Bulletin of Glaciological Research ,1 (,**3) 1ῌ+.
ῌJapanese Society of Snow and Ice

7

Development of a hot water drilling system for subglacial and englacial
measurements
Shun TSUTAKI+, , and Shin SUGIYAMA,+ Graduate School of Environmental Science, Hokkaido University, Nishi-/ Kita-+* Sapporo, *0*ῌ*2+* Japan, Institute of Low Temperature Science, Hokkaido University, Nishi-2 Kita-+3 Sapporo, *0*ῌ*2+3 Japan(Received April +, ,**3; Revised manuscript accepted May ,/, ,**3)

Abstract
Hot water drilling is a technique suitable for drilling boreholes in a glacier, especially those meant
for installing instruments. This method is considerably faster than a mechanical drilling. Moreover, the hot water drilling system is easy to operate and can be constructed by assembling simple
devices. This paper reports on the development of a hot water drilling system for temperate ice +**ῌ,** m thick. The system consists of water basin, high-pressure pump, heater, tripod, pulley, hose,
drilling stem and nozzle. The total weight of the system, including a ,/* m length of hose, isapproximately -** kg. The system generates a hot water jet at a temperature of 0*ῌ10῍ and a ﬂow
rate of 3/*ῌ+*** l hῌ+ using straight jet nozzles of +.0, ,.* and ,./ mm diameter. The drilling system
was tested at Rhonegletscher, Switzerland during the summers of ,**1 and ,**2. Eight boreholes
with a total depth of 3,/ m were drilled in ,**1, and twenty-four boreholes with a total depth of +++2m were drilled in ,**2. The mean drilling rates achieved for each borehole were in the range of ,1ῌ
1* m hῌ+, depending on the drilling depth, the distance between the drilling site and the heater, and theelevation di#erence between the drilling site and the pump. During drilling at the glacier, the diesel
and petrol consumption rates of the heater and pump respectively were 0.3 l hῌ+ and +.2 l hῌ+.

+.

Introduction

Subglacial and englacial measurements can provide a wealth of information on glacier sliding (e.g.
Fischer and Clarke, +331; Engelhardt and Kamb, +332),
basal sediments (e.g. Fischer and Clarke, +33.; Tulaczyk
et al., ,**+), subglacial hydraulic conditions (e.g.
Engelhardt and Kamb, +331; Iken and Tru#er, +331;
Fudge et al., ,**2), ice temperature (e.g. Lüthi et al.,,**,) and internal deformations (e.g. Hooke et al., +33,;
Harper et al., ,**+). To drill a borehole for such measurements, it is preferable to employ a faster methodthan mechanical drilling, which is normally used forice coring.
A hot water drilling system generally consists ofwater basin, high-pressure water pump, heater, hoseand jet nozzle (Fig. +). The nozzle, supported by tripod and pulley, emits a jet of water heated close to theboiling point at a glacier surface. As the drilling proceeds, the stem and hose are lowered into a boreholeof about +** mm in diameter created in the glacier ice.
Hot water drilling has been used for a wide variety ofmeasurements, both inside and underneath glaciers.
The advantages of this method over mechanical drill-ing are as follows: (i) a much faster drilling rate of /*ῌ
+** m hῌ+, (ii) the ability to drill both temperate andcold ice (e.g. Humphrey and Echelmeyer, +33*), (iii)
simplicity of construction using commercially available devices, and (iv) ease of operation.
Hot water drilling systems have been developedby many researchers and employed at numerous mountain glaciers and ice sheets: South Cascade Glacier in
the USA (Taylor, +32.; Fountain, +33.), Findelengletscher in Switzerland (Iken and Tru#er, +331), Storglaciären in Sweden (Hanson et al., +332), JakobshavnsIsbræ in Greenland (Iken et al., +33-), Ice Stream B(Engelhardt et al., +33*), Amery Ice Shelf (Craven et al.,,**.) and Dome C in Antarctica (Koci, +32.). No such
system has ever been constructed in Japan.
We have developed a simple hot water drillingsystem for englacial and subglacial measurements,
able to drill up to ,** m of temperate ice. This report
describes the conﬁguration of the system, test results,
and its drilling performance at Rhonegletscher, Switzerland during the summers of ,**1 and ,**2.

