Climatological and land use evaluation to maintain water supply in Pulai reservoir, Bintan island - Indonesia

Abstract

Pulai reservoir with an area of 49.9 ha and maximum depth of 12 m, serves as clean water resources for Tanjung Pinang city, Bintan island. The objective of this research was to evaluate the fluctuation of water level on reservoir, related to the climatological and land use conditions. Water level in January 2009 was 400 cm and continued to decrease to 105 cm in August 2009 that ceased the water supply. The rainfall during ten months study period (January – October 2009) was 1,968 mm, below of its average level of 2,447 mm. The dry spell reduced the water supply input to reservoir for about 2.5 million m3 or equivalent to four months of clean water supply. Mean monthly air temperature was also increased by 1 °C compared to the last 29 years. A similar trend was observed for humidity, where its mean value of 85.9% decreased to 83.3%. Initially, the catchment area was 474.12 ha, covered by protected forest (98%). However, in 2009 the remaining forest area was only 8.15%. It suggested the decreasing of water storage capacity. It could be explained that the climate change and uncontrolled land use may contribute to the water crisis of Pulai reservoir.