You may look for  traces of salty or muddy marks on specific land marks, rocks or similar features on the cost line.

You may look for  traces of salty or muddy marks on specific land marks, rocks or similar features on the cost line.

You may look for  traces of salty or muddy marks on specific land marks, rocks or similar features on the cost line.

Actually I'm going to define the OHWM to be used for long-term management decisions. The method you have proposed would show the present conditions of the sea and must be repeated several years to give the acceptable values along the coastlines.

I'm not sure that your question has a proper answer. In a closed basin where the water budget is balanced by evaporation a water body's depth in a function of inflow and evaporation. Its level is going to fluctuate as climatic conditions change. If you have long term measurements you can say things like "the annual high water in the 20th Century ranged from x to y meters above sea level with a mean of z meters asl." For levels beyond the instrument record you might find date-able terraces marking high stands and measure salt concentrations or hiatuses in cores to look for low stands. In the very long run tectonic events will be important. Recently, human consumptive use of water in inflowing rivers is probably important.

Dear Peter, Many thank for your answer. The water level of Caspian Sea is controlled by evaporation, precipitation, and river input (specially Volga river). I have the long-term water level records, but I'm wondering whether the maximum historical water level must be selected as OHWM or not?

Dear Mostafa,

It seems to me that OHWM is only a well defined concept in an open basin whose level is controlled by an outflowing river. In such a basin, there is generally a modest seasonal fluctuation in level that is controlled by variation in inflow, outflow and evaporation. Under a given climate regime there is an average annual seasonal fluctuation, giving you the OHWM. As lake level drops or rises, outlow decreases or increases, stabilizing the lake level to a modest seasonal variation. In a basin without an outlet, there is no such stabilizing factor. The level wanders erratically in response to climate change and diversion of inflows, as the Caspian seems to do. Has it ever dried up completely? Has it ever filled to a sill and acquired an outlet? At least in our smaller lakes in the Great Basin of Nevada and adjacent states, Pleistocene Pluvial periods saw many lakes grow to large size and achieve outlets. In drier periods like today many are reduced to salt flats that flood briefly in big rain years but are normally dry. Some like the Great Salt Lake persist but fluctuate in level much 

Best, Pete