,.

A hot water drilling system,.+ Conﬁguration of the system

8Bulletin of Glaciological Research

The drilling system is shown in Figure ,. Hot
water is generated by a commercially available highpressure hot water machine, the Kärcher HDS+***BE(Fig. -a), which is commonly used for cleaning vehicles and buildings. The same device has been usedby a research team for drilling mountain glaciers(Hubbard and Glasser, ,**/). A petrol-driven water
pump engine (Honda GX-3*) and diesel combustion
heater are combined to achieve ﬂow rates in the range
of ./*ῌ3** l hῌ+, pressures of 0ῌ,+ MPa, and temperatures of -*ῌ+.*῍ when they are used with a cleaning
nozzle which is specially designed to change the ﬂow
rate for a cleaning purpose. The total weight of themachine is +0/ kg. A safety device is installed between the pump and the heater, which turns o# theheater when the water pressure drops below an operating threshold. The pump draws water from a -*** lbasin with a diameter of , m and a weight of ,2 kg(National Marine Plastic Inc. Type E) (Fig. -b). On
site, it can also draw water from natural streams.
The drilling hoses, which individually are /*ῌ+** mlong and have an internal diameter of 2 mm, are connected with couplings to obtain enough length. During drilling, the hose is supported by a pulley hung ona tripod (Fig. -c). The pulley is designed to measure
the length of hose by counting rotations. The aluminum tripod has a length of ,., m and a weight of +* kg,and can be disassembled for transportation. The drilling stem was constructed at the workshop of theInstitute of Low Temperature Science, Hokkaido University. The nozzle (Katorigumi Seisakusho Inc.
Type K-+2) is mounted on the stem to produce anarrow and straight jet (Fig. -d). Two +./ m long stainless steel pipes with internal and external diameters of+3.0 and ,1., mm were connected with a brass coupling (Fig. -e). Two pieces of pipe were used in orderto have enough length and weight to drill a straightborehole. A conic spray nozzle (Type K-,*) is used toenlarge the diameter of a borehole after drilling (Fig.
-f). The total weight of all equipment (hot watermachine, water basin, tripod, pulley and drilling stem)
is approximately ,,* kg, plus -* kg per +** m of hose.
,. ,Fig. +.

Schematic of a hot water drilling system.

Laboratory performance test
To test the performance of the drilling system, its
water temperature and ﬂow rate were measured while
directly connected to a tap in a laboratory. The test
was conducted using hoses with lengths of +, /*, +**and +/* m, straight jet nozzles with diameters of +.0,,.*, ,./ and -.* mm, and a conic spray nozzle with adiameter of ,.* mm. The cleaning nozzle provided by
the manufacturer was also used to change the ﬂow
rate only in the laboratory test. Because the water
jet was very narrow, an accurate measurement ofwater temperature in the vicinity of the nozzle was
di$cult (Fig. -e). The jet was trapped in a +* l plastic

Fig. ,. Block diagram showing the conﬁguration of the hot water drilling system constructed for thisproject.

Tsutaki and Sugiyama

9Fig. -. (a) The high-pressure hot water machine (Kärcher HDS+***BE), (b) the -*** l water basin, (c) the tripod with
its pulley, (d) a jet nozzle mounted at the tip of the drilling stem, (e) a water jet from a - m long drilling stem witha straight nozzle, and (f) a water jet from the conic spray nozzle.

bottle, and the water temperature in the bottle wasmeasured every +/ seconds as it ﬁlled using a temperature logger (HIOKI -0--). During the water jet temperature measurement, the temperature setting of theheater was gradually raised from /* to +-/ῌ+/*῎.
The water ﬂow rate was calculated from the timerequired to ﬁll a box of *.*, m-. The consumption
rates of petrol and diesel during the experiments were
measured as well. The drilling performance of thesystem was tested by drilling ice blocks of *./῍*.,/῍+ m- with the /* m hose, the ,.* mm straight jet nozzle,

and water supplied from the basin.
,.-

Results
The -.* mm diameter straight nozzle was not suitable for the system because the pressure dropped below
operating range and the heater was automatically shut
down by the safety device. In laboratory tests thediesel consumption rate of the heater was ..1 l hῌ+, andthe petrol consumption rate of the pump was +.3 l hῌ+.
Using the ,.* mm straight nozzle, we measured
the water temperature as a function of time for vari-

10

Bulletin of Glaciological Research

Fig. /. Drilling nozzle and water jet in the ice blockused for the test. The nozzle was lowered quicklyin (a), while it was lowered slowly to enlarge theborehole diameter in (b).

