At 100% capacity, the dam wall holds back approximately 85,500 megalitres (3,020×10^6 cu ft) and creates the impounded reservoir of Lake Yarrunga that has a surface area of 831 hectares (2,050 acres), drawn from a catchment area of 5,750 square kilometres (2,220 sq mi).

21,800 megalitres (770×10^6 cu ft) is available to be transferred to the Sydney water supply.

[3] Other water from Tallowa Dam is provided to Shoalhaven City Council for supply to local communities.

Water is also released from the dam as environmental flows for the Shoalhaven River.

[4][5] The construction of a large barrier across the river has meant that the means of travel for fish has been completely confounded.