Lumang Gewog shares its border with Uzerong Gewog in the west, Nanong Gewog in the South, Khaling Gewog in the north and Thrimshing Gewog in the east. Lumang Gewog is 103 km away from Trashigang Dzongkhag administration; the central administration for the District.The climate is mainly temperate in the northern part of the Gewog and sub- tropical in the southern part of the Gewog with an annual rainfall between 1000 mm and 2000 mm.
Lumang Gewog has a total area of 102.9 square kilometers. It has a total of 750 households with population of 6514. The density of population is 64 per sq.km. The forest cover accounts for 85 percent of the total. The Gewog has arable land of 3.64 percent of its total area.The Gewog center is located at Kurchelu village under Kharphu Chiwog and the main town are located at Wamrong, which falls under Kheshing Chiwog. Lumang Gewog is administratively divided into six Chiwogs.
The name of the Gewog was kept as Lumang even though the Gewog center is located at Kurchelu village after the first elected Gup from Lumang Nangtsahng located at 10 killometers from the current located Gewog office. The name of village, Lumang was derived from the rock located at the hub of the village which is believed as the edfice of many sarpents blessing wealth and good agriculture harvest to the people in the locality.
The Gewog is divided into 32 major villages and 53 minor villages. The soil fertility is generally poor and is prone to land slides in most of the villages. The Gewog has 114 kms length of farm roads connecting almost every village located within the Gewog. The telecommunication and electricity supply coverage of the Gewog is 100 percent and rural water supply schem percentage is 99.8 as of the statistic obtained from the fiscal year 2015-16. The Gewog is one of the largest Gewog under Trashigang Dzongkhag administration with total 11th five year plan out lay of Nu.55.065M. The total expenditure during past three fiscal years including GDG budget is Nu.27.088M and the financial achievements at the end of third fiscal year is 62 percent. The approved budget for the fiscal year 2016-17 is Nu.21.6M including the budgets of all the sectors falling under the administrative authority of Gewog administration.