Table +. Time required drilling through + m thick ice
blocks and drilling speed. Water temperature was1..῍ in the case of no heating.

Fig. .. Water jet temperature vs. time with (a) various
hose lengths and (b) various jet nozzle diameters.
(c) Flow rates and water jet temperatures obtainedwith the three jet nozzles and the cleaning nozzle.

ous hose lengths (Fig. .a). The maximum temperatures reached ranged from 0.ῌ10῍. The temperatureis generally higher for shorter hoses, although the
maximum temperature at +/* m length hose exceedsthat at +** m. As the water pressure from a tap is

expected to be unstable, the ﬂow rate may have ﬂuctuated in these experiments and inﬂuenced the watertemperature. When we ﬁxed the hose length at /* m,
the maximum temperature for +.0ῌ,./ mm nozzles ranged
from 0*ῌ0/῍ (Fig. .b). The temperature reached 2*῍for the conic spray nozzle, as its ﬂow rate was much
lower. These results indicate that the temperature of
the water jet is higher than 0*῍ and it is slightly
inﬂuenced by hose length and nozzle diameter. The
jet temperature is saturated when the heater setting isabove 1*῍ because the heater is designed for a ﬂow
rate lower than our use.
The relationship between ﬂow rate and temperature was investigated using a /* m long hose by andthe cleaning nozzle (Fig. .c). The temperature isvery close to the boiling point when the system isoperated at ./* l hῌ+, and decreases as the ﬂow rateincreases. For the jet nozzles with diameters of +.0ῌ,./ mm, the temperature is about 0*῍ and the ﬂow
rates are 3/*ῌ+*** l hῌ+. This rate is the upper limit of
the pump capacity. With the -*** l water basin, drill-

Tsutaki and Sugiyama

11

ing can continue for - hours at this rate.
Testing the system on an ice block conﬁrmed thatthe drilling process is very fast. It took about -*seconds to drill through a + m thick ice block, excavating a hole of /* mm diameter (Fig. /a). A wider holecan be drilled by lowering the nozzle more slowly (Fig.
/b). The times required to drill through + m of ice
were measured at various temperature settings of theheater (Table +). As expected from the abovementioned results (Fig. .a, b), the drilling speed is nearly
constant when the heater setting temperature is higher than 1*ῌ. Drilling is even possible with cold
water (1..ῌ).

-.

Drilling on Rhonegletscher-.+

Study site
Rhonegletscher is located in the Swiss Alps at thesource of the Rhone River. This temperate valley
glacier is 1.2/ km long, with an area of +/.3 km,. Its
terminus is ,,** m a.s.l. (Huss et al., ,**2). The glacierlength has decreased by approximately ++/* m from+22* to ,**- (Zahno, ,**.). A proglacial lake formed
in ,**/ because the terminus position retreated behinda bump of the bedrock (Sugiyama et al., ,**2). The
formation of this lake is expected to accelerate theglacier’s retreat by initiating an ice calving process.
The inﬂuence of the lake water on the subglacial
water pressure reaches further upglacier if the lake
will more enlarge in the near future, which is likely toincrease the glacier’s ﬂow speed. To investigate theimpact of lake formation on the glacier, both subglacial and englacial borehole measurements are crucial
in addition to surface observations. In particular,boreholes are required for accurate measurements ofice thickness, subglacial water pressure, basal ﬂow
speed, internal ice deformation, and subglacial sediment properties. As part of ongoing research on the
response of Rhonegletscher to lake formation, we carried out hot water drilling at the terminal part of theglacier in ,**1 and ,**2.

