Conversation with Dean Orbison

Hi all, here's a short summary of our conversation today. Hopefully I got this all correct.

USGS is contracted to make some of the measurements for operation of the facility and helps estimate inflow.

Discharge (inflow??) into Blue lake is measured directly at USGS gauge 15088000 (at Sawmill Creek) which has a discharge record from 1920 onward. We should verify on a map that this gauge captures some or all of the inflow to the lake or whether USGS estimates inflow indirectly based on this discharge record. The Blue Lake facility came online around 1960-1961. Dean estimated the glacial contribution to inflow at Blue Lake Creek to be about 20%. Blue Lake Creek contributes about 50% of the inflow to the Blue Lake reservoir, making the glacial melt input about 10% (back of an envelope). The total drainage into the reservoir is about 37 sq. mi, according to Dean.

Inflow into Green Lake is estimated by USGS from what sounds like a water balance method. Direct observations were made from 1915-1925 only (USGS gauge 15090000). This facility came online in about 1982.

Dean warned that switching from measured inflow to estimated inflow would create inhomogeneities in the record that might be incorrectly interpreted as climate change. (Did I remember this right??)

Digital Elevation Model: airborne LiDAR was flown to estimate inundation before most recent expansion. Other elevation information has been taken by hand from USGS topo maps and from the U.S. Forest Service (possibly in GIS?). Glacial contribution to Green Lake is unknown.

USGS Contact in Juneau is Jeff Goetz (formerly Dan Hess): jgoetz@usgs.gov, 907-586-7216 x23.

Model: NDT model (??) built in 1996 and modified specifically for Sitka over the years. Modifications before 2000 may not have been documented. Modifications since then are posted on the 'Interface' tab of the model posted here. I'm not sure which of the inputs to the model are estimated and which are measured. Of those that are measured, I'm not sure which ones are measured by USGS on contract and which are measured by the city site operators.

I also have a summary of some (but obviously not all) USGS records from Southeast AK Lakes here.

Please post comments/corrections if you have them! Thanks.