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King County Major Lakes Monitoring


For questions about the King County Major Lakes Monitoring Program, please contact Sally Abella (206) 477-4605, or Debra Bouchard (206) 477-4650.
Lake Union photo

Lake Union Monitoring Overview


Physical Characteristics

Watershed Area 365,440,000 acres (571 miles2) 255 km2
Lake Surface Area 580 acres 2.3 km2
Lake Volume 20,000 acre-ft 2.5x1078 m3
Mean Depth 34 ft 10 m
Maximum Depth 50 ft 15 m
Flushing Rate 52 per year
Main Inflow Lake Washington Ship Canal
Main Outlet Hiram Chittenden Locks
Trophic State Mesotrophic

Monitoring Overview

Lake Union is the smallest of the three major lakes in King County. It is the most heavily urbanized, of the three, draining residential, commercial, and industrial neighborhoods. Its shores are completely lined by marinas, house boat moorage, commercial docks and dry-docks, and industries..

There are four current sampling stations in Lake Union; Station 0512 located in the ship canal east of the Chittenden Locks, Station 0518 located below the Fremont Bridge, and Station 0522 at the southwest end of the lake, where it is deepest. Two stations are no longer monitored as of 2008: 0518 and 0536. Samples are collected twice monthly from March through November, and once monthly from December through February.

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Water Quality Data

View or Download Data

Use this tool to view or download data from the lake in tabular format. You can define date ranges and select which parameters to view or download.

Chart Data

Use the charting tool to look at graphs showing single parameters.

Data Map

Choose a sampling location on the map to view or download data.

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