Growing sugar requires water, lots of it. Plantations developed intricate collection and distribution system of flumes, ditches, tunnels and reservoirs. Kōloa was water poor and depended on excess water from its neighbors. Constrained by the lack of surface and groundwater sources, Kōloa concentrated on developing water storage. The Kōloa Marsh (above the present Kōloa Town) was an ideal location for a reservoir. Ultimately, a 2.3-billion gallon capacity reservoir was constructed (second in overall size to Oʻahu’s Lake Wilson with 3-billion gallon capacity.)
Waita Reservoir (also referred to as Hauiki Reservoir, Marsh Reservoir or Kōloa Reservoir), initially built in 1906 and expanded in 1931, covers an area of approximately 525-acres. The water source was supplied by the Wilcox Ditch and Kōloa Ditch (Waiahi-Kuia Aqueduct.) This enabled irrigation of over 70-percent of the fields.
Located on private property, Waita Reservoir not only provides irrigation to local agricultural ventures, through private fishing charter arrangements it is also a popular bass and other sport fishing location on the island.