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Ground Water Assessment Water Quality >>Watershed Management Surface Water Management Land Use/ Land Cover Changes in Phewa Lake Watershed Area in Pokhara, Nepal Tara R. Khanal Lecturer, Department of Geography, Tribhuvan University, Prithiwi Narayan Campus, Pokhara, Nepal Keshab R. Bastola Lecturer, Department of Geography, Tribhuvan University, Prithiwi Narayan Campus, Pokhara, Nepal Abstract Nepal is a mountainous landlocked country with an area of 147181 sq. km. and 23.15 million populations. It presents a great physical and cultural diversity due to its geology, altitude, relief and location. The mountain and hill regions have complex geological structure characterized by marginality, fragility, inaccessibility, diversity, low economic opportunities and traditional technology. It has five Development Regions among them the Western Development Region is one where 'Phewa Lake Watershed Area in Pokhara' is located. Out of the total 42602 sq. km. catchments area of the country Phewa Lake Watershed Area of Pokhara covers about 118.19 sq. km. (11818.77 ha) of land with several rivers and rivulets. The change of land use of Phewa Lake Watershed Area in Pokhara valley represents the mountain land use of the Himalayan region. The present study Phewa Lake Watershed Area in Pokhara valley is significant in agriculture and tourist point of view both nationally and internationally. The study area has been analyzed precisely and logically by using GIS tools and techniques with the help of available Aerial photos and topographic maps during the periods of 1978 to 1998. GIS Software, PC ARC/Info and ARC View have been applied to detect the land use changes of Phewa Lake Watershed Area on micro level. The entire works have been analyzed on the basis of manipulation of empirical data. Natural and cultural factors are involved for the change in land use pattern as well as the integrated land use policy for the overall economic and environmental development in the country. The land use of Phewa Lake Watershed Area in Pokhara has changed drastically due to the opening of highways, urban facilities of sub-metropolitan Pokhara city. Thus, the result shows that most of the changes have occurred on agricultural land, forest area and built-up-area and minor changes have been found in different land cover in Phewa lake Watershed Area of Pokhara, Nepal. Introduction Nepal with an area of 147181 sq. km. represents a great physical and cultural diversity in terms of geology, altitude and location. It consists of many landscapes of different geological formation. It has complex geological structure characterized by marginality, fragility, inaccessibility, diversity, low economic opportunities and traditional technology. The mountain and hill regions have covered 77 percent area of the country and the rest is covered by basins, tars, lowland of plain area. The altitude ranges from 61 metre in the south up to 8848 metre (Mt. Everest) in the north from the sea level. The plain, Terai region, in the south is the extension of Indo-gangetic plain; the Siwalik range is composed of Tertiary sandstone, siltstone and shale, the Middle Mountains and High Mountains are composed of phyllites, quartzite and schist of Tethys sediments. East-west length of the country is 885 km. with an average breadth of 193 km. from north to south. Because of these altitudinal variations, the climate ranges from tropical in the south to arctic in the High Himal in the north. The orientation of Mountain ranges has caused to several micro-climatic conditions (Shrestha, 2000) The total population of the country is 23.15 million with 157 persons per sq. km and 2.25 annual population growth rates (CBS 2001). More than 80 percent of the total population is engaged in subsistence agriculture. Only 14.20 percent of people are living in urban area and the rest of others are in the rural part of the country. Besides, Nepal lies on the cross road of a number of Floristic regions including the Sin-Japanese, Irano-Turanian, Central-Asiatic and Indo-Malayan. Because of these diverse bio-physical conditions in the country, it presents more than 35 forest ecosystems and covers 4500 species of vascular plants including 240 species of endemic plants and 700 species of medicinal plants, 130 species of mammals and 800 species of birds (Gorkhali, 1991). Water and forest resources are the most important natural resources of the country. In water resources, it is ranked on the second position in the world in its potentiality. The country possesses more than 6000 rivers and streams and several lakes covering about 42602 sq. km. catchments area, which accounts for about 29 percent of the country's total confine (Yogacharya, 1998). The change of land use of Phewa Lake Watershed Area in Pokhara valley resembles to mountains land use of the Himalayan region. Land is basic natural resource for human being. The concept of changing land use pattern is often considered a holistic approach of land surface, which is related to the use of land in space and time. Changing land use pattern is a geographical phenomenon. Generally, the time and geographical unit is influenced by natural environment. In the recent years, the land use pattern is changed due to the government policy and technical development (Chauhan, 1996). Many countries, therefore, have directed their national policies and programmes for the development of the resources; and have launched a number of projects to measure the present capabilities. Land use pattern is always a reflective to the number of population, functional establishment and infrastructure development on site, situation and time. It is further stated that land use depends upon their physical and technological environment, and somewhere the national policy (Sharma and Khanal, 1996). Land use is the outcome of interaction between man and environment. Some