High Water Mark?

In NY a call to HW generally includes the area between HW and LW. So, here the face of the wall would be it. Unless of course the contrary could be shown; bunch of exceptions.

1. Is it a 'by' call or a call terminating at the high water? High water mark or mean high water?

2. Did the concrete wall require a license, permit or other document? Who owns this wall?

Here in MA, we have licenses from the state for structures below the mean high water. I like littoral boundaries terminating at shoreline structures, it's a definitive monument/object not a line drawn in the sand. It can also set the boundary in a permanent location in the case of fill. Ownership extends to low water (don't ask which low water, the original cases called for 'ordinary' and the courts cannot and will not decide whether it was intended to mean mean low water or extreme low water or some other measure (Rockwood v. Snow Inn)) In the case of fill, a license is granted from the state to fill the tidelands upon which the public still retains the rights of fishing, fowling and navigation. Fill can be granted below the low water line and using an assumption of Mean Low Water (as that is required on the plans), the boundary would then be a line that would not move, the remainder being licensed land. These practices also apply to 'great ponds' who exceed 10 acres in size in their natural state, I just happen to work on a sand bar so I look at things with salty lenses.

I'll assume things work a bit differently, but the record should give you some details as to the nature of this wall.

to the high water mark, thence along the high water mark.

to the high water mark, thence along the high water mark.

That should be equivalent to a BY call (Kingman's notes on Legal Aspects) so you are covered there. Now it's just the matter of the record of the wall.

Building a wall will not change boundary

I don't know what state you're in, but I would investigate the construction of the wall. Were any easements or takings recorded? Absent that, the boundary is the pre-wall high water line. The builder of the wall can’t unilaterally change the boundary without going through the appropriate legal process. Have fun figuring out where the original high water line is, although since this was a man made reservoir there may be a sufficient record to locate it without too much trouble.

Building a wall will not change boundary

In the absence of a survey, I think my first attempt would be to try to find an aerial photo of the lake before the wall was built. If you get lucky, the wall may not be too old. I agree that the property owner can't arbitrarily change the location of the water line and have the property line go with it unless the proper legal channels have been followed. If the water line had changed naturally, it would be a different story.

> Does anyone have any experience in handling this type of situation.>

Quite often.

You need to check this against the statute and case law of your state if there is any. In CA, where there has been some artificial influence on the water body, for purposes of determining where State ownership is (beds of navigable waters), we determine where the last natural location of the OHWM and the LWM are (State owns to LWM in CA but there is a Public Trust Easement to the OHWM).

On a reservoir, you have another level of complexity. The reservoir itself is a result of artificial influence in the form of the dam and its result of elevated locations for the OHWM and LWM.

Does your description predate the reservoir or was it written after the reservoir first reached capacity? The difference will be whether the HWM referred to is that pertaining to the free-flowing stream or that pertaining to the filled reservoir.

If it predates the dam, investigate any land acquisitions made by the entity which created the reservoir. It's possible that your reference to the HWM was made pursuant to such an acquisition.

If the HWM in the description is in reference to that of the dammed state (reservoir in place), determine whether the HWM is in reference to the dam at full capacity or in reference to a normal high water year, which may be at somewhat less than full capacity. Guidance for that might be found either in the original land acquisition records for the reservoir or in court records. Lacking such guidance, if the shore were in a natural state, I would lean toward identifying the OHWM like I would on other inland bodies of water: indications where the action of water has scoured the ground of any upland vegetation, or where upland vegetation gives way to primarily aquatic vegetation.

As someone else mentioned, see if there are any records for the wall construction. Plans, approvals, design surveys. An approval by the agency responsible for the reservoir made without reference to an existing HWM would generally imply an agreement that the review associated with the approval & permit to build found that the wall was to be placed essentially at the OHWM, making the face of the wall the now fixed location of the OHWM.

Such approvals or other documentation regarding the wall construction may alternately give information that the pre-wall OHWM was at some other location, which may preserve the right of the upland owner or the owner of the bed of the reservoir to claim to the pre-existing line. Again, probably depends upon any conditions of approval associated with the permit to build the wall. If the wall was built without benefit of a permit, the owner of the bed probably still has the right to attempt to determine where the pre-wall OHWM was and claim to it.

Investigate the various avenues for information, but if you come up empty, go with the face of the wall knowing that you met your obligation in making a reasonable attempt to find information that would guide and inform your decision. Any contrary claim would have to be supported by a survey that finds more & better evidence than you were able to find.