Total internal renewable water resources (IRWR)
Internal Renewable Water Resources (IRWR): Long-term average annual flow of rivers and recharge of aquifers generated from endogenous precipitation. Double counting of surface water and groundwater resources is avoided by deducting the overlap from the sum of the surface water and groundwater resources.
[Total internal renewable water resources (IRWR)] = [Groundwater produced internally]+[Surface water produced internally]-[Overlap between surface water and groundwater]
Climate, water resources
FAO, 2003. Review of World Water Resources by Country, Water Report 23 (ftp://ftp.fao.org/agl/aglw/docs/wr23e.pdf)
View data for this variable  in the AQUASTAT Main Database