of the land use is directly related to cultural, social and economic conditions of the people (Vink, 1975). However, human domiciles and their cultural and socio-economic conditions development had been overruled on land use since long historic period. Pokhara Valley has been a centre of the human civilization since long back (Gurung, 1970). The prehistoric men should have lived on the hilltops in the vicinity of Pokhara before settling down in the valley (Shrestha, 1971). The historical settlements were found mainly in the ancient villages like Kaskikot, Sarangkot, Chapakot, Khadgaon, Serachour, Purunchour, and Dhampus (Lamichhane, 1996) whereas a few dispersed rural houses were found in plain area. However, the urban settlement came into existence after Chhabis Kuria (26 households) of Newars settlers from Bhaktapur at mid-eighteen century (Gurung, 1971). From these considerable historical evidences, Pokhara town should have emerged before the unification of the Kingdom by gorkha rulers (Gurung, 1985).  Fig. 1 The present study area particularly "Phewa Lake Watershed Area of Pokhara valley" is located in the Western Development Region of Nepal. It has been the most popular as well as valuable region in terms of touristic and administrative point of view both nationally and internationally. The present paper aims to discuss on the Land use/Land cover changes in Phewa Lake Watershed Area of Pokhara Valley in order to understand the causes, processes and rate of land use\land cover changes in the study Area. Study Area The study area lies in the south-western part of Kaski district. Both the rural and urban sectors of this realm extend between 28° 11' 39" - 28° 17' 25" N latitude and between 83° 47' 51" - 83° 59' 17" E longitude are also included for the study. Most of the rural sectors of the watershed area are situated in the hilly areas whereas the urban sectors are situated in the Pokhara sub-metropolitan city. On the whole, the study area of Phewa Lake Watershed covers about 118.19 sq. km. area with its average geometrical length of 17 km. and the width of 7 km. Phewa Lake itself cover about an area of 4.43 sq. km. (443 hectare). The length of the lake is about 4 km. and width varies from 100 metre to 2000 metre. The study area in the eastern part of Phewa Lake has the extension of seven Wards of Pokhara sub-metropolitan city and six Village Development Committee such as Sarangkot, Kaskikot, Chapakot Bhadaure-Tamagi, Bharat-pokhari, Dhikur-pokhari and some parts of Phumdi-bhumdi. The variation of altitude is from 793 metre (Lake Level) to 2508.81 metre in the west Panchase, which is the highest summit of the watershed area. Climatically, tropical monsoon, sub-tropical monsoon and the alpine climate have been characterized with 29.7° C to 30.3° C maximum temperature from April to June in comparison to the mean temperatures from 22.5° C to 23.5° C recorded at Pokhara Airport Station. Similarly, Pokhara records the highest precipitation in the country. The meteorological station of Pokhara recorded that the highest annual rainfall was up to 6561.4 mm in 1995 and the lowest annual rainfall up to 4852.8 mm in 1987. Comparatively, Bhadaure-deurali, which is situated in the Phewa Lake Watershed Area, receives less annual rainfall than Lumle but more than Pokhara.  Fig. 2 The bottom of Phewa Lake is the main drainage basin into which all the streams join lake from its watershed areas. This watershed stretches form south-east to north-east. Harpan River is the major river system in Phewa Lake watershed originated form Panchase and joins in the lake Phewa. Altogether, there are 54 tributaries which join the Harpan River. Andheri stream comes from the north-western section and enters into the Harpan river system at Thulakhet as a principal tributary. Besides this, the other tributaries such as Handi Khola (stream), Tora Khola, Thiri Khola, Marshe Khola, Chisa Khola, Birim Khola, Betyani Khola, Saureni, Thotne are the major streams of Phewa Lake Watershed Area. Soil and their formation in the Phewa Lake watershed realm as well as in Pokhara have had a great influence of climates and geological structures since the ancient periods which ultimately have made soils and rocks in Pokhara as well as the crucial factors of environment because they have become mischievous for the development of the urban settlement due to many invisible voids underneath the surface (Lamichhane, 1996). The main soils of Pokhara are dry and moist grey, dry/dark grayish and yellow and brown (Kollmansperger, 1974). Moreover, Phewa Lake Watershed realm consists of acidic, moderately fine-textured and non-stony clay (LRMP, 1983). The Phewa Lake Watershed Area has a great variation of altitudes form 793 metre to 2508.81 metre. Therefore, numerous plant species have flourished long since. The major plant species like Shorea robusta is observed mainly on the southern hills. The city rarely possesses such vegetation. The other species in the northern and western hills outside the city limit as well as within the city are Schima wallichii, Castanopsis indica, Alnus nepalensis, Woodforida, Pinus roxburghii, Dendrocalamus hamiltonii, Cinnamomum zeylanicum, Dalbergia latiflora, Artemisia vulgaris, etc. The vegetation covers from 793 metre up to the altitude of 20508.81 metre from the sea level in the Phewa Lake Watershed Area is slightly different form the vegetation species of Pokhara. Phewa Lake Watershed Area situated in the west part of Pokhara city consists of almost of six Village Development Committees (VDCs) such as Sarangkot, Kaskikot, Dhikurpokhari, Bhadaure-Tamagi and Chapakot and some parts of Pumdi-Bhumdi. Besides these, VDCs ward number two, three, four, five, six seven and eight of Pokhara sub-metropolitan city are also included in Phewa Lake Watershed Area. According to the 2001 Census report, 62.32 percent people are living in urban area and the rest are in the rural areas. 
