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Journal of Hydrology: Regional Studies
journal homepage: www.elsevier.com/locate/ejrh
Improving irrigation efficiency will be insufficient to meet future
water demand in the Nile Basin
S. Multsch
a,⁎
, M.E. Elshamy
b
, S. Batarseh
a
, A.H. Seid
b
, H.-G. Frede
a
, L. Breuer
a,c
a
Institute for Landscape Ecology and Resources Management (ILR), Research Centre for BioSystems, Land Use and Nutrition (iFZ), Justus Liebig
University, Giessen, Germany
b
Nile Basin Initiative Secretariat (Nile-SEC), Entebbe, Uganda
c
Centre for International Development and Environmental Research (ZEU), Justus Liebig University, Giessen, Germany
ARTICLE INFO
Keywords:
Irrigation
SPARE:WATER
future projection
Nile
irrigation efficiency
ABSTRACT
The Nile River Basin covers an area of approximately 3.2 million km
2
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 (67 km
3
yr
−1
) and Sudan
(19 km
3
yr
−1
) consume the highest share of the 84 km
3
yr
−1
total (2011). Assuming today’s poor
irrigation infrastructure, the total consumption was predicted to increase to 123 km
3
yr
−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
5km
3
yr
−1
. For more likely efficiency improvement scenarios, the deficit ranged between 23 and
29 km
3
yr
−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 Region: The Nile River Basin covers an area of approximately 3.2 million km
2
and is shared
by 11 countries. Rapid population growth is expected in the region.
Study Focus: Record 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 Region: Egypt (67 km
3
yr
−1
) and Sudan (19 km
3
yr
−1
) consume
the highest share of 84 km
3
yr
−1
(2011). Assuming today’s poor irrigation infrastructure, the total
demand were predicted to increase to 123 km
3
yr
−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,
http://dx.doi.org/10.1016/j.ejrh.2017.04.007
Received 11 October 2016; Received in revised form 20 April 2017; Accepted 30 April 2017
⁎
Corresponding author at: Heinrich−Buff−Ring 26, 35392, Giessen, Germany.
E-mail address: sebastian.multsch@umwelt.uni-giessen.de (S. Multsch).
Journal of Hydrology: Regional Studies 12 (2017) 315–330
2214-5818/ © 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/BY-NC-ND/4.0/).
MARK
the deficit would still be 5 km
3
yr
−1
. For more likely efficiency improvement scenarios, the
deficit ranges between 23 and 29 km
3
yr
−1
. Our results suggest that improving irrigation effi-
ciency may substantially contribute to decreasing water stress on the Nile system but would not
completely meet the demand.
1. Introduction
1.1. Irrigation efficiency
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). In particular, 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). As a consequence, surface and groundwater resources are under severe pressure worldwide (Gleeson et al., 2012;
Hoekstra et al., 2012). Nevertheless, irrigation is indispensable for feeding people (Siebert and Döll, 2010). Hence, the management
of irrigated areas was addressed in this study for one of the world’s largest river basins, where irrigation has shaped agriculture for
thousands of years: the Nile River Basin. In particular, 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).
Irrigation efficiency has been discussed in great detail (Howell, 2003; Jensen, 2007; Lankford, 2012), and general instructions for
the estimation of irrigation efficiency have been provided by the FAO Irrigation and Drainage guidelines (Brouwer et al., 1989). The
efficiency of an irrigation scheme is derived from two components. The conveyance efficiency (off-farm, e
c
) is calculated according to
water losses that occur when water is delivered to farms (e.g., through leakage and evaporation from canals and cracks in canal
bunds). The application efficiency (on-farm, e
a
) is calculated according to losses on fields, e.g., evaporation from the soil surface and
open waters and interception and deep percolation into the groundwater. The scheme efficiency (e) is derived by multiplying both
components (e = e
c
xe
a
/100).
Water savings through improved irrigation efficiency has been discussed for Saudi Arabia, where arid climate and irrigation with
fossil groundwater resources are dominant, and the agriculture sector consumes most of the scarce water resources (Multsch et al.,
2016b). Multsch et al. (2016b) have shown that national water consumption could potentially be reduced by 32% if no salt sensitive
crops are grown and modern irrigation technology is adopted. Hence, irrigation efficiency plays a major role, as shown in a global
study (Jägermeyr et al., 2015) highlighting the likely water savings gained by decreasing non-beneficial consumptive use, i.e., by
limiting losses through evaporation and interception and decreasing non-recoverable return flow (e.g., water flows to salinized water
bodies).
1.2. Objective and approach
We evaluated the water consumption of irrigated agriculture in the riparian countries of the entire Nile River Basin, because a
substantial expansion of irrigation schemes is expected in the coming decades (BCEOM, 1999; WREM, 2006; Awulachew et al., 2012).
Previous studies have highlighted that the accompanying agriculture water demand cannot be met in the future (Awulachew et al.,
2012). This situation is likely to worsen because many dams are being constructed, which will alter river flows, most probably
decreasing water resources for downstream users (McCartney et al., 2012). Collaboration between riparian countries is important to
solve the current and future water resources demands in the Nile River Basin (Abdelhady et al., 2015). Furthermore, technical
approaches, such as improving irrigation efficiency, may be a measure to partly counteract future water scarcity (McCartney et al.,
2012), but it is currently unknown to what degree this is feasible.
