11:15 AM - 11:30 AM
[AHW18-09] Possible sources of groundwater in the Hondo-Shiromawari area, Misato Town, Akita Prefecture
Keywords:groundwater, Rokugo district, source, chemical composition
Introduction
The study area, the Hondo-Shiromawari area is located on the northeast side of the Rokugo district, Misato Township of Akita Prefecture. The Hondo-Shiromawari area is surrounded by four main rivers ( the Mahiru River, Akakura River, Kawaguchi River, and Maruko River). Furthermore, the study area is divided into three areas: Hilly mountainous area, Alluvial fan area, and Plain area. The hilly mountainous area has high elevations, and the plain area has low elevations. The hilly mountainous area is mainly covered by vegetable fields, while the plain area and alluvial fan area are widely covered by rice paddy fields. The Akakura River and Mahiru River surround the alluvial fan area. Each area has one or more springs (groundwater discharge). In the Hondo-Shiromawari area, there is the Tazawa Irrigation canal for agriculture from north to south.
Purpose
This study investigates the chemical compositions (major dissolved ions and trace elements) of groundwater in the area. This study aims to infer the groundwater sources and to evaluate groundwater contamination based on the data on the characteristics of chemical compositions of groundwater in this area.
Samples
The water samples were collected from the following a total of 12 sites: ell (Hoidosuzu well in the plain area), springs (Hayasaka spring from the plain area, Oo-shimizu Spring, Nogiwa-shimizu Spring, Furuyashiki-shimizu Spring (pipe & pond) from the alluvial fan area, Kogane-shimizu Spring from Hilly mountainous area), three river water (the Akakura River, Mahiru River, and the Omono River), irrigation canal (Tazawa canal), and precipitation by using a collecting tank monthly.
Results
The Kogane-shimizu Spring of the hilly mountainous area is classified into the Ca-Mg-Cl type, and the origin of this spring is thought to be the Akakura River and Mahiru River, however, the contribution of the Akakura River seems to be larger. Based on the difference in elevation level, there is no effect from the Tazawa irrigation canal. The Kogane-shimizu Spring contains higher concentrations of NO3 than the Akakura River and Mahiru River, which shows contamination due to agricultural fertilizer.
In the alluvial fan area, the samples were collected from the three springs (Oo-shimizu Spring, Nogiwa-shimizu Spring, and Furuyashiki-shimizu Spring (pipe & pond)). The Oo-shimizu Spring and Furuyashiki-shimizu Spring (pond) are classified into the Ca-Mg-Cl type. The origin of these groundwaters is thought to be the Akakura River and mainly the Mahiru River. The chemical composition of the groundwater of Furuyashiki-shimizu Spring (pipe) and Nogiwa-shimizu Spring are different from the groundwater of Oo-shimizu Spring and Furuyashiki-shimizu Spring (pond). The chemical composition of major dissolved ions of Furuyashiki-shimizu Spring (pipe) suggests a slight effect of the Tazawa irrigation canal. However, based on B and Sr concentrations of various water in the area, it is unlikely that the water from the Tazawa irrigation canal is affecting the groundwater in this area. Therefore, there is a possibility that the Furuyashiki-shimizu Spring (pipe) is present in the groundwater in this area as one of the end-member components.
The Nogiwa-shimizu Spring has also a different chemical composition from the springs in the Alluvial fan area. The chemical composition of Nogiwa-shimizu Spring is similar to that of thermal water gushing from a shallow portion of the ground about 5 km north of this area. The Nogiwa-shimizu Spring may be another end-member of the groundwater in this area.
In the Plain area, the Hoidosuzu well and Hayasaka Spring are classified into the Na-Cl-SO4 type, and the chemical composition of these two sites is similar to the chemical composition of the precipitation. This fact suggests that the origin of the groundwater in the two sites is local precipitation.
The study area, the Hondo-Shiromawari area is located on the northeast side of the Rokugo district, Misato Township of Akita Prefecture. The Hondo-Shiromawari area is surrounded by four main rivers ( the Mahiru River, Akakura River, Kawaguchi River, and Maruko River). Furthermore, the study area is divided into three areas: Hilly mountainous area, Alluvial fan area, and Plain area. The hilly mountainous area has high elevations, and the plain area has low elevations. The hilly mountainous area is mainly covered by vegetable fields, while the plain area and alluvial fan area are widely covered by rice paddy fields. The Akakura River and Mahiru River surround the alluvial fan area. Each area has one or more springs (groundwater discharge). In the Hondo-Shiromawari area, there is the Tazawa Irrigation canal for agriculture from north to south.
Purpose
This study investigates the chemical compositions (major dissolved ions and trace elements) of groundwater in the area. This study aims to infer the groundwater sources and to evaluate groundwater contamination based on the data on the characteristics of chemical compositions of groundwater in this area.
Samples
The water samples were collected from the following a total of 12 sites: ell (Hoidosuzu well in the plain area), springs (Hayasaka spring from the plain area, Oo-shimizu Spring, Nogiwa-shimizu Spring, Furuyashiki-shimizu Spring (pipe & pond) from the alluvial fan area, Kogane-shimizu Spring from Hilly mountainous area), three river water (the Akakura River, Mahiru River, and the Omono River), irrigation canal (Tazawa canal), and precipitation by using a collecting tank monthly.
Results
The Kogane-shimizu Spring of the hilly mountainous area is classified into the Ca-Mg-Cl type, and the origin of this spring is thought to be the Akakura River and Mahiru River, however, the contribution of the Akakura River seems to be larger. Based on the difference in elevation level, there is no effect from the Tazawa irrigation canal. The Kogane-shimizu Spring contains higher concentrations of NO3 than the Akakura River and Mahiru River, which shows contamination due to agricultural fertilizer.
In the alluvial fan area, the samples were collected from the three springs (Oo-shimizu Spring, Nogiwa-shimizu Spring, and Furuyashiki-shimizu Spring (pipe & pond)). The Oo-shimizu Spring and Furuyashiki-shimizu Spring (pond) are classified into the Ca-Mg-Cl type. The origin of these groundwaters is thought to be the Akakura River and mainly the Mahiru River. The chemical composition of the groundwater of Furuyashiki-shimizu Spring (pipe) and Nogiwa-shimizu Spring are different from the groundwater of Oo-shimizu Spring and Furuyashiki-shimizu Spring (pond). The chemical composition of major dissolved ions of Furuyashiki-shimizu Spring (pipe) suggests a slight effect of the Tazawa irrigation canal. However, based on B and Sr concentrations of various water in the area, it is unlikely that the water from the Tazawa irrigation canal is affecting the groundwater in this area. Therefore, there is a possibility that the Furuyashiki-shimizu Spring (pipe) is present in the groundwater in this area as one of the end-member components.
The Nogiwa-shimizu Spring has also a different chemical composition from the springs in the Alluvial fan area. The chemical composition of Nogiwa-shimizu Spring is similar to that of thermal water gushing from a shallow portion of the ground about 5 km north of this area. The Nogiwa-shimizu Spring may be another end-member of the groundwater in this area.
In the Plain area, the Hoidosuzu well and Hayasaka Spring are classified into the Na-Cl-SO4 type, and the chemical composition of these two sites is similar to the chemical composition of the precipitation. This fact suggests that the origin of the groundwater in the two sites is local precipitation.