A2: Argo Spillway

A sometimes Stopped.Watched. contributor Voxphoto documents the water level in the Argo headrace compared to the spillway lip near the canoe portage. The city stopped the flow into the headrace last week on order from the MDEQ.   In a Tweet he writes: “Curiously, Argo millrace still dropping, below spillway level. I estimate >80,000 gals in last 24 hrs. Is the berm that leaky?” [Source Photos] Related Chronicle coverage: “City, MDEQ Agree: Argo Headrace Shut

Updated layout by Voxphoto: [Argo Spillway]


  1. By Dave Askins
    November 8, 2009 at 11:00 am | permalink

    For a layout and more complete narrative of the photos, Voxphoto has put together the following: [Link]

  2. By Tom Whitaker
    November 8, 2009 at 11:34 am | permalink

    Evaporation perhaps? It’s been quite warm and breezy. Anyone who’s ever maintained a swimming pool can tell you that they lose a lot of water daily due to evaporation. Maybe it doesn’t explain the total amount, but I bet it’s not an insignificant factor.

  3. By Ross Orr (Voxphoto)
    November 8, 2009 at 1:50 pm | permalink

    I originally observed a 1-1/4″ drop between midday Thursday and midday Friday. That was before the recent warm & sunny weather–it was basically cloudy & cool. But you’re right that I haven’t tried to estimate evaporation.

  4. By Russ Miller
    November 8, 2009 at 3:00 pm | permalink

    Evaporation is probably a small effect. Mean pan evaporation around here for October is ~3 inches/month and free surface water evaporation is usually estimated at 75% of that, so we should expect less than 0.1 inch of evaporation per day.

    Historical pan evaporation data
    [link to .pdf file]

  5. By Ross Orr (Voxphoto)
    November 8, 2009 at 5:25 pm | permalink

    I’m concluding the real wild card is whether any water still passes through the Edison Substation’s disconnected hydropower equipment.

    I assumed not. But investigating further, I discovered the concrete pedestrian path below the south corner of the substation has a rather hidden outlet grille beneath it. (location–foot of the steps here: Google Maps Link )

    Dropping some twigs in the water, there did seem to be a barely-perceptible downstream flow emerging from that. Enough to explain 70,000 gallons in one day? I couldn’t guess.

  6. By Ross Orr (Voxphoto)
    November 30, 2009 at 12:48 pm | permalink

    Nov. 30th update: The mystery may be solved. As the water level has dropped, another outlet to the millrace has surfaced, a couple of yards to the east of the spillway.

    This muck-covered grille is making gurgling water noises, and presumably connects through the Edison substation in some way…