Most of the forest in Phu Pha Lek National Park is productive. It is the source of the main rivers—which can be called “Forest of Water” an only one remained and very important for people in upper Northeastern Thailand, of Song Kéhram River, Shi River, Uun River, Huy Lamphanchard, Huy Kracher etc. There are also the main reservoirs, under the patronage of His Majesty the King, such as Nam Uun Dam, Lampaow Dam and about 20 reservoirs around the park for people to use in consuming and agriculture.
Phu Pha Lek National Park, locates between latitude 17 o 15;'– 16o 49 ' north and longitude 103o 15' – 103o 50' east, is a part of Phu Phan Mountain Range lying east and west about 54 kilometers and approximately 200 – 600 meters above sea level. The highest mountain is Phu Ang Sor about 695 meters above sea level. The area is the source of many big and small important-rivers such as Song Kram River, Yam River and Uum River. The soil in semi-evergreen forest is sandy soil, and in mixed forest and deciduous forest is laterite. And the stone is mostly sandstone.
The weather in this area is monsoon climate. Summer is from March to May; it is very hot approximately 40 o C so that can often cause forest fire everywhere. Rainy season is from June to October and about 1,000 – 1,300 mm. of rain all the year round. Winter is from November to February; it is cold approximately 15 -20 o C.
There is deciduous forest spreading all over the foot and top of mountains which consists of valuable plants such as Siamese sal, ingyin, Hiang (a kind of Dipterocarpaceae) and eng, and lower bracken such as slender bamboo (a kind of Graminceae) and Krajeaw (a kind of Zingiberaceae). At the valley is mixed forest, and plants found are rosewood, ironwood, Burmese ebony, Makhaa Tae, and many kinds of bamboo such as sang, Khao Larm bamboo, Rai, Ruag and wild bamboo. Along the streams are semi-evergreen forest, and plants found are Yang, Krabak (a kind of Dipterocarpaceae), Malabar ironwood, Tabak (a kind of Lagerstroemia), Makhaa mong, and lower bracken such as rattan, palm and many kinds of herb. And animals found are wild boar, barking deer, mouse deer, monkey, langur, squirrel, land monitor, snake, and many kinds of bird. The other kinds of animal are also in being threatened condition because local people still hunt.