Rivers and Streams - Lyndon B Johnson National Historical Park (U.S. National Park Service) The Pedernales River is located in the LBJ Ranch District. Within the park there are two dams, the Jordan Dam and Johnson Dam, that impound water for use in irrigation of pastures. Erosion is severe in the Hill Country because of periodic heavy rains, thin soils, poor percolation, and severe runoff leading to incidents of extreme flooding.