Report Number: 114
Year: 2007

A Preliminary Report on the Sabana Watershed/Talakhaya Spring System Rota (Luta), CNMI

Rota in the Mariana Islands is unique in that chain, because it gets its municipal water from high elevation contact springs (Water Cave and As Onan Spring), not from the freshwater lens. These springs, located near the top of an area known as the Talakhaya, are fed by recharge from the Sabana. Very little spring discharge has been found on the other flanks of the Sabana, leading to the hypothesis that most of the water recharged on the Sabana discharges along the Talakhaya. This relationship would be better understood with the application of a water budget, which will require a rain gage on the Sabana and a recording stream gage at least at Water Cave and possibly at As Onan Spring and other springs. The majority of the surface of the Sabana is highly permeable limestone with very fast, autogenic recharge. The summit of the Sabana is an outcrop of weathered volcanics that the feed ephemeral streams during rain events. These streams provide allogenic recharge at the contact between the volcanics and the overlying limestone. These streams were instrumental in locating insurgences along the contact, particularly north and west of the Peace Memorial. Much of the contact can be located by the presence of a "moat". South of the Sabana summit, Summit Cave is located on the contact and also captures a stream from the volcanics. On the east side of the Sabana volcanic outcrop, the contact is more difficult to locate, possibly because of human disturbance.

Thomas "Monty" M. Keel
John E. Mylroie
John W. Jenson