The document summarizes a water accounting analysis of the Nile River basin. It finds that of the 1745 km3 of annual rainfall in the basin, only 76.6 km3 (4%) is available for diversion due to high evapotranspiration rates. Natural land uses like forests and savannah account for 85% of the basin's water consumption, while irrigated agriculture accounts for just 4% despite occupying a larger area. There is potential to increase water productivity in natural lands through improvements that benefit livestock grazing without increasing river diversions.

1. FU Berlin
Improved Agricultural Water Management In the Nile Basin
Nile Water Accounting: How much is water resources and use in the Nile basin?
1. Introduction
The Nile water accounting (WA) assesses availability and use of the Nile waters considering
all water supplies (rainfall, river flows, groundwater), and all uses (rainfed agriculture,
wetlands, irrigation, pasture land, natural cover etc.). The computation procedure is based
on water balance principles, utilizing satellite measurements of rainfall (P),
evapotranspiration (ET), biomass production (Bio), and limited ground information of river
flows (Q). The derived results helps to identify opportunities and constraints for basin‐wide
water management, providing insights on how to manage water better, and hints to guide
future analysis.
2. Materials and methods < 25
25 - 50
50 - 100
Water use in the Nile basin is represented by 15 100 - 200
200-400
land use and water use classes, aggregated into 3 400 - 600
600 - 800
water management categories: natural land use 800 - 1000
1000 - 1200
1200 -1400
(NL), managed land use (ML) and managed water 1400 - 1600
>1600
use (MW). The categorization reflects to what
extent the Nile basin is regulated.
Spatio‐temporal variability of rainfall and potential evapotranspiration
Rainfall is the main water supply, as there are no
inter‐basin water transfers. Total outflow to the
Mediterranean Sea was estimated as the closure
term of the water balance. The ratio of biomass
Natural land use Managed land use Managed water use
production to evapotranspiration provides an
Natural forest Forest plantation Irrigation
indicator of water productivity. Savannah Rainfed agricutlure Managed wetlands
Desert Drinking water
15 land use and water use classes
3. Results
P-ET= 81.4 P-ET= 5.0 P-ET= -57.4
The water accounting results over 1 km2 pixels, aggregated to NL, ML, and MW for year 2007 is
Available flow= 76.6
shown in the figures and charts. Of the 1745 km3 of rainfall, only 76.6 km3 (4%) is available for
ΔS= 0.0
diversion. The total ET is 98% of the total water supply showing that the Nile is nearly a closed
basin with little opportunity to increase diversions. The majority of ET (85%) is consumed by Outflow = 29.0
Aquifer & reservoirs
natural land use 85% (forests, savannah, etc. much of which supports livestock); with 11% Committed = 9.8
consumed by managed land use (mainly rainfed crops); and only 4% by managed water use (mainly
irrigation). About 76% of the total ET is beneficial (economical or environmental), and only 24%
non‐beneficial largely as soil evaporation from different land use classes.
5. Conclusion
The analysis shows that irrigation is just a small piece of the water
use within the Nile basin. Rainfed agriculture (7% of area), produces
80% of the biomass, while irrigated land (1.6% of area) produces
20%.
Opportunities to increase water productivity without influencing
river flows lies within the natural land use (Savannah, shrub land,
forest, etc.), much of which supports livestock. The analysis shows
that there is scope for water productivity improvements, and scope
to convert non‐beneficial evaporation to productive transpiration.
For more information contact: e‐mail address
Y.Mohamed@unesco‐ihe.org