Geothermal Linkage Between a Hydrothermal Pond and a Deep Lake: Kuttara Volcano, Japan
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hydrology Article Geothermal Linkage between a Hydrothermal Pond and a Deep Lake: Kuttara Volcano, Japan Kazuhisa Chikita 1,*, Yasuhiro Ochiai 2, Hideo Oyagi 3 and Yoshitaka Sakata 4 1 Arctic Research Center, Hokkaido University, Sapporo 001-0021, Japan 2 Japan Petroleum Exploration, Co., Ltd., Tokyo 100-0005, Japan; [email protected] 3 College of Humanities and Sciences, Nihon University, Tokyo 156-0045, Japan; [email protected] 4 Faculty of Engineering, Hokkaido University, Sapporo, 060-8628 Japan; [email protected] * Correspondence: [email protected]; Tel.: +81-11-706-2764 Received: 24 October 2018; Accepted: 27 December 2018; Published: 6 January 2019 Abstract: Kuttara Volcano, Hokkaido, Japan, consists of temperate Lake Kuttara and the western Noboribetsu geothermal area. In order to explore geothermal relations between Lake Kuttara and the geothermal area, the heat budget of a hydrothermal pond, Okunoyu, was evaluated, and the heat storage change in the lower layer of Lake Kuttara was calculated by monitoring the water temperature at the deepest point. The lake water temperature consistently increased during the thermal stratification in June–November of 2013–2016. The heat flux QB at lake bottom was then calculated at a range of 4.1–10.9 W/m2, which is probably due to the leakage from a hydrothermal reservoir below the lake bottom. Meanwhile, the heat flux HGin by geothermal groundwater input in Okunoyu was evaluated at 3.5–8.5 kW/m2, which is rapidly supplied through faults from underlying hydrothermal reservoirs. With a time lag of 5 months to monthly mean QB values 2 in Lake Kuttara, the correlation with monthly mean HGin in Okunoyu was significant (R = 0.586; p < 0.01). Applying Darcy’s law to the leakage from the hydrothermal reservoir at 260–310 m below the lake bottom, the time needed for groundwater’s passage through the media 260–310 m thick was evaluated at 148–149 days (ca. 5 months). These findings suggest that the hydrothermal reservoir below lake bottom and the underlying hydrothermal reservoirs in the western geothermal area are both connected to a unique geothermal source in the deeper zone as a geothermal flow system of Kuttara Volcano. Keywords: Kuttara Volcano; Lake Kuttara; hydrothermal pond; heat budget 1. Introduction There are many volcanic lakes that are geothermally affected by magmatic activity of volcanoes or their eruptions throughout the world, as typified by Lake Nyos, Cameroon, with the lower magma’s pocket [1]. For Crater Lake, Oregon, USA, the US Geological Survey has provided a volcano hazards program for a possible future eruption [2], though the volcano at present seems to be undergoing stable magmatic activity. In New Zealand, the activity of Ruapehu Volcano is explored by using acoustic and seismic signals and estimating the water and heat budgets of Ruapehu Crator Lake [3–6]. Geothermal and hydrothermal systems of volcanic origin are proposed by White and Brannock [7] and Fukutomi et al. [8] from a geophysical viewpoint and by White [9] from a geological viewpoint. Terada and Hashimoto [10] proposed a numerical model for a thermal response of a crater lake to lower geothermal activity. As for other studies for volcanic activity, there are many geochemical investigations about interrelations between hydrothermal lakes and lower magmatic activity [11–15]. However, there are few field studies on estimates of water and heat budgets of hydrothermal lakes or ponds [3,16]. This is because high water temperature at more than 50 ◦C and volcanic heated gases Hydrology 2019, 6, 4; doi:10.3390/hydrology6010004 www.mdpi.com/journal/hydrology Hydrology 2019, 6, 4 2 of 11 Hydrology 2018, 5, x FOR PEER REVIEW 2 of 11 such as water vapor, SO2 and CO2 could damage instruments for monitoring water level and water waterproperties level suchand water as pH, properties electric conductivitysuch as pH, electr andic water conductivity temperature. and water The water,temperature. heat and The chemical water, ◦ heatbudgets and ofchemical Ruapehu budgets Crator of Lake Ruapehu (water Crator temperature Lake (water of less temperature than about of 50 lessC) werethan about estimated 50 °C) for were25 years estimated [3]. However, for 25 years spatial [3]. However, distributions spatial of water distributions temperatures of water in temperatures the lake are not in the shown, lake are and notgroundwater shown, and input groundwater and output input in theand wateroutput budget in the water are not budget estimated. are not In estimated. a volcanic In caldera a volcanic lake, calderaLake Kussharo, lake, Lake Japan, Kussharo, Chikita etJapan, al. [17 Chikita] evaluated et al. groundwater [17] evaluated outflow groundwater and groundwater outflow inflow and groundwaterincluding the inflow input ofincluding geothermal the input water of by geotherm estimatingal water the water by estimating and chemical the water budgets and of chemical the