[AHW32-P17] Spatial distributions in groundwater (SGD) and nutrient discharge on tidal flat with the area of around 100m square in a small and steep island, western Japan
Abstract
The purpose of this study was to confirm spatial distribution in groundwater (SGD) and nutrient discharge on tidal flat with the area of around 100m square in a small and steep island. The experimental sites were located on Ikuchi Island in Onomichi City, Hiroshima Prefecture, western Japan. Pore water samples were collected and water levels were monitored at 10 and 17 piezometers on two experimental tidal flats, which is composed of E site (100m x 30m) at the alluvial fan edge of an experimental catchment and W sites at the steep mountain slop foot (300m x 30m), respectively. In addition, rain water samples were collected monthly at seven plots with different elevation from April 2019 in an experimental small and steep catchment with a maximum altitude of 400 meters The stable isotope ratio and nutrient concentration of water samples were analyzed by PICARO and SWAt of Beltech, respectively.
Various groundwater and nutrient discharges were observed at the W and E sites. E site on the catchment foot with a stream had smaller groundwater and nutrient discharge with the pore water of low nutrient concentration and flesh water content as compared at W site. Though experimental Ikuchi Island was small with the altitude of only 400m, we could confirm the elevation effects of stable isotopic ratios in rain waters. However, the rainfall volumes were not clarified to increase with the altitude. These results were only based on the observations for only about six months from April to September 2019, we will show more detail results for more than one year in the presentation, Based on the relationship between the altitude and stable isotopic ratios in rainwater, we could estimate groundwater recharge altitude at some pore waters at W site. It was estimated to be 50m to 300m in altitude. The lower area is covered by the citrus plantation, and high dissolved nitrogen and phosphorus was contained by leaching of fertilizer component. On the other hand, groundwater from the higher area flows longer and deeper path, and high silica was contained. We were able to confirm the difference between groundwater well-rising in tidal flats at low and high tides at the At W test site, the nutrient load was large in the west side.
The purpose of this study was to confirm spatial distribution in groundwater (SGD) and nutrient discharge on tidal flat with the area of around 100m square in a small and steep island. The experimental sites were located on Ikuchi Island in Onomichi City, Hiroshima Prefecture, western Japan. Pore water samples were collected and water levels were monitored at 10 and 17 piezometers on two experimental tidal flats, which is composed of E site (100m x 30m) at the alluvial fan edge of an experimental catchment and W sites at the steep mountain slop foot (300m x 30m), respectively. In addition, rain water samples were collected monthly at seven plots with different elevation from April 2019 in an experimental small and steep catchment with a maximum altitude of 400 meters The stable isotope ratio and nutrient concentration of water samples were analyzed by PICARO and SWAt of Beltech, respectively.
Various groundwater and nutrient discharges were observed at the W and E sites. E site on the catchment foot with a stream had smaller groundwater and nutrient discharge with the pore water of low nutrient concentration and flesh water content as compared at W site. Though experimental Ikuchi Island was small with the altitude of only 400m, we could confirm the elevation effects of stable isotopic ratios in rain waters. However, the rainfall volumes were not clarified to increase with the altitude. These results were only based on the observations for only about six months from April to September 2019, we will show more detail results for more than one year in the presentation, Based on the relationship between the altitude and stable isotopic ratios in rainwater, we could estimate groundwater recharge altitude at some pore waters at W site. It was estimated to be 50m to 300m in altitude. The lower area is covered by the citrus plantation, and high dissolved nitrogen and phosphorus was contained by leaching of fertilizer component. On the other hand, groundwater from the higher area flows longer and deeper path, and high silica was contained. We were able to confirm the difference between groundwater well-rising in tidal flats at low and high tides at the At W test site, the nutrient load was large in the west side.