The earth dam, built by the Commonwealth of Pennsylvania, is 34 feet high and 422 feet long. The basin of Hills Creek Dam is long and narrow ending in an irregular triangle at the north end. The elevation is 1,486 feet and the nearby mountains rise to an elevation of 2,200 feet. The lake watershed consists of 4 square miles of gently rolling land which is presently in a state of secondary succession from agricultural land to forested area. The lake is fed by two small unnamed streams and Hills Creek that contribute only slightly more water than is lost by evaporation during normal summer months.
Bottom contours are regular.
In the southern portion of the lake the shoreline drops rather abruptly from shallow water to about 14 feet or more in depth. In the northern portion there are very wide and shallow reaches which have numerous stumps throughout the area. The general area now covered by water has been almost continually, since the end of the last ice age, under the influence of beaver dams and beavers. Beaver still abound in the locality, including Hills Creek Lake. It is believed this is a significant factor in the prevailing fertility of the lake.