Why is Lake Tapps drained each winter, and when is it full?

Lake Tapps, the Pierce County reservoir beside Bonney Lake, is not drained each winter; it is lowered about four feet to protect its dikes. Its owner, the Cascade Water Alliance, has agreed to keep the reservoir between 541.5 and 543 feet from April 15 through September 30, river flows permitting, then drops it to about 538 or 539 feet, which it says lets it maintain the earthen dikes and keeps winter wind and waves off them. As of October 2026, the active drawdown begins November 1, refill is expected to begin in mid-February 2027, and the summer level is due back by April 15. The water is the White River's, taken out of its bed at Buckley, just across the river from Enumclaw.

There is no plug, but there are valves in the old powerhouse, and Cascade uses them for the active drawdown in November. The rest of the year the lake leaks through that powerhouse on its own, at a rate the 2008 agreement governing the river estimated, under the conditions of that time, at 50 cubic feet per second, so staying full takes a steady share of the river. That share comes second. The 2009 agreement that commits Cascade to a summer lake ranks the river's flow first, lake levels second and future drinking water third. In the drought summer of 2026 the river collected: Lake Tapps fell below its agreed level by the end of July, and both public boat launches got closure notices.

Why is Lake Tapps lowered every winter?

Cascade lowers the lake to protect and repair the dikes that hold it on its plateau. Its September 29, 2026 notice, on Cascade's Lake Levels page, says the drawdown "allows Cascade to perform necessary maintenance on the dikes and ensures safety from wind, storm, and wave action during the winter months." A December 2025 update was plainer: too much water, wind and waves could break a dike and flood the communities around it, so the winter level is kept where the State Dam Safety Office requires.

The 2008 agreement names a second purpose. It defines the fall drawdown as exposing parts of the lakebed "for the purpose of preventing macrophyte growth," meaning large water plants such as milfoil, or for maintenance. Cascade's notices of 2023, 2025 and 2026 give neither weed control nor owners' dock work as a reason.

How far does it drop, and is Lake Tapps ever drained?

The usual drop is about four feet, in a lake roughly 89 feet deep at its deepest, by a 2011 management plan from Pierce County, Cascade and neighboring cities. Cascade says it normally keeps the summer level between 542.5 and 542.8 feet, and that 538 to 539 is low enough to protect the dikes and allow routine inspections. These are gage heights, readings on a federal gage at the lake, not depths.

Cascade's page says specific dike projects need 533 to 535 feet, sometimes lower, and the 2008 agreement would permit 530. In the winter of 2014 to 2015, by Cascade's property policy, the lake went below 500 feet for major repairs and stayed closed to the public until it was refilled in July.

When does the drawdown start, and when does Lake Tapps fill up?

The active drawdown starts November 1 and refill starts in mid-February; Cascade confirms both in a notice each season. The 2009 agreement asks Cascade to make reasonable efforts to hold the summer level through October 31, and its notices for 2023, 2025 and 2026 all name November 1. The lake can sink sooner in a dry autumn; in 2025 Cascade advised having boats out by mid-October. Its chart of a typical year shows the winter level reached about the second week of November.

Refill has a floor date. Under the 2008 agreement the most Cascade may divert rises on February 15 from 150 cubic feet per second to 1,000, and only while the river at Buckley stays above a set minimum. Cascade set the 2026 refill for that day, and a 2017 release put the rise at as much as three to four inches a day. Once a year, around May 1 in 2026, Cascade takes the lake to 543 feet so owners can see where high water falls on their property.

Who decides the Lake Tapps water level?

Cascade decides, within limits set by its state water rights and two agreements. It bought the lake and the diversion from Puget Sound Energy on December 18, 2009, and the Department of Ecology issued the water rights on December 10, 2010.

The White River Management Agreement of August 6, 2008, between Cascade, the Puyallup Tribe of Indians and the Muckleshoot Indian Tribe, sets the flow that must stay in the river, 500 cubic feet per second from early August to mid-November, and has Cascade consult the tribes on each year's plans.

