10:15 AM - 10:30 AM
[HGM22-06] Earth-surface processes on the basis of instrumental observations in Takidani-ike lake-catchment system, central Japan
Keywords:lake-catchment system, earth-surface process, pond sediment, sedimentation rate
Lacustrine sediments contain both high-resolution regional environmental records and global information in lake-catchment systems. They are also of great use for reconstructing short-term environmental changes (precipitation, water discharge, etc.) and understanding earth-surface processes (erosion, transportation, sedimentation) in the lake-catchment system. Process understanding is essential for clarifying causal relations in earth surface phenomena and proper interpretation of sediment information. Instrumental observation (monitoring) is of great use for the process understanding. This study deals with the instrumental observation for a small pond-catchment system (Takidani-ike) near Kanazawa University. The pond is storage reservoir. It is used for agricultural irrigation in summer. Therefore the water level shows highly fluctuation. Our observation consists of sediment sampling with trap, water level measurement, temperature measurement, and precipitation measurement. Observation in Takidani-ike using sediment trap has continued since June 2000. Observational and analytical results for Takidani-ike show that; the sedimentation rate (both monthly and seasonal sedimentation) is expressed as a function of two factors; precipitation intensity (external factor) and water level change (system factor, closely related to size of erosible area). The correlation for the seasonal relationship is better than one for the monthly relationship, suggesting that reservoir effect in the catchment should be considered. The results also show that mineral grain size may be used as proxies for sedimentation rate.