Southern slopes of the Himachal Range are steep and nearly uninhabited due to a major
fault system called the 'Main Boundary Thrust". The crest and northern slopes slope gently enough to support
upland pastures and terraced fields. Nepal's densely populated
Middle Hills begin along the crest, extending north through lower valleys and other "hills" until population thins out above 2,000 m and
cereal-based agriculture increasingly gives way to seasonal herding and cold-tolerant crops such as
potatoes. Most ethnic groups found along the Himachal Range and northward into the Middle Hills have
Tibeto-Burman affinities including
Nepalese origins of
Newar,
Magar,
Gurung,
Tamang,
Rai and
Limbu, however the most populous ethnic group is Indo-European
Hindus called
Paharis, mainly of the upper
Brahman, and
Kshatriya, or
Chhetri castes. Lower terrain south of the escarpment was historically
malarial and inhabited by apparently aboriginal peoples with evolved immunity, notably the
Tharu and
Maithil people. The Himachal Range is an important hydrographic barrier crossed by relatively few rivers. Drainage systems have evolved candelabra configurations with numerous tributaries flowing south from the Himalaya through the Middle Hills, gathering immediately north of the Himachal Range and cutting through in major gorges as the
Karnali in the west, the
Gandaki or Narayani in central Nepal, and the
Kosi in the east. With temperatures persisting around forty degrees Celsius in the plains of India from April until the onset of the
summer monsoon in June, but ten to fifteen degrees cooler atop the Himachal Range, various
hill Stations have developed in the region. == References ==