| Rawa Pening | |
|---|---|
| Rawa Pening in 2008 | |
| Basin countries | Indonesia |
| Surface area | 2,500 to 2,670 hectares (25 to 26.7 km2; 9.7 to 10.3 sq mi) |
Rawa Pening (literally meaning 'Clear Swamp', from the Javanese Bening) is a lake in the Ambarawa Basin in Central Java. It serves as a source of power, irrigation, and flood control, and is used for fishing. Due partly to high numbers of aquatic plants, it may dry out by 2021.
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Rawa Pening is located in the volcanic Ambarawa Basin in Central Java, [1] between Ambarawa and Salatiga. It covers a total area of 2,500 to 2,670 hectares (25 to 26.7 km2; 9.7 to 10.3 sq mi).[2][3] It is shallow and swamplike, [1] with muddy banks.[4]
Rawa Pening is estimated to have been formed between 18,000 and 13,500 BC after a period of increased precipitation. It reached its largest size from 11,000 to 9,000 BC, but shrank until it reached its current size around 6,000 BC.[5]
One of the major roles of Rawa Pening is as a source of hydroelectricity, with a power station located on the Tuntang River near the lake. Fishing is common as a source of supplementary income, and the water from the lake irrigates nearby rice fields. It has also been cited as being used for flood control.[4]
Numerous species of aquatic plant live in Rawa Pening, including Panicum repens,[6] Eichhornia crassipes, Salvinia cucullata,[7] and Hydrilla verticillata.[3] Estimates of the total number of species vary, from 20 in 1949 to 19 aquatic and 71 semi-aquatic species in 1972.[8] According to Soenarto Hardjosuwarno, P. repens is one of the main contributors to the formation of floating islands in the lake,[6] with M. Soerjani noting that E. crassipes and S. cucullata also contribute.[7] The aquatic plants, such as H. verticillatta, take root in the large amount of peat (in some places measuring 2 metres (6.6 ft) thick), causing more peat to gather. Eventually, terrestrial plants take root in the floating islands as well.[9]
According to Tri Retnaningsih Soeprobowati, a researcher at Diponegoro University in Semarang, Rawa Pening could become dry by 2021 due to increasing sedimentation. She reports a total rate of deposition of 270 to 880 kilograms (600 to 1,900 lb) per day, averaging 780 tonnes yearly,[2] with the water level dropping 29% since 1989.[3] The overabundance of aquatic plants has been blamed, especially E. crassipes. As such, there are calls for a culling of the E. crassipes population to 20% by 2030.[3] Other suggestions include the introduction of grass carp to control the plant population and the use of herbicides as last resorts.[2][3] The destruction of H. verticillatta had earlier been attempted beginning in 1932, originally using mechanical methods but later switching to herbicides. These efforts were discontinued in the 1960s.[10]