G. Tartari et al. : GIS for Environmental Assessment
181
The chemical composition of lake water is mainly characterized by calcium,
among cations, and by hydrogen carbonate and sulphate, among anions. On the
basis of these hydrochemical observations, the probable watershed lithology would
be dominated by limestone and gypsum. This conclusion does not include
complexity in hydrochemical phenomena nor other factors (morphometry,
vegetation cover, etc.) responsible for solution processes inside catchments.
In fact, the chemical analysis discrepancies between different lake waters are
probably due to different rock presences inside the catchment, to outcrop, plunge
and steep conditions and to dealing between on and under-surface waters. The
general occurrence of calcium values, higher in lake waters than in wet depositions,
as well as of hydrogen carbonate, cannot be directly related to lithologies crossed
by drainage basins.
This anomaly needs further geological field observations and analysis. The
magnesium and potassium concentrations, higher in most of the sampled lakes
than in wet deposition ones, are caused by the dominant presence of mica in the
gneisses and micaschists of the basal complex and in some moraine elements.
The high content of sulphate ions in lacustrine waters is probably related to the
presence of hydrothermal stage minerals, connected to the presence of granitic
dykes in the Black Gneiss Formation.
Finally, dissolved silicate, total phosphorous and total nitrogen concentrations are
also represented in Table 1. Collected values of the latter two parameters may
indicate that the majority of lakes are oligotrophic.
4
GEOGRAPHIC INFORMATION SYSTEM SETTLEMENT
To create a broad distributable G.I.S. we used the Auto Cad (Auto Desk) software
program, PC version, to digitize spatial data, and Access (Microsoft) software
program, PC version, to create a data-base collecting other data.
To realize the G.I.S. we integrated information obtained from three maps:
"Khumbu Himal", scale 1 :50,000 and the extracted "Mahalangur
HimallChomolonga Mount Everest", scale 1:25,000, edited by Schneider, Wien,
(1957); "Mount Everest", scale 1:50,000, by National Geographic, Washington
D.C. (1988). As a reference to digitized map we used the 1 :25,000 "Mahalangur
Himal" map integrated with a photostatic enlarged 1 :25,000 "Mount Everest" map.
We digitized all 100 m contour lines, and all 20 m contour lines near the mountain
tops, creating a layer. Both U.T.M. and Geographic coordinates were introduced
in it to allow an easier comparison between different maps. The available
geological map, "Geological map of the Upper Imjia Khola", scale 1 :25,000,
C.A.I./C.N.R.(1981), was digitized as a separate layer.
Other layers were created to represent rivers, lakes, watersheds, elevations of lakes
and mountains, toponyms.
181
The chemical composition of lake water is mainly characterized by calcium,
among cations, and by hydrogen carbonate and sulphate, among anions. On the
basis of these hydrochemical observations, the probable watershed lithology would
be dominated by limestone and gypsum. This conclusion does not include
complexity in hydrochemical phenomena nor other factors (morphometry,
vegetation cover, etc.) responsible for solution processes inside catchments.
In fact, the chemical analysis discrepancies between different lake waters are
probably due to different rock presences inside the catchment, to outcrop, plunge
and steep conditions and to dealing between on and under-surface waters. The
general occurrence of calcium values, higher in lake waters than in wet depositions,
as well as of hydrogen carbonate, cannot be directly related to lithologies crossed
by drainage basins.
This anomaly needs further geological field observations and analysis. The
magnesium and potassium concentrations, higher in most of the sampled lakes
than in wet deposition ones, are caused by the dominant presence of mica in the
gneisses and micaschists of the basal complex and in some moraine elements.
The high content of sulphate ions in lacustrine waters is probably related to the
presence of hydrothermal stage minerals, connected to the presence of granitic
dykes in the Black Gneiss Formation.
Finally, dissolved silicate, total phosphorous and total nitrogen concentrations are
also represented in Table 1. Collected values of the latter two parameters may
indicate that the majority of lakes are oligotrophic.
4
GEOGRAPHIC INFORMATION SYSTEM SETTLEMENT
To create a broad distributable G.I.S. we used the Auto Cad (Auto Desk) software
program, PC version, to digitize spatial data, and Access (Microsoft) software
program, PC version, to create a data-base collecting other data.
To realize the G.I.S. we integrated information obtained from three maps:
"Khumbu Himal", scale 1 :50,000 and the extracted "Mahalangur
HimallChomolonga Mount Everest", scale 1:25,000, edited by Schneider, Wien,
(1957); "Mount Everest", scale 1:50,000, by National Geographic, Washington
D.C. (1988). As a reference to digitized map we used the 1 :25,000 "Mahalangur
Himal" map integrated with a photostatic enlarged 1 :25,000 "Mount Everest" map.
We digitized all 100 m contour lines, and all 20 m contour lines near the mountain
tops, creating a layer. Both U.T.M. and Geographic coordinates were introduced
in it to allow an easier comparison between different maps. The available
geological map, "Geological map of the Upper Imjia Khola", scale 1 :25,000,
C.A.I./C.N.R.(1981), was digitized as a separate layer.
Other layers were created to represent rivers, lakes, watersheds, elevations of lakes
and mountains, toponyms.