OutdoorNebraska

46 46 46 46 46 46 46 46 46 46 46 46 46 46 46 46 46 46 46 46 46 46 46 46 GUIDE TO NEBRASKA'S WETLANDS increased sediment storage in upstream reservoirs, changes to water quality, invasive species, sand and gravel mining, and agricultural conversion have greatly altered the Central Platte River. From 1860 to the early 1980s, the Central Platte River lost up to 73% of active channel areas (Sidle et al. 1989), and this affected the associated wetlands. Upstream from the Central Platte, active channel losses on the river have reached 85%. In many areas, channel width has been reduced to 10-20% of its historic size (U.S. Fish and Wildlife Service 1981). Unobstructed channel width at the main channel of the Platte River decreased by 59% from 1938 to 2016 (Caven et al. 2019a). Yet, conditions remain highly variable throughout the Central Platte. For instance, unobstructed channel width at the main channel between Kearney and Odessa decreased by 82% from 1938 to 2016, but only by 15% between Alda and Wood River. This likely is a function of two factors. First, channel width loses have been greater in reaches that were historically one large channel, as areas with multiple channels simply lost functionality in side- channels while largely maintaining it in their main channel (Caven et al. 2019a). Secondly, conservation actions that have been taken improve and maintain functional braided river areas (Farnsworth et al. 2018, Caven et al. 2019a). Since the mid-1880s, the acreage of wet meadows, a type of wetland, in the Central Platte has declined 73% (Currier et al. 1985). An increase in shrub and forested wetland types has occurred at the expense of riverine, emergent wetlands and wet meadows as a response to decreased scouring fl ows. The increase in the shrub and forested wetlands has been detrimental to fi sh and wildlife resources that historically used the river valley (Currier et al. 1985; U.S. Fish and Wildlife Service 1981). Drainage and conversion to grain crops and sand and gravel mining operations pose the biggest immediate threats to wet meadows adjacent to the Platte River. In fact, Pauley et al. (2018) indicated that from 1957 to 2016, sand and gravel mine site acreage within the Central Platte River Valley fl oodplain increased by 538%. Loss of instream fl ows, groundwater depletions, and degradation of the riverbed continue to pose a long-term threat to the source of water for the remaining wet meadows. Once this source of water is lost, the Least terns nest on river sandbars. They feed in the nearby river and wetlands capturing small fi sh to feed their mate and their young. MICHAEL FORSBERG

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