Characteristics of Processes of Groundwater Discharge into a Distributary Channel on Tedori River Alluvial Fan, Ishikawa Prefecture, Japan

Abstract

Groundwater discharge into distributary channels on an alluvial fan is a local hydrological process distinct from the regional water cycle of the whole fan. Radon and chemical composition analyses of water samples from the Tedori River alluvial fan, within a local area of such groundwater discharge, revealed that the discharging groundwater occurs through the flow paths and recharge sources that differ from those of artesian groundwater in the aquifer at the seaward edge of the fan. Cross-correlation analysis of rainfall and riverbed water temperatures identified a 2–3-day episodic process linking rainfall and groundwater runoff in summer. This finding implies that in winter, the persistent wet condition of the surrounding paddy fields would cause continuous groundwater discharge. This small-scale groundwater process may be influenced by water management practices in paddy cultivation.