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r, <br /> Exhibit A-1 <br /> Everett Comprehensive Water Plan <br /> Contract Amendment No. 1 <br /> DATE: March 12, 2007 <br /> Subject: Amendment for Additional Services <br /> To: Souheil Nasr, City of Everett FROM: Jim Peterson <br /> Public Works Department HDR Engineering <br /> 3200 Cedar Street 500 108tn Ave NE <br /> Everett, WA 98258 Bellevue, WA 98004 <br /> PROJ. NUMBER: 022254 TELEPHONE: 425-450-6308 <br /> E-Mail: jim.peterson@hdrinc.com <br /> Amendment Item 1 — Task 7 Climate Change Analysis <br /> The following summarizes the revised approach to climate change modeling discussed at a <br /> meeting at HDR on September 7, 2005. <br /> Modified Yield Analysis Approach <br /> 1. Everett will consult with Phil Mote, Washington State climatologist, to develop <br /> appropriate temperature and precipitation distributions for the year 2000, and well as <br /> for future forecasted climate conditions in 2050 and 2100. So that the yield analysis <br /> encompasses the range of flow possibilities, two forecasts will be r generated for 2050 <br /> and 2100, reflecting optimistic and pessimistic climate change scenarios. <br /> 2. Dr. Palmer will translate these forecasted future precipitation and temperature <br /> distributions for 2050 and 2100 into streamflow sequences using the DHSVM <br /> watershed model. The streamflow sequences will be as long as the historic <br /> streamflow record and will serve as input data for the CRYSTAL-Everett model. <br /> 3. Dr. Palmer will also use DHSVM to generate a streamflow sequence reflecting year <br /> 2000 conditions, using the year 2000 precipitation and temperature distributions <br /> provided by Phil Mote. This sequence will be compared to actual data from the <br /> historic streamflow record as a reflection of potential bias within the climate change <br /> models. <br /> 4. In total, Dr. Palmer will be developing five sets of streamflow data using DHSVM: <br /> streamflow input for 2000 (based on climate change models), streamflow input for <br /> 2050 (optimistic), 2050 (pessimistic), 2100 (optimistic), and 2100 (pessimistic). In <br /> addition to the data, Dr. Palmer will provide the HDR Project Team with a brief <br /> description of how these forecasts were developed. <br /> 5. The HDR Project Team will use the input data developed by Dr. Palmer to run three <br /> scenarios using the five sets of data (total of 15 model simulations): <br /> 1. 3 • Unconstrained Yield —The maximum yield of the system when it is operated only <br /> for water supply. <br /> Everett CWP 1 of 8 Amendment No. 1-Exhibit A-1 <br />