An email from a reader of the site posed a few interesting questions about the two small lakes in the northern sections of Seattle, specifically discussing the current and historical outflows of these lakes. I’ve discussed the small lakes in brief here, related maps of their bathymetry and tangentially in the context of Licton Springs. However, this was a good instigation to to focus on some more specifics of these urban water bodies. I will refrain from my tendency to write another way-too-long post (of which this will inevitably turn into) and parcel this out in a few shorter ones, the first focusing on drainage questions (of which these are all connected) and then individual posts on Haller Lake, Bitter Lake, and Green Lake, as they are important parts of the hydrological history of Seattle.
To understand the overall configuration of water in Seattle, I did find this document by Seattle Public Utilities (SPU) titled ‘City of Seattle State of the Waters 2007‘. The first volume covers Seattle Watercourses, (which we will probably return to in the future), and in particular for our purposes here we look to Volume II: Seattle Small Lakes’ (both links above go to the PDFs – as I couldn’t find a page with a direct link) and it sounds like a great resource in need of an update.
For some general contents, a bit on lakes in general and their outfalls, from Vol. II, p.3: “Lakes receive inflow from their surrounding watersheds through rivers, watercourses, overland and subsurface flow, and — in developed areas — from drainage pipes. Water typically exists a lake through a watercourse or river, although the outflows of most lakes in Seattle have been channeled into constructed drainage systems.”
In general, all three lakes are formed from Vashon glaciation, and as I mentioned previously, per geologist Stan Chernicoff, both Bitter and Haller lakes would be considered true kettle lakes, and Green Lake a hybrid, although still formed by glaciation. The 1850s map locates the three Lakes, all of which are in the north portion of Seattle, but doesn’t offer too much in terms of drainage direction, aside from implying proximity between Thornton Creek drainage for Haller Lake, and Bitter Lake likely draining west due to proximity, neither show a visible outfall creek.
Green Lake it’s more obvious, with multiple inflows, including Licton Springs Creek, and the very distinct outflow that drains through Ravenna Creek southeast into Union Bay.
The 1894 USGS map offers us the aid of topography, along with a bit more more comprehensive creek coverage. Bitter Lake hints at the possibility of outfalls either direction, heading to the northwest down to ravines that skirt The Highlands and the Seattle Golf Club and outlet near Spring Beach, and also draining southeast towards a seasonal drainage. Haller Lake (titled Welsh Lake on the map) also has no visible outfall as well, but adjacent creeks that are part of Thornton Creek drainage nearby, and a wetland area to the south make me infer that these would be like to be the natural drainage course of the lake.
Green Lake’s hydrology is a lot simpler to discern, with the similar inputs and outputs via the Ravenna outlet to the wetland zones near University Village and outlets into Union Bay.
TWO ALTERNATIVE THEORIES ON HISTORICAL DRAINAGE
One part I’ve always been a bit skeptical about in the USGS map is the location and extent of the drainage from Thornton Creek that looks to curve way west and intercept any south flow from the Bitter and Haller Lakes and direct it to the east to the larger Thornton Creek Basin. Licton Springs Creek also flows south, and is in reality much further north than shown on maps, and the interface between the two basins if filled with springs and wetlands, so it’s likely there could have been some disconnect between what was there flowing south, and what was mapped flowing east. However, Alternative 1 uses the basis of the map as the correct flowline, so shows both Bitter Lake and Haller Lake draining towards a seasonal creek and wetland that exists in the South Branch of Thornton Creek, and a smaller drainage picking up Licton Springs Creek draining into Green Lake. This mapped, overlaid on the 1894 map, shows an option for the lakes draining east, into Lake Washington. Dashed lines, for reference, are really basic watershed delineations, and the arrows show flow from lakes.
My gut is that both lakes flowed into Green Lake, via Licton Springs Creek, and then continued out to Ravenna. Alternative 2 looks at a version of this where there is more of a distinct ridgeline separation between the Thornton Creek Basin and the drainage that flows north south, and that the survey misinterpreted the flowline that heads towards the east due to the aforementioned springs and wetlands. The fact that the Licton Springs Creek is much further north than mapped, makes me posit that the upper lakes drained to this transfer point, and that instead of falling east, the flows kept going south into Green Lake, via the Licton Springs. Overlaid on the modern topography gives a bit of context to this configuration.
