Numerous ephemeral streams link the glaciers and lakes within the dry valleys for 6 to 14 weeks during the austral summer. These glacial meltwater streams recharge the dry valley lakes and are important sources of nutrients to the lakes. The McMurdo LTER has in place an extensive network of gauging stations where streamflow is continuously measured throughout the austral summer. To quantitatively describe the relationship between climate and flow in the glacial meltwater streams that feed the lakes, streamflow measurements are being used in conjunction with data on climatic conditions to develop a watershed scale model of ecological dynamics in Taylor Valley. Additionally, detailed ecological and geomorphological characteristics of 16 stream sites have been mapped using a total station and GPS equipment, establishing permanent stream sites at which the ecological responses to increased streamflow can be monitored over long time scales. Microbial mat and moss communities are often found within and along the margins of streams in the dry valleys. Of primary interest is determining the processes that control distribution, biomass, and productivity of these communities. Despite the extreme harshness of the environment, a total of 30 taxa of cyanobacteria and chlorophytes and 38 species of diatoms are present in dry valleys streams.