95

Bulletin of Glaciological Research ,- (,**0) 3/ῌ33
ῌJapanese Society of Snow and Ice

Water levels and temperatures in moulins, and other hydrological observations
at Bashkara Glacier in Caucasus, Russia, in September ,**/
Evgeny ISENKO
Institute of Low Temperature Science, Hokkaido University, Sapporo *0*ῌ*2+3, Japan(Received October 1, ,**/; Revised manuscript accepted November 3, ,**/)

Abstract
In order to investigate hydrology and, in particular, drainage systems of glaciers, measurementsof water temperatures and water levels in moulins, water temperatures along glacial surface water
streams, and other glacio-speleological observations were carried out at Bashkara Glacier in Caucasus,
Russia, from +* to +. September, ,**/. Extremely high amplitude of water level oscillations in moulins
demonstrates plausibility of the approach, when a channel consists of a wide vertical part (moulin)
and narrower subhorizontal part deep in a glacier. Water temperature measurements in one of themoulins revealed that it grows with the distance from the glacier surface, but much quicker thanestimated by the loss of potential energy. It probably means that the heat exchange with the air ismuch more signiﬁcant than was expected.

+.

Introduction

The water ﬂowing on the glacier surface andpenetrating into the inner and subglacial parts makesa complicated channel network, consisting of surface
streams, moulins (vertical shafts), intraglacial pressurized or open conduits, and subglacial tunnels. The
question of where and how water circulates withinglaciers is of considerable interest from various pointsof view (Röthlisberger, +31,). Knowing the structureof a glacial drainage system and the parameters of thewater ﬂowing through it, we can understand glacier
dynamics, inner ablation, outﬂow hydrograph andother hydrological processes.
Glacial water channels, or glacial caves, can also
be a subject of speleological interest. Collaboration
between glaciologists and speleologists started withthe rapid development of speleology in the middle ofthe ,*th century, when a lot of speleologists actively
studied glacier caves and caverns (Potts, +3/*; Halliday,+3/.). Nevertheless, even now such joint expeditions
are very seldom, although they give glaciologists unique possibility of exploring the subject of their study
directly from inside. Moreover, most of the reports on
glacial moulins explorations (Badino +333; Holmlund,+322; Reynaud, +321) contain mainly qualitative results, rather than the results of strict measurements.
The ﬁeld work on Bashkara Glacier in Caucasus,Russia, that was carried out from +* to +. of Septem-ber, ,**/, was exactly such a speleo-glacio- joint expedition. We measured water temperature and registered water level oscillations, along with mapping, in
two largest moulins, traced water temperatures alongtwo glacial surface water streams, and conducted
some other glacio-speleological and hydrological observations.

,.

Study area

Bashkara Glacier is placed in the Central Caucasus about .* km south-east from Mt. Elbrus just nearwell studied Djankuat Glacier. Bashkara Glacier isrelatively large. Its total length is about . km, andmaximum ice thickness is thought to be about ,** m.
The accumulation area (Fig. +) is situated on the steep
slopes of several .*** m peaks, heavily crevassed, witha lot of avalanche areas and ice-falls that makes massbalance measurements almost impossible there. Incontrary, the ablation area is almost ﬂat, with many
water streams and moulins, and easy to explore.
There are a large ice-dammed lake in the middle
part of the tongue and several small moraine-dammedlakes near the terminus. All these lakes are supposed
to be outburst-dangerous (for example, Chernomorets,,**/), although not everybody shares this opinion.
There are not so many glaciers with lakes in that area,and this is one of the reasons, by which Bashkara
Glacier attracts attention of many glaciologists. The
small lakes continue to grow. One of the lakes, ap-96

Bulletin of Glaciological Research

Fig. +. The accumulation area and the upper part of
the ablation area of Bashkara Glacier. The moulins
are marked by the arrows.

Fig. -. A huge tunnel at the west side of the glacierterminus.

Because the glacier tongue is relatively ﬂat andwith a few crevasses, a lot of water ﬂows on thesurface and mostly make a way into the ice throughmoulins. Two large and one small moulins, as well as
two long surface water streams were the subject ofour measurements.

-.

Fig. ,.

The newly formed lake at the glacier terminus.

peared during the last three years in the ice at thetongue (Fig. ,), is ice-dammed, and the dam is expected to be melted away in two or three years. In thatcase, the east part of the glacier terminus would retreat sharply by more than +** m.
A huge tunnel at the west side of the terminus,
from where most of the water discharge (about , msῌ+) occurs, exists at least during the last several years(Fig. -). According to our survey, its width and heightin the widest part is +2 m and / m respectively. By
water traces on the ice wall, we concluded that it wascompletely ﬂooded recently.

Members

The expedition was put just after the Conference
on Glacier Caves and Karst in Polar Regions that washeld near the same region from / to 3 of September,,**/. The idea of the expedition was proposed by theauthor as a continuation and an important experiencefor participants of the conference. However, only six
could take part in the ﬁeld work.
Research group:
Dr. Bulat Mavlyudov (Institute of Geography, Russian
Academy of Sciences). Leader, Glaciologist
Dr. Evgeny Isenko (Institute of Low Temperature Science, Hokkaido University), Glaciologist
Dr. Pavel Sivinskih (Perm State University), Speleologist
A team of experienced cavers:
Mr. Yuri Kosorukov (Russia), Mr. Ryo Matsuzawa(Japan), Ms. Olga Chervetsova (Russia)..

