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Impact of the Drought on the City of Laramie’s Water Supply Public Works Department, Utility Division September 2012 1 Laramie’s water supply has been impacted by this year’s drought. The spring snow pack was 23% of the 30 year average. Peak flow in the Big Laramie River recorded at Laramie’s Water Treatment Plant during the spring runoff was 357 cubic feet per second (CFS). This peak occurred on April 26, 2012. What a difference a year makes. In 2011 , we had a snow pack of 194% of normal with a peak flow of 3,164 CFS on June 9, 2011. The Casper Aquifer received a very large recharge in 2011. The snow pack in the area was 214% of normal. In 2012 the snow pack was 0% of normal. The large recharge in 2011 and careful management of the Casper Aquifer supplies have Laramie’s wells in good shape at this time. There is enough water in the aquifer to sustain Laramie for another summer if this year’s drought shows up for an encore next year. Laramie constructed several projects that have facilitated the management of the water supplies. These projects include Spur Wells and the Laramie River Pipeline. The Laramie River Pipeline was constructed in 2010 and plays a significant role in the management of the water supplies. This project enabled delivery of raw water to the treatment plant despite the low water levels in the river. During the drought of 2002, the full appropriation of raw water could not be delivered to the treatment plant near the end of the summer and Laramie had to rely completely on the aquifer for about a month. Water restrictions were in place. The aquifer was drawn down and took the next 8 years to recover. This year’s low water levels have elevated the total dissolved solids (TDS) in the raw water supply. One water quality parameter, related to TDS, that customers may notice is hardness. Typically the water from the river is around 60 mg/l hardness. This summer it is around 90 mg/l. Daily temperature and pH swings have made water treatment more challenging. Lack of water has concentrated both wildlife and live stock closer to the river, adding to the total suspended solids load (TSS). The recent wild fires have also impacted the water supply. Ash from the fires raise the raw water pH and exposed ground allow soot and soil to enter the river further increasing both the TDS and TSS. The monsoonal rains and intense isolated thunder storms have resulted in several minor flash floods. These flash floods have elevated the silt load coming into the plant to over 500 time normal levels. This extra loading lasts for several days following a storm. These are just a few of the challenges the drought and wild fires are creating for the water supply. The water delivery has exceeded all the EPA quality requirements. There are other communities that cannot make this claim this year. Water treatment staff has been very proactive in finding solutions to the treatment challenges. Providing water through the fires and the drought has not come without cost. Staff has to adjust to ---PAGE BREAK--- Impact of the Drought on the City of Laramie’s Water Supply Public Works Department, Utility Division September 2012 2 changing raw water conditions several times each day. Water treatment supplies have been consumed at higher than normal rates. Most importantly, our long term planning, supply management, and investment in projects, like the Spur Well and Laramie River Pipe Line, has allowed Laramie the ability to provide quality water through the tough years. Laramie is not resting on this year’s successes. We are actively planning for the future. Future projects include pump stations, reservoirs, additional distribution piping, and additional water supplies from the Casper Aquifer and Big Laramie River. If you would like more information about this topic, please contact the City of Laramie Utility Division at 721-5206.