8  Model Description    8.1.2  Reservoir Operations    8.1.3  Instream Flows    8.1.4  Demands    8.1.5  Conservation/Curtailment    8.1.6  Future Sources    8.1.7  Hydrologic Data

This section provides an overview of the Everett water supply system. It includes a summary of the system, reservoir operations, current instream flow requirements, demand forecasts for this area, and future water supply options. A description of the hydrologic data incorporated into Cascade Regional Yield and Simulation Analysis Model (CRYSTAL) concludes the System Description Section.

Everett's water supply is provided by Spada Reservoir, formed by the George Culmback Dam on the Sultan River and a much smaller surface water source, Lake Chaplain (Figure 8.1). Spada Reservoir is part of the Henry M. Jackson Hydroelectric Project, owned and operated by Snohomish County Public Utility District No. 1 (SnoPUD). Water from Spada Reservoir flows to the Jackson Powerhouse where it is either released to the Sultan River or piped to Lake Chaplain. Everett's M&I demands are met with water taken directly from Lake Chaplain. At times, water from Lake Chaplain is transported back to the Sultan River through a supply tunnel to meet fish flows on the Sultan River above the Jackson Power House.

Everett has four certificates of water rights for the Sultan River system, totaling to 246 mgd for instantaneous municipal and industrial uses (Q_I) and 129 mgd for average water withdrawal (Q_A).  In 1954 Everett requested to withdraw an additional 129 mgd from the Sultan River; but this water right has yet to be approved by Ecology. Upon approval, Everett will be required to maintain minimum instream flow requirements established under the IRPP established for the Sultan River. In addition, Everett and the Weyerhaeuser Timber Company have applied to transfer 65 mgd of Ebey Slough water from Weyerhaeuser to Everett. This lower quality water could be used for industrial purposes or treated and sold to Snohomish or North King County Purveyors. Everett's current average daily demand is about 84 mgd and daily peak demand is around 120 mgd. The location, type of permit, and volume of the permit is summarized in Table 8.2.

A primary concern in the operations of the Spada Reservoir system is the generation of hydropower. Water is diverted from the George Culmback Dam to the powerhouse, where electricity for SnoPUD is generated through either Francis or Pelton turbines. The Pelton turbines return water to the Sultan River, while the Francis turbine outflow is routed (using hydraulic head from Spada Reservoir) to Lake Chaplain for the City of Everett's water supply and (on occasion) to meet instream flow requirements on the Sultan River. The distinction between the turbines is very important. The Pelton turbines are more efficient and operate under higher head. SnoPUD incurs a monetary loss when a higher percentage of water is sent through the Francis turbines.

Water is supplied to Lake Chaplain via the Francis turbines from the powerhouse through a 380 cfs capacity pipeline. Water from Lake Chaplain serves as a supply to nearly two-thirds of Snohomish County’s population and augments flows for fish in the Sultan River. The "Fresh-Water" return line runs from Lake Chaplain to the Sultan River below the "old" Everett Diversion Dam. The flows transmitted in this line augment fish flows on the Sultan River. This pipeline is also acts a backup transmission line to Lake Chaplain. Pipe capacities are presented in Table 1.

The Jackson Powerhouse receives water from Spada Reservoir through an eight mile-long subsurface pipeline. Water reaches the powerhouse at an average velocity of nearly seven feet per second and is diverted into 1 of 4 turbine/generator units. Two of the units are Pelton-type vertical shaft turbines that drive generators rated at 47.5 megawatts each, the other two are Francis-type, horizontal shaft turbines that drive generators rated at 8.4 megawatts each. Total installed capacity at the powerhouse is about 112 megawatts. The electricity generated is transmitted to the PUD's distribution system. The power generated at Jackson provides approximately 8% of the PUD's needs.

Table 8.1  SnoPUD and Everett Operations Pipeline Capacities

Table of Contents    8.2.1  Overall Seattle Operations    8.3.1  Overall Tacoma Operations