Class-A Pan Evaporation Calculation

This problem involves calculating lake evaporation using measurements from a Class-A evaporation pan and applying a pan coefficient.

Given Evaporation Data

• Initial water depth in pan: $250 \text{ mm}$
• Rainfall during the week: $10 \text{ mm}$
• Final water depth in pan: $240 \text{ mm}$
• Pan coefficient ($K_P$): $0.8$

Pan Evaporation Calculation

First, determine the actual evaporation from the pan ($E_P$). The change in water level accounts for both evaporation and rainfall.

Change in pan water level: $\Delta h = \text{Initial Depth} - \text{Final Depth}$

$\Delta h = 250 \text{ mm} - 240 \text{ mm} = 10 \text{ mm}$

The pan evaporation is calculated using the relationship:

$E_P - \text{Rainfall} = \Delta h$

Substituting the known values:

$E_P - 10 \text{ mm} = 10 \text{ mm}$

Solving for $E_P$:

$E_P = 10 \text{ mm} + 10 \text{ mm} = 20 \text{ mm}$

Lake Evaporation Estimation

Next, estimate the lake evaporation ($E_L$) using the calculated pan evaporation ($E_P$) and the given pan coefficient ($K_P$).

Formula: $E_L = K_P \times E_P$

Substituting the values:

$E_L = 0.8 \times 20 \text{ mm}$

$E_L = 16 \text{ mm}$

Resulting Lake Evaporation

The estimated lake evaporation for the week is 16 mm.