Water Yield Analysis on Area Coveredby Pine Forest at Kedungbulus Watershed Central Java, Indonesia
The analysis of water yield is conducted to provide information on the availability of water resources at a particular location in a watershed. Kedungbulus watershed is located at an area with plantation of pine forest. The pine forest area varies from 7% to 95% of the sub watershed areas. The plantation of this kind of vegetation (Pinusmerkusii) in some regions may cause water availability problem due to it may consume much more water rather than others. The objective of this study is to analyze the effect of pine forest area and its characteristics on the water yield in several of sub watershed at Kedungbulus Watershed. Direct measurement and prediction were used to estimate the water yield. A Thorthwaite and Mather method was used in this study to estimate the water yield. It was completed with data of rainfall, air temperature, soil properties, and land cover. Stand density varies from 388 to 644 stand/hectare and diameter at breast height (DBH) varies from 20 to 40 cm. The annual rainfall during the year of 2015 at the location was 2525 mm. It was found that the water yield tends to decrease with the increase of pine forest area. The water yield of the watershed with pine forest covered of 7% was 1520 mm/year, while watershed with pine forest covered 95% was lower (1289 mm/year). In order to increase the water yield, the pine forest plantation is not recommended in a certain area with low rainfall. Modified Thorthwaite-Mather Water Balance method was successfully applied to this case with a significant increase in determination coefficient from 0.3 to 0.7.
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Published by INSIGHT - Indonesian Society for Knowledge and Human Development