Table: 1 indicates that Rural/Hilly Watershed Area comprises of 10908.77 hectares of land whereas in urban sector is only 910 hectares. The population density in rural area is 3.31 person/hectare whereas it is 65.6 person/hectare in urban area. The growth rate of population per annum is 2.7 percent in urban areas but it is negative growth rate (-0.04%) in rural area. Methodology The present study involves both the primary and the secondary information. This study focuses land use changes from 1978 to 1998 in Phewa Lake Watershed in Pokhara, Nepal. To obtain the land use pattern of 1978 aerial photo (scale 1:50000) and land use map (scale 1:50000) prepared by Land Resource Mapping Project (LRMP) in 1986. Land use types of 1978 have been categorized on the basis of land use category classified by LRMP viz, agriculture, forest, built-up area, water bodies and barren land. Similarly, for land use data of 1998 toposheets (scale 1:25000 to topographic map) generated by department of survey, HMG; Nepal based on aerial photo (scale1:5000) and field verified in 1997. Different land use categories have taken as a categories classified by department of survey during preparation of topographic map viz agriculture, forest, built-up-area, water bodies, landslide, sand/sediments, fallow/grazing and bush/shrub. All the required data layers for the present study such landuse map 1978, landuse map 1998, roads, rivers, settlements contours have been converted into 'digital' form through manual digitizing using PC ARC/Info 3.5 software with the help of digitizer and tablet. Keen attention has been made to minimize errors during digitizing and editing phases, other required information have been taken from Central Bureau of Statistics (CBS) and related offices and presented in different tables and diagrams to enhance the present study. Different spatial analyses have been accomplished with map query and overlay operation to detect landuse changes in each category between 1978 and 1998 using ARC View 3.3 version GIS software Land Use/ Land Cover Pattern in Nepal: In Retrospect Land use/ land cover information for the whole country was published in 1986 by the Land Resource Mapping Project (LRMP) based on Arial photographs taken in 1978/79 for the first time. Though major land cover types (cultivated land, reserved protected forest, wooded area, grass and shrub land and water bodies) in the form of toposheets based on vertical photograph taken from 1952 to 1958 and field verification were prepared for the whole country by the Surveyor General of India. But tabular data based upon this survey is not available yet. Cadastral survey has not yet been completed in the country. Moreover, the districts where Cadastral survey is completed does not show the real picture of land cover/ land use because of the propose of the survey itself and definition used in classifying land and legal provision made for ownership right of the land. The National Sample Census of Agriculture is undertaken in every ten year (1961/62, 1971/72, 1981/82 and 1991/92) but comparison on the changes in agriculture holdings beyond national and regional level is difficult due to frequent change in district boundary. Analysis and Result Land use/Land cover pattern Landuse survey of 1978/79 indicates that agriculture land accounts for 20 percent, forest, shrub and grassland together account for 54 percent of total area of the country. About 7 percent land has been defined as non-cultivated (barren land and water bodies). As the geology, steepness of the slope and climatic condition differs by physiographic region land use/land cover pattern also differs accordingly (Khanal, 1999). In 1978 land use/land cover of Phewa Lake Watershed Area was 11818.77 hectares. During the time proportions of agricultural and forest lands were 49.61 and 43.59 percent, respectively. The water bodies covered only a few percentage (3.30) followed by barren land and built-up-area. Such types of land coverage have been changed in various uses from five to eight major uses in 1998. The land cover data for 1978 and 1998 by various uses is shown in Table 2. 
