Dear Sultan,   You can ...

Dear Sultan,

You can calculate if you know any measure or can assume any estimated value of the seepage in the place you are thinking construct the reservoir.

Initially you must look for the appropiate seepage (or infiltration) measuring technical approved or used in your country to you can do any soil analysis and contract that service. Then using the obtained data and the appropiate calculation method you can calculate the required incognit.

On the other hand you can do an intial approximationt using the data you can obtain in a visit to the site (soil and other data), and some local or experience assupmtions to use the seepage tables.

Regards,

Orlando D. Gutiérrez Coronado