Pokhara has been crammed by splendid variety of natural beauties. The majesitc and panoramic view of Mt. Annapurna ranges, enchanting scenes of the lakes, terraces covered by colourful floras, playgrounds of endangered mammal species and pheasant birds, and running of sacrosanct streams are the distinct characteristics of Pokhara valley. Likewise, Pokhara valley is a harmonious confluence of different ethnic communities having rich cultures and traditions. It is a famous destionation of international and national tourists and holiday makers. It is an emerging city with modern infrastructure development at fastest rate.
1. Locaton and extent :
Pokhara valley is located in between 27055′-28023′ north latitude and 83048′-84011′ east longitude. This valley is extended about 50 km from north Bharabhuri village to the south Bhimad village in Tanahun district. The shape of the valley looks like meandering or alphabet ‘Z’ shaped. The whole Pokhara valley accounts 850 square km area, and Pokhara sub-metropolitan city commands only 55.66 square km, and Lakhnath mumicipality has 77.75 square km. The northern and southern part of the valley are narrowed and central part is broadened. Most of the settlement and functions are confined on the same broadend area.
2. Geomorphic Configuration:
The location between the southern laps of the Mt. Annapurna ranges, Mt Machhapuchhre and green hill terraces resemble Pokhara an Intermontane valley. The valley is blending of different landscapes, it has congergated snow-clad high mounmtains, alpine mountains, breath taking gorges, terraces and valley lands. The geomorphic configurations are anamalous, from Pokhara city to the top of Mt. Machhapuchhre is just at 30 km distance. Within the subtropical climatic region, premanent snowclad mounation has become a unique and charming example in the world. Pokhara is a valley of micro-valleys. The micro valley maker streams are the tributaries of the River Seti (trunk-river) in Pokhara valley.
a. Geological structure:
There are two types of geological structures in Pokhara, sloppy areas around the valley is exposed bedrock and quaternary deposition along the Seti River terraces. Bedrock geological structure is prevalent with metamorphic rocks. This type of structure is exposed in some parts and hidden under about one meter thick soil cover. The exposed bedrock is weathered with different agents like solar temperature, rainfall and chemicals. The bedrock is classified into six groups on the basis of their presence and parent rocks. Such as Kunchha formation, Sandy formation, Dandagaon sedimentary rocks, Naurpul Formation, Dhading dolomite, Benighat Sedimentary and Himalayan gneiss (metamorphic rock) (Dept. of Mines and Geology, 1998). The bedrocks are not distributed equally, somewhere they are underlying in great depth and some are on the surface, and in some parts it is densely distributed and on the other these are in mixed conditions. These type of rock structures are hard and tough, so they are used mostly in building and construction works.
The quaternary deposition in the Pokhara valley floor is the major phenomenal study. The valley is filled with detrital materials (pebbles, graves, sands, mud etc) mainly calcareous and some amount of sedimentary rocks like gneiss and mica-schists (Fort and Freytet, 1982). This deposition has been interpreted variously as the result of fluvioglacial and lacustrine sedimentation (Hagen 1969, Sharma 1975, Sharma et al. 1978) fluvial and fluvioglacial deposition (Gurung 1970, Hormann 1974 and Yamanaka et al. 1982) and colluvial, alluvial and fluvioglacial action (Fort and Freytet 1982). The quaternary deposits are widely distributed in and around Pokhara and some of them have been formed river terraces. The identification of ther deposits have been made from the village names.
i. Ghachok Formation:
This name is derived from the Ghachok village (Yamanaka et al, 1982) and situated about 15 km north of Pokhara town. This type of formation has been distributed widely in the Pokhara valley. This is the oldest of all the deposits during the glacial age (Hormann 1974). The Ghachok formation is composed of sub-angular to sub- rounded gravels of limestone, sandstone, gneiss, granite, quartzite, calcareous cemented fanglomerate and schist gravel. The size of the grains varies from huge boulders to silt. The clasts are composed of limestone, gneiss and quartzite. The thickness of the Ghochok formation is more than 100 meters at Ghachok and about 100 meters in the central part of the Pokhara valley. Downstream from Pokhara, its base is situated below the Seti river bed. Its volume above the river bed is estimated at 8.7 cubic kilometer.
