A community of Vedda people, the indigenous ethnic group of Sri Lanka lives within the park boundary in Henanigala.

[2] Situated in the dry zone of Sri Lanka, the climatic conditions are dominated by the north-east monsoon, which persists from October to February.

Buddhist ruins of shrines, temples, dagobas, statues, and hermitages are found in Henanigala, Kudawila, Gurukumbura, Ulketangoda, and Werapokuna belonging to various periods of Sri Lankan history.

The Veddas, said to be descended from King Vijaya and Queen Kuveni, were living in Sri Lanka long before the arrival of the Sinhalese people from India 543 BC.

[2] The climax community of the area is tropical dry mixed evergreen forests characterized by Drypetes sepiaria, Chloroxylon swietenia, Manilkara hexandra, Pterospermum canescens, wood apple Feronia limonia, Cassia fistula, and Dimorphocalyx glabellus.

[3] A rare and endemic tree Vatica obscura, the only Dipterocarpaceae species to occur in the dry zone, is found in limited locations on the banks of the Maduru Oya and Gallodai Aru.

[2] Threatened mammal species include elephant Elephas maximus, of which there were 150-200 before the establishment of the park, sloth bear Melursus ursinus, leopard Panthera pardus, and water buffalo Bubalus bubalis.

[5] Other mammals are toque monkey Macaca sinica, common langur Presbytis entellus, jackal Canis aureus, fishing cat felis viverrina, wild boar Sus scrofa, Indian muntjac Muntiacus muntjak, spotted deer Cervus axis, and sambar C. unicolor.

Small mammals include porcupine Hystrix indica, black-naped hare Lepus nigricollis, Indian pangolin Manis crassicaudata, squirrels, rats and mice.

Notable forest species are endemic Sri Lanka junglefowl Gallus lafayetii, the rare broad-billed roller Eurystomus glaucurus (possibly the only dry zone haunt), common tailorbird Orthotomus sutorius, shama Copsychus malabaricus, black-hooded oriole Oriolus xanthornus, and brown-capped pygmy woodpecker Yungipicus nanus.

[2] The reservoirs harbor several species of bird including Oriental darter Anhinga melanogaster, spot-billed pelican Pelecanus philippensis, Asian openbill Anastomus oscitans, black-headed ibis Threskiornis melanocephalus, and Eurasian spoonbill Platalea leucorodia.

Feared effects of the Accelerated Mahaweli Development Programme include conflicting interests between wildlife and settlers in the areas of the park that are bordering the development area: elephants and wild boars raid and damage crops, while cattle and other domesticated animals trespass into the park.