Mountains
of the World
A Global Priority
Edited by B. Messerli and J. D. Ives
A CONTRIBUTION TO CHAPTER 13 OF AGENDA 21
Editorial Advisory Committee
Jayanta Bandyopadhyay, Francesca Escher
Lawrence S. Hamilton, Pauline A. Ives,
and Martin F. Price
IDRC
@
~
~HH~ ~
W
CRDI
~~
~~
This publication has been made possible by grants from:
SDC Swiss Agency for Development and Cooperation; UNU Programme: Mountain
Ecology and Sustainable Development; UNESCO International Programmes on
Man and the Biosphere and Geological Correlation; FAOTask Manager for
Chapter 13,Agenda 21; IDRC International Development Research
Centre, and CIp' International Potato Centre
The ParthenonPublishing
Group
International Publishers in Medicine, Science & Technology
--
NEW YORK LONDON
Highland waters - a resource of 7
global significance
J. Bandyopadhyay, J. C. Rodda, Rick Kattelmann, Z. W. Kundzewicz, and
D. Kraemer
INTRODUCTION
research agenda and recommendations for water-
Background shed management as an approach to addressing
problems of mountain water resources.
Almost all the world's major rivers, and many of
the minor ones, begin in mountainous regions and
supply a large percentage of the water resources of Hydrological characteristics
the entire globe. Countries that contain significant
From the hydrological point of view, mountains
areas of mountains are usually well blessed with
present a paradox. Although they are the source of
water resources, often much of it initially in the
the greatest part of the world's water resources,
form of snow and ice. Rivers draining the moun-
knowledge of the hydrology of mountains is gener-
tains convey a share of these resources to neigh-
ally much less extensive, reliable, and precise than
bouting nations through the basins that they oc-
that of other physiographic regions. And it is this
cupy jointly. In the arid and semi-arid areas of
knowledge on which the assessments of water re-
western Asia and Latin America, the juxtaposition
sources are based. Indeed, some authorities con-
of well-watered mountain ranges and dry plains
crossed by rivers draining from the mountains, sider that mountain regions represent, in practical
highlights this point. Even in temperate parts of the terms, 'the blackest of black boxes in the hydro-
logical cycle'. Only their output is known to any
globe, downstream countries depend on mountain
areas in upstream countries for much of their water degree of exactitude. Yet mountain hydrology is a
challenge to researchers and practitioners wishing
resources. The earliest civilisations, Egypt, Me-
to improve their understanding. Hydrological stu-
sopotamia, and China, for example, owed their
dies in mountain areas are often pursued under the
existence to copious water resources provided by
various programmes of representative and experi-
the rivers flowing trom the mountains upstream,
mental catchments. Significant failures of hydraulic
particularly in the form of annual floods. In these
engineering projects in mountain areas are rela-
and later civilisations, water was esteemed because
tively common when the projects have been de-
it was thought to be endowed with special life-
signed with only the sketchy data that are normally
giving powers. For example, in the case of the Celts,
available. Within a few years, or decades, the an-
who inhabited much of Europe prior to the Ro-
nual runoff or flood magnitudes may turn out to
mans, water was basic to their rituals and practices,
be much different than those anticipated.
a position it occupies today in a number of re-
The particular form and structure of mountain
ligions.
areas provide most of them with three important
This chapter examines the role of mountains
hydrological attributes:
with respect to water resources. It discusses how
these resources are assessed and some of the prob- (1) Temporary storage in the form of snow and V-
lems involved. It briefly mentions floods and ice that brings about a delay in runoff. Snow
droughts in the context of mountain communities. cover built up in the higher regions during the
The health of aquatic systems in terms of human winter months melts in the spring and con-
impacts and prospects for sustainable development tributes the largest volume of water on a sea-
of mountain water resources are discussed in the sonal basis to river flows and, in particular
following sections. The chapter concludes with a areas, to ground water recharge.
131
MOUNTAINS - A GLOBAL PRIORITY
'\
}
1000- 3OOOm
- Ml\iorRiver
-IDOO- Mean Annual Precipi1ation(mm)
1
Figure 7.1 Global distribution of precipitation in relation to mountain ranges
132
HIGHLAND WATERS
133
MOUNTAINS - A GLOBAL PRIORITY
,/
(2) Natural lakes and man-made storage reserv- construct of the distribution of observing sites. On
oirs in mountain areas may be used for a leeward sides of mountains precipitation gradients tl~"J
number of purposes, but especially for water are usually less steep, distribution patterns are more
supply, irrigation, power generation, and variable, and significant areas can be found with
flood control. The runoff retained to reduce low totals in 'rain shadows'. Of course, there are
flooding downstream can be employed later some mountains where there are not clear-cut
and beneficially. windward and leeward sides and where the pat-
~3) Potential energy that can be utilised to terns of precipitation do not exhibit such obvious
generate hydroelectricity. A number of coun- differences. Figure 7.1, showing the global distribu-
tries meet much of their demand for electricity tion of annual precipitation totals, illustrates these
in this way: Norway, Switzerland, and points on the macro-scale. It also demonstrates that
Canada, for example. mountains have a significant effect on the distribu-
tion of the world's climatic zones, not only in terms
The importance that mountains enjoy, in terms of of precipitation but also for other va,iables. On the
water resources, derives principally from the en- micro-scale, mountains can also cause large differ-
hanced precipitation that they engender due to the ences in climate, and these effects can be of consid-
uplift and ascent of moist air over them. This erable economic importance.
