Yeah, I get that's the effect you were going for. Let me try to explain what Im seeing though,


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The mountainous ridge seems like it should connect along a line (highlighted as the orange line) so that would be the highest land near it. The green area seems to be a lower grassy valley. The problem is your river runs down towards the valley, and then crosses over the mountainous area, which is more than likely going to be higher altitude. If you removed the mountains circled in purple, it would make more sense (to me, anyways). Im definitely not an expert though like I said, its just what popped out to me. The river going through there is possible, just doesn't seem likely.