Can't divide land by the river

[C. Milintsevich]

I have such a problem: I can't divide a land by the river. It always ends at one side near the sea, just look at the picture below. How could I make river to separate an island from a continent?

 

[Sneaks]

I am not sure you can without doing some XML/Lua digging and redefining how rivers are drawn.

 

[C. Milintsevich]

I tried this lua code but it didn't work

local iW, iH = Map.GetGridSize()
for x = 0, iW - 1 do
	for y = 0, iH - 1 do
		if x == 27 and y == 45 then
			local plot = Map.GetPlot(x, y)
			plot:SetNWOfRiver(true, FlowDirectionTypes.FLOWDIRECTION_NORTHEAST)
		end
		
		if x == 25 and y == 44 then
			local plot = Map.GetPlot(x, y)
			plot:SetNWOfRiver(true, FlowDirectionTypes.FLOWDIRECTION_SOUTHWEST)
		end
	end
end

But I don't know lua