lake. budgetsIn the present of the study,lake. In the the heat present budget study, of a hydrothermalthe heat budget pond of a with hydrothermal water temperature pond with of mostlywater ◦ temperature50–70 C is estimatedof mostly 50–70 over four°C is years.estimated Such over a long-term four years. estimate Such a long-term under heated estimate conditions under heated is very conditionsrare in the world.is very Kuttara rare in Volcano,the world. Hokkaido, Kuttara Japan,Volcano, consists Hokkaido, of the westernJapan, consists Noboribetsu of the geothermal western Noboribetsuarea and eastern geothermal Lake Kuttara area and (Figures eastern1 Lakeand2 ).Kutta In thera (Figure Noboribetsu 1 and geothermalFigure 2). In area,the Noboribetsu in order to geothermalwatch volcanic area, activity, in order seismographs, to watch volcanic clinometers, activity, infrasound seismographs, meters, clinometers, GNSS and infrasound video cameras meters, have GNSSbeen setand by video the Japan cameras Meteorological have been set Agency. by the Kuttara Japan Meteorological Volcano is currently Agency. at theKuttara first levelVolcano for theis currentlyfive volcanic at the alert first levels level (the for Japanthe five Meteorological volcanic alert Agency:levels (the URL Japan http://www.data.jma.go.jp/svd/ Meteorological Agency: URL http://www.data.jma.go.jp/svd/voivois/data/tokyo/STOCK/kaisetsu/English/level.htmls/data/tokyo/STOCK/ kaisetsu/Eng)[18]. Thus, thelish/level.html) volcanic activity [18]. Thus, present the is 2 volcanicrelatively activity stable. present Fukutomi is relatively et al. [16] numericallystable. Fukutomi obtained et al. the [16] heat numerically flux HGin (W/m obtained) by the groundwater heat flux HinputGin (W/ in m a2) hydrothermal by groundwater pond, input Ohyunuma, in a hydrothermal in the Noboribetsu pond, Ohyunuma, area by in estimating the Noboribetsu the water area andby estimatingheat budgets. the water Boehrer and et heat al. [budgets.19] estimated Boehrer the et bottom al. [19] geothermalestimated the heat bottom flux geothermal at the deepest heat points flux atof the four deepest Japanese points volcanic of four lakes, Japanese Shikotsu, volcanic Kuttara, lakes, TowadaShikotsu, and Kuttara, Tazawa, Towa atda 0.29 and W/m Tazawa,2, 1.0 at W/m 0.292 , W/m18.6 W/m2, 1.0 W/m2 and2,0.27 18.6W/m W/m2 ,and respectively. 0.27 W/m This2, respectively. suggests that This of suggests the four that lakes, of Kuttarathe four and lakes, Towada Kuttara are andaffected Towada by relatively are affected high by volcanic relatively geothermal high volcanic activity. geothermal A magneto-telluric activity. A (MT) magneto-telluric survey for internal (MT) surveystructure for of internal Kuttara structure Volcano byof Kuttara Goto and Volcano Johmori by [20 Goto] indicates and Johmori that the [20] zone indicates of relatively that the low zone specific of relativelyresistivity low underlying specific theresistivity bottom underlying at the deepest the point bottom of Lakeat the Kuttara deepest may point be aof hydrothermal Lake Kuttara reservoir.may be aGoto hydrothermal and Johmori reservoir. [20] also Goto pointed and outJohmori that there [20] also is a geothermallypointed out that active there zone is a just geothermally below the western active zoneNoboribetsu just below geothermal the western area. InNoboribetsu this study, the geothermal heat budget area. of a In hydrothermal this study, pondthe heat in the budget Noboribetsu of a hydrothermalarea is continually pond estimated in the Noboribetsu over four years,area is andcontinually then the estimated question ofover how four the years, evaluated and then heat the flux questionby geothermal of how groundwaterthe evaluated input heat flux is related by geot tohermal the bottom groundwater geothermal input heat is related flux in to Lake the bottom Kuttara geothermalis discussed. heat flux in Lake Kuttara is discussed. FigureFigure 1. 1. LocationLocation of of Kuttara Kuttara Volcano Volcano in in Hokkaido Hokkaido (i (inserted),nserted), Lake Lake Kuttara Kuttara with with the the bathymetry bathymetry (blue(blue isopleths isopleths of of 20 20 m, m, 100 100 m m and and 140 140 m m in in wate waterr depth) depth) and and hydrothermal hydrothermal ponds, ponds, Ohyunuma Ohyunuma and and Okunoyu,Okunoyu, in in the the geothermal geothermal area area (red (red dotted dotted line). line). Th Thee deepest deepest point point of of Kuttara Kuttara is is located located at at site site MD MD (148(148 m m in in depth), depth), and and a a meteorological meteorological st stationation at site KM on the lake shore. Hydrology 2019, 6, 4 3 of 11 Hydrology 2018, 5, x FOR PEER REVIEW 3 of 11 FigureFigure 2. Location2. Location of two of two hydrothermal hydrothermal ponds, ponds, Ohyunuma Ohyunuma and Okunoyu, and Okunoyu, and a meteorological and a meteorological station (sitestation M) in (site the catchment,M) in the catchment, upstream ofupstream the small of boilingthe small pond boiling of a squarepond of shape a square (2 m shape× 2 m).