Joint Front Range Climate Change Study SOW

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This section includes the scope for the entire project which contains tasks performed by the PSC, WWA, CWCB, AwwaRF, and PI(s). Re nest Climate derived weekly streamflow sequences need to be developed for gauging sites important to the study participants (PSC). These new streamflow sequences should be generated from the climate change scenarios and should be representative of two future years of 2040 and 2070. The number and location of these streamflow sites depends on finding and the requirements of the study participants. Streamflow sequences are needed in the upper portions of the Colorado, Arkansas, South Platte, Cache la Poudre, St. Vrain, Boulder Creek„ and Big Thompson River Basins. The PSC further asks that the investigators do a s temperature sensitivity analysis on all basins to verify that the expected results are obtained. Hydrology Models To take advantage of modeling that is already finished or underway, the WEAP (Water Evaluation and Planning) model (developed by the Stockholm Environment Institute) and the Sacramento model (used by the National Weather Service river basin forecast centers) are being considered to convert the climate scenarios to streamflows. Dr. David Yates of NCAR is one of the developers of the WEAP model, and he, along with Colorado Springs Utilities and AwwaRF, is in the process of calibrating that model for the Upper Colorado River Basin down to the Colorado River at Cameo gauging station. If a satisfactory contractual relationship is established with Dr. Yates, he will be asked to calibrate WEAP for the other basins of interest to the project participants (including the Upper Arkansas, Upper South Platte, Big Thompson and Cache la Poudre, St. Vrain, Boulder Creek, Basins). The Sacramento Soil Moisture model is often used in conjunction with the Snow -17 model (also known as the Anderson snow model) to predict streamflow in snowy watersheds based on temperature and precipitation. (Henceforth in this document, the name "Sacramento model" shall mean the linked Snow -17 and Sacramento Soil Moisture models.) The Sacramento model is currently being used by the National Weather Service (NWS) in the Colorado and Missouri River Basins to predict near -term streamflow, and it is already calibrated for significant portions of the Upper Colorado and South Platte River basins. Riverside Technology, a water resources consulting firm in Fort Collins, Colorado, has expertise in the use of the Sacramento model, and has participated in projects to calibrate that model for portions of the Upper Colorado and South Platte River basins. If a satisfactory contractual relationship is established with Riverside Technology, that firm will be asked to calibrate the Sacramento model for the other basins of interest to the project participants. It is believed that better historic natural flow data are available for the South Platte Basin than the data used previously by Riverside in calibrating the model; therefore some recalibration of the South Platte Basin will be necessary.