Journal of Japan Society of Civil Engineers, Ser.
B1 (HydraulicEngineering),
Vol. JSCE,
68, No.Vol.56,
4, I_247-I_252,
2012.
Annual Journalof HydraulicEngineering,
2012, February

WATER BALANCE OF GLACIERIZEDCATCHMENTS IN TROPICS: A CASE STUDY IN
BOLIVIAN ANDES
Tong LIU1and Tsuyoshi KINOUCHI2
1Student Member of JSCE, M.Sc., Interdisciplinary Graduate School of Science and Engineering,Tokyo Institute of Technology (4259 Nagatsuta, Midori, Yokohama, Japan)
2Member of JSCE, Ph.D. Eng., Associate Professor, Interdisciplinary Graduate School of Science and Engineering,Tokyo Institute of Technology (4259 Nagatsuta, Midori, Yokohama, Japan)

On outer-tropical glaciers, mostly in Peru and Bolivia, ablation and accumulation occur all year
round whereas maximum in wet seasons. This study investigated glacier mass balance and catchment
scale water balance of Glacier Tuni and Huayna Potosi, which locate at the west side of Bolivian Andes.
Remote sensing and hydrological methods have been applied to conduct glacier mass balances monthly
and annually in recent years. With remote sensing method, glacier volume change has been derived basedon glacier area change obtained utilizing cloud free Landsat Thematic Mapper (TM) scenes. Results ofcommonly negative glacier mass balance have revealed that glaciers in this region are retreating. Despiteof interests on glaciological aspects, water balances of glacierized catchments have been carried out.
Except for in a few months glaciers got positive mass balance, glaciers continuously contributed todischarge.
Key Words: Glacier mass balance, water balance, tropical glacier, remote sensing

1. OBJECTIVE
Approximately 99% of tropical glaciers arelocated in South America which store large volumesof precipitation during wet seasons and gradually
release into rivers in dry seasons 1), 2). The dry Andes
in South America, where glaciers feed rivers all year
round, are the regions where most at risk fromglaciers melting due to climate change. The selectedglaciers in this study, Glacier Tuni and Huayna
Potosi in Bolivian Andes are the major water
resources for the two main cities nearby, La Paz and
El Alto. The rapid glacier retreat may lead to water
shortages for millions of local residents depending
on glacier melting water in the way of drinking andhydroelectric power. Therefore, glacier mass balance
and water balance of glacierized catchments in thisregion are essential to estimate water availability forthe future. In addition, catchment-scale waterbalance will become significant after the glaciers
retreat or complete disappearance. Therefore, waterbalance characteristics are also need to be clarified.
Previous studies in Bolivian Andes focused on
Glacier Zongo which has been under a glaciologicalprogram by the Institut de Recherche pour leDéveloppement (IRD), France since 19913), 4).
Previous studies showed great interests in energybalance of glacier surface5), glacier mass balance4),
or runoff directly from glacier 3). Three main
methods have been applied to assess glacier massbalances using glaciological data3), hydrologicaldata4) and geodetic data6). Hydrological analysis has
been performed to compare mass balance derived
from glaciological and hydrological methods,
concluded that hydrological method gives lower
mass balance than glaciological method7). Later
studies utilized photogrammetric data to reconstruct
the cumulative glacier mass balance and achieved
satisfactory agreements6). However, for Glacier Tuniand Huayna Potosi that this study concerns, there
are either field measurements available for
glaciological methods or high resolution aerial
images with short time intervals for geodetic
methods. Therefore, an independent method
utilizing satellite images has been developed in thisstudy to assess glacier mass balance comparing withhydrological method. Another purpose is to obtainwater balance of the glacierized catchments. There

I_247

are few studies working on the catchment-scalewater balance in tropical glacierized regions.

temperature and discharge of Huayna Potosi
catchment are shown in Fig. 2.
Temperature(℃ )2. STUDY AREA

Discharge (m3/s)

