State of water environmental issues
Geographically located between India (east, south and west) and China (north) with 147181 square kilometers of area, Nepal occupies 0.3 and 0.03 percentage of land area of Asia and the world respectively. In the northern hemisphere, Nepal is situated within latitude 260 22' N to 300 27' N and of longitude 800 4' E to 880 12' E. The country is land-locked without any border touching an ocean. The altitude ranges from a minimum of 64 meters to a maximum of 8848 meters above sea level whereas the climate varies with its topography. Mt. Everest – the top of the world – is both the identity and glory of this Himalayan country. The average width (North to South) is 193 kilometers whereas the average length is 885 (East to West) kilometers and nearly rectangular in shape. Kathmandu is the capital city of Nepal.
According to the Population Census 2011, the total population is 26.5 million with annual growth rate of 1.35 per annum and 54,27,302 individual households. From the same census it is found that 6.7, 43.0 and 50.3 per cent of total population is living respectively in the Mountain, Hill and Terai. Urban population is only 19% of the total population but it is increasing rapidly at the rate of 4.5% as of 2011 census. The population density in the year 2011 was 180 people per square kilometer. In reference to Human Development Report 2014 of the UNDP, Nepal's HDI is 0.490.
Topography and Climate
The country has great variety of topography which is reflected in the diversity of weather and climate simultaneously. Specially, the country experiences tropical, meso-thermal, micro-thermal, taiga and tundra types of climatic regimes and precipitation pattern across the country.
Average precipitation of Nepal is 1530 mm but they show huge variation from the south to north as well as east to west. There are two patterns of monsoon seasons appearing in summer (easterlies) and winter (westerlies). Summer monsoon advances from Bay of Bangel to the west and it is the wettest period when 75% of total rainfall occurs during a few months (June-September) time. Usually, the western parts receive lesser amount of rainfall than the east during summer monsoon due to decreased moisture gradient in the wind approaching from the east. The winter monsoon (originating from the Arabian Sea) usually brings cold air and modest precipitation along the northwest regions. The winter is the driest period in Nepal. Based on the similarity of landform and terrain, Nepal can be divided into five distinct physiographic zones: Terai, Siwaliks, Hills, Middle Mountains, and High Mountains/Himalayas.
These are alluvial plains lying in the range of 60-200 m.a.s.l. Terai covers 14% of the country area. These areas have sub-tropical climate with reasonably hotter summer and mild winter (mostly above freezing temperature). Most of the rainfalls are concentrated in monsoon season. Major rivers usually deposit a lot of sediments in Terai plain where river flow decelerates significantly. This is also the fertile region of Nepal and considered as grain basket of Nepal.
This region covers about 13% of the country area. These are foothills regions immediately north to Terai region reaching up to 1800 m.a.s.l. and stretching from East to West. There are also Terai like valleys in between Siwalik Hills. The climate in this region is also sub-tropical. Siwaliks are considered as important groundwater recharge zone for Terai.
The hills are characterized by moderate elevation range of 1500-2500 m.a.s.l. and covers 29% of the country area. There are steep slopes and narrow valleys. These areas have sub-tropical climate at the bottom of the hills but it gradually gets cooler and experiences warm temperate climate toward higher elevation. Some higher elevation experiences occasional snowfall during winter season.
The topography of middle mountains is also characterised by steep slopes and narrow valleys lying north to hills and it covers 20% of the country area. The elevation could range from 2000 to 4000 m.a.s.l. The climate is cold temperate and temperature in some higher elevation often remains below freezing point for 5 months in a year. Snowfall often covers the mountain tops during winter.
This is the northern most part of the country and it covers 24% of country areas. The elevation in this region is above 4000 m.a.s.l. and reaches to the highest point in the earth at 8848 m.a.s.l. The climate is alpine to tundra and most of the parts are under permafrost, snow or glaciers throughout the year.