ii. Tallakot Formation:
This name is got from the Tallakot village (Yamanaka et al, 1982) and is about 8 km north of Pokhara town. The stratigraphics of the Tallakot formation are absolutely of limestone, strongly cemented by calcareous materials and are angular to sub-angular in features, brought from Tibetan-Tethys group rock. The conglomerates in lithofacies were deposited during the last two Himalayan glaciation (Hormann, 1974). The weathering product of the Tallakot formation is dark yellow soil, exposing pinnacles and similar type of highly karstified limestone. The exposed thickness of the deposit is above 100 meters. Topographically, the extent of the Tallakot formation is assumed from is elongated hill to the slopping terrace of Khadarajung.
iii. Mardikhola Formation:
The Mardikhola formation is the lacaustrine facies developed after the deposition of Tallakot formation. From the field observation the Mardikhola (tributary of Seti of river) was dammed by Tallakot debris flow and developed as the Mardikhola formation. It is apparent that the lithostratigraphic compositions are silt and clay soil of dark yellow colour, and along the breached coures of the stream are grits, pebbles and cobbles.
iv. Pokhara Formation:
Pokhara formation is structured of fluvioglacial and fluvial deposition (Gurung 1970, Harmann1974, Sharma 1975, sharma et al. 1978 and Yamanaka et al. 1982). The name is derive from Pokhara area and was used first as ‘Pokhara schotter’ by Hormann (1974). The Pokhara formation consists of silt, sand, gravels, calcareous silt and conglomerates. This formation existed due to the fluvial depositional work of the Seti river from the old terrace deposist. Most of the Materials accumulated are limestone and some clasts of quartzite, granite and gneiss. The top part of terrace deposit is calcareous crusts, but those crusts are not distributed for a longer distance.
The accumulation of Pokhara formation has been considered during the last glacial age. Yamanaka et al. (1982)has revealed that the age was between 1100 and 600 years B.P. by radio- carbon dating method, and belongs to the Holocene, Post-glacial age. The thickness of the Pokhara formation is about 100 meter.
The Pokhara formation has a high permeability character due to the low amount of matrix and clastic contact of granular materials. Karstified limestone, exposed pinnacles and sinkholes are in the old terraces, where the old deposits of limestone are weathered and occurred elsewhere in hazara-prone conditions.
As per climatic division, Pokhara falls under the microthermal climatic zone. The valley has humid-temperate to alpine conditions in elevated parts and humid-subtropical in the lower valleys. The Himalayan ranges have a direct effect on precipitation and temperature conditions. Humid air streams coming from the south or bay of Bengal are trapped in this area and are forced to rise and condense to shed most of their moisture, which makes the valley a rainiest place of the Nepal. The abruptly rising. 7000-8000 meter, high Mt. Dhaulagiri ranges in a short distance play an important orographic lifting of moist air over this area. The Mt. Annapurna ranges is at a distance of 40-50 km in the north, Mt. Dhaulagiri range is at 50-60 km in north-west and the Mt. Manasulu and Lamjung Himal is at 40-50 km in the north-east surrounded by on its three sides act as the three sides of a room. In monsoon season (June-September) it receives 80 percent of the total rainfall of the year. The undermentioned table will reveal the rainfall pattern in Pokhara valley.