1.0
0.0
-1.0
Air Temperature

-2.0
0.5

Discharge

250

0.4

Precipitation

200

0.3

150

0.2

100

0.1

50

0.0

0

Precipitation(mm)Glacier Tuni and Huayna Potosi are located in theSouthern part of Cordillera Real, Bolivia (16°S,
68°W), 30km north of La Paz, with dry Altiplano in
the west and wet Amazon in the east. Tunicatchment is 9.78km2 with about 7.50% covered byglaciers, while Huayna Potosi catchment is 7.99 km2
with about 22.88% of its area glacierized. The
catchments with altitudes ranging from 4400 m to6000 m a.s.l have been covered by Landsat TM
scenes available online since 1980s (Fig. 1).

2.0

Fig.2 Precipitation, discharge and air temperature of Huayna
Potosi from Sept. 2005 to Aug. 2006

3. METHODOLOGY
Glacier mass balances of Glacier Tuni and
Huayna Potosi and water balances of eachcatchment have been constructed respectively in
2000s using remote sensing and hydrological data.

Tuni
Huayna Potosi(1) Remote sensing method
Catchment boundaries have been identified andconducted using ASTER 30m Global Digital
Elevation Model (DEM) data.

La PazFig. 1 Overview of the study region(Landsat TM with RGB=432, July 26th, 2008)

The meteorological conditions of the region aredetermined by seasonal oscillation in theintertropical convergence zone (ITCZ). During
winter, the ITCZ is north of Bolivia and tropical
anticyclones produce a cold and dry season, whereas
in summer, from December to March, is the wet andwarm, coinciding with the eastern intertropical fluxthat brings water vapour from the Atlantic 4). Theintertropical zone has been further distinguished into
two regions: the inner tropics with almost no
seasonality in precipitation and the outer tropics
with strong seasonality in precipitation2). The
meteorological differences have greatly influenced
glacier mass balance. In the inner tropics, bothaccumulation and ablation occur throughout theyear. In the outer tropics, accumulation andice/snow melt occur mainly during wet seasons.
During dry seasons, ice/snow melt reduces andice/snow sublimation increases8), 9). Glaciar Tuni and
Huayna Potosi focused in this study are located in
the outer tropics 9). Examples of precipitation, air

I_248

b

a

Tuni Bajo
Tuni Altoc

Tuni
HuaynaPotosi

Zongo

Fig. 3 Glacier outlining (a:Tuni,b:Huayna Potosi) by L4/L5>5
comparing to ALOS image (c)Glaciers have been identified with scenes ofLandsat TM. The individual bands TM4 (near infrared: 0.76 – 0.90μm) and TM5 (mid - infrared:
1.55 – 1.75μm) of Landsat TM have been converted
to at - sensor spectral radiance (Lλ) 10). Band ratio
L4/L5 when greater than 5 has been proved to bebetter suited threshold value in outlining glaciermaps validated by comparing to ALOS AVNIR-2
images (Fig. 3)11). This method has well defined
glacier under the shadow according to the false
color composite by ALOS and field observation.
The accuracy of remote sensing method depends ondata process, which has been evaluated within 5%
by comparing to true value.
Methods of converting glacier area to volume
have been proved to have satisfactory agreementwith field measurements12) (Fig. 4). Glacier areas
obtained in our study region ranging from 0.68 to
1.85 km2, which lay within the scale of previous
study observed; therefore the relationship shown in
Fig.4 were used in this study.
100
Bolivian glaciers

750

1
y = 0.0484x1.36

0.1

Zongo+37%

Nov-2003 to Mar 2004 Zongo+37%

Tuni Bajo

650

Relationship between precipitation and elevation
Huayna Potosi

0.001
0.00010.00001
0.01

Nov-2003 to Mar-2004

700

600

0.01

Precipitaiton/mm

Volume (km3)

