The Udawalawa national park was established on 30 th July 1972.It lies in the lower catchment of Udawalawa Reservoir in the country's Intermediate Lowland region. This area falls into two administrative districts in two provinces. The parkland on the right bank of Walawe ganga is within Ratnapura district in the province of sabaragamuwa and the parkland on the left bank falls within Moneragala district in the province of Uva . This Park is located approximately between the latitudes 6 25'E and 6 35' N and longitudes 80 45'N and 81 00' E.
The dry land area of the Park is about 119 Sq miles or 308 Sqm, approximately 28910ha. The Udawalalawa reservoir is situated within the park premises, the total surface area of which at full supply is 3405ha. The total area of the park within the declared boundary including the reservoir is 32,315ha.
Altitude ranges from about 100m on the plains to 373m at the top of the deep Walawe Reservoir (3,400ha), which is surrounded by open plains and foothills. The most prominent feature is the kalthota Escarpment and spectacular Diyawinne Fallto the north. Ulgala, in the west of the most prominent peak.