The Lake Tapps agreement of May 13, 2009, between Cascade, the Lake Tapps Community Council and seven homeowner groups, commits Cascade to the 541.5 to 543 range from April 15 through September 30. That holds until the later of 30 years after it took effect or the day the lake begins supplying drinking water, which Cascade, as of October 2026, expects in the 2060s. It allows variances for weather and the water rights, and calls for a full review by 2030.

Why is Lake Tapps so low some summers?

When the White River runs short the river has first call, and 2026 showed how. Ecology declared a statewide drought emergency on April 8, 2026. By July 14, Cascade reported, the White River was below its minimum flow, the point at which the water rights forbid diverting any water to the reservoir. The level was 541.79 feet that day and 541.28 on July 31. Bonney Lake closed its launch on July 27; Pierce County announced an August 14 closure at North Lake Tapps Park. A warm spell in August sent down melt from the Mount Rainier glaciers that feed the White River and let Cascade take some.

On September 29, 2026, Cascade gave the level as 540.55 feet, still under the summer range, and said it would add water in October if it could.

Where does Lake Tapps get its water? The White River at Buckley

Lake Tapps is a man-made reservoir, filled from the White River through a diversion at Buckley. The gage that decides whether Cascade may take water is the federal one named White River above Boise Creek at Buckley; Boise Creek is the salmon stream that runs south of Enumclaw. Upstream is Mud Mountain Dam, whose flood releases Cascade reported watching in December 2025.

How the river came to be detoured is told in this site's history of the White River diversion. The federal engineering record supplies the local detail: the water was led into "the large natural basin on the Enumclaw plateau," which held four small lakes named Tapps, Kirtley, Church and Crawford, and earthen embankments raised it 35 feet. Power was delivered commercially for the first time on November 1, 1911. None of the lake's water reaches Enumclaw's taps; the town drinks from its own springs and wells.

What are the stumps, and can you walk on the lakebed?

The stumps appear to be older than the lake. The engineering record calls the country at the lake's outlet heavily timbered, enough that the builders ran a sawmill there, and the 2011 plan lists tree stumps and snags on the bottom as an ongoing problem. No record opened for this article says how much of the basin was logged before the water rose.

Walking out to them is not allowed. Cascade owns the lakebed and shoreline up to the 545-foot contour, a line its property policy says a 1954 deed fixed by reference to a bronze plaque in the gate house floor, and the policy says "the lakebed is not open to recreational use at any time, including during typical winter drawdown." The dikes are closed too. Ahead of the deep drawdown of 2014, Joe Mickelson, then Cascade's Lake Tapps operations manager, warned of unstable ground, stumps and "soft areas where individuals and vehicles might be injured or become stuck."

Can you boat or fish on Lake Tapps in winter?

Fishing stays open; the public boat launches generally do not. The Department of Fish and Wildlife lists Lake Tapps as open year-round and cautions that the water is "normally down throughout the winter and early spring, which may limit boat access." The department requires a fishing license for anyone 16 or older.

Pierce County's North Lake Tapps Park, at 2022 198th Avenue East, is open October through March from 7 a.m. to 3:30 p.m. The county calls its boat launch typically closed from November to March and lists parking fees as collected May through September. Bonney Lake's launch at Allan Yorke Park, limited in 2026 to city residents with a $43.80 annual pass, reopens when Cascade judges the lake back at recreational level.

Where to check the Lake Tapps water level today

The USGS gage for Lake Tapps gives the current level: read the line labelled gage height, the scale Cascade uses, and not the elevation line, which runs half a foot lower. Cascade's Lake Levels page carries the season's notice, and its number for level questions is 425-453-0930.

Lakefront owners need more lead time. A new or altered dock, bulkhead, boat lift, ramp or boathouse below the 545-foot line requires a license from Cascade before work begins, plus any permits from Bonney Lake or Pierce County, the Department of Fish and Wildlife and the Army Corps of Engineers. Cascade's policy says there is no administrative fee for a license, though an applicant may be asked to pay for professional services used in processing it, and Cascade's license page adds insurance requirements.

If the lake looks low in late summer, look at the river first. When the White at Buckley drops below its minimum, Cascade cannot divert, and Lake Tapps starts down on its own.