10

Precipitation measurements directly affectglacier mass balance.Therefore, precipitation
data need to be calibrated or validated.
As shown in Fig. 3, there are three rain gauges
in Tuni catchment and one in Huayna Potosi
catchment. Besides, data from a rain gauge in Zongo
is just on the other side of Huayna Potosi.
Furthermore, among all the rain gauges in the study
region, Tuni and Zongo have continuous
measurements while others rarely have records after
2004. Consequently, in order to testify the datareliability and find out if there is any relationshipbetween precipitation and elevation, data from other13 stations have also been utilized.
Precipitation records from November 2003 to
March 2004 have been plotted in Fig. 5 forcomparison. There are two main reasons of data
selection. One is that data from all stations areavailable during this period of time. Another reason
is that historical data showed that over 80% of
annual precipitation occurred from November toMarch in this region.

Area (km2)

0.1

1

10

100

550

Tuni Alto
Vino Tinto
Chuquiaguillo
El Tejar
El Alto Aasana
Collana
ViachaSan Calixto
Villa Adela
Tuni
Achocalla
Villa Nueva
La Paz Central
Pasanker

500
450
400

Fig. 4 Relationship between glacier area and volume in
Bolivian Andes12)350(2) Hydrological method
By neglecting the amount of ice and snow lostby sublimation, the glacier mass balancecan becalculated from the difference between precipitationand discharge out of basin7):

250

300

Where
is the glacier area (m2),is the2basin area (m ),is the discharge out of the basin(m3year-1) and is the runoff coefficient (ratio of
runoff to precipitation) of the non-glacierized surface.
is the average of the precipitation in the basin.
In this study, the value 0.8 has been used for
runoff coefficientof the area not covered by
4)
glaciers . According to field observations, most of
the regions are covered with almost impermeable
rocks. Therefore, the value 0.8, which was roughly
estimated in previous study4), is reasonable though
the uncertainty of which remains unknown. Large
value ofdecreases the fraction of discharge
coming from glacier melting and increases theglacier mass balancein equation (1).

y = 0.1206x - 9.9094
R² = 0.5174

Mecapaca

Zongo

Palca
Elevation/m

Fig. 5 Relationship between precipitation and elevation

There are three points worth noticing in Fig. 5.
(a) Tuni, Tuni Alto and Tuni Bajo are locatedbeside each other at the same elevation, but
Tuni Bajo had much more precipitation than any
other rain gauges. Hence, data from Tuni Bajo
have been considered unusual and been ignoredin this study.
(b) Rain gauge Tuni has been measured andrecorded monthly by Institut de Recherche pourle Développement (IRD) (GLACIOCLIM: http://www-lgge.ujf-grenoble.fr/ServiceObs/index.htm) that may have missing readings.
(c) Previous study revealed that the rain gauge
P4750 in Zongo basin have underestimated
precipitation by 37% 6). Zongo data with 37%
increase has been added to Fig. 5, whichappears to be larger than Huayna Potosi. This
result is reasonable since Zongo locates in theeast side of Andes with wet Amazon aside,
while Huayna Potosi has dry Altiplano aside.

I_249

which have just agreed with the characteristics ofglaciers in outer tropics, i.e. glacier melting occurs
mainly during wet season from October to March,while during dry seasons melting decreases andsublimation increases. As the sublimation has notbeen considered in this study, we may only observe
melting decreases during dry season. Moreover,both glaciers had negative mass balance most of themonths, while only a few had positive value. These
results have been supported by the fact that tropicalglaciers has been retreating in decades2).
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1
-1.2

Glacier mass balance(m/month)

