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Kinbasket and Revelstoke Reservoirs are part of the Columbia River system in eastern British Columbia, Canada. Hydroelectricity from these large reservoirs represents about 30% of the province's generation capacity. Of interest to water use planning is the effect of reservoir operation on pelagic productivity. We address one small part of this question, namely, the supply of nutrients carried by inflows that plunge below the photic zone during the summer. Using an idealized water balance for the photic zone, three cases are considered: (1) a shallow outlet, (2) a deep outlet, and (3) no outflow. For a shallow outlet, all inflow that plunges below the photic zone is upwelled into the photic zone on its way to the outlet. For a deep outlet, inflow that plunges below the photic zone will short circuit or pass directly to the outlet unless entrainment generates upwelling of the inflow into the photic zone. For a reservoir with no outflow, such as a reservoir that is filling, inflow that plunges below the photic zone remains at depth unless either entrainment or a bathymetric effect generates flow into the photic zone; nutrients are then released when the reservoir is drawn down, often in winter. [ABSTRACT FROM AUTHOR]

In the last 16 years, fisheries agencies and power producers in the Columbia River Basin have increasingly relied on hydroacoustic assessments of downstream migrating, anadromous Pacific salmon smolts (Oncorhynchus spp.) when evaluating bypass system designs at hydroelectric dams. Accompanying this reliance has been an interest in comparing hydroacoustic estimates of smolt passage with net catch estimates. Since the objectives could be addressed effectively with relative estimates of fish passage, single-beam hydroacoustic techniques were used. The correlation between hydro-acoustic and net catch estimates of smolt passage into the sluiceway at Ice Harbor Dam was statistically significant (r=0.96, n=26, p<0.001). Rocky Reach Dam hydroacoustic and fyke net catch vertical distributions were very similar. At Lower Granite Dam, the correlation between net catch estimates and hydroacoustic estimates of smolt passage was statistically significant (r=0.96, n=21, p<0.001). At Wanapum Dam, in 1994, there was a significant correlation between net catch and hydroacoustic estimates of smolt passage (r=0.96, n=10, p<0.001), and there was no statistically significant difference between the paired estimates. From 1991 to 1994, there was a significant correlation between mean hydroacoustic and net catch estimates of in-turbine diversion screen fish guidance efficiency (r=0.36, n=37, p=0.031), with no significant difference between the paired estimates. [ABSTRACT FROM PUBLISHER]