G. Tartari et al. : GIS for Environmental Assessment
177
The initial aims of limnological research in high altitude lacustrine environments
in the Khumbu Valley - as resumed in Gosso et al., 1993 - were an evaluation of
the long-range pollution effect of rising anthropic influence, due to touring and
trekking, as achieved from trophic alterations in aquatic environments.
The possibility to join multidisciplinary research results, added other aims: evaluation of the possibilities and potentialities of this tool in environmental modeling.
The aims of this paper are:
a presentation of the lake cadastre in the study area and of
hydrochemical frames in lacustrine environments, used for qualitycharacterization modeling;
• a presentation of the basic decisional stages in the creation of a large
diffusion-allowing G.I.S., with low costs and small software/hardware
tool dimensions.
2
GEOGRAPHICAL AND GEOLOGICAL DATA BASE
The study area (Fig.I) is located in the Khumbu-Himal region, between 27°50'
and 28°01' latitude North and 86°45' and 86°59' longitude East and it is included
in the High Imja Khola basin. This area, about 440 km 2 wide, has been arbitrarily
chosen on the basis of the most recent available topographic map ("Mount
Everest" map, 1:50,000, National Geographic Society, Washington D.C., 1991). It
considers two large valleys formed by the Khumbu Glacier, starting from Everest
(8846 m), Lhotse (8501 m) and Pumori (7145 m) Mounts, and by the Nupse
Glacier, starting from homonymous Mount Nupse (7896 m). The study area is
about 35% covered by glaciers, and it lies between the thermic zero summer limit
(at about 5600 m) and an altitude of about 4100 m.
Localization, altitude, catchment limits, catchment area and lake area have been
defined for each lake - presented on topographic maps - except for glacier tongue
lakes. Three main morphological features, altitude distributions, lake and
catchment areas, are summarized in Figure 2. Most of the 64 environments studied
have an altitude ran~in~ from 5200 to 5600 m a.s.l. Usually lake areas are quite
small, at least 5 x 10 m, although their watershed areas are comparatively larger,
100-2500 x 10 3 m 2 .
From a climatic point of view the Khumbu Valley is characterized by a monsoon
seasonal type, less rainy than in other Himalayan regions. Indeed measurements
taken in the Periche station, located in the central part of the lake cadastre zone
(Fig. 1), indicate a mean annual precipitation of about 450 mmly; moreover 75%
of that value is related to the summer monsoon period only (Grabs and Pokhrel,
1993).
From a geo-lithological point of view there are three main formations involved in
assessed lake drainage basins. Two of them are early Paleozoic-Precambrian in age
- the Island Peak Complex and the Black Gneiss Formation - the other is
characterized by Moraines formed in Quaternary times (Bortolami et al.,1976).
177
The initial aims of limnological research in high altitude lacustrine environments
in the Khumbu Valley - as resumed in Gosso et al., 1993 - were an evaluation of
the long-range pollution effect of rising anthropic influence, due to touring and
trekking, as achieved from trophic alterations in aquatic environments.
The possibility to join multidisciplinary research results, added other aims: evaluation of the possibilities and potentialities of this tool in environmental modeling.
The aims of this paper are:
a presentation of the lake cadastre in the study area and of
hydrochemical frames in lacustrine environments, used for qualitycharacterization modeling;
• a presentation of the basic decisional stages in the creation of a large
diffusion-allowing G.I.S., with low costs and small software/hardware
tool dimensions.
2
GEOGRAPHICAL AND GEOLOGICAL DATA BASE
The study area (Fig.I) is located in the Khumbu-Himal region, between 27°50'
and 28°01' latitude North and 86°45' and 86°59' longitude East and it is included
in the High Imja Khola basin. This area, about 440 km 2 wide, has been arbitrarily
chosen on the basis of the most recent available topographic map ("Mount
Everest" map, 1:50,000, National Geographic Society, Washington D.C., 1991). It
considers two large valleys formed by the Khumbu Glacier, starting from Everest
(8846 m), Lhotse (8501 m) and Pumori (7145 m) Mounts, and by the Nupse
Glacier, starting from homonymous Mount Nupse (7896 m). The study area is
about 35% covered by glaciers, and it lies between the thermic zero summer limit
(at about 5600 m) and an altitude of about 4100 m.
Localization, altitude, catchment limits, catchment area and lake area have been
defined for each lake - presented on topographic maps - except for glacier tongue
lakes. Three main morphological features, altitude distributions, lake and
catchment areas, are summarized in Figure 2. Most of the 64 environments studied
have an altitude ran~in~ from 5200 to 5600 m a.s.l. Usually lake areas are quite
small, at least 5 x 10 m, although their watershed areas are comparatively larger,
100-2500 x 10 3 m 2 .
From a climatic point of view the Khumbu Valley is characterized by a monsoon
seasonal type, less rainy than in other Himalayan regions. Indeed measurements
taken in the Periche station, located in the central part of the lake cadastre zone
(Fig. 1), indicate a mean annual precipitation of about 450 mmly; moreover 75%
of that value is related to the summer monsoon period only (Grabs and Pokhrel,
1993).
From a geo-lithological point of view there are three main formations involved in
assessed lake drainage basins. Two of them are early Paleozoic-Precambrian in age
- the Island Peak Complex and the Black Gneiss Formation - the other is
characterized by Moraines formed in Quaternary times (Bortolami et al.,1976).