Three objectives were focused on in this study. First, the water consumption of today’s irrigated agriculture (existing areas) was
estimated on the basis of current irrigation technology. National plans show considerable increases in the extent of irrigation schemes
during the coming decades up to 2050. Therefore, in a second step, we estimated the water consumption for additional planned
irrigated areas up to 2050, assuming that the irrigation efficiency remains at today’s level. When summing up existing and planned
irrigated areas, a prediction of the future water demand in the Nile River Basin can be done.Third, scenarios were assessed that
assumed stepwise improvements in irrigation efficiencies as well as a theoretical best technology scenario leading to maximum
efficiency. Our key question addressed the problem of whether the quantity of likely water savings through improved irrigation
technology might be sufficient to provide for the total water consumption of planned irrigation schemes in the future.
The study relied on existing data obtained primarily from the Nile Basin Initiative (NBI) (such as the Nile Basin Decision Support
System (NB DSS), Multi-Sector Investment Studies for the Eastern Nile and the Nile Equatorial Lakes region) and from public data
sources. The field level water demand model SPARE:WATER (Multsch et al., 2013), which was integrated into a geographic in-
formation system, was set up with site-specific crop parameters and high resolution gridded climate data to assess the water re-
quirements for growing field crops and to evaluate the water savings from improved irrigation efficiency.
S. Multsch et al. Journal of Hydrology: Regional Studies 12 (2017) 315–330
316
2. Methods: SPARE:WATER model
The Site–sPecific Agricultural water Requirement and footprint Estimator (SPARE:WATER, www.uni-giessen.de/cms/hydro/
download)(Multsch et al., 2013) is a spatial decision support system for estimating the fate of water consumption in agricultural
production systems. SPARE:WATER enables the spatially explicit calculation of crop-specific water requirements, considering all
water resources needed, including green (consumed rainfall), blue (consumed irrigation) and gray (salt leaching) water. Equipped
with a graphical user interface, SPARE:WATER calculates the crop water requirement according to the Food and Agricultural Or-
ganization FAO56 crop water guidelines (Allen et al., 1998). This study focused on the consumption of blue and gray water by
irrigation schemes, as calculated as follows:
=−+IRR ET P
eLR
max( , 0)
gross
ceff
a
Blue
add
Grey
(1)
with gross irrigation IRR
gross
, crop specific evapotranspiration ET
c
,effective rainfall P
eff
and leaching requirement LR
add
in (m
3
ha
−1
) and the application efficiency e
a
in (dimensionless). The application efficiency, e
a
, refers to on-farm efficiency and accounts for
unproductive water losses. In particular, managing salt leaching is an important task (Ayers and Westcot, 1985), because salinization
is an increasing issue worldwide (Fischer et al., 2008; Rengasamy, 2010), especially in Egypt and Sudan, where one-third of irrigated
Fig. 1. (a) Map of the Nile River Basin and existing and planned irrigated areas. The black dots indicate climate stations from the Climwat 2.0 database (FAO, 2015),
and the red dots highlight the stations from which the reference evapotranspiration (ET
o
) and rainfall data shown in b-d were taken.
S. Multsch et al. Journal of Hydrology: Regional Studies 12 (2017) 315–330
317
areas are salinized, comprising 900,000 ha and 500,000 ha, respectively (FAO, 2016). The leaching requirement is the water needed
to wash salts from the rooting zone. LR
add
refers to the additional water requirement when ineffective irrigation losses through
percolation are insufficient to cover the potential leaching requirement (Howell, 2003). The leaching requirement was calculated
according to Ayers and Westcot (1985) on the basis of a crop salinity response function, in which two parameters describe the salinity
tolerance of a field crop, including the maximum value of the electrical conductivity of irrigation water without any yield losses
(ECe100%) and the electrical conductivity at which crop growth is fully limited (ECe0%). A linear relationship between crop growth
and conductivity is assumed between these values. ET
c
is derived by multiplying reference evapotranspiration (ET
o
) by a crop-specific
parameter (K
c
) to adjust ET
o
to the crop-specific development, according to the single crop coefficient concept (Allen et al., 1998).
The development of a field crop is divided into four development stages (initial stage, growth stage, mid-stage, and late stage). Three
crop coefficients are defined for the initial stage, the mid-stage and the last day of the late stage. Values for the development stage, as
well as the time during the late stage, are interpolated according to the number of days after sowing. ET
o
is calculated by using the
FAO56 Penman-Monteith equation, which is based on temperature, humidity, wind speed and radiation derived from sunshine hours.
P
eff
is derived from the difference between rainfall and surface runoff. A detailed overview of the underlying equations is given in
Multsch et al. (2013).
IRR
gross
was derived for each crop for the entire Nile River Basin at a grid cell spatial resolution of ∼5 km x 5 km. An average of
IRR
gross
for all grid cells per irrigation scheme (m
3
ha
−1
) was calculated to derive the annual IRR
gross
(km
3
yr
−1
) of the existing and
planned irrigation schemes of the Nile River riparian countries. Subsequently, irrigation efficiency scenarios were evaluated on the
basis of country-specific assumptions regarding current and future technological improvements. Further details on the underlying
meteorological data, irrigated areas and irrigation efficiency and the scenarios are described in the following sections.
