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ti ~ ~ , At discharges exceeding 13,500 cfs, both inlet control and outlet (drain) control would be necessary to avoid excessive water surface elevations in the wetlands. For example, in June, 1993 the water surface elevation at E-17.5 (outlet drain) corresponding to a discharge of approximately 19,000 cfs was 4832.4. Based on the proposed drainage design and an assumed preferred water surface elevation for the wetlands, there is an optimum range of discharges for inflow to the wetlands. If the preferred wetlands water surface elevation was 4830.5, then the range of river discharge for inflow to the wetlands may be from 12,000 to 14,000 cfs. To avoid further increases in the wetlands water surface elevation and undesirable inundation, the outlet drainage would have to be designed with a gate. Another solution to create effective hydraulic control would be to locate the outlet further downstream. This would require additional drainage channel excavation. Cross section E-14.5 appears to have a more favorable response at high flow for providing opportunities for the larval fish to enter the wetlands channel than at E-15. The advantage of having a slight discharge through the wetland .inlet channel is to sweep the larval fish into the wetlands area. Cross section E-14.5 was fairly stable with a uniform bed elevation. Enhancements to assist the fish in entering the channel inlet such as a jetty would - have to be evaluated for potential sediment deposition response. It was discovered that the groundwater in upstream northern area of the old meander bend where the proposed channel from E-14.5 to the wetlands would be located has high selenium concentrations (Cooper and Severn, 1994). This may preclude consideration of the proposed inlet and channel location near cross section E-14.5 or E-15. Further investigation may reveal the potential for mitigating this problem by removal or dilution of the high selenium concentration with a surface flow through the selenium rich area. Biological impacts of transporting selenium into the wetlands area would also have to be assessed. Cooper and Severn (1994) suggested alternate wetlands inlet locations downstream of E-14.5 between cross sections E-16 and E-17. These sites did not appear to have the same advantages that the upstream sites have but should be considered regardless. The principal disadvantages of these sites include limited hydraulic control, more active river bed, and excavation of the channel through the mature cottonwood forest. Since the wetlands water surface (4830.5) is lower than the river water surface for discharges exceeding 12,500 cfs at cross section E-17, any inlet to the wetlands in the area would have to be gated to avoid undesirable inundation of the wetlands area. Wetland drainage and outflow would be limited to periods when the river discharge was less than 12,500 cfs. Finally, the channel bed between 35