The water level of the Lake Mead/Lake Powell system is decreasing every year, and it could completely dry up with the next two decades (cf. Barnett and Pierce. When will Lake Mead run dry? J. Water Resources Research, 2008). This exercise takes a (grossly simplified) look at the problem and compares a worst-case estimate based on constant rates with an estimate based on a hybrid model with switching rates. For solutions and model files, see here.