4. Biogeographical Diversity :
The Pokhara valley is posing in the very central part of the middle mountain region of the country. As mentioned earlier, it is an intramontane valley, watershed of the Seti river and its tributaries. Biogeographically, the region concerns the distribution pattern of flora and fauna specie. Wild life and plant communities have intimate relation. Plant communities provide food and shelter to the animals. Wildlife in turn, helps in plant species dispersed through seeds and pollen transfer.
a. Topography :
The valley portrays a combination of different topographic features, they are highly elevated snow-clad ranges, summital convex and concave ridges, free-face slopes, rectilinear slopes, gullies, gorges, terrace and valleys. The convergence and divergence of connecting ranges exaggerated the complexity of the terrain, which are eroded and dissected by the drainage network systems (Shrestha, 1999). There is a big variation of elevation between 1000 meters in the low land valley and 7000 meters in the northern mountains. The multitudes of relief categories have been differentiated by two factor : elevation and inclination. On the basis of this, two broad relief types are grouped, they are valley and mountains.
The valleys are diverse in size and shape. Most of the valleys are posed along the Seti river and its tributaries. Withing the valley there are some micro valleys formed along their tributaries, namely, Sardikhola, Bhurjung Khola, Kudikhola, Lastikhola, Chitepanikhola, Yamdikhola, Kalikhola, Kahumkhola, Phusrekhola, Bijayapurkhola and Khudikhola.
b. Phytogeography :
From the view point of Phytogeography, the valley includes three types of forest region: Subtropical forest, Temperate forest, Alpine shrub and meadows. The Subtropicla forest has further been sub-divided into three microfloral zones, viz. mixed shorea robusta, mixed castanopsis-schima wallichi and quercus languinosa and associates. These species are known as hydrophytic plants, commonly seen along the stretch of streams and watersheds. Temperate forest has been sub-divided into three micro-floral zones. This includes pinus species and associates, mixed oak and Rhododendron-juniperous species. This phytogeographic region is extended from 1800-3000 meter above sea leval and it has humid and cool climate condition. The phytogeographic region of alpine shrub and meadows resembles to Trans-Himalayan region. It has rain shadow and steppe vegetation type of Central Asia. This region situates at the elevation above 3000 meters of sea-level.
As mentioned above, the valley harbours the high number of floral diversity exceeding 1500 species (Dobremez, 1996). The major species are shorea-robusta, dalbergia sisso, acacia catechu, terminalis chebula, terminalis belerica, bahunia purpurea, ficus species, bombax mallabaricum, dendrocalamus species, michelia champaca, castanopsis species, coriaria nepalensis, flaxinus floribunda, elaeocarpus sphaerieus, maesachisia, artemisia vulgaris, dryoupteris species, cedrella toona etc. in subtropical type. Temperate floral diversity ranges under collinean and mountain ecological zone. The floral species are pinus species, quercus species, juglans regina, fern species, betula utilis, rhododendron arboreum, oak, lithecarpus species, juniperous species, arundinaria Intermedia, delphinium denudatum, cinnamomum tamala etc. Alpine Floral diversity ranges above 200 species. The prominent species are dwarf pinus, rhododendron, juniperous, thorny and spiny bushes. The herbal plants like orchis latifolia, caragana geradiana, ephedra geradiana, artemisia, polygonum vaccinifolium etc. This ecological region is good rangeland for ranching and grazing. Additionally, the floral regionbs are sources of fuelwood for cooking and fodder for domestic animals.
The valley is a small habitat for faunal diversity. However, the valley has a good number of faunal species with 440 birds, 280 butterflies, 70 fishes, 40 reptiles, above 1000 types of mammals etc. Between lower and middle region the common species include the rhesus macaque, grey langur, wild cats, wild boar, rodents and squirrels. At middle to high elevation existing faunal species are black bear, yellow throated marten, musk deer, tahr, marmot and pike. The snow leopard, one of the highest living and endangered wildlife also exists.
Pheasants are also called the game birds (galliformes). According to the biodiversity profile there are 21 species of galliformes in Nepal. Red jungle fowl (Luiche) and Kalij are common in subtropical zone. The temperate zone has Cheer Pheasant (Cheer Kalij), Koklass (Phukars), Blood Pheasant (Chilime), Satyr Tragopan (Munal) and Imppheyan Pheasant (Danfe/Lophophorous). In addition, about 40 species of migratory birds fly to the warmer southerly region from the Tibetan plateau and Siberian steppe in winter.