Indonesia's major freshwater lakes: A review of current knowledge, development processes and threats

Abstract

Indonesia has over 500 lakes, varying from deep tectonic basins to volcanic, glacial and ephemeral floodplain types, but the paucity of data is striking. Hydrological data, for example, are scarce, and information on aquatic fauna mostly consists of lists of commercial fish, many of which have been introduced. Indonesia's lakes are valuable assets. Flood-plain lakes such as those of the Ogan-Komering (Sumatra), Upper Kapuas (Kalimantan) and Lake Tempe (Sulawesi) form the basis of important fisheries which in the case of Lake Tempe are at least as productive as artificial fishponds. Tectonic and volcanic lakes such as Lake Toba (Sumatra) and Lake Batur (Bali) are popular tourist destinations, and lake water resources are important for potable water, irrigation and hydropower. Large and ancient lakes often harbour endemics. Those of the Matano-Towuti lake system in Sulawesi, for instance, include more than 20 fish, 12 molluscs and 7 plant species.

A review of 35 large lakes throughout the archipelago shows that many have undergone major changes over the past decades, often resulting in degradation, and development plans threaten to disturb those relatively unaffected up to now. Dams occur in one third of all lakes and have been planned in another five. Siltation is a major problem in at least three lakes, while the introduction of water hyacinth and exotic fishes has been ubiquitous. Although poorly documented, losses of fishery production and fish extinctions are apparent. A combination of surveying, data evaluation and the formulation of a national strategy for the wise use of Indonesia's lakes and lake resources is urgently required to curb further loss of natural assets.