Jahs. 47(2): (2017)

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1 * 2 1 Newly discovered lake bottom springs from Lake Kawaguchi, the northern foot of Mount Fuji, Japan Shinya YAMAMOTO 1 *, Takashi NAKAMURA 2 and Takashi UCHIYAMA 1 Abstract In Lake Kawaguchi, the existence of lake bottom springs have been estimated based on the patchy distribution of lake ice during winter. However, our knowledge on the detailed distribution and the source of these springs are still limited. In this study, we conducted hydrological and lake bottom survey using a Conductivity Temperature Depth CTD profiler, underwater camera and sonar to explore lake bottom springs in Lake Kawaguchi. We found upwelling of relatively warm water with low electrical conductivity EC at the 100 m east of the Unoshima Island, suggesting the existence of springs at this point. In addition, the results of lake bottom survey revealed the lack of muddy sediment on the lake bottom surface, a general feature observed in bottom springs, within a radius of 25 m around the springs. Stable isotope ratios of the lake bottom waters around the springs showed the values that are close to those in groundwater around the lake, suggesting that groundwater from the surrounding mountains likely wells out from the lake bottom at this location. Key words: Lake Kawaguchi, lake bottom springs, water quality, stable isotopes ; Mount Fuji Research Institute, Yamanashi Prefectural Government 2 Interdisciplinary Graduate School, Research Center for River Basin Environment, University of Yamanashi s.yamamoto@mfri.pref.yamanashi.jp 49

2 100 m 3 m 4 m ; 1963; CTD km m 17.4 km 833 m m 1700 m 1200 m 1300 m 840 m m Fig m 100 m 25 C CTD Sontek CastAway 30 cm General Mapping Tool GMT surface Wessel and Smith, 1991 surface CTD 0.01 C 0.05 C 1 µs/cm 0.25% 5 µs/cm Olympus Stylus TG835 GPS HDS-9 Gen3, HDI 50/200 khz Fig. 1b, Table 1 50

Fig. 1 Map showing the location of Fuji-Goko Fuji Five Lakes area, Yamanashi prefecture, Japan a, observation points and the sampling localities of lake water in Lake Kawaguchi b and ground water c.

3 Fig. 1 Map showing the location of Fuji-Goko Fuji Five Lakes area, Yamanashi prefecture, Japan a, observation points and the sampling localities of lake water in Lake Kawaguchi b and ground water c. Sampling localities of lake water in Uchiyama et al are also shown. Table 1 List of lake bottom water samples collected from Lake Kawaguchi. Water quality data are also shown. Sample ID Date Time Latitude Longitude Depth Temp m C ph EC DO ORP δ 18 O δd µs/cm mg/l mv K March : K March : K March : K March : K April : K April : K April : K April : K April : K April : K May : K May : K May : K May : K June : K June : K July : K July : K July :

3 L CTD 500 ml ph, 25 C ph, ph HM-14P CM-14P Martini ORP ORP57 HACH HQ30d 1 Fig. 2 11 3 2004 2015 2 0.5 C Figs. 2a, c A Fig. 2a 8 10 3 0.

1c V-SMOW δ sample R sample R standard /R standard 1000 R D/H 18 O/ 16 O V-SMOW, SLAP, GISP 3 1 0.1 n 4 Fig.

4 3 L CTD 500 ml ph, 25 C ph, ph HM-14P CM-14P Martini ORP ORP57 HACH HQ30d 1 Fig C Figs. 2a, c A Fig. 2a µm PICARRO L1102-i, m 300 m Fig. 1c V-SMOW δ sample R sample R standard /R standard 1000 R D/H 18 O/ 16 O V-SMOW, SLAP, GISP n 4 Fig. 2 Vertical distributions of water temperature a, c and electric conductivity b, d along the observation lines A and B. The measurements were conducted on 24 February 2015, at the western and eastern side of the Unoshima Island, Lake Kawaguchi. 52

5 m 8 m Fig. 2a A 300 m Fig. 2a 3 B 100 m Fig. 2c 3; B 3 8 m Figs. 2c, d B 3 30 m 40 m 2 B 3 Fig. 3 B 3 7.5 m 1963 Fig. 3a B 3 1979 Fig.

5 5 m 8 m Fig. 2a A 300 m Fig. 2a 3 B 100 m Fig. 2c 3; B 3 8 m Figs. 2c, d B 3 30 m 40 m 2 B 3 Fig. 3 B m 1963 Fig. 3a B Fig. 3 Underwater pictures of the lake bottom covered by mud a and gravel b. Both pictures were taken at the eastern side of the Unoshima Island, Lake Kawaguchi, on 22 May cm 15 cm Fig. 4 1 E1 1 2 E2 Fig. 4 Lava 100 m 25 m Fig. 4 53

6 Fig. 4 Map showing bathymetry and rugosity of bottom sediment in the eastern side of the Unoshima Island, Lake Kawaguchi. Difference in darkness corresponds to difference in roughness of lake floors. Darker parts indicate the area with a strong E1 return with high rugosity Fig. 5 B 3 δd 54

7 Fig. 5 Relationship between hydrogen and oxygen stable isotopes in lake bottom water collected at the eastern side of the Unoshima Island, Lake Kawaguchi, from March to July δ 18 O Fig. 5 δd δ 18 O /100 m 2007 Fig Table 2 Fig , m 2700 m m δd δ 18 O Table 1 δd δ 18 O δd δ 18 O r δd δ 18 O

8 Table 2 Hydrogen and oxygen stable isotope ratios of groundwater around Lake Kawaguchi. Sample ID Date δ 18 O δd GN GN GN GN GN GN GN GN GN GN GS GS GS GS GS GS GS GS GS GS GS GS GS GS GS GS GS GS GS GS δ 18 O 5 δd δ 18 O 2 δd 2σ L δd δ 18 O K C µs/cm Table Fig. 2 δd, δ 18 O

9 CTD m 8 m 2 25 m V 406p Proceedings of the 15th Symposium on Geo-Environments and Geo- Technics, p p

10 , p p p Wessel, P. and Smith, W.H.F Free software helps map and display data. EOS Transactions AGU, 72,

11 1 * 2 1 CTD 100 m 25 m 59

LAGUNA LAGUNA 10 p Water quality of Lake Kamo, Sado Island, northeast Japan, Katsuaki Kanzo 1, Ni

LAGUNA LAGUNA 10 p Water quality of Lake Kamo, Sado Island, northeast Japan, Katsuaki Kanzo 1, Ni LAGUNA10 47 56 2003 3 LAGUNA 10 p.47 56 2003 1997 2001 1 2 2 Water quality of Lake Kamo, Sado Island, northeast Japan, 1997 2001 Katsuaki Kanzo 1, Niigata Prefectural Ryotsu High School Science Club, Iwao