amount of water; water level; water adjustment
Refers to the quantity or level of water, especially in cooking, gardening, or when adjusting consistency.
When cooking rice, the amount of water is important.
Check the water level of the soup and add a little more.
火加減 refers to heat control or flame adjustment, while 水加減 is about water quantity.
Compound of 水 (water) and 加減 (adjustment, degree). The combination straightforwardly means 'water adjustment' or 'amount of water'.