I've had a quick look at the web - and the only thing that has all those abbreviations is this page! However - is it is possible that these are related more to dams? I found some dam-related documents that referred to FSL as Full Supply Level and RL as Reservoir Level. TOC could be Top Of Crest, and TOS Top Of Spillway. I'm only guessing here...

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oops. Wrong place...

I've had a quick look at the web - and the only thing that has all those abbreviations is this page! However - is it is possible that these are related more to dams? I found some dam-related documents that referred to FSL as Full Supply Level and RL as Reservoir Level. TOC could be Top Of Crest, and TOS Top Of Spillway. I'm only guessing here...