orographic effect results from the operation of A unique feature of mountain regions is the large
several meteorological mechanisms, which may act amount of cloud. In some semi-arid areas, substan-
singly or together, according to the circumstances. tial amounts of water are harvested from these
"
Part of this enhanced precipitation falls as snow at clouds, but their role is probably more significant j
higher altitudes and latitudes, resulting in glaciers in humid mountain areas, particularly where for- '~
and ice sheets at locations where conditions favour ests are present. There the forest canopy (Chapters
/ the process of firnification. The exact relation be- 13 and 15), continually wetted by moisture inter-
tween precipitation and altitude varies consider- cepted from the cloud, can alter net precipitation
ably in different parts of the world, depending on and evaporation rates much more than short stat- '
the volume of moisture in the air and its tempera- ure vegetation and, in turn, it alters the water
ture, the steepness of the ascent, the mechanism (or balance. The presence of clouds also reduces the
mechanisms) operating, and several other factors .,
such as time of year. However, within the extensive
incoming radiation and consequently, depresses
rates of evaporation. In contrast to precipitation,
I
literature on this topic, most results fall in the range the literature is sparse on the relation betwe~n
between 0.05 mm and 7.5 mm per metre for the evaporation and altitude. However, it seems logical
uniform increase in annual precipitation totals with to a~sume that evaporation decreases with altitude,
altitude on windward slopes. There is also a range although all the main controls do not respond in
of altitudes in some mountain ranges within which the same way (Lang, 1981). For the Alps, evapora-
maximum precipitation occurs; this is usually be- tion/altitude relationships show gradients from
tween 1500 and 4000 m, with totals decreasing 0.07 mm to 0.36 mm per metre for annual totals.
above these levels, although this topic is subject to The precipitation that reaches the ground,
considerable debate and the inference may be a liquid or solid, is partitioned over time between
Box 7.1 Switzerland - The water tower of Europe
Switzerland, a small mountainous country in south- them in the basins of the Rhine and Danube. Within
central Europe, is sometimes called the water tower Switzerland, 136 km3 of water is stored in lakes and
of the continent. The country receives on average reservoirs and a further 74 km3 in glaciers, sufficient
1450 mm of precipitation annually, which amounts water to maintain river flows for almost 5 years in
to some 60 km3 of water. It supplies four major the absence of further precipitation. There are simi-
European rivers with much of their flow - the Rhine, larly-placed countries and regions in other parts of
the Rhone, the Danube, and the Po. These four rivers the world, but the data from them are not sufficiently
and a number of smaller ones, carry 67 percent of reliable to enable similar assessments to be made to
this water across the borders of Switzerland into the the same precision.
neighbouring countries, namely France, Germany, Source: John Rodda,
Austria, and Italy, and to the other countries below President IAHS, Yngslas, UK
134
~
HIGHLAND WATERS
evaporation, saturated and unsaturated subsurface tains will be less able to meet the demands for water
flow, and overland flow, the relative magnitude of resources than in the past.
each component being largely determined by the Pressures on water resources in mountains were
nature of the particular surface, including factors initially associated with development of natural
., such as gradient and soil depth. When typically thin resources, such as, minerals, forest products, agri-
j , mountain soils are saturat:d, frozen, or replac~~by culture, and water itself. More recently, they have
, Dare rock, overland flow IS enrurncecl.-WgetatlOn resulted from continued expansion of settlements,
type, areal ext~nt, and canopy 1ienslry can: affect agriculture, transportation corridors, and also
nycrrorogiZ-~esponse. Coniferous trees, for ex- from the growth of leisure pursuits, particularly
~Ie, can intercept precipitation, modify micro- winter sports (Chapter 12). These activities occur
climate and local energy balance, alter evaporation within mountain regions, but in recent years,
rates, and delay snow melt. Trees alter soil condi- mountains have been subject to increasing pres-
tions via their litter, roots, and soil moisture uptake sures generated from outside, with air pollution
and affect the pattern of overland and subsurface and acid rain being prime problems. Cloud droplets
J flow and the time taken for the concentration of charged with emission products, such as sulfur
these flows into the network of stream channels compounds, are intercepted by the forest canopy,
(Chapter 15). Except where deep percolation and particularly conifers. Deposition of these products
ground water recharge occur, mountains ensure a occurs in large volumes due to the increased
high specific runoff, the basis of their importance precipitation, while the process of acidification is
in water resources terms. Runoff efficiency (steam- further enhanced because of the lack of soil buffer-
ing in many mountainous regions and the existence
J flow as a proportion of total precipitation) gener-
of acidic granitic bedrock over wide areas.
