Then the question to ask is; what are you trying to achieve?
COE lake managers will give you the water elevation of the day by simply calling them.
I like to go to the spillway and establish a reference to the water elevation and then apply that to the actual lake level. That can be carried all around the lake by the water level that day. It does help to check the reference at the end of day also and see if it has changed.
@jules-j It would be a bucket with no bottom that would interrupt any surface motion inside while keeping the elevation the same. Pascal's principle.
The OP said a "still pond" but since that may not be the case at the time you want to visit, the stilling pool is a good idea.?ÿ It's best if the bucket has a small hole so it takes longer to respond to a change in level than the time between waves.?ÿ Let it sit for a while to stabilize, i.e., take an average.
We do this all the time, there are many different types of ponds but they share some characteristics.
There is always a source, there is always a outflow point. The elevation of the outflow point determines the capacity of the pond and the maximum elevation, except when there is a major flood event which could raise the elevation above the spillway elevation.
Where the waterline is at any point in time isn't much of a consideration, ponds filled by an alluvial source can have a more stable elevation, but even those will rise and fall with the alluvial source, evaporation, rain fall, snow melt events.?ÿ
I suppose you can determine a mean elevation of some kind, that should be done with a gaging station installed. Those are on many reservoirs and I suppose natural lakes and ponds. I would consult an engineer that deals in safety of dams, they are the go to guys for this.?ÿ
We always determine the spill point, that is the elevation of the pond/reservoir that counts.
But then I'm not in the flatlands.?ÿ
Kind of getting off the topic a little, but generally speaking I would wonder if you were readying to the nearest foot, or the nearest hundredth of a foot (Or whatever). That is what I would mean if I was asking what your precision is.
Anyway, if anything was possible, I would use something like this, and check with occasional physical measurements.
We had a few wet well gaging stations that were deployed prior to my position as the Utility GIS Coordinator of a water hungry city along the front range of Colorado. During construction/repair, They were measuring the water with a cm accurate Single Base solution and were "getting close" enough with a flat rock in the shoreline until it was windy.?ÿ I helped the GIS Tech 'build' a 'stilling' buck to attenuate the waves caused by the wind and waterfowl etc,to use the topo shoe for the .01 plate as a guide,?ÿ and was imbued by the water resource engineer to beware the seiche, and always take several measurements before collecting and heading back to the office.
We'll be using the level and rod for an elevation at the pond. One hundredth may be achievable. The data is for an elevation certificate and latter of map amendment.
We will try to use the pond elevation as a bench mark on the same day to get the elevation of the dam and free board. We will also be using the survey instrument (1 second resolution) for a three dimensional coordinate at the dam and compare the results.
It's not a long term project so I doubt if I can afford the data logger.?ÿ?ÿ
I'm applying to FEMA for a letter of map amendment on two properties at the pond.
You mention a dam, this implies the pond is a reservoir, unless it's a pit/dike structure. Anyway what FEMA needs is a flood elevation which in a normal dam/reservoir will be the spillway elevation plus the elevation of a 100 year flood event overtopping the spillway. The critical information is the spillway elevation, spillway capacity and the calculations that determine a 100 year flood volume.
You need the critical information of drainage pipe and trickle tube, what they are made of and how they work, the trickle tube elevation and capacity, the drainage pipe, nice to get it's elevation but often that isn't possible easily.
Topo the spillway or cross-section profile it.
Hand all this information to an engineer and they will do the calculations to determine the 100 year flood elevation of the reservoir. The water level in the pond has little to do with a flood elevation or HWL of the pond. I wouldn't have even bothered with it. My guys have learned to ignore the water in any reservoir/dam job.
I'm assuming that there is no FEMA map for this area.
They will or should want an engineer's report. I can't imagine anyone built a house lower than the spill elevation behind this dam, that would be a problem.
If I can walk up to the edge of the pond I just shoot where the water intercepts the land, but any of the means stated above would work.
@mightymoe I am learning the history of the area surrounding the pond and it seems to have been constructed to serve as a recreational area. I have yet to visit the dam as it is on private property and so I have scheduled an appointment.
I do know that there have been 8 or more letters of map amendment approvals in the near vicinity. So, I will ask if any engineering studies were done for those approvals, but, I doubt it. There is a FEMA map of the area, but no base flood elevation.
Thank you and everyone else for your thoughts and advice.
If I can walk up to the edge of the pond I just shoot where the water intercepts the land, but any of the means stated above would work.
All day long.
All day long.
Water's edge changes ALL DAY LONG too unless it's frozen