3. Data
3.1. The Nile Basin
The Nile is the longest river in the world (6,700 km) (Fig. 1a). The basin covers an area of approximately 3.2 million km
2
and is
shared by 11 countries. The total population living within the basin is estimated to be 238 million, whereas the total population of the
riparian countries is currently 437 million inhabitants. Further rapid population growth is expected, and the population has been
predicted to increase to 648 million inhabitants in the riparian countries in 2030 (NBI, 2012).
Compared with other large rivers worldwide, the Nile has a relatively small annual runoff, with an average discharge between 40
and 150 km
3
yr
−1
at the High Aswan Dam (Johnston, 2012) and a long-term average of 84 km
3
yr
−1
per year. River flow in the Nile
River Basin is generated from an area less than one-third of the total basin area. Approximately 85% of the river flow received at the
High Aswan Dam in Egypt is generated in the Ethiopian highlands (Blue Nile, Baro-Akobo, and Tekeze-Atabara), and the remaining
flow is delivered from the Equatorial Lakes region and South Sudan (Awulachew et al., 2010) (note that the 85% contribution is at the
higher range of published estimates; e.g., Conway (2000) has reported a value of 60%). A strong climate gradient affects the river
basin, with almost no rainfall in Egypt (Fig. 1b) and higher rates in Ethiopia (Fig. 1c), particularly around Lake Victoria (Fig. 1d).
Further, we found two to three times higher reference evapotranspiration in Egypt than in Ethiopia or Uganda.
The downstream parts of the Nile River Basin in Egypt and Sudan are characterized by relatively high levels of water resource
development for agriculture and power generation, whereas the upstream parts largely depend on traditional subsistence level rain-
fed agriculture and, as a result, very low levels of water extraction from the river. Concordantly, the current level of dependence on
Nile waters for energy and food production is highly skewed, with Egypt being the most Nile-dependent country.
However, national plans show a considerable increase in water resource development over the coming decades (Nedeco, 1998;
BCEOM, 1999; WREM, 2006). On the basis of national plans available for this study, the total increase in irrigation areas by 2050 is
estimated to be 3.2 million ha (Fig. 1a, light green areas). More than half of this increase is expected to be in upstream countries.
Given that the Nile is shared by 11 countries and that agriculture consumes most of the Nile waters, one of the most important
questions to address is how the Nile River Basin’s water resources will evolve under the anticipated water extractions to meet the
growing demands for food production.
3.2. Meteorological data
The FAO Climwat 2.0 database was used for this analysis (FAO, 2015). The dataset includes over 5,000 climate stations
worldwide, from which 425 were considered for this analysis (Fig. 1). The climate time series provides long-term averages of at least
15 years (1971–2000) of various variables (minimum and maximum temperature, relative humidity, wind speed, and sunshine hours)
as monthly averages. These were used to derive ET
o
according to the FAO56 Penman-Monteith method as well as monthly sums of
rainfall to estimate P
eff
. Grid maps were interpolated by using the Inverse Distance Weighted method (Philip and Watson, 1982;
Watson and Philip, 1985) to derive maps for the Nile River Basin at a spatial resolution of 0.041° (∼5 × 5 km at the equator), by
using ArcGIS™Spatial Analyst (Fig. A1a, b).
S. Multsch et al. Journal of Hydrology: Regional Studies 12 (2017) 315–330
318
3.3. Irrigation technique, efficiency and salinity
Irrigation technologies can generally be divided into two types. In surface (gravity flow) systems, water is transported from the
source by a system of (open) canals and ditches. In such systems, there are several different methods for applying the water to
irrigation fields, such as basin inundation systems or furrows (small ditches between rows of plants). The degree of maintenance of
the canals is an important topic. Well-maintained canals provide little hydraulic resistance to flows and hence decrease the residence
time of the water in canal systems, which in turn contributes to decreased evaporation losses. In pressurized systems (sprinkler or drip
systems), water is conveyed in closed pipes under pressure and is either ‘sprayed’on the crops or provided through a system of
flexible pipes with small nozzles, from which ‘drips’directly supply water to the plants. Such systems have the highest irrigation
efficiencies but also the highest implementation costs. The dominant method in the Nile River Basin is surface irrigation, according to
FAO Aquastat (FAO, 2016). Sprinkler irrigation is used in Egypt (5%), Ethiopia (2%), Uganda (25%) and Kenya (60%). An even lower
percentage of areas in the Nile River Basin are irrigated by drip irrigation, with, e.g., the highest values in Egypt (6%), Uganda (3%)
and Kenya (2%). The data from the FAO were considered in the calculations in this study, except for Egypt, for which regional data
were available (Table 1).
