8  Model Description    8.1.1  Everett Water Supply System    8.1.3  Instream Flows    8.1.4  Demands    8.1.5  Conservation/Curtailment    8.1.6  Future Sources    8.1.7  Hydrologic Data

Reservoir operation in the CRYSTAL model is based on the Snohomish County PUD Jackson Operations model (JKSOPR).  Release policies depend on the "state" of both Spada Reservoir and Lake Chaplain.  The state of the reservoir is determined by comparing the storage to maximum storage capacity, rule curves, and minimum storage capacity.  When water is in abundance, releases are dependent on the capacity of Jackson Powerhouse transmission line.  Otherwise, releases are functions of instream flows, demands, and relative storage.

Snohomish County PUD No. 1 (SnoPUD) operates Spada Reservoir using two rule curves based on storage (Figure 8.3).  In addition, a "poweroff" storage may be used during extreme conditions (Spada reservoir has yet to reach the poweroff storage).  Comparing the reservoir storage to the Full Storage condition (FS), Upper normal rule curve, and Lower normal rule curve determine the state of the reservoir.  If reservoir storage is between the rule curves (State 3), then a variable amount of flow (based on a ratio of storage to lower rule curve and time of year) is conveyed through the Powerhouse pipeline.  If storage in Spada is below the Lower normal rule curve (State 4) then minimum flow to meet instream flow requirements and M&I demand is conveyed.  The maximum flow of 1300 cfs is conveyed if the reservoir is above the Upper normal rule curve (States 1&2). No flow is conveyed if storage is below the "Power off" level.

Lake Chaplain is not used for storage or flood control, so it does not have a rule curve that reflects these functions. Instead, Lake Chaplain has an upper, lower, and min elevation targets that are reflected in its "rule curve" (Figure 8.4). If Lake Chaplain exceeds its maximum elevation; water is spilled into Chaplain Creek, a tributary to Sultan River.

Lake Chaplain receives water from two sources, local inflow and flow from Francis turbines.  Flow through Francis turbines is comprised of two parts:  flow to satisfy Everett’s M&I demands and SnoPUD's Sultan River instream flow requirements below the diversion dam.  The state of Chaplain reservoir is determined, and a proportion of demand is transmitted to Lake Chaplain, as shown in Figure 8.5. The remaining demand is composed of Lake Chaplain storage or local inflows.

Lake Chaplain outlets are the Sultan River return flow pipeline, the Everett Supply pipelines, the Kimberly Clark pipeline and the overflow to Chaplain Creek.  These pipeline capacities are shown on Figure 8.2 in the Everett Water Supply System section.

Table of Contents    8.2.1  Overall Seattle Operations    8.3.1  Overall Tacoma Operations