Question

A Class-A pan was setup adjacent to a lake for measuring evaporation losses in the lake. The depth of water in the pan at the beginning of a certain week was 250 mm. In that week, there was a rainfall event with 10 mm depth. Water depth in the pan at the end of the week was 240 mm. The pan coefficient is 0.8.
The estimated lake evaporation during the week was |_________mm (an integer value).

Answer 1

Correct Answer: 16

Step 1: Calculate the expected water level in the pan after rainfall. \[ \text{Initial level} + \text{Rainfall} = 250 \text{ mm} + 10 \text{ mm} = 260 \text{ mm} \] Step 2: Determine the actual water level change due to evaporation. \[ \text{Expected level} - \text{Final level} = 260 \text{ mm} - 240 \text{ mm} = 20 \text{ mm of evaporation} \] Step 3: Apply the pan coefficient to estimate lake evaporation. \[ \text{Pan evaporation} \times \text{Pan coefficient} = 20 \text{ mm} \times 0.8 = 16 \text{ mm} \]