A comprehensive list of irrigation efficiencies according to irrigation method has been published by the FAO (Brouwer et al.,
1989) and by Howell (2003). Often, values of 60%, 75% and 90% have been reported for surface, sprinkler and drip irrigation,
respectively (Brouwer et al., 1989). We used this information along with the expert knowledge of NBI staffmembers who are familiar
with local management and practices. See Table A1 for a detailed description of the irrigation efficiencies for each country and
province for gravity and pressurized systems. On average, the values ranged between 60 and 70% for Ethiopia, Kenya, Rwanda, South
Sudan, Sudan, Tanzania and Uganda. The irrigation efficiency of Egypt was assumed to be slightly higher (between 70 and 80%). The
calculations presented in this work are related to application efficiency (on-farm) without considering off-farm losses such as the
maintenance conditions of the canals or farmer discipline. In our concept, water quality is related to the salinity concentration in
irrigation water, because this is the largest driver of additional water needed to wash salts from the soil. The salinity is commonly
measured in terms of total dissolved solids (TDS in mg L
−1
or ppm) or electric conductivity (EC, dS m
−1
), whereby an EC of 1 dS m
−1
equals a TDS of approximately 640 ppm. A detailed map is available for parts of the Nile Delta in Egypt (Abu-Zeid, 1990) and shows a
strong downstream increase in Nile River salinity, with values up to 13 dS m
−1
in the coastal area. Such high salinity water is caused
by river water mixing with brackish water from the Mediterranean Sea and is unsuitable for irrigation. Therefore, the total salinity
Table 1
Irrigation technology in the Nile River Basin.
Country District Baseline, Sce1, Sce2 Sce3 Sce3
%Gravity %Pressurized %Gravity %Pressurized
Egypt
a
Aswan 100% 0% 0% 100%
Egypt
a
Qina 100% 0% 0% 100%
Egypt
a
Sohag 100% 0% 0% 100%
Egypt
a
Asyiut 100% 0% 0% 100%
Egypt
a
Al Fayyum 100% 0% 0% 100%
Egypt
a
Al Jizah 44% 56% 0% 100%
Egypt
a
Al Minya 100% 0% 0% 100%
Egypt
a
Beni Suwayf 100% 0% 0% 100%
Egypt
a
Al Bahayrah 66% 34% 0% 100%
Egypt
a
Al Daqahliyah 97% 3% 0% 100%
Egypt
a
Al Gharbiyah 100% 0% 0% 100%
Egypt
a
Al Minufiyah 100% 0% 0% 100%
Egypt
a
Al Qalyubiyah 80% 20% 0% 100%
Egypt
a
Ash Sharqiyah 73% 27% 0% 100%
Egypt
a
As Ismailiyah 39% 61% 0% 100%
Egypt
a
Dumyat 100% 0% 0% 100%
Egypt
a
Kafr-El-Sheikh 100% 0% 0% 100%
Egypt
a
Matruh 0% 100% 0% 100%
Egypt
a
Al Qahirah 100% 1% 0% 100%
Egypt
a
Al Iskandariyah 27% 73% 0% 100%
Egypt
a
Bur Said 0% 100% 0% 100%
Egypt
a
Shamal Sina 0% 100% 0% 100%
Sudan 95% 5% 0% 100%
South Sudan
b
100% 0% 0% 100%
Ethiopia
b
98% 2% 0% 100%
Kenya
b
38% 62% 0% 100%
Tanzania
b
100% 0% 0% 100%
Rwanda
b
100% 0% 0% 100%
Uganda
b
73% 27% 0% 100%
a
Information from the Nile Basin Decision Support System (NB DSS).
b
FAO Aquastat (FAO, 2016).
S. Multsch et al. Journal of Hydrology: Regional Studies 12 (2017) 315–330
319
level is limited to 2.5 dS m
−1
in the Nile delta and 0.4 dS m
−1
at the Aswan dam (personal communication with NBI staff). A linearly
declining salinity level was assumed for the areas between the Aswan dam and the Nile delta (Fig. A2). Other upstream river parts
had a salinity level equal to that of the Aswan dam.
3.4. Irrigated areas and cropping pattern
The study relied on data collected from NBI’s previous work, national plans and other published materials. Data on irrigated areas
in the Nile Basin were collected from various reports and studies conducted by the Nile Basin Initiative (Bart et al., 2011; NBI-
NELSAP, 2012; NBI-ENTRO, 2014). Table 2 provides a summary of existing irrigation areas and those planned for the 2050 time
horizon. The existing areas represent the current state in 2011. The planned areas represent additional irrigation areas according to
national development plans. To calculate the total amount of irrigated areas in 2050, both values were added. It is important to note
that the reported areas include double cropping, i.e., the cropping intensity in Egypt is 136% because some fields are harvested twice
per year. Most of the irrigated areas exist in Egypt and Sudan. Other Nile countries depend primarily on rain-fed agriculture and flood
recession agriculture. However, this pattern is expected to change because other countries also plan to implement ambitious irri-
gation schemes, e.g., the Grand Ethiopian Renaissance Dam (GERD) in Ethiopia (Abdelhady et al., 2015). Overall, nearly 90% of the
planned expansion in irrigated areas is expected to occur in the Eastern Nile countries of Egypt, Ethiopia, South Sudan and Sudan.
Cropping patterns and crop coefficient (Kc) values for Egypt were taken from FAO F4T (Bart et al., 2011) for the different districts
(governorates). Cropping patterns for Sudan (and corresponding crop coefficients) were taken from the EN MSIOA (NBI-ENTRO,
2014) database and those for Ethiopia were taken from the ENIDS CRA2 documents (2009), supplemented by data from the Baro-
Akobo-Sobat and Tekeze master plans from Ethiopia. Data for the other Equatorial countries were obtained from NEL MSIOA
documents and a GIS database (NBI-NELSAP, 2012).
