lake; lake water
Refers to a lake as a body of water, or the water within it. Slightly more formal or literary than 湖 (みずうみ).
The lake water was surprisingly clear.
The Lake District is popular with tourists.
limnic eruption
Compound of 湖 (こ, 'lake') and 水 (すい, 'water'). The reading こすい is the standard on'yomi combination.