ARCA 2015 Annual Meeting Exhibits

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1. General During water year 2015, activities of the U.S. Army Corps of Engineers (USACE), Albuquerque District, in the Arkansas River Basin consisted of reservoir . regulation, flood control related studies, floodplain management �� services, regulation under Section xai , 404 of the Clean Water Act, and 0` � t emergency assistance. 2. Water Control Operations Trinidad Lake, 2005. USACE photograph. The May 1 basin wide snowpack for the Arkansas River Basin was 89% of median with the Upper Arkansas Basin reporting 103% of median and the Purgatoire River Basin reporting only 7% of median. During the first two weeks of May, a series of moderately sized events over the Fountain Creek watershed triggered minor flooding on the Arkansas River at both Avondale and La Junta in Colorado. High river stages in these locations resulted in inundation of both agricultural lands and residential areas. In early May, storage at Pueblo Dam remained within the conservation pool, but runoff from late season snowfall and the above average snowpack in the upper basin threatened to push the reservoir into the flood pool. On May 19, the Arkansas River above Pueblo Dam rose rapidly due to a rain-on-snow event in the upper watershed. This same weather system created significant widespread rains within the Fountain Creek watershed, and a flood peak (approximately 7,200 cfs at the Fountain Creek at Pinon Gage) began flowing towards the confluence with the Arkansas River. USACE coordinated operations with the Colorado Division of Water Resources (CDWR) and U.S. Bureau of Reclamation (USBR), and the decision was made to cut flows out of Pueblo Dam to 75 cfs to minimize impacts along the Arkansas River in the middle valley. This outflow cut at Pueblo Dam resulted in a moderately rapid increase in storage, which brought the reservoir water surface to within 1 ft of the top of the conservation pool by May 25. Over the next five days, conditions in the basin improved and the pool was drawn down by approximately 10,000 ac-ft. In the early morning hours of May 30, a significant rain event centered over the City of Pueblo and the Saint Charles River watershed resulted in increased flows on the Arkansas River. In response, the rate of outflow from Pueblo Dam was reduced. On June 2, CDWR began increasing the releases out of Pueblo Dam in an effort to keep pace with the increasing rate of spring runoff. CDWR continued to pass reservoir inflow to remain below the flood pool until the night of June 12 when a moderately 1