This report presents the first evaluations of 5 algorithms for converting global horizontal and direct normal solar irradiance components to global irradiance on tilted surfaces using measurements from the Solar Radiation Research Laboratory (SRRL) at SERI. High resolution (15-min) measurements from 8 thermopile radiometers oriented vertically in the 4 cardinal directions were available for a 169-day period ending 31 December 1984. Concurrent measurements of global horizontal and direct normal solar irradiance components were also used. The pyranometers used were intercompared on horizontal, north-facing, and south-facing vertical orientations. The conversion algorithms each attempt to account for the very complex atmospheric interactions with incoming solar radiation. The sky and ground radiance contributions to tilted surface are assumed to be isotropic, anisotropic, or a combination of the two depending on the algorithm. Results from the analysis of measurements on vertical surfaces for 22 July through 4 September indicate a general overestimate (18% to 46.5%) of solar irradiance on north-facing surfaces by all 5 of the algorithms. The best agreement with measured data was demonstrated for south-facing surfaces where all but one algorithm were within the present measurement by as much as 23% of the observed 15-min data.

The extent of predation on juvenile salmonids in John Day Reservoir was determined. Salmonids were the single most important food item by weight for northern squawfish (Ptychocheilus oregonensis) in the restricted zones at McNary tailrace and John Day forebay during all sampling periods. Salmonids accounted for 18.1% of the weight in the diet of walleyes (Stizostedion vitreum vitreum) in 1984 which was at least twice that found in previous years. In smallmouth bass (Micropterus dolomieui) salmonids contributed little to their diet whereas for channel catfish (Ictalurus punctatus) fish accounted for 64.1% of the weight in their diet with salmonids responsible for approximately half of this weight. An intensive search of the fisheries literature was conducted to review various fish capture and control techniques which might have potential as predation control measures for the major predators of juvenile salmonids in the Columbia River system. Most prey protection measures were judged to have high potential and direct predator control measures were judged to have moderate or low potential.