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ICE EFFECTS ON STREAMFLOW
The formation of ice on rivers can cause discharge values to appear unusually high. Display of these erroneous discharge data may result in improper assessment of flow conditions and misuse of the data. For this reason, display of discharge values for streams significantly affected by ice may be disabled from view. Display of discharge data will resume when ice conditions are no longer present. Discharge values for streams minimally affected by ice will continue to be displayed. Flows for streams with these conditions appear to increase during the night and decrease to near-base-line conditions around midday. To estimate the correct discharge for these streams, use the flow rate that corresponds to the bottom of the discharge curve, rather than the peak that corresponds to the top of the curve. Note that this method of estimation is possible only when no surface runoff is occurring. Daily mean discharges for periods of both significant and minimal ice-effect will be estimated and published in the Annual Water-Data Report for the water year in which they occurred.
LOCATION--Lat 42o12'39", long
70o55'46", Norfolk County, Hydrologic Unit
01090001, on Whitmans Pond Dam, approximately 1,000 ft upstream from
Iron Hill Dam, and 1,300 ft upstream from Whitman's Pond Outlet
gage below Iron Hill Street, at East Weymouth, MA.
DRAINAGE AREA--12.4 mi2.
PERIOD OF RECORD--Gage height: January 2002 to current year.
GAGE--Data Collection Platform with telephone telemeter. Datum of gage at Town of Weymouth datum. Subtract 6.67 ft from gage height values to adjust to NAVD 1988. Subtract 5.87 from gage height values to adjust to NGVD 1929.
REMARKS--Flows affected by withdrawals for public water supply of Weymouth. The Old Swamp River gage (01105600) is located 0.4 mi upstream from Whitman's Pond, South Cove, and points of water withdrawals and diversions. Discharge record below 10 cfs considered poor.
COOPERATION BY--Town of Weymouth, MA
FLOOD BY-PASS SIPHON INFORMATION--Whitman's Pond Dam contains four siphon openings which are designed to by-pass high flows around the Whitman's Pond Dam fish ladder directly to the lower Iron Hill Pond. The four siphon openings located at Iron Hill Pond Dam are designed to by-pass flood flows around the Iron Hill Pond Dam fish ladder directly to the flood by-pass system that discharges flood flows to the inter-tidal zone downstream of Jackson Square. The following list shows the bottom elevations for the Whitman's Pond Dam siphon openings. Siphon Unit 2 is the first unit to by-pass flood flows to Iron Hill Pond and is at the same elevation as the spillway.
Whitman's Pond Dam--flows by-pass Whitman's Pond fish ladder when Whitman's Pond elevation exceeds the following siphon inlet elevations (Town of Weymouth Datum, in feet):
|Siphon Unit 2||72.47|
|Siphon Unit 3||72.57|
|Siphon Unit 1||72.67|
|Siphon Unit 4||72.77|