Evaluation of land use impact on soil and water quality degradation in Santan and Marangkayu Wathershed

Watersheds in Santan and Marangkayu are involved in Kutai National Park area as a conservation forest area. The forest area is decreasing due to illegal logging, forest clearing, mining, plantation and agriculture. The changing of land use which not followed by preventing steps causes degradation. Hence, this study aims to figure out the level of land degradation to determine the appropriate conservation direction to make the land use sustainable. This study applied USLE equation to predict soil erosion rate, Geographical Information System (GIS) to determine critical land through overlay analysis, and STORET method to measure the water quality index. The result shows that the danger level of erosion in Marangkayu watershed is higher than in Santan watershed. Land degradation caused by mining activity raises critical land and contaminated water. Index of land closure is about 69%, which is still suitable as buffer zone for Santan watershed area. Meanwhile, Marangkayu watershed results 22% of land closure index which is no longer appropriate as buffer zone. This study also found that land degradation is caused by land clearing for mining, with 10.746,20 hectares of critical land in Santan watershed and 485, 83 hectares of critical land in Marangkayu watershed. In addition, the water quality of rivers in Santan and Marangkayu have low level of contamination considering the high Fe content as the result of mining activity at the river upstream. Referring to the research result, intensive forest security efforts are highly needed to prevent illegal logging, monitor activities causing expansion of open land use and critical land that also create water pollution.