Abstract
The Nile River Basin covers an area of approximately 3.2 million km2 and is shared by 11 countries. Rapid population growth is expected in the region. The irrigation requirements of Nile riparian countries of existing (6.4 million ha) and additional planned (3.8 million ha, 2050) irrigation schemes were calculated, and the likely water savings through improved irrigation efficiency were evaluated. We applied SPARE:WATER to calculate irrigation demands on the basis of the well-known FAO56 Crop Irrigation Guidelines. Egypt (67km3yr−1) and Sudan (19km3yr−1) consume the highest share of the 84km3yr−1 total (2011). Assuming today’s poor irrigation infrastructure, the total consumption was predicted to increase to 123km3yr−1 (2050), an amount far exceeding the total annual yield of the Nile Basin. Therefore, a key challenge for water resources management in the Nile Basin is balancing the increasing irrigation water demand basin-wide with the available water supply. We found that water savings from improved irrigation technology will not be able to meet the additional needs of planned areas. Under a theoretical scenario of maximum possible efficiency, the deficit would still be 5km3yr−1. For more likely efficiency improvement scenarios, the deficit ranged between 23 and 29km3yr−1. Our results suggest that that improving irrigation efficiency may substantially contribute to decreasing water stress on the Nile system but would not completely meet the demand. Study RegionThe Nile River Basin covers an area of approximately 3.2 million km2 and is shared by 11 countries. Rapid population growth is expected in the region. Study FocusRecord population growth is expected for the study region. Therefore, the irrigation requirements of Nile riparian countries of existing (6.4 million ha) and additional planned (3.8 million ha, 2050) irrigation schemes were calculated, and likely water savings through improved irrigation efficiency were evaluated. We applied a spatial decision support system (SPARE:WATER) to calculate the irrigation demands on the basis of the well-known FAO56 Crop Irrigation Guidelines. New Hydrological Insights for the RegionEgypt (67km3yr−1) and Sudan (19km3yr−1) consume the highest share of 84km3yr−1 (2011). Assuming today’s poor irrigation infrastructure, the total demand were predicted to increase to 123km3yr−1 (2050), an amount far exceeding the total annual yield of the Nile Basin. Therefore, a key challenge for water resources management in the Nile Basin is balancing the increasing irrigation water demand and available water supply.We found that water savings from improved irrigation technology will not be able to meet the additional needs of planned areas. Under a theoretical scenario of maximum possible efficiency, the deficit would still be 5 km3yr−1. For more likely efficiency improvement scenarios, the deficit ranges between 23 and 29km3yr−1. Our results suggest that improving irrigation efficiency may substantially contribute to decreasing water stress on the Nile system but would not completely meet the demand.
Highlights
We investigated the likely effects of improved irrigation efficiency for the future, i.e., the ratio between the water made available for plant water uptake and the water taken from the source
The IRRgross to grow crops in the Nile River Basin was calculated for existing harvested areas (6.4 mio. ha) under the assumption of the baseline scenario, i.e., most schemes were equipped with gravity irrigation systems (85%), and only a minor fraction of the schemes were equipped with pressurized systems (15%), most of which were located in Egypt (Table 3)
A further differentiation in relation to irrigation systems showed that 73 km3 yr−1 (87%) and 11 km3 yr−1 (13%) would be consumed in areas equipped with gravity and pressurized systems, respectively
Summary
Water consumption is globally driven by agricultural demand to grow food and feed for people and animals (Rost et al, 2008; Siebert and Döll, 2010; FAO, 2016). Strategies for decreasing water consumption by agriculture include better management of rainfall (Rockström et al, 2009) and irrigation (Pereira et al, 2002). The latter is important because unsustainable irrigation is globally a major driver of water resource depletion, e.g., of river flows (Döll et al, 2009) and groundwater aquifers (Wada et al, 2012). We investigated the likely effects of improved irrigation efficiency for the future, i.e., the ratio between the water made available for plant water uptake and the water taken from the source (surface and groundwater)
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