USGS Washington Water Science Center
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0. Existing Conditions Model
A transient-model simulation for the period of water-years 1960-2001 that is based on calibration to observed streamflow and water levels. The existing conditions model is considered the base-case model.
A. Existing conditions with all pumpage turned off.
This scenario was formulated to estimate the long-term (1960-2001) effects of pumpage in the basin. In comparison, base model (0) addresses the changing affects of pumpage for the last 42 years.
This scenario will be based on a 42-year simulation using all the information from the base-case model but without pumpage. Streamflow at selected sites would be compared to the simulated base-case model (0) streamflow.
B. Existing conditions with basalt pumpage turned off.
This scenario tests the potential effects of basalt pumpage on the groundwater-flow system and streamflow. The base-case model would be operated for the 42-year simulation period but the basalt pumpage would be eliminated. Comparisons will be made for streamflow between the base case and this simulation.
C. Existing conditions with exempt pumpage turned off.
This scenario tests the potential effects of exempt pumpage on the streamflow. The base-case model would be operated for the 42-year simulation period but the exempt pumpage would be eliminated. Comparisons will be made for streamflow between the base case and this simulation.
D. Existing-conditions projected into the future.
This scenario is a transient-model simulation using pumpage for the period 10/1993 through 9/2001. This period captures dry, average, and wet years and thus, a large range in reservoir operations, including accounting for Title XII flows. From 1994-2001 water years, there are 2 prorating year (1994, 2001) or 25% of the record. This period is likely representative because some 29% of years have been proratable from water years 1976 through 2010. In addition, pumpage does not change very much from 1994 to 2001. Starting conditions will be simulated water-levels from 9/1993. Simulated streamflow and water levels at a time in the future from the starting date will be compared to simulated base-case model results.
E. Existing-conditions and pumpage from pending groundwater applications projected into the future.
This scenario is a future projection similar to scenario D but includes additional pumpage estimated for the outstanding (pending) groundwater applications. This transient simulation uses the pumpage for the period 10/1993 through 9/2001 and this additional estimated pumpage. The groundwater-application pumpage is assumed to start in 10/1993. Simulated streamflow and water levels from scenario D would be compared to those from this simulation.
This scenario addresses the potential impact on streamflow and water levels if all but five pending applications were approved. The five applications not included are for Frost Protection use because the potential frost-protection pumpage in the future is unknown.