Lake Washington is situated adjacent to the city of Seattle and is the second largest natural lake in the State of Washington. Lake Washington is one of the best examples in the world of of a successful lake restoration by the diversion of sewage, and has been extensively studied and researched. 

The basin of Lake Washington is a deep, narrow, glacial trough with steeply sloping sides, sculpted by the Vashon ice sheet, the last continental glacier to move through the Seattle area. The lake is 20.6 feet above mean lower low tide in Puget Sound, to which it is connected via Lake Union and the Lake Washington Ship Canal, constructed in 1916. 

Lake Washington’s two major influent streams are the Cedar River at the southern end, which contributes about 57 percent of the annual hydraulic load and 25 percent of the phosphorus load, and from the north, water from Lake Sammamish via the Sammamish River contributes 27 percent of the hydraulic load and 41 percent of the phosphorus load. 

The lake received increasing amounts of secondary treated sewage between 1941 and 1963, which resulted in eutrophication and declined water quality of the lake. Planktonic algae was dominated by cyanobacteria from 1955 to 1973. Sewage was diverted from the lake between 1963 and 1967, with discharge of untreated effluent, except for combined sewer overflows (CSO’s) reduced to zero by 1968. Rapid and predicted water quality improvements followed, cyanobacteria decreased and have been relatively insignificant since 1976. 

The Ship Canal is the only discharge from Lakes Sammamish and Washington via the locks and dam at the western end. Prior to construction of the canal, the only significant inflow was from the Sammamish River in the north. Construction of the canal resulted in the lowering of the lake 9 feet to its present level, leaving the Black River dry and the Cedar River diverted into Lake Washington. 

Mercer Island lies in the southern half of the lake, separated from the east shore by a relatively shallow and narrow channel, and from the west shore by a much wider and deeper channel 

This model grid contains 1,183 cells, and orthogonal deviation of 0.28. This grid was built using EFDC+ Explorer and Grid+. An running demonstration model is also downloadable from this site.