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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 42o12'40", long
70o55'47", Norfolk County, Hydrologic Unit
01090001, on Whitman's 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--January 2002 to current year.
GAGE--Data Collection Platform with satellite telemeter. Datum of gage at Town of Weymouth datum. Subtract 6.67 ft from gage height values to adjust to NAVD 1988. Subtract 5.83 ft from gage height values to adjust to NGVD 1929.
REMARKS--Flows affected by withdrawals for public water supply of Weymouth. High flows affected by diversions to flood by-pass system at Iron Hill Dam. 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.
COOPERATION BY--Town of Weymouth, MA
FLOOD BY-PASS SIPHON INFORMATION--The flood by-pass system includes four siphon openings located at Iron Hill Pond Dam which are designed to by-pass flood flows around the Iron Hill Pond Dam fish ladder directly to the flood by-pass system. By-pass flood flows discharge to the inter-tidal zone downstream of Jackson Square. The following list shows the bottom elevations for each set of four siphon openings. Siphon Unit 2 is the first unit to by-pass flood flows.
Iron Hill Pond Dam--flows by-pass Iron Hill Pond fish ladder and enter flood by-pass system when Iron Hill Pond elevation exceeds the following siphon inlet elevations (Town of Weymouth Datum, in feet):
|Siphon Unit 2||65.25|
|Siphon Unit 3||65.35|
|Siphon Unit 1||65.45|
|Siphon Unit 4||65.55|
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