Sediment monitoring of glacial rivers in Iceland:: new data on bed load transport

Sediment monitoring of glacial rivers in Iceland has been carried out at the Hydrological Service of the National Energy Authority during the past five decades. This paper describes the expansion of the monitoring in recent years, with special emphasis on recent bed load sampling. As an example, the results from an extensive sediment sampling project in the harnessed glacial river Thjorsa, south Iceland, are discussed and compared with results from three other glacial rivers (Skafta in south Iceland and Jokulsa a Fjollum and Jokulsa a Dal in north and northeast Iceland) where bed load studies were carried out in 2001. Great changes in "at-a-point" bed load rate measured with a Helley-Smith sampler are seen among the four rivers, and variability within individual channels and sampling campaigns at diverse river discharge is prominent. Mean total bed load discharge for an individual sampling campaign was lowest in Thjorsad (0.03 kg s(-1) m(-1)) and highest in a June campaign in Jokulsa a Dal (1.58 kg s(-1) m(-1)). The mean total bed load transport rates in this study are higher than many published rates for arctic and alpine environments.