I've entered the digital age at least as far as cameras are concerned.
Thought I would add some pic's so theory can be seen in practice.
Pics from Sept, 2007. Using a 2" ball valve to throttle the drawdown speed so my sides don't sag. Took about 4 weeks to draw down 70". Plan is to Rotenone my LBM and GSF to restock with SMB, YP, and possibly walleye.
Note: the lighter areas around the tripod is the bedrock bottom.
Also note the rocks stacked over the pipe and concreted to keep the pipe from floating up if the bottom flap valve in the pond is closed,and the outflow is open in the basin (the pipe would be filled with lots of air).
Rope is used to open the flap valve at the bottom. Stainless steel pulleys used (three strands to overcome the force of the water). It takes a pretty good pull to open.
The Standpipe in the dam is visible in the foreground. Not sure what that board looking thing in the picture is that points toward the swim platform ladder. There is nothing there! Ghost pixels!
Looking down to the 10" T that controls the pond level. Overflow is through a 12" corrugated culvert buried in the backside of the dam.
Looking down into the drainage basin. 8" PVC and flange cover plate are visible under the water. The overflow culvert is just under the rocks to the right of the flange. The vinyl was to prevent my two inch stream of drawdown water from doing any erosion. It is not normally there.
View to the North East of auxiliary spillway area.
Spillway down to the basin.
I have about 680' of dam. No surface water runs into the pond.
Standpipe capacity is 140% of 100 year rain event plus spring flow.
Auxiliary spillway is 160% of 100 year rain event.
You can't have too much...
Hope this helps someone considering with dam designs.