The Segara Anakan lagoon in Cilacap, Central Java, has receded to 90 percent of its original size as a result of large-scale sedimentation from the Citanduy and Cimeneng rivers, says a local official.

Sediments carried by the two major rivers in West and Central Java have reduced the lagoon's surface area from 6,460 hectares in 1903 to only around 700 ha today.

"An average of 1 million cubic meters of silt flow into Segara Anakan every year, which definitely poses a threat to the marine ecosystems there," Segara Anakan Management Agency (BPKSA) head Supriyanto told The Jakarta Post recently.

The huge volume of silt, Supriyanto said, originates from six regions, four of them located in West Java (Ciamis, Tasikmalaya and Kuningan regencies and Banjar municipality) flowing through Citanduy River, and two others in Central Java (Cilacap and Banyumas regencies) carried by the Cimeneng River.

"The greatest volume comes from West Java. Our survey shows 760,000 cubic meters of sludge flow from the Citanduy. Only a quarter comes from the Cimeneng," said Supriyanto.

The silting up of the lagoon, added Supriyanto, would have an adverse impact on thousands of fishermen not only in Cilacap but also in Kebumen and Yogyakarta.

"That's because Segara Anakan, with its abundant mangrove swamp, is a key part of the marine ecosystem. Spawning prawns, for example, seek protection and food in the mangroves," said Supriyanto.

Based on studies conducted by marine ecologists, he added, Segara Anakan was special in the Asia Pacific region for its biodiversity and size.

The Segara Anakan lagoon and estuary is located on the south coast of Java at the border between the provinces of West and Central Java near the port of Cilacap. It is protected from the Indian Ocean by Nusakambangan Island and has two outlets to the sea.

The marine zone is home to 8,300 ha of mangrove swamp, home to 26 species of mangrove trees and hundreds of species of shrimp and fish which breed there.

"In economic terms each hectare of mangrove can cultivate shrimp and fish worth Rp 17 million (US$1,700). Just multiply that by 8,300 ha. Billions of rupiah of fishing assets are located in the area," said Supriyanto.

However, the lagoon has continued to shrink from the alarming rate of sedimentation. The mangrove forest has also diminished due to diminished water supply, a result of the sludgy build-up.

Supriyanto said the huge volume of silt in the run-off is due to illegal logging and farmers' improper planting patterns in the river basin areas of the Citanduy and Cimeneng.

"The only effective method to overcome sedimentation is by digging a channel for water to flow directly to the sea. But action hasn't been taken because each regency has its own interests," said Supriyanto.

He said Ciamis and Banjar were among those which disagreed with the idea of a waterway incision because it could lead to pollution at Pangandaran beach, one of West Java's top tourist sites.

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