What is a 'hedging rule' for a channel. ARSP is a simulation program, not an optimization program. Although it optimizes the allocation of water in each time step, it cannot look ahead to see if it can do better in the long run by choosing a sub-optimal solution in this time step. A hedging rule is a means to overcome this limitation to a certain extent. Its purpose is to determine a reasonable level of demand for a water use that spans several time steps.
Irrigation is a good example of such a demand.
If a crop is planted at the beginning of the irrigation season and is fully supplied with water for the first half of the season, but receives no water during the second half, the entire crop will die. Therefore, the water received during the first half of the season provided no ultimate benefit. If, on the other hand, only half the crop is planted at the beginning of the season and it can be fully supplied with water for the entire season, there is a benefit from supplying the water. In essence, a hedging rule allows ARSP to decide, at the beginning of the irrigation season, how much of the full crop should be planted. The decision is based on the amount of water in designated reservoirs at the start of the season.