3.5. Irrigation efficiency scenarios
We estimated plausible irrigation efficiency improvements, taking into account pertinent factors that might influence the per-
formance of irrigated agriculture in the Nile Basin. The extent to which such improvements can be effected for a given irrigation area
depends on many factors.
1. Size and ownership types of schemes: Often, the financial resources of owners are small, and irrigation efficiencies tend to be low,
with no major improvements expected on a small scale for household-owned irrigation systems. In cases in which individual
schemes are part of larger-scale irrigation schemes (e.g., Gezira in Sudan, most of the irrigation areas in Egypt, and the Koga
scheme in Ethiopia), the conveyance and distribution system is maintained by the state or Water Users Association. These systems
tend to be in good condition, whereas farm-level water applications remain less efficient. Such distinctions need to be made when
assigning improvements.
2. Technical and institutional capacities for managing irrigation agriculture: More experienced regions/countries, such as Egypt and
Sudan, tend to be aware of the needs for irrigation efficiency improvements. Hence, larger effects of irrigation efficiency im-
provements can be expected for these regions compared with regions with little experience.
3. Main purpose of irrigation: Irrigation for high value crops tends to be better managed and to have higher efficiencies and higher
likelihoods for improvements; often, the intended use is commercial or for own-consumption, with some surplus being marketed.
4. Type of irrigation technology in use: Improvements in irrigation efficiencies are expected to be due to one of the following: (i)
Changes in water application techniques, such as changing from a surface-gravity (e.g., furrow) system to a pressurized system
(e.g., drip). (ii) Changes in application efficiency for the same water application technique (e.g., lining of canals or improving land
leveling).
Table 2
Harvest area of existing irrigation schemes in 2011 and planned in 2050 (including double cropping).
Existing (2011) Planned (2050)
Country Gravity Pressurized Gravity Pressurized
(million ha) (million ha)
Egypt 4.16 0.9 0.58 0
Ethiopia 0.12 0 2.05 0.04
Kenya 0.02 0 0 0
Rwanda 0 0 0 0
South Sudan 0 0 0.27 0
Sudan 1.11 0.06 0.84 0.04
Tanzania 0.01 0 0 0
Uganda 0.01 0 0 0
Sum 5.43 0.96 3.74 0.09
Sum 2011: 6.4 Sum 2050: 3.82
S. Multsch et al. Journal of Hydrology: Regional Studies 12 (2017) 315–330
320
We acknowledge that many detailed effects of the various irrigation technologies and practices cannot be incorporated in a large-
scale assessment such as the one presented in this study. Thus, three normative scenarios of irrigation efficiency improvements (Sce1,
Sce2 and Sce3) were used to evaluate potential water savings on the basis of available reports and the expert knowledge of NBI staff
members. In summary, the irrigation efficiency of gravity and pressurized systems in Egypt was raised by 5%, 10% and 15% for
scenarios Sce1, Sce2 and Sce3, respectively. Improvements in gravity systems of 5%, 10% and 20% for scenarios Sce1, Sce2 and Sce3
were assumed for the other countries, in addition to enhancements of 15%, 20% and 25% for pressurized systems under each
scenario, respectively. Specific values per country and province of irrigation efficiency improvements are given in Table A2. Note that
the improvements apply to current and planned irrigation areas.
4. Results
4.1. Gross irrigation of existing and planned irrigation schemes
The IRR
gross
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). The IRR
gross
totaled 84 km
3
yr
−1
(Table 3). A further differentiation in relation to irrigation systems showed that 73 km
3
yr
−1
(87%) and 11 km
3
yr
−1
(13%)
would be consumed in areas equipped with gravity and pressurized systems, respectively. Egypt and Sudan have the largest areas
under irrigation, 5.06 mio. ha and 1.17 mio. ha (97%), and were responsible for almost the entire IRR
gross
(99%), with 65 km
3
yr
−1
and 19 km
3
yr
−1
, respectively. The situation slightly changed when the additionally planned irrigation schemes up to 2050 (3.82
mio. ha) were considered, which would lead to a total irrigated area of ∼10 million ha in the Nile River Basin. Although most of these
schemes are planned for Ethiopia (55%), Egypt will still have most of the irrigated areas (55%). In total, the IRR
gross
is expected to
increase by approximately 46% (39 km
3
yr
−1
) to 123 km
3
yr
−1
in 2050 (existing + planned areas). Egypt will be still the largest
water consumer, with 61%, followed by Sudan and Ethiopia, with 27% and 9%. An interesting point is the rather low IRR
gross
of
Ethiopia in comparison with that of Sudan, given that both countries will irrigate roughly the same area (∼2 mio. ha). The reasons
are the less favorable climatic growing conditions in Sudan in comparison with Ethiopia, thus leading to a three times higher IRR
gross
in Sudan.
A further differentiation of IRR
gross
can be made for crop categories (Fig. 2a). A more detailed overview per crop and country is
given in Appendix A Figs. A3 and A4. Regarding existing areas, grains shared the highest fraction of the IRR
gross
, with 44% and 38%
for existing and planned areas. The second largest group was formed by other crops, dominated by cotton, sugarcane and groundnuts
(Fig. A3e). Most of the water is consumed in May to August by grains (Fig. 2b) such as maize, wheat and barley, which are grown in
Egypt in particular (Fig. A3a). Other important crops driving the high IRR
gross
were fruits, vegetables, cotton and sugarcane in Egypt
as well as groundnuts in Sudan at that time of year. November to February are dominated by clover in Egypt and cotton in Sudan.
