2,000 1,500 1,000 500 0 DEPTH, IN METERS holes (fig. 1). DEPTH, IN METERS DEPTH, IN METERS conducted in 1996 (T. Faber, U.S. Environmental Protection DISTANCE FROM "NEW" CHARLES RIVER DAM, IN METERS DISTANCE FROM "NEW" CHARLES RIVER DAM, IN METERS DISTANCE FROM "NEW" CHARLES RIVER DAM, IN METERS DISTANCE FROM "NEW" CHARLES RIVER DAM, IN METERS DISTANCE FROM "NEW" CHARLES RIVER DAM, IN METERS DISTANCE FROM "NEW" CHARLES RIVER DAM, IN METERS Agency, written commun., 1997), and the ongoing water Other important morphological features of the Basin that monitoring activities of the Massachusetts Water Resources affect the distribution of the salt wedge are berms beneath the Authority (MWRA) and the Charles River Watershed Longfellow and Harvard Bridges (fig. 1). These berms are only about 4.6 m below the water surface at some spots, and November 17, 1998 December 29, 1998 February 10, 1999 March 17, 1999 April 28, 1999 Association (CRWA). The data collected by this investiga- 234,000235,000 236,000 234,000235,000 236,000 234,000 235,000 236,000 234,000 235,000 236,000 235,000 236,000 tion supports the Clean Charles 2005 Task Force by provid- they deter the movement of the salt wedge upstream, because ing detailed information concerning a major factor limiting the salt wedge must fill the downstream part of the Basin to a The average daily mean discharge from the Basin into “fishable and swimmable” conditions in the lower Charles level greater than the height of the berm before it can spill Boston Harbor over the next 49 days (August 19 through 902,000 902,000 902,000 902,000 River. Finally, the study will be used to assist current plan- over the berm and move upstream. October 7) was the lowest average discharge measured in ning efforts of the Metropolitan District Commission (MDC) Several other factors control the distribution and temporal 1998 (5.7 m3/s) and, although there were fewer than 25 lock variability of the salt wedge, including freshwater discharge cycles per day, by October 7 the salt wedge had advanced to to restore the historic parklands of the lower Charles River. 902,000 The “Basin” is the local term for the reach of the Charles of the Charles River; number of lock cycles; pumping; and just downstream of Harvard Bridge, and reached its River that begins at the Watertown Dam in Watertown, Mass., opening and closing of the lock gates, culverts, sluice gates, maximum volume (2.6 x 106 m3) for 1998.