Hi Sultan, a few questions ...

Hi Sultan,

a few questions to help us understand your question better:

• are you interested in calculating the seepage lost through soil at the bottom of the reservoir? or the seepage through an earthen dam /embankment that holds the water back? or both?
• Also, are you looking for a quick "back-of-the-envelope" estimate that you can calculate in the office without collecting any additional field data? Or you are trying to come up with a detailed comprehensive estimate for a site already in development?
• How is the reservoir going to be filled? (e.g. stream/river that will be blocked with dam?, pumping water in?, rainfall. etc..?, and will there be ongoing sources of inflow to the reservoir (e.g. streams, rainfall, etc..)?

You will need to evaluate if the seepage rate will be greater or smaller than other inflow rates (such as from stream, rainfall, surface runnoff, etc..), and you most likely will need to assemble the following information (and possible other info as well).:

• estimate the soil hydraulic properties (e.g. if you have no field measurements, then you can estimate  upper and lower bounds based on literature value for loamy soils)
• develop estimates for other inflow rates to the reservoir (e.g. rainfall, streams, surface runoff, etc..)
• you also need to establish the depth to shallow groundwater and if there are any impermeable to low permeability soil horizons in the top few meters of soil, as this may limit seepage.
• you might also need to consider evaporation depending on the climate of the area where the reservoir will be constructed.

Pascual