Topic: Getting Lake Temperature

[George Richardson]

Hello,

I have a project that I would like to solicit ideas for. I live on a pump storage hydro electric lake operated by the local power company and overseen by the Corps of Engineers. I want to provide the current "Lake Water Temperature" on my web site. For the past year I have had a temperature probe dropped of the end of my docked boat so that it stays at a constant depth below the surface of the water. After several months, and about the time the lake level fell so low that the probe probably was on the bottom, the original stainless steel probe failed and I obtained the inexpensive (plastic) replacement. This functioned until last week when some upstanding person cut the probe from the cable.

I would like to replace the probe more securely and have a few questions:

1) How deep below the lake surface should the probe be? I'm thinking 1'

2) I would like to put a ~2 1/2" PVC pipe adjacent to a pile and run the sensor inside up and down on a bobber. I think I will need circulation holes in the pipe for accurate water temperature. So, needed? if so what size, 1/4", 1/2", what depth interval? 1', 6". The full pond lake depth at the pile I plan to use is 5 1/2'.

Comments appreciated.

George

[Bushman]

The typical scientific standard is 1 meter below the surface.  Right at the surface ( say a couple inches) your probe is subject to the vagaries of  solar heating etc.  Still valid for swimmers and the like though.

If you use the pipe idea (good one BTW) be sure it is not on the sunny side.  I would perforate it  as much as I could (in fact that is exactly what mine is but smaller diameter plastic pipe.) And use the white PVC, not grey or  black.

[Dr Obbins]

For my swimming pool, I used a 1/2" pipe to protect it from the rowdy swimmers. It has many 1/4" holes drilled through it and the bottom is not capped. The pipe is mounted on the back side of the ladder. Obviously the pool level (48") stays more consistent than a lake and the sensor is at about 18" below the surface. I would take pics, but currently the pool has a tarp over it. 

[Beaudog]

I would use a 1 inch piece of PVC  (color of your choice) 3 feet long (close enough to 1 meter) put the sensor right at he bottom.   Two 1/4 inch holes every 6 inches should provide more than enough thermo siphon of the water.