Planned irrigation schemes showed a different distribution between months, because the highest IRR
gross
would occur between
December and April, with a maximum in March (Fig. 2c). Cropping patterns would then be mainly driven by the cultivation of wheat
and cotton in Sudan as well as by sugarcane and soybean in Ethiopia (Fig. A3). The combined IRR
gross
of existing and planned areas is
expected to lead to more constant and higher water demand throughout the year, which must be provided by the Nile River.
4.2. Evaluation of irrigation efficiency scenarios
The evaluation of the scenarios of irrigation efficiency improvements is shown in Fig. 3 for existing (a-c) and planned (d-f)
irrigation schemes and in Table 4 (see Table A3 for a differentiation according to country). The total area remained constant
throughout the scenarios (Fig. 4a, d), whereas the fractions of gravity and pressurized irrigation systems, as well as efficiencies
(Fig. 3b, e), were modified. The water savings ranged between 7% and 26%, under Sce1 (slight increase of efficiency) and Sce3
Table 3
Gross irrigation (IRR
gross
) of Nile River riparian countries for existing and planned schemes.
Existing (2011) Planned (2050)
Country Gravity Pressurized Gravity Pressurized
(km
3
yr
−1
) (km
3
yr
−1
)
Egypt 54.06 10.25 11.26 0.00
Ethiopia 0.47 0.01 10.06 0.18
Kenya 0.08 0.00 0.00 0.00
Rwanda 0.01 0.00 0.00 0.00
South Sudan 0.00 0.00 3.05 0.00
Sudan 18.18 0.89 13.80 0.67
Tanzania 0.13 0.00 0.00 0.00
Uganda 0.04 0.01 0.00 0.00
Sum 72.97 11.16 38.17 0.85
Sum 2011: 84.12 Sum 2050: 39.02
S. Multsch et al. Journal of Hydrology: Regional Studies 12 (2017) 315–330
321
Fig. 2. Comparison of the gross irrigation (IRR
gross
) of existing and planned irrigation schemes grouped by crop categories (a). (b) and (c) show further differentiation
of IRR
gross
per month for existing and planned irrigation schemes.
Fig. 3. The evaluation of irrigation technology scenarios Sce1-3 is shown in (a-c) and (d-f) for existing and planned irrigation schemes for Nile River riparian countries.
Table 4
Evaluation of irrigation efficiency scenarios for existing and planned irrigation schemes.
Scenario Status Harvest area Irrigation efficiency Gross irrigation
(ha yr
−1
)(−) (km
3
yr
−1
)
Gravity Pressurized Gravity Pressurized Gravity Pressurized
Baseline Existing 5.433 0.964 0.6–0.7 0.7–0.8 73.0 11.2
Baseline Planned 3.737 0.086 0.6–0.7 0.7–0.8 38.2 0.9
Sce1 Existing 5.158 1.240 0.65–0.75 0.85 64.5 13.8
Sce1 Planned 3.011 0.811 0.65–0.75 0.85 29.8 5.1
Sce2 Existing 5.158 1.240 0.7–0.8 0.90 60.9 13.4
Sce2 Planned 2.711 1.111 0.7–0.75 0.90 23.8 9.4
Sce3 Existing 0.000 6.397 0.7–0.8 0.95 0.0 62.5
Sce3 Planned 0.000 3.822 0.7–0.8 0.95 0.0 26.8
S. Multsch et al. Journal of Hydrology: Regional Studies 12 (2017) 315–330
322
(theoretical possible improvement) for existing areas. The total savings was −6, −9 and −22 km
3
yr
−1
for scenarios Sce1, Sce2 and
Sce3, as compared with the current consumption of 84 km
3
yr
−1
.
Relative water savings in the planned irrigation schemes amounted to a reduction of 10%, 15% and 31% for scenarios Sce1, Sce2
and Sce3. The reason for the higher water savings in these planned areas was the higher fraction of schemes located in Ethiopia (∼2
mio. ha, 55%, Table 1), where the currently implemented irrigation techniques are of low efficiency and will therefore benefit
substantially from improvements. Importantly, when the possible water savings in existing areas was compared with the future water
needs of planned areas, even when considering the highest technological improvement (Sce3), the water savings of 22 km
3
yr
−1
in
the existing areas was predicted to be insufficient to meet the future water demand. This demand of 27 km
3
yr
−1
(Sce3) would result
in a water deficit of 5 km
3
yr
−1
. Under the more likely Sce1 and Sce2 scenarios, the deficit would be even larger: 29 and 23 km
3
yr
−1
,
respectively. Hence, water savings via improved irrigation efficiency will not be able to meet the demand of the planned irrigation
schemes.
5. Discussion
5.1. Validation of results
The results of this study were compared with results from other studies on a national level and for the entire Nile Basin. However,
a detailed comparison is difficult, because manifold model settings, such as irrigation use efficiency (off-site and on-site), the con-
sidered spatial model input data, such as the irrigated area, and information on cropping patterns and dates or cropping intensity
differ among studies. We therefore note that results between the different studies should explain similar regional patterns and be in
the same range rather than providing identical values.
