SFPUC diversion logic

[drheinheimer]

The diversion logic for deliveries to SFPUC needs to be improved. Generally, two issues need to be accounted for:

1. Urban water demand decreases (due to SFPUC policy & water service agreements) by 10%, 20% or 25% depending on system-wide reservoir storage. For us, this is challenging because we don't actually have system-wide storage, just storage in the higher elevations.
2. During drought, there is an increase in dependency on Tuolumne reservoirs for urban deliveries. I.e., diversions to the SJPL increases as water availability (supply) decreases. However, when/how this occurs is uncertain within the limited spatial scope of the present model.