枯竭 (kū jié) means 'dried up, exhausted' and is used for water sources, resources, or creativity that have completely run out. It is more formal and literary than 光 (guāng, 'used up, finished'), which is a colloquial adjective often used as a complement (e.g., 吃光了). Unlike 干枯 (gān kū, 'withered, dried-up'), which describes physical drying of plants or skin, 枯竭 applies to abstract or large-scale depletion.