To sum up, data from Tuni has been raised
14.58% to Tuni Alto as precipitation for Tuni
sub-catchment. While Zongo data has been adjusted
30.87% to Huayna Potosi as precipitation foranalysis in Huayna Potosi catchment. Moreover,there has been an obvious increasing trend of
precipitation as elevation goes up. The twocatchments have been divided into 100m elevation
zones afterwards in order to reflect dependency on
elevation. Eventually, the in the equation (1) is thearea-averaged precipitation of the whole catchment
derived from different elevation zones.
(3) Water balance of the catchments
By considering the water catchment as a basic
hydrologic system, the total volume of water
discharging from a catchment is equal to the volume
of water entering the catchment plus a change instorage. In this study, discharge ( ) leaving thecatchment were used, whereas the only input isprecipitation ( ). Losses from the system include
evaporation/sublimationand groundwater
recharge ( ). The change in storage is considered
to be a gain or loss of glacier volume ( ), where aloss of glacier volume contributes to . Thus thewater balance is expressed as:

In this study, the catchments consist mainly
impermeable bedrock, thus groundwater recharge( ) can be ignored. The water balance can be
simplified and rearranged to consider the glacial
meltwater contribution to stream discharge as thechange in the storage .
(3)

Sept. Oct. Nov. Dec.
Glacier mass balance(m/month)

0.4
0.2
0

-0.2
-0.4

Huayna Potosi-0.6

Sept. Oct. Nov. Dec.

2004-2005
2005-2006
Jan. Feb. March April May June July Aug.

Fig. 6 Glacier mass balance by hydrological method

Glacier mass balances deduced from hydrologicalmethod are strongly related to precipitation so thatprecipitation has been plotted with glacier massbalance in Fig. 7 as reference. Both graphs in Fig. 7
indicate that during wet season, precipitation is
maximum value while melting also achieves peaknegative value through the year. Besides, as shownin Fig. 2, air temperature in high altitude Andes
ranges from -2 to 5°C all year round that it
contributes to glacier melting in less direct way.
2
1.5

Tuni

1

Glacier mass balance
Precipitation

150

100
50

0.5
0

0

-0.5

-50

-1

-100

2
1.5
1

0.5
0

-0.5
-1

Huayna Potosi

Glacier mass balance
Precipitation

230
180
130
80
30
-20
-70
-120

Precipitation (mm)Glacier mass balance(m/month)

3. RESULTS AND DISCUSSION(1) Glacier mass balance by hydrological method
Hydrological year starts from September in
Bolivia. In this study, precipitation and discharge of
Glacier Tuni have been measured from September
2000 to August 2004, September 2004 to August
2005 and September 2006 to August 2007. While
the measurements of Glacier Huayna Potosi coveredfrom September 2004 to August 2006.
As shown in Fig. 6, both Glacier Tuni and
Huayna Potosi have marked seasonal variations ofglacier mass balance within each hydrological year,

Jan. Feb. March April May June July Aug.

Precipitation (mm)Measurement of(m3s-1) and precipitation ( )are concerted to a depth measure (mm) to comparewith other variables. Likewise,
calculated byremote sensing or hydrological methods illustrated
above is also converted to a depth covering thewhole catchment.

Tuni

0.6

Glacier mass balance(m/month)(2)2000-2001
2001-2002
2004-2005
2006-2007

Fig. 7 Glacier mass balance by hydrological method in
2004-2005 comparing with precipitation(2) Glacier mass balance by remote sensing
methodFig. 8 has shown annual glacier mass balances

I_250

of Glacier Tuni and Huayna Potosi by comparing
results from remote sensing and hydrologicalmethod. Results obtained from both methods
showed no significant difference except for thevalues of Tuni from 2001 to 2002 and values of
Huayna Potosi from 2004 to 2005. According tomonthly glacier mass balance deduced fromhydrological method (Fig. 6), during thehydrological year 2001 to 2002, Glacier Tuni had
positive and negative mass balance fluctuated frommonth to month that the net mass balance over theyear was small comparing to other years. In
addition, tropical glaciers are highly sensitive toclimate conditions, e.g. El Nino and La Nina events,
variation of solar radiation, wind velocity, humidity
etc., which may have impacts on glacier massbalance to some extent. Glacier Huayna Potosi had
an unusual low precipitation in 2004 to 2005 (Fig.
6), which may due to data loss or catch deficiency ofrain gauges especially for solid precipitation. In
such condition, with the less precipitation and usual
discharge, glacier melting has been regarded toincrease as the source of discharge.