-.,

Borehole drilling
From +- to ,3 July ,**1, eight boreholes (BH+-BH2)
were drilled to the glacier bed at positions -**ῌ2** mfrom the terminus (Fig. 0). The pump and heater
were always located near BH+, while the hose was
extended to each drilling site. Before drilling, therequired length of hose was piled up and insulatedwith cotton cloth. The hose would melt a groove
into the ice during operation, increasing its contact
with the ice surface. To minimize heat loss, the hose
was often taken out of this groove. We normally
pumped water into the hot water machine directlyfrom a supraglacial stream. The basin was used only
when the amount of running water was not su$cient.
At times the heater would automatically shut down

Fig. 0. Map of the study site in Rhonegletscher withthe borehole locations from ,**1 marked (῍). The
black contours indicate surface elevation at ,* mintervals. The gray contours are bedrock elevations estimated by Zahno (,**.) at +** m intervals.
The shaded regions indicate marginal lakes. The
o$cial Swiss coordinate system is used in thismap.

due to the accumulation of black sediment from theglacier in a ﬁlter installed at the water intake (Fig. ,).
The drilling was carried out using either the ,.* or,./ mm jet nozzle. For some boreholes, the ,.* mmconic spray nozzle was also used to enlarge the borehole. The maximum borehole depth was determinedby the length of the hose used for drilling, and thecurrent depth was recorded every /ῌ+/ minutes tomeasure the drilling speed. During the drilling, operator kept the nozzle slightly above the boreholebottom to drill a straight borehole. Drilling continued until the nozzle reached the glacier bed, a moment
which could be recognized by the change in hosetension. The reported borehole depths may be underestimated by +ῌ, m because the hose stretched during drilling. The fuel consumption rates of petroland diesel were also calculated.
The drilling was repeated in ,**2 in the lower
reaches of the ,**1 drilling sites. During these experiments, the heater and pump were located at BH2(Fig. 0) while the hose was extended downglacier very
close to the calving front. We drilled twenty-fourboreholes with depths ranging from +2ῌ33 m. In thefollowing section, we compare total drilling depths tothose measured in ,**1, and refer to the fuel consumption rates to calculate a mean value.
-.-

Results and Discussion
The depths of BH+ -BH2 range from 21 ῌ +-2 m(Table ,). The diameters of these boreholes were +**ῌ+/* mm near the surface, but are expected to be narrower at depth (Fig. 1). The total drilling depths in12Bulletin of Glaciological Research

Table ,. Depth and mean drilling rate of the boreholes in ,**1. Horizontal distanceand elevation di#erence between the drilling sites and the hot water machine
are also indicated.

Fig. 1.

The appearance of a borehole at the surface.

,**1 and ,**2 were 3,/ m and +++2 m respectively.
Figure 2 plots borehole depth vs. drilling time for BH+BH2. The mean drilling rates ranged from ,1ῌ1* m hῌ+.
Hubbard and Glasser (,**/) used the same hot watermachine at an altitude of ,2** m a.s.l in Haut Glacierd’Arolla, Switzerland. The pump drew water from a.*** l basin which was ﬁlled by melting snow. Theyobtained drilling rates of +,* m hῌ+ near the ice surface
and -* m hῌ+ at depths greater than +,* m. They reported the water temperature as 2*῍. In order todetect the bedrock from a change in hose tension, thedrilling rate was deliberately decreased during thelast +*ῌ,* minutes. This e#ect can be observed in theplots for BH+, BH,, BH-, BH0 and BH2. In BH., BH0
and BH1, the drilling rate decreased when waterdrained from the borehole. Drilling in an empty borehole is more di$cult. This was because the loss ofbuoyancy force makes the operation of the hose hanging in the borehole more di$cult. Other factors may
have inﬂuenced the drilling rate in some cases, such as
the experience of the operator and interruptions due
to refueling or ﬁlter cleaning.

Fig. 2. Drilling depth as a function of drilling time forthe boreholes from ,**1.