Measurements

The water temperature in two longest glacier surface water streams were measured with the distancestep of / to /* m depending on the local conditions. We
used a waterproof digital thermometer CT-2**WP
with a sensor LK-2**WP (accuracy *.+῍). The ﬁrst
stream (total length ../ m) begins from the most upper part of the ablation zone, slightly covered by freshsnow, as several small (-ῌ/ l sῌ+) streams. It ﬂows along
the middle moraine and ﬁnally drops into the moulin,where discharge reaches up to /* l sῌ+. Water ﬂow

Isenko97

Fig. /. The entrance pit to the deepest (ῌ/1 m) moulin(the moulin B).

Fig. .. Water temperature proﬁle along surface waterstreams. a) at the upper part of the ablation area;
total length ../ m, discharge from ,ῌ- to /* l sῌ+. b)
near the terminus; total length .+* m, discharge
from - to -* l sῌ+.

discharges were calculated by the measurements ofwater ﬂow speed and channel size. The second stream(total length .+* m) is situated much more downstream and begins from moraine covered ice surface.
The results of the water temperature measurements
are shown in Fig. ..
When we tried to explore two large moulins, wefaced with the problem that they were ﬂooded up tothe level of about ῌ,* m from the glacier surface.
However, in the early morning, when the water discharge was minimal, we managed to descend deeper
ῌ/* m. In the moulin A we reached the water, whichlevel was rising approximately ,ῌ. m per hour at thattime. In the moulin B (Fig. /) we could not reach thewater level and stopped at the depth ῌ/1 m because oflack of the ice-screws. The map (proﬁle sweeping andtop view) of the moulin B is shown in Fig. 0 and thevertical proﬁle of water temperature is shown in Fig. 1.

/.

Discussion

The structure and evolution of glacial drainage
systems depend on a plenty of factors and one of thesigniﬁcant ones is the water temperature, because itcontrols the melting rate on the channel walls. The
water temperature can vary along its ﬂow line because the water temperature depends on the air temperature, solar radiation, the ﬂow discharge, the amo-Fig. 1. Vertical proﬁle of water temperature in themoulin B. The maximum rate of water temperature increase, estimated by the loss of potential
energy, is shown by the dashed line.

unt of sediments, and also the channel’s form, size, andslope. According to Isenko et al. (,**/), the temperature of water ﬂowing in a glacial channel tends to theequilibrium, whose value is usually less than *.+῍,unless there is no environmental inﬂuence such asheat exchange with the air or warming by the solarradiation. Otherwise, the water temperature can riseup to much higher values as in our case. Two examples of water temperature proﬁle along the stream line
are shown in Fig. .. It is very di$cult to explain allchanges in the temperatures in the graphs, because inthis case we have to measure strictly a huge numberof parameters, such as channel geometry, sediments

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Bulletin of Glaciological Research

Fig. 0. The map (proﬁle sweeping and top view) of the moulin B. The right boundary and the ceiling of the upper part ofthe moulin are unclear, that illustrated by the dashed line.

quantity, distribution and albedo, solar radiation, airtemperature, wind speed, and so on.
Both streams were heavily sedimented. Sediments make the heat exchange between ice and water
more di$cult (Isenko et al., ,**/). Therefore the watertemperatures should be rather high. In the case of thewater stream that originates from a snow covered
area (Fig. .a), water temperature rises gradually fromῌ*῍ to *.. ῌ *.0῍. In the case of the water streamthat originates from the moraine (Fig. .b), temperature of water drops a little, when water enters the areaof pure ice, and then rises to the usual value. From
both graphs we can see that the water temperature
responds to the changes in the channel very quickly(,*ῌ/* m along the ﬂow). It means that the temperature balance in the water is near the equilibriumalmost at all points along the stream.
Direct consequence of the energy conservation

99

Isenkolaw indicates that the lost of potential energy forsome volume of water is su$cient for its warming by*.,῍ each +** m of lowering (Zotikov, +32,). Usually
this warming is much lower because of the heat exchange with the ice (Isenko at al., ,**/). Nevertheless,water temperature in one of the vertical shafts (moulins), that we explored, increased with depth with
unexpectedly high rate (Fig. 1). The maximum rate ofwater temperature increase, estimated by the loss ofpotential energy, is shown by the dashed line. Thiscan be explained only by an extreme high rate of theheat exchange with the air in the vertical parts (waterfalls), where the continuous water stream turns intodrops and smaller streams. However, we need morestatistics to make more profound conclusions.
Typically, the upper part of an intraglacial channel is wide, non-pressurized, and usually vertical (shafts, moulins). The lower part is narrower because of ice
contraction, completely ﬁlled with water (pressurized),and usually subhorizontal (Badino +333; Holmlund,+322; Isenko, ,**/; Reynaud, +321). Water level in theupper part of such a channel should change responding to changes of both water ﬂow discharge and channel size. Our observations did show such water level
oscillations: the amplitude in the moulin A was about-* m and more than .* m in the moulin B. Thesechanges in water level are supposed to be diurnal or atleast weather dependant.

0.

Acknowledgment

I express my sincere thanks to Bulat Mavlyudov,
who undertook all organization of the expedition andprovided all participants with the permits to the fron-tier area. I also thank and express my respect to Yuri
Kosorukov ῌ one of the most experienced cavers inRussia ῌ for speleo- and ice-climbing outﬁt supportand supervising during glacier caves explorations.
Collaboration with all other participants of the expedition was also extremely fruitful.
My personal participation was supported by theInoue Field Study Foundation in April, ,**/.
I am grateful to N. Azuma of Nagaoka Universityof Technology and R. Naruse of Institute of Low
Temperature Science for their critical comments on
the manuscript.

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