Among the total land of Phewa Lake Watershed Area, only 3180.59 hectares of land had changed from 1978 to 1998. In percentage, only 26.91 percent of land use/land covers are found changed. In 1998 data, four major land uses such as landslide sand/sediments, fallow/grazing and bush/shrub are presented. Barren land of 1978 was totally disappeared in 1998 data. Both agricultural land and forest land were decreased by 0.98 percent (115.10 ha) and 2.4 percent (283.98 ha) within a span of 20 years. But in contrast, built-up-area and water bodies are increased. Thus, the above table shows that five land covers were converted into eight major land uses.  Fig. 3  Fig. 4 The Trend of Land use and Land cover change Land use/land cover of Phewa Lake Watershed Area has been shown in Table 3 which gives a clearer picture of out-going and in-coming area both in hectares and percentage. 
Table-3 clearly indicates that the decreasing (13.2) percentage is higher than that of increasing (12.29) percentage of agricultural land followed by forest cover but in the case of barren land, the whole land cover is changed into agriculture, forest and fallow/grazing land uses. The increasing trend of Land use/land cover changes are found only in built-up-area, sand/sediments, fallow/grazing and bush/shrub land cover.  Fig. 5 Major Land use/Land cover changes: 1978-1998 The data on major land use/land cover changes of Phewa Lake Watershed Area of Pokhara Valley from 1978 to 1998 are given in Table 4. Agricultural land use converted into the forest by 32.06 percent followed by built-up-area (10.21%) and water bodies (2.24%). The rate of change is very high from agriculture to forest land which is about 1.61 percent per annum. But it is lower in bush/shrub area. Similarly, the highest land use change found from forest to agricultural land, the rate of change is 40.809 percent that is followed by fallow/grazing (1.225%). The annual change is also very high (2.04%) form forest to agriculture. 
In the case of barren land, it is totally changed to other land categories like agriculture (3.933), forest (2.171) and fallow/grazing (0.181). The annual rate of change is high in agricultural land (0.196) followed by forest land (0.10). The land use change from built-up-area to agriculture is only 5.85 hectare and 0.183 in percent over 20 years. About 23.38 hectares of land are changed from water bodies to agricultural land, built-up-area and forest. The absolute land cover changed from water bodies to other land categories is about 25.31 hectares. It is very high in agriculture land (0.731) followed by forest (0.053). Specifically the changes in land cover/land use by various land uses is shown in Table 5. This table shows the major land use/land cover changes found in agriculture, forest, built-up-area and water bodies are more than 98 percent and the rest of other changes are negligible. It was found that about 45.65 percent area came under agricultural land. Among the major uses the highest percentage is from forest (40.809) and the lowest percentage from built-up-area (0.183). 
The above table shows that about 34.53 percent of land converted from agricultural land, barren land and water bodies to forest. Among them the highest percentage (32.306%) is from agriculture to forest land, followed by barren land and water bodies. Likewise, 10.226 percent of land converted into built-up-area from agriculture (10.241%) followed by forest and water bodies. But in contrast, sand/sediments have not yet been seen in 1978 data, which is influenced by both agricultural and forest land. Similarly, such cases happened to fallow/grazing and bush/shrub lands. Changes from agricultural land and forest to water bodies accounted for 2.67 percent of the total land changes in Phewa Lake Watershed. Land Cover: Use and Change The 1998 data reveals that only 3180.59 hectares of land has been interchanged among different use categories in Phewa lake Watershed Area of Pokhara. The use and change over the period of 20 years is positive in Built-up-area (+2.7%), Water bodies (+0.51%), Landslide, Sand/sediment, Fallow/grazing and Bush/shrub. But it is found negative in Agricultural land, Forest and Barren land. The rate of change in different categories is clearly cited in Table 3. The highest annual rate of change is positive in built-up-area (+0.135%) and the lowest is in bush/shrub (+0.001%). It occurs negative in Agriculture (-0.49%) and Barren land (-0.084%) areas. 1. Agriculture: On the whole country, agricultural land has been increasing annually by 0.40 percent (Khanal, 1999), but in Phewa Lake Watershed Area of Pokhara, agricultural land is decreasing annually by 0.49 percent. About 50 percent of the total land use changes occurs from agricultural land into other different uses (Table 4) The vast amount of agricultural land converted into forest land (1027.53 hect) which is the highest percent (32.306) from agricultural land into other uses (Table 4). The second highest percent (10.214) agricultural land is occupied by built-up-area due to rapid growth of urban population, expansion of urban area of Pokhara sub-metropolitan city. It covers 324.87 hectares of agricultural land over the period from 1978 to 1998. About 117.4 hectares agricultural land turned into sand/sediments due to siltation and debris accumulation along