8.0  Model Description    8.3.1  Tacoma Supply System    8.3.2  Reservoir Operations    8.3.3  Groundwater Sources    8.3.4  Instream Flow Requirements    8.3.5  Demand Forecasts    8.3.6  Conservation    8.3.7  TSI Intertie    8.3.8  Future Sources    

 

8.3.9  Tacoma Hydrologic Data

The U.S. Geological Survey and the Army Corps of Engineers (Corps) provided hydrologic data for the portion of the CRYSTAL concerning the Green River. Historical hydrologic data are used in CRYSTAL under the assumptions that the historical data set is fairly reliable (i.e., within the normal 10% accuracy expected from gaging programs) and that historical flows are easier for the general public to understand and trust as compared to simulated stream flow data Table 9 summarizes the relevant inflow data for the Tacoma portion of the model.

Table 9  Tacoma Inflow Information

Location

Source

Represents

HAH Inflows

USGS Data-1929 to 1963

Corps-1963-present

Daily inflows into HAH were provided by an upstream gage for the period before the dam was built and operational (circa 1963) and by Corps monitoring records after the dam was constructed. All daily flows were averaged for use in a weekly timestep.

Inflows between HAH and Palmer

USGS Data-1929 to 1963

Corps- 1963 to present

According to the Draft EIS for the Additional Water Supply Project (1998), local inflows between HAH and the Palmer gage are estimated to be approximately 3% of inflows into HAH.

Inflows between Palmer and Auburn

USAGS Gages 1210-6700 and 1211-3000

Data from the Palmer gage (1210-6700) represent flows in the Green River downstream from the Tacoma Headworks. To calculate local inflow between this point and the auburn gage (1211-3000), daily average flows between the gages were subtracted for the entire period of record. If negative values were obtained, these values were set to zero. Flows after 1963 represent regulated flows; however, flows at both gages are regulated and no other diversions occur between these points. Therefore, the differences between the two data sets are considered natural flows.

 

Table of Contents    8.1.1  Everett Supply System    8.2.1  Seattle Supply System