47 2 49 59 2017 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 1900 1902 1928 1995 2005 1981; 1995 1 2007 1978 1979 1980 1981 2004 1 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
100 m 3 m 4 m 2007 1934; 1963; 2001 1902 CTD 1 5.96 km 2 16.1 m 17.4 km 833 m 2004 1400 m 1700 m 1200 m 1300 m 840 m 2005 2 2015 2 24 700 m Fig. 1 30 m 100 m 25 C CTD Sontek CastAway 30 cm General Mapping Tool GMT surface Wessel and Smith, 1991 surface 0.25 0.75 CTD 0.01 C 0.05 C 1 µs/cm 0.25% 5 µs/cm 2015 5 22 Olympus Stylus TG835 GPS HDS-9 Gen3, HDI 50/200 khz 2015 3 7 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. Sampling localities of lake water in Uchiyama et al. 2014 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-150330-14 30 March 2015 13:32 35 30 50.09 138 44 54.12 8.5 10.9 7.5 110.2 10.1 64 9.3 63 K-150330-15 30 March 2015 14:01 35 30 50.20 138 44 53.32 7.5 10.9 7.4 125.1 6.3 57 9.3 63 K-150330-16 30 March 2015 14:36 35 30 49.25 138 44 54.45 8.2 9.9 7.3 122.7 9.2 89 9.2 63 K-150330-17 30 March 2015 15:12 35 30 51.89 138 44 53.67 7.7 9.9 7.1 124.4 10.0 68 9.2 62 K-150430-14 30 April 2015 12:00 35 30 49.53 138 44 53.59 8.0 13.4 7.6 120.8 7.2 5 10.5 69 K-150430-15 30 April 2015 13:59 35 30 49.50 138 44 53.64 8.0 14.2 7.7 130.6 6.4 21 10.6 70 K-150430-16 30 April 2015 14:07 35 30 49.60 138 44 53.59 8.2 14.2 7.7 113.9 9.2 38 9.2 62 K-150430-17 30 April 2015 14:23 35 30 49.45 138 44 53.93 8.4 14.2 7.8 114.2 8.9 89 9.3 63 K-150430-18 30 April 2015 14:31 35 30 49.74 138 44 52.93 7.1 15.4 7.7 112.5 9.4 93 9.1 62 K-150430-19 30 April 2015 14:37 35 30 48.61 138 44 54.68 7.8 14.3 7.7 111.8 9.2 59 9.3 63 K-150522-14 22 May 2015 13:41 35 30 49.65 138 44 54.08 8.5 18.3 7.7 142.0 8.4 25 9.1 61 K-150522-15 22 May 2015 14:29 35 30 49.80 138 44 54.16 8.6 14.5 7.6 113.0 8.6 41 10.6 69 K-150522-16 22 May 2015 14:32 35 30 49.72 138 44 54.46 9.0 12.5 7.6 103.3 8.7 58 11.2 72 K-150522-17 22 May 2015 14:58 35 30 50.24 138 44 53.33 7.3 17.8 7.7 138.9 8.4 85 9.0 61 K-150630-14 30 June 2015 11:45 35 30 49.26 138 44 54.13 7.8 15.1 7.1 134.9 6.2 4 10.4 68 K-150630-15 30 June 2015 14:03 35 30 49.22 138 44 54.12 7.6 18.9 7.3 201.0 5.5 40 9.6 64 K-150724-14 24 July 2015 11:07 35 30 49.39 138 44 54.01 8.5 21.2 7.3 134.0 4.3 34 10.0 67 K-150724-15 24 July 2015 11:19 35 30 49.28 138 44 54.03 8.4 21.2 7.6 127.0 4.4 3 9.9 66 K-150724-16 24 July 2015 11:20 35 30 49.27 138 44 54.01 8.5 16.4 7.5 115.0 6.5 36 10.7 70 51
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 0.2 µm PICARRO L1102-i, 2014 7 2015 10 50 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 3 1 0.1 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. 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 2015. 7 cm 15 cm 1981 1985 1995 Fig. 4 1 E1 1 2 E2 Fig. 4 Lava 100 m 25 m Fig. 4 53
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. 1995 3 Fig. 5 B 3 δd 54
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 2015. δ 18 O 2007 2014 Fig. 5 δd δ 18 O 1995 2007 0.18 /100 m 2007 Fig. 5 2014 2014 Table 2 Fig. 5 1 2005 2014, 2 1400 m 2700 m 2007 1700 m δd δ 18 O 72 61 11.2 9.0 Table 1 δd 63 56 δ 18 O 8.9 7.7 2014 δd δ 18 O r 2 0.99 δd δ 18 O 2005 2013 0.9 55
Table 2 Hydrogen and oxygen stable isotope ratios of groundwater around Lake Kawaguchi. Sample ID Date δ 18 O δd GN01 2014.7.25 10.1 71 GN02 2014.7.25 11.3 75 GN03 2014.7.25 10.8 73 GN04 2014.7.25 11.2 76 GN05 2014.7.25 10.7 74 GN06 2014.7.25 10.7 74 GN07 2014.7.25 11.2 75 GN08 2014.7.25 11.2 74 GN09 2014.7.25 10.0 66 GN10 2014.7.25 10.7 71 GS01 2015.10.7 10.9 76 GS02 2014.7.25 11.1 76 GS03 2014.7.25 11.3 76 GS04 2015.10.7 10.8 75 GS05 2015.10.7 11.1 78 GS06 2015.10.7 10.8 75 GS07 2015.10.7 11.8 84 GS08 2015.10.7 10.7 76 GS09 2015.10.7 10.4 73 GS10 2015.10.7 11.7 83 GS11 2015.10.7 10.7 75 GS12 2014.7.25 11.0 76 GS13 2015.10.7 11.5 80 GS14 2014.7.25 11.2 75 GS15 2015.10.7 11.3 79 GS16 2015.10.7 10.7 75 GS17 2015.10.7 11.1 77 GS18 2015.10.7 11.1 77 GS19 2014.7.25 11.9 81 GS20 2014.7.25 11.7 79 δ 18 O 5 δd 2014 0.4 δ 18 O 2 δd 2σ 2014 2014 3 L δd δ 18 O 2015 5 22 K-150522 16 12.5 C 103.3 µs/cm Table 1 5 2 Fig. 2 δd, δ 18 O 1964 1975 1976 56
CTD 1 100 m 8 m 2 25 m 25 27 2 2001 45 45 48. 2004 48 64 71. 1928 V 406p. 2014 9 67 85. 2005 Proceedings of the 15th Symposium on Geo-Environments and Geo- Technics, 209 214. 1978 51 49 59. 1963 1 1 1995 103p. 1980 28 47 50. 1900 12 608 614. 1902 14 154 165. 1995 25 71 81. 1964 37 475p 1976 57
27 59 66. 2005 47 11, 3 14. 2007 157 177. 1995 25 1 12. 2007 133 154. 1934 1 30 33. 2007 389 405. 1985 30p 1963 9 13 14. 1975 41p 1981 75p 2005 49 54 59. Wessel, P. and Smith, W.H.F. 1991 Free software helps map and display data. EOS Transactions AGU, 72, 441 446. 2017 1 27 2017 3 7 2018 2 28 58
1 * 2 1 CTD 100 m 25 m 59