Estimate the constant rate of withdrawal from a 1375 ha reservoir in a month of 30 days during which the reservoir level dropped by 0.75 m in spite of an average inflow into the reservoir of 0.5Mm3/d?

To estimate the constant rate of withdrawal from the reservoir, we need to calculate the total volume of water that was withdrawn during the month.

First, we need to calculate the total volume of water that flowed into the reservoir during the month:
Inflow = 0.5 Mm3/d * 30 days = 15 Mm3

Next, we need to calculate the total volume of water that was lost due to the drop in reservoir level:
Volume lost = 1375 ha * 0.75 m = 1031.25 Mm3

Therefore, the total volume of water withdrawn from the reservoir during the month is:
Withdrawn = Inflow - Volume lost
Withdrawn = 15 Mm3 - 1031.25 Mm3
Withdrawn = -1016.25 Mm3

Since the volume withdrawn is negative, it means that more water was lost from the reservoir than was added through inflow. This could be due to evaporation or other factors.

Therefore, the constant rate of withdrawal from the reservoir cannot be accurately estimated with the given information.