Water Committee Agenda and Packet 2015 04 03

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1 PROFILE EXISTING WATER SYSTEM The 2003 Raw Water Master Plan Update included an analysis of baseline yields of the City's raw water supply system. Determining the water yield is a complex analysis that attempts to account for the details of water rights, including return flow obligations, legal priority of the water right, and conveyance. The master plan estimated the maximum divertible yields from South Boulder Creek range from 2,000 to 4,700 acre -feet each year, and nearly 80 percent of that amount is divertible only during the months of May through July. The Southern Water Supply Project (SWSP) includes C -BT and Windy Gap water. The average available C -BT yield is 1,4471 acre -feet, with average Windy Gap yield assumed to be zero and a maximum of 9002 acre - feet. The master plan included many assumed supply and demand scenarios; the 2003 Raw Water Master Plan estimated that under future conditions the raw water supply system would provide a firm yield of 5,400 acre -feet. Deficits were predicted during drought years but the demand used in the scenarios was very high at 7,120 acre -feet. The master plan was completed more than 10 years ago. Therefore, it is recommended the City update the plan to incorporate changes since 2003, including improvements to the raw water infrastructure, improved information on water supply from C -BT and Windy Gap, updated demand data, and resiliency to climate variability. At this time, no major raw water acquisitions are planned by the City. Overall, there is limited raw water storage in the City's system and additional storage would be beneficial. The total raw water storage capacity of 3,392 to 4,912 acre -feet is lower than the City's forecasted annual water consumption (See Section 2.4 Demand Forecast). The storage system would provide approximately 6 months of water at forecasted baseline demands at the lower end of storage volume. The City is planning on continued efficient water use, but additional water rights acquisition will most likely be required. 1.3 Supply -Side Limitations and Future Needs As mentioned above, the City has water rights along South Boulder Creek, a tributary to the South Platte River. In the most recent Statewide Water Supply Initiative (SWSI) completed in January 2011, the South Platte Basin is one of the basins facing a municipal and industrial (M &I) gap in 2050. The M &I gap is the difference between the projected municipal and industrial water demand and supplies from existing sources and supplies from Identified Projects and Processes (IPPs). The M &I gap for the South Platte Basin is projected to be 36,000 to 170,000 acre -feet per year, depending on the success rate of IPPs (see Table 5 -19 of the January 2011 SWSI). The SWSI also noted that from "a regional perspective, the largest gaps occur in the Northern region, consistent with the high levels of current and future demands and urbanization in Boulder, Larimer, and Weld Counties." There is also little to no unappropriated water remaining in the South Platte Basin. Based on the outlook from SWSI efficient water use will need to continue as a component of the City's raw water master planning. Limitations and future needs for the City's raw water and treated water systems are summarized in Table 2. TABLE 2 Summary of Supply Side Limitations and Future Needs Limitation or Future Need Comments on Limitation or Future Need How is Limitation or Future Need Being Addressed Raw water supply 1 2,067 shares at 0.7 acre - feet /share firm yield. 2 9 shares at 100 acre - feet /share. 1 -2 The estimated firm yield from the City's 2003 Raw Water Master Plan was approximately 5,400 acre -feet. Drought years may result in a deficit. Efficient water use especially during drought years will be required. Monitor growth of commercial properties that are not yet developed. WBG071714052946BSO