The waters of Lake Vanda, Wright Valley have risen at a rate of 1m per year. The rise was largely attributed to increased flows in its only significant inflow, the Onyx River. Prior to the first flows of the season of the Onyx River into Lake Vanda, the physical structure of the lake water column, the penetration of radiation into the lake, the composition, biomass and activity of the microbial ... communities, and the distribution of biologically important chemicals (nitrogen, phosphorus, oxygen and inorganic carbon) was determined. How these factors changed over short time periods was monitored and how they changed when the river began to flow into the lake was determined. The path taken by water as it entered the lake and the concentrations of suspended sediments and dissolved nutrients in this inflowing water was determined. A network of sampling stations on Lake Vanda and a grid of stations spreading out from the eastern (inflow) end was established. The physical structure of the water column was determined by obtaining profiles of temperature and conductivity, dissolved oxygen, nutrients, dissolved organic carbon, pH, chlorophyll a and total suspended solids. Samples were also preserved for enumeration of phytoplankton, picoplankton, flagellates and bacteria. Penetration of light through the ice cover into the water column was determined with coloured filters to determine the penetration of red, blue and green light. Photosynthetic activity of plankton samples and nutrient status from 10, 21, 37 and 63m depth was assessed.