The study looked at how the health of the Upper Citarum watershed in West Java, Indonesia changed over 30 years based on the amount of vegetated land cover. Using satellite images, researchers found that the area of vegetated land decreased from 1990 to 2000, increased from 2000 to 2010, and then decreased again from 2010 to 2020. These changes affected the health of the watershed, with more unhealthy areas appearing over time, especially in the Ci Kapundung and Ci Sangkuy sub-watersheds.