Groundwater modeling in Hawaii: A historical perspective
Lau, L. Stephen, and John F. Mink
Water supply has been a dominating feature in the evolution of the Hawaii economy since the first settlement of the islands more than a millennium ago. The early Hawaiians relied on water from streams, springs, and shallow excavations to irrigate crops, taro in particular. Water use was regulated by the Hawaiian chiefs and their land managers according to strict rules. The source and delivery systems were so well designed that they served the expanding economy for a century after the opening of the archipelago to the western world by Captain James Cook in 1778.
The prediscovery Hawaii economy was highly organized and successful. When Cook arrived the population of the islands was about 300,000, but a century later it had declined to about 60,000 as a result of devastation caused by western diseases and the breakdown of a unifying culture. The demand for water increased to meet the needs of new agricultural initiatives, especially sugarcane, exceeding the supply available from the intricate Hawaiian distribution network. Collection works and transmission systems were constructed by western entrepreneurs. By 1910 virtually every major surface water resource had been seized for plantation agriculture.
Still, not enough water was available to satisfy the thirst of the arid lands planted in sugarcane. The greatest impetus to the advancing agricultural economy came with the discovery of artesian groundwater in the Ewa Plain in southwestern Oahu in 1879. Widespread drilling followed, proving the existence of vast groundwater resources. The experience was quickly repeated on all of the major islands. The arid leeward plains of each island, blessed with a bounty of sunshine, became the premier agricultural lands through irrigation with groundwater. Honolulu, served by an unreliable surface water supply for all of the 19th century, prospered and grew after voluminous artesian groundwater resources were discovered beneath the coastal plain. The city became the uncontested urban and commercial center of the island chain.
Groundwater became the first choice for municipal drinking water, and as the public appreciated its purity and reliability it also worried about its sustainability. A severe drought in 1926 magnified the concern, leading to the creation of the City and County of Honolulu Board of Water Supply. Basic investigations by the U.S. Geological Survey, which had started a few years earlier, were expanded.
The adequacy of the groundwater resources of southern Oahu was severely tested in World War II when a large military population was grafted on the existing civilian and agricultural economy. Then in 1959 Hawaii became a state, setting off a wave of economic activity which concurrently expanded demand for water. By the 1970s the combined agricultural, military, and civil economy water demands in southern Oahu were rapidly approaching sustainability of the aquifers. Elsewhere in the islands economic expansion also strained water source and distribution systems. The adequacy of the groundwater supply persisted as an unusually widespread concern among the public. Finally, after nearly a decade of legislative attempts, a State Water Code regulating all water development became law in 1987.