- )
~ \ally increases with increasing altitude and increas-
ing precipitation. Mountain catchments, even Within mountain regions, production of miner-
when undisturbed, are also effective producers of als causes water quality problems through removal
sediment, the other principle constituent of stream- of vegetation, soil disturbance, mine drainage,
flow. Some runoff from mountain areas may result washing of products, and leaching from the heaps
from glacier melt at higher locations where the of waste. These difficulties can continue long after
configuration of the topography allows this type of the mining has ceased (Chapter 9). Clearing of
storage, but seasonal snow melt is a feature of more forest for roads, agriculture, residential develop-
- widespread significance. These factors, together
J with others such as aspect, exposure, the presence
ment, or ski runs, can also change the quality of
mountain rivers and streams, especially by increas-
I
of peat and natural pipes, endow mountain regions ing the volume of sediment transported (Chapter
with a variety which other physiographic regions 15). In addition, forest felling changes the volume
may lack. This hydrological heterogeneity provides and distribution of runoff. The most noticeable
) a basis for many of the features that attract effect is that storm runoff is more rapid and con-
mankind to mountain regions: it is also the source centrated within a shorter period of time, while
of most of the hazards which endanger human over longer periods the total volume of runoff is
occupancy of mountains (Chapter 16). increased, until the vegetation cover regrows.
When forests are not allowed to regenerate and
when conversion to other land uses is semi-per-
Human impacts manent, hydrologic impacts persist. Roads are a
Mountains may appear to offer a pristine environ- particularly significant conversion because vegeta-
ment, one free from the problems of lowlands and tion is eliminated, soils are severely compacted and
other regions. However, this impression is not true. effectively sealed, natural slope drainage is inter-
In most parts of the world, mountains are presently rupted, routes are often located in the riparian
subjected to intense pressures from human activity, zone, and the road network may occupy a substan-
pressures that will rise as the population of the tial proportion of a catchment. Building and con-
Earth explodes and mobility increases so that re- struction can cause similar problems locally, while
moteness is no longer a safeguard. Most of these water pollution can result from the discharge of
J
pressures act on the hydrological cycle to change untreated waste from settlements and drainage
the quantity and quality of water yield and these from paved surfaces. Human activities that occur
changes, in turn, have impacts on other sectors. within and near streams have much greater hydro-
One major consequence is that in the future moun- logic impact than those located well away from
135
MOUNTAINS - A GLOBAL PRIORITY
-,I B
~
"F
-~ "~
't:"< " ,r"
. ~-,,> 'y ,
Plate 7.1 Dam and Lake Oberaar
(2303 m) with the calving glacier. This
lake is part of a complex system of
altitudinal lakes and power plants in the
high mountain region of the Grimsel Pass,
Switzerland (Photograph: KWO, Bern)
watercourses. Because the dimensions of the water what is available for use; mountain water resources
balance for mountains are generally larger than for are no exception. Water resources assessment
j other physiographic regions, and gradients are
( much steeper, the loads of materials transported are
usually greater, causing the degradation of basins
programmes consist of a number of components:
collection of hydrological data; collection of data
about the basins where the assessment is being
to proceed more rapidly. Leaching of nutrients made, such as data on geology, vegetation, and
takes place at a greater pace, impoverishing the soil soils; and the application of scientific methods for
and polluting the receiving waters. These condi- using these data in the assessment (WMOIUN-
tions have obvious consequences for the sustaina- ESCO, 1991). Education, training, and research
bility of mountain ecosystems. are often parts of such programmes. Networks of
instruments have to be established to collect the
hydrological data and they must be operated con-
ASSESSMENT OF MOUNTAIN WATER tinuously to record the main variables, namely:
RESOURCES l2£eciEitation. exaporation, river flow. soil m..2is-
!!Ire~rot.!nd »,ateLcontent. and_storage in lakes
Methodology
- ---
and reservo irs an.d_assnow and ice. These netWOrks
,
Water resources, world-wide, can neither be pro- ;Ind allied observations .c@ a!§o collect data on
tected nor managed rationally without the continu- ~ter quality.aDd..the.transport and deposition of
ing assessment of their quantity and quality, and ~imel}t. Remotely-senseddata from satellites and
136
