On the Water Sources in Hatano Basin

Abstract

The floor of Hatano basin, Kanagawa prefecture is consisted of higher plain for the most part excepting the lower plain on which the city of Hatano is located. The most of the basin is used as cultivated fields. It is said that the prevalence of the use of local and less elaborate water-works in this basin is the highest of the nation. The water is mostly supplied from valleystreams and springs at the foot of mountain, around the foot of mountains around the basin.
The writer thinks that these phenomena are due to the fact that the rivers in the basin are exhausted owing to underground run-off, making the level of the groundwater very low.
In search of the sources of the water for the farm irrigations in the north-western part of the basin, the writer surveyed the topograraphy, geology using the electrical prospector at about 100 stations. In the years 1957-58, writer made survey of the river-streams, underground flow, groundwater and their relations to the topography and geology.
I came to the conclusion that the water sources in this area are summarized as follows……
river-streams
↑↓
(underground flow water )
↓ groundwater
The topography of the basin surfaces are not so simple. The geomorphological processes of the rivers in this basin are diversified, and different from a river to another. The stratigraphy of this basin is classified as follows ……
1. the fluvial sand and gravel bed
2. the upper loam bed
3. the older fluvial sand and gravel bed (I)
4. the lower loam bed
5. the older fluvial sand and gravel bed (II)
The aqifers in this basin basin are the gravels beds of (3) and (5).
In the south-eastern part of the basin, the author we could see pretty many flowing wells and concluded that the aquifer for these wells is the layer (3). The gravel bed at the springs along the foot of hills resembles closely to the layer (5) seen from the electric resistance. According to the past records, the topographical unconformity along the Muro-Kawa to the south of the basin is attributed to a faulting. The outcrops of the of the layer (5) along the foot-hills were caused by the fault-movement. It is presumed that there are gravel beds with abundant water under the basin judging from the geological circumstances of the widespread sedimentation around Kanto Plain.
Recently in the basin plain, some industrial estates by the famous companies have been planned and some factories have started to make use of the confined water (each well: -70-80m deep, pumping volume 2000t/day.)