Hydrological study of purpose and role on a “pond” constructed in Rokugo alluvial fan within the mid-Edo—In focusing on the function of artificial groundwater recharge—

Abstract

The author met to a pictorial map of Rokugo-Kouya Village in the Tenmei era. This map draws that a “pond” was existed in the center of Rokugo alluvial fan, Akita Prefecture. Ruins of the “pond” is still remain. An analysis on old documents found a couple of findings. Firstly, the “pond” is estimated to have been constructed for paddy rice irrigation in the mid-Edo. Secondly, the “pond” could not store water, because it was located in the part of alluvial gravel layer where infiltration capacity is high. As a result, the “pond” is inferred to have unexpectedly played the same role as groundwater artificial recharge basins.