Page 119 - CIWA Water Data Revolution Overview Report

Figure 6: Water accounts for the Volta basin for the period 2025-2050 for the ensemble
mean of GFDL-ESM4 Model and MPI-ESM1-2-HR Model.

• Inflows: The gross inflow into the basin predominantly precipitation is expected to
be 406.0 km³/year. Storage changes, including variations in surface water,
groundwater, and soil moisture, will contribute an additional 7.8 km³/year, resulting
in a net inflow of 413.8 km³/year.

• Landscape AET: A significant portion of the net inflow (382.0 km³/year) will be
consumed across the landscape as actual evapotranspiration (AET). This includes:

o Rainfall AET (Green Water): 219.5 km³/year, directly derived from rainfall.

o Incremental AET (Blue Water): 162.5 km³/year, sourced from irrigation and
other water uses.

• Exploitable Water: The remaining 31.8 km³/year represents the portion of net inflow
not lost to evaporation. This exploitable water is available for withdrawals or
downstream use but is subject to constraints:

• Reserved Outflow: 8.5 km³/year is set aside for environmental flow requirements
and downstream commitments.

• Available Water: After accounting for reserved and non-utilizable outflows, 23.0
km³/year remains for potential use.

• Utilized Flow: Of the available water, 10.8 km³/year is consumed, while 7.2 km³/year
is lost as non-recoverable flow due to degradation. The remaining 12.2 km³/year
constitutes utilizable outflows for future allocation.