Both of these options are plausible, and the current outflows of the lakes (seen below) support this, with Bitter Lake draining to the Southeast and Haller Lake draining West. This at least gives us the indication that these both flowed to the low north/south valley (where current Highway 99/Aurora Avenue runs), however, where they go after is still a bit of a mystery. My follow-up plan is to look at some Lidar or a DEM to provide a much clearer picture of the flowlines and ridgelines, which we can assume, much like the current topo, is mostly similar to its predevelopment configurations (i.e. places in Seattle where we didn’t move hills). This will go beyond this back of the napkin approach above and see if that higher degree of detail unlocks any new info.
While it’s hard to determine the exact nature of pre-development drainage on these lakes, we can infer much from these historic documents and topography. The current system is more clear, although not visibly inherent due to the modernization and piping of drainage through large intercepter sewers – in this case the Densmore Avenue Drainage System, which runs north/south around the low flowline at Aurora Avenue (Highway 99).
The first hint of the split of drainage is in the State of the Waters, where both Bitter Lake and Haller Lake fall outside of their adjacent drainages going west to Piper’s Creek and east to Thornton Creek. Figure 1 from the report shows a narrow band that is bisected by this linear north south zone, with both creeks located inside the boundary.
A search for the nature of this basin configuration is somewhat frustrating, mostly as it seems to be specifically not related to a creek so isn’t referenced as a watershed in the same way. The SPU site on Urban Watersheds breaks down the city into four distinct areas of drainage, including the Puget Sound, Lake Washington, and the Duwamish River, as well as this uniquely land-locked zone we’re focused on, known as the Ship Canal/Lake Union basin
This is subdivided into some smaller sub-basins,including the Ship Canal Basin, the South Lake Union, and our zone, the North Lake Union Basin, which stretches up to the northern lakes, in that same narrow band, encompassing their drainages, then around Green Lake, and south to the interface with Lake Union.
The specific acrobatics that the Densmore Basin does to get down to Lake Union is hinted at but there’s not a lot of great maps, in particular the last section which . This excerpt from the Seattle Comprehensive Plan Update Draft EIS from May 4, 2015 shows the ‘capacity constrained’ condition. but does highlight the basin and it’s
I dug a bit more and found another mystifyingly badly interfaced GIS portal, this time Drainage Basins layer from City of Seattle, embedded below. Again, need to download the data and have a bit more freedom to sort it out in order to display it in a better way, but you get the idea from this map (especially if you zoom in on the areas below Green Lake, and can see the basin outline snaking in a thin, gerrymandered strip beside I-5.
The lakes themselves fit within the infrastructure systems, as seen below. The City of Seattle Water and Sewer Map , which I thought would be helpful but really isn’t because you have to zoom way in to show pipes and so lose context, so it doesn’t clearly articulate the drainage system elements enough to isolate (i included a few screenshots), so probably need to get some GIS files to draw these and separate mains, branches, etc. to isolate systems, but the narratives are pretty clear in explaining the outfall scenarios.
Haller Lake, which is around 15 acres of drainage, and has a maximum depth of 36 feet, get’s inputs from adjacent residential drainage areas (280 acre drainage), now drains via the Densmore system, as mentioned in State of the Waters, Vol II, the lake “…discharges through an outlet control structure on the western side of the lake, eventually draining to Lake Union via the Densmore storm drain system.”
Bitter Lake, measures 18.4 acres with a max depth of 31 feet, draining a smaller area (159 acre drainage). This lake is also being drained into the Densmore system, from the State of the Waters, Vol II, page 25: “At its southeastern end, Bitter Lake drains through a piped outlet that runs through a series of small ditches and culverts before entering the Densmore storm drain system on Aurora Avenue North. The Densmore system is equipped with a low-flow bypass, which conveys runoff directly to Lake Union. Under high-flow conditions, runoff passes through Green Lake before discharging to Lake Union.”
Green Lake, has a surface area of 259 acres, and a shallow depth, maxing out at around 30 feet, drains a basin of 1875 acres of surrounding area, as well as getting inputs from the Densmore system, as mentioned above. Alas, it now no longer drains into Ravenna Creek, but is diverted, per the State of the Waters, Vol II, and“now discharges to Lake Union through a single outlet located near Meridian Avenue North. In the past, Green Lake also discharged to the combined sewer system via a number of outlets around the lake. However, these outlets were recently blocked and now are used by Seattle Parks and Recreation only during rainstorms of long duration when the Meridian Avenue North outlet is not adequate to maintain water levels in Green lake.”
HEADER: Haller Lake from above – via Windemere