Beginning in 1911, the level of the lake was lowered seven feet, which added 100 acres of dry land once it had been graded and filled. This process was completed by the early 1930s with the filling of the southern end of the lake using material excavated from Woodland Park during the construction of Aurora Avenue in 1932. By 1909, the amusement park at the northwest corner of the lake had long ceased to operate and had become known as the "Old Picnic Grounds." In 1914, the Parks Department constructed the first frame bathing station at the southwest corner of the lake where Guy Phinney had developed his Woodland Park. Within a year, it was necessary to enlarge the structure due to its popularity. However, its location proved to be problematic due to frequent water stagnation, which tended to attract waterfowl. As a temporary solution, the Parks Department moved the structure to the northern end of the lake in 1922. Five years later, the first phase of a new brick bathhouse was completed at the site of the "Old Picnic Grounds." Initially, only the north and sound ends containing the dressing room and restroom facilities for men and women were constructed. The following year, the central portion was completed, which contained a public lobby and locker room. At the same time, the Parks Department constructed identical bathhouses at Madrona and Seward Parks. However, the central portion of the Seward Park Bathhouse was not completed until 1940. It may have been at this time that the small concession stand was constructed just to the north of the bathhouse to serve swimmers who frequented the West Green Lake Beach. A 1930 photograph in the municipal archives appears to show this building on the western shores of Green Lake near the bathhouse. In subsequent years, additional concession facilities were constructed at the northeastern and southwestern corners of the lake. This building is significant for its association with the development of Green Lake Park.
In more recent times, Green Lake has suffered from stagnation and pollution problems, as well as algae blooms. Milfoil and swimmers itch (caused by parasites from waterfowl) are still a consideration for those who swim in the lake.