the river bed of Harpan River and its tributaries in plain area. Another interesting change has been seen in water bodies from agricultural land. The built of dam by Pokhara Hydro-electricity Project contributes 71.31 hectares (2.242%) agricultural land turned into water bodies around Phewa Lake. The changes from agricultural land into fallow/grazing (0.76%), bush/shrub (0.024%) and landslide (0.033%) are negligible in comparison with other changes in Phewa Lake Watershed Area 2. Forest: The rate of change in forest cover is very high in the study area. The forest cover in Phewa Lake Watershed decreased from 1978 to 1998. Annually -2.4 percent of land is turned into other different uses (Table 3). It covers 43.45 percent of the total land use changes. Due to encroachment by the people and marginal use of land, vast amount of forest cover (1297.98 hectare) turned into agricultural land (Table 4) which is the highest change (40.809%) in land use changes in Phewa Lake Watershed Area. About 40 hectare forest land is converted into fallow/grazing land which shows 1.22 percent of the total changes. Similarly, about 14 hectare forest land turned into water bodies due to the construction of Phewa Dam. Some forest land changed into bush/shrub (0.089%), sand/sediments (0.90%) and built-up-area (0.001%) during the period. 3. Barren land: It occupies 199.93 hectare in 1978 but in 1998 this category has been collapsed. The use of marginal land results 125 hectare barren land converted into agricultural land (Table 4). The extension of community forest 70 hectares barren land turned into forest cover. 4. Built-up-area: At this period built-up-area increased from 212.5 hectares to 531.99 hectares (annual rate of change 2.7%) (Table 3). But the change from built-up-area into other uses is very negligible (0.18%) in total land use changes which accounts for only 5.85 hectare of land (Table 4) turned into agricultural land over the period. 5. Water Bodies: The land occupied by water bodies was 390.42 hectares in 1978 which increased by 0.51 percent per annum and reached 450.19 hectares in 1998 (Table 3). The changes from water bodies into other uses is less significant. Table 4 reveals that 25.31 hectare land of water bodies turned into agriculture (23.28 hectares), forest (1.70 hectares) and built-up-area (0.38 hectare). The change from water bodies into the other uses is 0.79 percent of the total changes in the Phewa Lake Watershed. Conclusion: Nepal with an area of 147181 sq. km. presents a great physical and cultural diversity due to its geology, altitude, relief and location. Among the five Development Regions of the country, Phewa Lake Watershed Area lies in the western hilly region of Western Development Region of the Kingdom. Both rural and urban areas of Pokhara valley partially included in Phewa Lake Watershed Area which ranges from 793 metres to 2508.81 metre from the sea level. The Phewa Lake Watershed Area lies in the west of Pokhara covering about 11818.77 hectares of total land with 95788 population. The main rocks found in Pokhara are Gneiss, sandstone, limestone, quartzite, dolomite and so on. Above all, the recent flood plain of the Phewa formation has been significant agriculturally and Phewa Lake is significant touristically. Climatically, the region influenced by sub-tropical monsoon up to the cool temperate monsoon because of abrupt variation of altitude. In this realm, the Harpan River is the main river system with 54 tributaries. The Andheri stream, which flows with the water of its 32 tributaries as a separate system before reaching the Lacustrine plain, is the principal tributary of the Harpan Khola. Residual, alluvial, colluvial, bright, reddish, dark reddish and dark brown are the major soils in the hilly areas with the Lacustrine plain of Phewa Lake. The major plant species Shorea robusta lies in the lower part up to Rhododendron and so on. Out of the total 11818.77 area, Rural Watershed and Urban Watershed area covers 10908.77 and 910.00 respectively. The study focuses on "Land use/land cover change of Phewa Lake Watershed Area" with the help of both primary and secondary information. Aerial photos and toposheets are the main bases of the study. GIS Software, PC, ARC/Info, ARC View are the main techniques applied in the study. Out of the total land, only 3180.59 hectares of land use have been changed within 20 years between 1978 to 1998 information. Most of the land use changes are found in all categories of land cover. The rate of land use change is found high in agriculture and forest. Land use changes have also been occurred in fallow/grazing, sand/sediment and landslide. But in contrary, the barren land was completely disappeared in 1998 data. Thus, the study shows that land use change is a continuous process of change from one aspect to another aspect. The natural factors and human beings are the major agents for the change in cultural landscapes of any region of the country. Land cover changes show that many socio-economic and political factors are responsible for the change in land use and it seems that it is leading to unsustainability. It is in this context, that the country should develop an integrated land use policy for the overall economic and environmental development in the country. 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