Hi Rob, Thank you so much! Following your hints we are now thinking about the question of water source flow change. Water source can't be shut down, and its flow rate can only change every 4 hours (at least). We tried to set a binary vector reflecting change in water flow from the previous hour: 1 means change, and 0 means no change (The first element is fixed to be 0). We will have to exclude the patterns (1,1), (1,0,1) and (1,0,0,1), which is doable. The tricky part is to transform this into linear constraints on water flow rate in every hour, which is one of the real decision variables in our optimization problem. How can we do that? Could you give us some hint? Thanks.

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