The highest current IRR
gross
occurred in Egypt, with 64 km
3
yr
−1
on 5 mio. ha of harvested irrigated crops. Comparable results
have been presented by others, e.g., a total IRR
gross
of 57 km
3
yr
−1
has been simulated with a global water balance and demand
model (PCR-GLOBWB) on the basis of the spatial locations of irrigated areas around 2000 (Wada et al., 2014). The total water
withdrawal, including on-farm and off-farm water losses, was 67 km
3
yr
−1
in 2010, considering 6.3 mio. ha of irrigated land (FAO,
2016). For this area, the authors considered a double cropping intensity of 176%, whereas in our study, an intensity of 136% was
assumed (a relative difference of 23%) for Egypt, which is the main reason for the different harvest areas and resulting higher water
withdrawal, with a relative difference of 15%.
In the case of Sudan, the IRR
gross
of the irrigated areas in 2011 and 2050 was 19 and 34 km
3
yr
−1
(1.2 mio. ha, 2.1 mio. ha). The
FAO (2016) has reported a water withdrawal of 26 km
3
yr
‐1
for the year 2010, also including off-farm water losses, on the basis of a
higher harvested area of 1.6 mio. ha. The difference between the harvested areas and the resulting 27% higher water withdrawal was
caused by the different cropping intensities of 68% and 91% (relative difference 25%) used in this study and by the FAO (2016).
Others have estimated the irrigation demand (i.e., only consumptive use by crops) of Sudan as being 8.5 km
3
yr
−1
and 14 km
3
yr
−1
for irrigated areas of 1.3 mio. ha and 2.2 mio. ha in 2008 and 2050 (McCartney et al., 2012). Their irrigation demand (i.e., net
irrigation, without assuming likely losses through inefficient irrigation) is somewhat lower than our results, but when an on-farm
efficiency of 60% is considered, the values given by McCartney et al. (2012) become closer to our results.
The IRR
gross
for the entire Nile Basin was calculated to be 84 km
3
yr
−1
(6.4 mio. ha) and 123 km
3
yr
−1
(10.2 mio. ha) for 2011and
2050. Two other studies (Sulser et al., 2010; Awulachew et al., 2012) have also reported current and future water consumption of the
Nile Basin. Awulachew et al. (2012) have calculated an IRR
gross
of 66 km
3
yr
−1
for today (5.6 mio. ha) and 128 km
3
yr
−1
for the long
term (10.6 mio. ha) with the WEAP model. Our estimate for the current IRR
gross
is 22% higher, a result that can be partly explained by
the higher harvest area of 13% used in our approach. Further reasons for the difference may be varying cropping patterns as well as
different assumptions regarding irrigation efficiency. The difference between the future predictions of IRR
gross
is low (∼4%). Sulser
et al. (2010) have calculated blue water consumption (consumed irrigation, without losses) for the years 2000 and 2050, obtaining
46 km
3
yr
−1
(5.8 mio. ha) and 57 km
3
yr
−1
(6.9 mio. ha), by using the IMPACT model. Considering on- and off-farm losses, the total
withdrawal of water for irrigation for 2000 is close to our IRR
gross
estimate. The prediction of the harvest area for 2050 appears to be
too low, because we, as well as Awulachew et al. (2012), generated higher predictions for the harvest area of approximately 10 mio.
ha in 2050.
As described, the differences between our study and others may have been caused by uncertainties in parameterizations, different
model structures or input data (Renard et al., 2010). For example, the models used by others (McCartney et al., 2012; Wada et al.,
2014), as well as our approach, are based on the single crop coefficient concept. In this concept, the crop specific evapotranspiration
is calculated on the basis of ET
o
and crop-specific Kc parameters that are applied to adjust ET
o
to specificfield crops (Allen et al.,
1998). Because ET
o
was derived with the Penman-Monteith equation in this study and that by Wada et al. (2014), the observed
differences may partly be related to the differences in Kc; we collected site-specific crop parameters for the different irrigation
schemes in the region from the literature, whereas the Kc values used by Wada et al. (2014) were based on a global parameter set
(Portmann et al., 2010). Moreover, the irrigation efficiency is often not accurately defined or communicated (Howell, 2003; Perry,
2007; Lankford, 2012) and therefore is difficult to compare. This inaccuracy is one of the major reasons for differences in the
calculation of IRR
gross
. For the assessment of the irrigation water requirement in the Nile Basin, we considered the on-farm irrigation
efficiency, i.e., the losses that occur during the application of the irrigation water to the plants at the field scale. Values were taken
from the literature according to the irrigation system as defined per country (FAO, 2016). Our assumptions may differ from those of
other studies. Different input data can also cause tremendous uncertainties, e.g., the extent of irrigated areas and, in particular, the
estimate for the planned future irrigation schemes. Wisser et al. (2008) have shown in a global scale analysis that irrigation demands
S. Multsch et al. Journal of Hydrology: Regional Studies 12 (2017) 315–330
323
vary by +/−30% for calculations based on two different datasets for irrigated areas and weather data. Finally, Multsch et al. (2015)
have shown that the structural model uncertainty can dominate global model uncertainty. Their study has found that the most
important factor driving the estimated irrigation requirement for the Murray Darling Basin is related to the underlying equation for
estimating ET
o
. Thus, various sources of uncertainty exist that can alter the model predictions. To overcome such uncertainties, our
input and output data were carefully revised in cooperation with local experts and compared with other localized simulations of
irrigation requirements by the WEAP model, which are unfortunately unpublished.