Tsutaki and Sugiyama

Two other relatively important factors are the distance and elevation di#erence between the hot watermachine and the drilling site. Table , shows that BH+
and BH,, located closest to the machine (* and 3/ m), hadrelatively high drilling rates (/* and 1* m hῌ+). BH1
and BH2, situated farther from the machine (,+0 and,/. m), had rather small drilling rates (,1 and .* m hῌ+).
This relationship is expected because the temperatureof the water decreases with distance from the heater.
BH. and BH1, situated at elevations +/ and -/ m higher than the machine, also had smaller drilling rates (-,and ,1 m hῌ+). This e#ect is probably due to the factthat the ﬂow rate decreases when the pump sends
water to higher elevation. During drilling at BH1,
the machine often turned itself o# because the waterpressure dropped below the threshold.
The mean petrol consumption rate was +.2 l hῌ+ inboth ,**1 and ,**2, which corresponds approximately
to the result of our laboratory tests (+.3 l hῌ+). However, there is a signiﬁcant di#erence between themean diesel consumption rates on the glacier (0.3 l hῌ+)and in the laboratory (..1 l hῌ+). The former rate isalso +.1 times greater than that obtained at Haut Glacier d’Arolla (Hubbard and Glasser, ,**/), even though
our petrol consumption rate agrees with that experiment within 3*ῌ. It is not clear why drilling at
Rhonegletscher consumed more diesel than drilling at
Haut Glacier d’Arolla, although both pumps drew cold
water from supraglacial stream or melted snow andthe drillings conducted at a high altitude. If we takethe mean drilling rate observed in BH+-BH2 (.1 m hῌ+)and the consumption rates measured at Rhonegletscher as benchmarks, our system is able to drill +** mof ice in a little more than two hours with +..1 l ofdiesel and -.3 l of petrol.
After drilling, the boreholes were used to measuresubglacial water pressure, vertical strain, and borehole inclination. Samples of the subglacial sedimentwere also collected. The closure rate of a borehole iscontrolled by the water level, but most of the boreholes remained open to the bedrock for at least several
months (Sugiyama et al., ,**2).

..

Conclusion

A hot water drilling system was constructed capable of drilling up to ,** m through temperate ice.
The system generates a hot water jet with a temperature of 0*ῌ10῍ and a ﬂow rate of 3/*ῌ+*** m hῌ+ using+.0ῌ,./ mm diameter nozzles. The temperature ismostly controlled by the ﬂow rate, and slightly dependent on the hose length and nozzle diameter. In
laboratory tests, one meter of an ice block could be
penetrated in -* seconds.
The system was used at Rhonegletscher, Switzerland in the summers of ,**1 and ,**2. Eight boreholes with a total depth of 3,/ m were drilled in ,**1,

13

and twenty-four boreholes with a total depth of +++2 mwere drilled in ,**2. The mean drilling rates ranged
from ,1ῌ1* m hῌ+. The drilling rate decreased withthe borehole’s distance from the heater, owing to a
reduction in the water temperature. The drilling rate
was also dependent on relative elevation, as the waterﬂows more slowly to elevations higher than the pump.
The system consumed 0.3 l hῌ+ of diesel for the heaterand +.2 l hῌ+ of petrol for the pump.

Acknowledgments
We would like to thank K. Chubachi of the Institute of Low Temperature Science at Hokkaido University for designing and constructing the drilling stem.
K. Nakamura of Nakamura Service Inc., K. Hirayama
of Kärcher Japan Inc. and S. Asai of Martech Inc.
provided useful information on the high-pressure hotwater machine. We would like to thank D. Nishimura
and T. Yoshizawa of Hokkaido University for their
help in the ﬁeld. H. Blatter of IAC-ETH Zurich constructed the tripod and helped with the drilling on theglacier. M. Funk, A. Bauder, T. Wyder and membersof VAW-ETH Zurich provided materials for the ﬁeld
campaign and helped with transportation to the glacier. T. Sato of Hokkaido University helped in the laboratory experiments. We would like to thank R. Narusefor his helpful review comments and Scientiﬁc Editor
N. Naito for handling the paper.
This research was funded by the Japanese Ministry of Education, Science, Sports and Culture througha Grant-in-Aid for Young Scientists (Start-up),+22.***,, ,**0ῌ,**1 and a Grant-in-Aid for ScientiﬁcResearch C (Capital), ,*/.*.+2, ,**2ῌ,*+*. It was also
supported by an internal funding program of the Institute of Low Temperature Science at Hokkaido University, and by the Inoue Scientiﬁc Field Study Foundation.

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