dry seasons, while in both Fig. 9 and Fig. 10,
evaporation was large during wet seasons.
(4) Annual water balance of the sub-catchments
According to Fig. 11, there is no significant
difference among years in the proportional of eachcomponent of annual water balances of Tunicatchment, which has 7.50% of its area occupied byglacier. Consequently, although glaciers account forwater resource to some degree, taking long views,
precipitation is the primary input to the catchment
and dominates the long-term variation trend.
In the catchment of Huayna Potosi, the glacierscover 22.88% of its area. Under such circumstances,glaciers may participate and influence water balance
more. However, there are no enough data to
sufficiently prove this hypothesis.
Sept.
Nov.
Jan.
March
May

2000-2001 2001-2002 2004-2005 2006-2007 2004-2005 2005-2006

Glacier mass balance(mm/year)0

Water Balance_Tuni
2000-2001
-300
-200
-100

-100
-200
-300

Tuni_remote sensing method-400

Tuni_hydrological method-500

Huayna Potosi_remote sensing method-600

Huayna Potosi_hydrological method

July
0

100

200

300 Sept.

Nov.
Jan.
March

Fig. 8 Glacier mass balance by two methods

May

As discussed above, both methods haveadvantages and disadvantages. Remote sensing
method is not precise enough to perform analysis
within short intervals, but since it is not affected by
precipitation and other meteorological data, as wellas catchment parameters, it can be analyzed as anindependent term. Although hydrological method isstrongly affected by precipitation or runoff
coefficient, field measurements can be used for
frequent and intensive studies.
(3) Seasonality of water balance
Fig. 9 showed monthly water balance of thecatchments as equation (3) illustrated. The left side
terms are going out of the hydrological system while
the right side terms are flowing into the system. In
some months, glaciers got positive variations whichindicated that accumulation was larger than ablationin that month although accumulation and ablation
occur simultaneously in tropical glaciers. According
to Fig. 9, glacier accumulated during such months
when precipitation is large, discharge is small.
Evaporation is also noticeable, which generally is
considered to be small in wet seasons and large in

I_251

Water Balance_Tuni
2001-2002
-300

-200

-100

July
0

100

200

300 Sept.

Nov.
Jan.
March
May
Water Balance_Tuni
2004-2005
-300

-200

-100

July
0

100

200

300 Sept.
Nov.
Jan.
March
May

Water Balance_Tuni
2006-2007

-300

-200
-100
Precipitation
Runoff DepthJuly
0 (mm) 100
200
300
Glacier mass balance
Evaporation

Fig. 9 Seasonal variations of water balance (Tuni)

Sept.

although glaciers account for water resource to somedegree, taking long views, precipitation is theprimary input to the catchment and dominates thelong-term variation trend. For the next step, runoff
coefficient needs to be survey and verified.

Nov.
Jan.
March
May

Water Balance
Huayna Potosi
2004-2005
-250

-150

ACKNOWLEDGMENT: This study was carriedout by project Glacier Retreat impact Assessment
and National policy Development (GRANDE)
supported by Science and Technology ResearchPartnershipforSustainable
Development(SATREPS) funded by JST and JICA.

July
-50

50

150

250

Sept.

Nov.
Jan.

