The first known self-draining of Summit Lake occurred in December 1961, followed by similar events in November 1965, September 1967, and November 1968. It has been noted that the rate of draining increases rapidly until the lake is empty (Mathews 1969). In August 1967 it was also noted that the runoff per unit area from the basin of Summit Lake, based on the rate of water volume change in the lake and overflow from the lake, was approximately one half the runoff per unit area from a glacierized basin to the north. It was suspected that at least part of this difference was due to leakage through the ice dam. More detailed observations made in July and August 1968 of the water balance of the lake basin indicate that, in August, there probably existed a leak possibly as large as 3 to 5 m³ sec ̄¹ . The tracing of lake water with fluorescent dye on three occasions also indicated the existence of a leak. Records of lake temperature from surface to bottom were kept from July through September with the results that: a) the warmest water was found at the bottom, and the coldest at approximately one third depth in most cases, b) the warmest temperatures occurred in the north end of the lake in early July; water temperatures decreased southward toward the ice dam and at all locations through the summer, and c) a mean water temperature of approximately 1°C is estimated for July decreasing to 0.7°C by September. For the 1965 draining a lake water temperature of 0.2°C is sufficient with the heat generated due to loss of potential energy to account for the enlargement of the tunnel in the terminal stages of draining, whereas a water temperature of 0.9°C is required for the 1967 flood. No evidence of sudden density overturn of the lake water could be found either from the temperature measurements or the results of dye tracing in the lake water in 1969. Water temperature records on three streams flowing into the lake indicate that from the entire drainage basin approximately 320 x 10¹º calories per day of heat may have been advected to the lake in August 1968. / Arts, Faculty of / Geography, Department of / Graduate

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Video summarizing Ph.D. dissertation for a non-specialist audience. / Civil and Environmental Engineering / College of Engineering

Thesis (Ph. D.)--University of Chicago. / Caption title: ... Statistics of Lake Commerce. Letter from the Secretary of the Treasury, transmitting a report made to the Bureau of Statistics by Mr. George G. Tunell, of Chicago, on Lake Commerce. Published also under the title: Statistics of Lake Commerce, House Doc. 277, 55th Cong., 2d Sess. Includes bibliographical references. Also available on the Internet.

Thesis (M.S.)--Oregon State University, 1975. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Since the 'discovery' of the high abundance of viruses in aquatic environments, it has been generally assumed that viruses in lakes are similar to those in oceans. I directly compared these two systems using a large, robust data set. Viral abundance was significantly different among the surveyed environments. The relationship between viral and bacterial abundance indicated a fundamental difference between lakes and oceans, and suggested that viruses infecting phytoplankton may be more important in lakes. Molecular techniques (PCR & DGGE) were used to document spatial and temporal variations in the richness of viruses that infect eukaryotic phytoplankton (Phycodnaviridae) in lakes at the Experimental Lakes Area (ELA). Phycodnavirus richness was highest in the eutrophic lake, and during the spring/early summer in all the lakes. Viral richness was closely associated with phytoplankton abundance and composition. As a result, richness was influenced by trophic status, while patterns of richness were affected by regional climatic conditions. Phylogenetic analysis of environmental Phycodnavirus DNA polymerase (pol) sequences indicated that freshwater Phycodnaviruses are genetically different from cultured isolates and marine environmental sequences. A genetic distance analysis indicated that polsequences > 7 % different infected different host species. Therefore, the 20 different freshwater sequences likely infected nine different hosts. Multivariate statistics identified seven possible phytoplankton hosts, including chlorophytes, chrysophytes, diatoms and dinoflagellates. Finally, the modified dilution experiment was evaluated as an approach for estimating viral-mediated phytoplankton mortality in two lakes at the ELA. Experiments resulted in non-significant apparent growth rate regressions. While a model analysis, indicated that the method was sensitive to poorly constrained parameters such as burst size and length of the lytic cycle, making it unsuitable for estimating mortality rates in these lakes. These studies indicate that Phycodnaviridae are a genetically rich and dynamic component of lakes. Their richness is influenced by both the chemical and physical components of their environment. Although the presence of these viruses indicates that they are a source of phytoplankton mortality, the magnitude of their impact on structuring phytoplankton communities awaits methodological advances. Nonetheless, these findings support the view that viruses infecting phytoplankton are ecologically important componentsof lake ecosystems.