The first zone roughly includes the whole of the southern ranges for a depth of about 20 to 30 miles. The annual rainfall
in this area is excessive (from 200" to 250") and the vegetation and forest are very dense.
The central zone consists mainly of valleys at elevations from 3500' to 10,00' and would include the valleys of Ha, Paro,
Thimphu, Punakha and Bhumthang. The rainfall is about 30 to 60 inches.
The elevation in Eastern Bhutan is less and the rainfall is between 50 to 80 inches.
The northern zone comprises valleys at elevation of 12,000 to 18,000 feet running down from the snow ranges
separating Bhutan and Tibet. These valleys are mainly used for grazing in the summer months