March
May

Water Balance
Huayna Potosi
2005-2006-250

REFERENCES

July

-150
-50
Precipitation
Runoff Depth

50 (mm) 150
250
Glacier mass balance
Evaporation

Fig. 10 Seasonal variations of water balance (Huayna Potosi)
2006-2007
2004-2005

Tuni
2001-2002
2000-2001

HuaynaPotosi

2005-2006
2004-2005

-1500

-1000

Precipitation-500
Runoff Depth

0 (mm)

500

Glacier mass balance

1000

1500

Evapotation

Fig. 11 Annual water balance in the two catchments

4. CONCLUSION
This study investigated glacier mass balance andwater balance of Glacier Tuni and Huayna Potosi,
which locate at the west side of Bolivian Andes.
Remote sensing and hydrological methods havebeen applied to obtain glacier mass balance andcatchment scale water balance. Results suggest that
remote sensing method is less affected bymeteorological factors but this method is suitable
for long-term cumulative glacier mass balance
study. On the contrary, hydrological method is
sensitive to precipitation and discharge but reliablemeasurements enable it to carry out frequent andintensive analysis. Glacier mass balance in the study
region behave as seasonal variations and had
negative mass balance most time of the year.
Meanwhile, water balances of the two glacierizedcatchments have been obtained monthly andannually. Except for in a few months glaciers got
positive mass balance, glaciers continuously
contributed to discharge. Tuni, with 7.50% of its
area glacierized, has no significant difference inannual water balances among years. Consequently,

1) Kaser, G.: A review of the modern fluctuations of tropicalglaciers. Global Planet. Change, 22(1–4), 93–103. 1999.
2) Kaser, G., and Osmaston, H: Tropical Glaciers, Cambridge
University Press, 2002.
3) Francou, B., Ribstein, P., Saravia, R., Tiriau, E.: Monthly
balance and water discharge of an intertropical glacier:Zongo Glacier, Cordillera Real, Bolivia, 16°S. Journal of
Glaciology, 41(137), pp.61-67, 1995.
4) Ribstein, P., Tiriau, E., Francou, B., and Saravia, R.:
Tropical climate and glacier hydrology: a case study in
Bolivia. Journal of Hydrology, 165, pp. 221-234, 1995.
5) Wagnon, P., P. Ribstein, B. Francou and B. Pouyaud.:
Annual cycle of energy balance of Zongo Glacier,Cordillera Real, Bolivia. Journal of Geophysical Research,104(D4), pp. 3907–3924. 1999.
6) Soruco, A., Vincent, C., Francou, B., Ribstein, P., Berger,
T., Sicart, J.E., Wagnon, P., Arnaud, Y., Favier, V., Lejeune,Y.: Mass balance of Glaciar Zongo, Bolivia, between 1956
and 2006, using glaciological, hydrological and geodetic
methods. Annals of Glaciology, 50, 2009.
7) Sicart, J.E., P. Ribstein, B. Francou, B. Pouyaud and T.
Condom: Glacier mass balance of tropical Glacier Zongo,
Bolivia, comparing hydrological and glaciological methods.
Global Planet. Change, 59(1-4), pp. 27-36, 2007.
8) Kaser, G.: Glacier–climate interaction at low latitudes.
Journal of Glaciology, 47(157), pp. 195–204, 2001.
9) Favier, V., Wagnon, P. and Ribstein, P.: Glaciers of theouter and inner tropics: a different behaviour but common
response to climatic forcing. Geophysical Research Letters,
31(16), L16403. 2004.
10) Chander, G., Markham, B., & Helder, D.: Summary of
current radiometric calibration coefficients for Landsat MSS,
TM, ETM+, and EO-1 ALI sensors. Remote Sensing ofEnvironment , 113, pp. 893–903, 2009.
11) Liu, T., Kinouchi, T., Asaoka, Y. and Mano, A.: GlacierRetreat Study in Bolivian Andes Utilizing Remote Sensing
and Water Balance Analysis, Asia Oceania Geosciences
Society (AOGS) 8th Annual Meeting and Geosciences
World Community Exhibition, Taipei, Aug. 201112) Klein, A. G., and Isacks, B. L.: Alpine glacial
geomorphological studies in the central Andes using
Landsat Thematic Mapper Images, Glacial Geology andGeomorphology, rp01/1998, 1998.
(Received September 30, 2011)

I_252