CP-1994-02
Hydrogeology of the Marshall Islands
Peterson, F.L.
The Republic of the Marshall Islands consists of 33 atolls containing some 1,136 separate islands in the west central Pacific. The atolls are aligned in a NW-SE direction and extend over a distance of nearly 1,100 km. They form two roughly parallel chains, the eastern Ratak (sunrise) group and the western Ralik (sunset) group.
The indigenous people of the Marshall Islands are Micronesians. The first European contact was by Spanish explorer Alvaro Saavedra in 1529. However, the islands’ general lack of wealth and resources did not encourage exploitation until 1885, when Germany declared the Marshall Islands a protectorate. In 1914, Japan took control of the Marshall Islands and after 1919 administered them under a League of Nations mandate. During World War II, U.S. forces occupied the Marshall Islands after heavy fighting on Kwajalein and Enewetak, and in 1947 the Marshall Islands became a U.S. trust territory. Finally, in 1986, under a compact of free association, the Republic of the Marshall Islands became fully self-governing and took control of all its internal and foreign affairs. Today the principal economic activities are still subsistence farming and fishing, with increasing effort being directed toward development of a tourist industry.
Although the Republic encompasses nearly 500,000 km2 of ocean, the total exposed land area is only about 176 km2 (Mink, 1986). Individual atoll islands are seldom larger than a few square kilometers and average only a few meters in elevation. Owing to their very small size, the lack of freshwater, and the danger of overtopping by storm waves, few of the islands are inhabited. The majority of the population lives on four major atolls: Majuro, the capital; Kwajalein, a center of U.S. defense activity; Jaluit; and Arno. The only public water systems in the Marshall Islands exist on several large islands in these atolls. Elsewhere, individual households obtain water from rainfall catchments and shallow dug wells (Mink, 1986). Most of the hydrogeologic information that serves as the basis for this chapter, therefore, comes from investigations conducted on the major atolls. In addition, a considerable body of information, especially geologic information, is from investigations conducted on Bikini and Enewetak Atolls prior to and after nuclear weapons testing during the 1940s and 1950s (Arnow, 1954; Emery et al., 1954; Ladd and Schlanger, 1960; Ristvet et al., 1978; Schlanger, 1963; Tracey and Ladd, 1974) [see also Chaps. 21, 22].