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<br />000632 <br /> <br />12 <br /> <br />Prairie Naturalist 24(1): March 1992 <br /> <br />Table 4. Elevation' measurements from ground surveys of 402-m (1/4 mile) <br />systematic river segments (n=29) and river segments (n=6) centered on least tern <br />and piping plover nesting sites on the Central Platte River (river mile 167-251), <br />1988. <br /> <br />Site <br />Mean <br />Elev, <br /> <br />Site <br />Max. # <br />[lev. Nests <br />Nesting Sites <br />0.12 1 0.09 <br />0,81 2.6 0.34 <br />1.34 6 0.73 <br />0,55 1.9 0.30 <br />Systematic Sample of River Segments <br />0.09 <br />0.42 <br />1.13 <br />0.10 <br /> <br />Nests <br />Mean <br />Elev. <br /> <br />Nests <br />Max. <br />Elev. <br /> <br />Min. <br />Mean <br />Max. <br />SI. Dev. <br /> <br />0.06 <br />0.30 <br />0.61 <br />0,23 <br /> <br />0.15 <br />0.43 <br />0.94 <br />0.36 <br /> <br />Min. 0.04 <br />Mean 0.13 <br />Max. 0.54 <br />51. Dev. 0.10 <br /> <br />1 m above stage of 11 .3 ems <br /> <br />Analysis of Hydrologic Records <br />We examined 30 water years (1 October 1958 to 30 September 1988) of <br />mean daily discharge records of U.S. Geological Survey gages in our study area <br />for computing long-term statistics. The Lower Platte was continuously gaged in <br />this period near the towns of North Bend (rm 72) and Louisville (rm 16). <br />Largely because of contributions of the Elkhorn River (rm 33) and Salt Creek <br />(rm 26), the mean annual volume of flow at Louisville (6.27x109 m') is about <br />50% greater than at North Bend (4.28x109 m'). Four gages are located on the <br />Central Platte, three of which have been operated for more than 30 years. There <br />are no major tributaries along the Central Platte, and mean annual volumes <br />measured are similar at all four gages (about 1.66x109 m'). We elected to repre- <br /> <br />500 <br /> <br />450 <br /> <br />- Louisville <br /> <br />100 <br /> <br /> <br />- Grand Island <br /> <br />400 <br /> <br />~ <br />VI 350 <br />E <br />~ 300 <br />w <br />0250 <br />'" <br />~ 200 <br />U <br />~ 150 <br />o <br /> <br />- North Bend <br /> <br />50 <br /> <br />o I I j I I I I I I I I <br />Oct Noy Dee Jon Feb Mar Apr May Jun Jul Aug Sep <br /> <br />Figure 6. Average daily discharges of the Platte River measured near <br />Grand Island, North Bend, and Louisvitle, Nebraska based upon U.S. Geo- <br />logical Survey data, 1958-1988. <br />