FLUVIAL MORPHOLOGY AND STREAMFLOW ON DECEPTION ISLAND, ANTARCTICA

The hydraulic geometry, runoff and sediment transport processes were s tudied during the 1991 summer season in two small pyroclastic drainage basins on Deception Island, South Shetland Islands. Daily discharge m easurements were conducted in two channels draining 0.65 km(2) and 0.1 2 km(2). The empirical relationship between the depth, velocity and wi dth exponents- f>m>b in channels with non-cohesive material is valid f or the studied area. Width is relatively conservative during increase of water discharge. Runoff was almost continuous for about 40 days, sh owing a strong association between streamflow and temperature. Two mai n periods are distinguished in the annual hydrological regime: 1. Runo ff during a short melting period of snow and glaciers. 2. Snow cover a nd frozen period of the entire drainage area. Temperature is the main factor affecting the hydrological regime of the rivers and snow availa bility during the summer season determines discharge water volumes in the nonglaciated basin. The specific discharge value was 3.42 1/sec/km (2). Fluvial sediment transport for the 1991 season was 46 ton/km(2)/y r, one order of magnitude less than values for Arctic rivers, but simi lar to average yearly sediment yield values of pyroclastic basins in m iddle latitude areas.