5.2. Impact of improved irrigation efficiency
Two aspects are important to discuss. First, how does the IRR
gross
of existing areas compare with the total water volume of the Nile
(under current and improved irrigation technology)? Second, can the water savings from improved irrigation efficiency meet the
additional water demand of planned irrigation schemes?
Water allocation underlies historical plans that regulate water allocation in accordance with the average Nile River flow at
the Aswan dam of 84 km
3
yr
−1
. Only Egypt and Sudan are part of the agreement, and the two countries agreed on an allocation
scheme in which Egypt receives 55.5 km
3
yr
−1
of the total flow, and Sudan receives 18.5 km
3
yr
−1
(Johnston, 2012), con-
sidering additional evaporation losses from the open water surface of 10 km
3
yr
−1
.TheIRR
gross
of existing irrigation schemes
was calculated to be 64 km
3
yr
−1
and 19 km
3
yr
−1
for Egypt and Sudan in this study. Hence, even the IRR
gross
of existing
irrigation schemes exceeded the average river flows as well as the amount stated in the 1959 agreement between Egypt and
Sudan. Similar results have been reported by other researchers (McCartney et al., 2012), who have emphasized that the Nile
River Basin cannot meet irrigation needs in the long term. Those authors have concluded that the implementation of water
saving measures, such as improved irrigation efficiency, is of high priority. We addressed, in particular, the potential of irri-
gation efficiency to meet the increased water needs of agriculture. By implementing more efficient irrigation technology, the on-
farm water losses can be limited. In the case of Egypt, at least scenario Sce2 (IRR
gross
=58km
3
yr
−1
) must be implemented to
approximately balance water consumption with the guaranteed water extraction. In the case of Sudan, Sce1 (IRR
gross
=17km
3
yr
−1
)wouldbesufficient. Thus, improved on-farm irrigation efficiency would aid in keeping the IRR
gross
of existing schemes
within the range of the average river flows currently reaching the Aswan dam.
The expansion of irrigation schemes (1.6 times larger in 2050 compared to 2011) will lead to a large increase in IRR
gross
in
thefuture(1.5largerin2020comparedto2011),whenallplanswillberealized.TheoverallIRR
gross
of 123 km
3
yr
−1
will far
exceed today’s average river flows. Even under Sce3, with a theoretical implementation of pressurized systems across all
irrigation schemes, we estimated a demand of 89 km
3
yr
−1
. Predictions of future river flows exacerbate the situation because
stream flows are expected to decrease in the time period after 2040, because of lower rainfall rates and increases in eva-
poration (Beyene et al., 2010), as calculated from a multi-model ensemble. The authors of that study have acknowledged the
underlying uncertainty related to emission scenarios as well as model projections. Thus, future water flows are not certain.
Nevertheless, the assumed decline in river flowsisinlinewithestimatesbyElshamy et al. (2009), who have shown that
temperature and rainfall will probably increase and decrease, respectively, thereby leading to decreased runoffin the upper
Blue Nile Basin.
6. Conclusions
The Nile Basin is expected to undergo expansion in irrigated agriculture in most countries to feed the fast growing population. The
populations of most Nile Basin riparian countries double every 20 to 25 years. This expected increase in irrigation water demand
exceeds the available water in the Nile Basin. Improved irrigation efficiency would aid in decreasing water resource consumption in
the Nile River Basin, in particular to balance the current demand and supply. However, our calculations of gross irrigation with
different irrigation technologies showed that the saving potentials are insufficient to meet the demand of planned irrigated schemes
in 2050. Hence, other measures are required to further optimize water resource utilization. A better management of green water
(consumed rainfall) in combination with supplementary irrigation is a promising opportunity to improve management of irrigation
schemes in the Equatorial Lake regions as well as along the Blue Nile in Ethiopia. The implementation of deficit irrigation may further
decrease gross irrigation in Egypt, Sudan and South Sudan. Locally, even solar desalination might be a problem-solving strategy in
regions where water quality has deteriorated over the past decades because of overuse.
Under current conditions, most of the annual river flows are consumed by irrigation schemes in Egypt and Sudan, which have
very little internally generated river flow. This situation will continue when all plans for future irrigations schemes are realized,
and the competition among users will be intensified because of the growing water demand of irrigation schemes in Ethiopia in
2050 as well as decreased river runoffin the future. Moreover, the construction of dams for energy production will further
increase competition for water in the absence of comprehensive management plans that integrate all types of uses (agriculture,
industry, households, and energy) in the whole Nile River Basin, on a detailed temporal and spatial scale, in order to implement
a legal framework for all users.
7. Outlook
Improving the utilization of local water resources by improving irrigation technology is only one way to meet future demands for
food and feed in Nile riparian countries. Virtual water trading has been highlighted as another useful measure to cope with water
S. Multsch et al. Journal of Hydrology: Regional Studies 12 (2017) 315–330
324
scarcity, particularly in the Middle East and North Africa (Allan, 1998). The Nile River Basin countries virtually export 39 km
3
yr
−1
and import 11 km
3
yr
−1
of water through crop trading, as recently reported by Zeitoun et al. (2010). The possible advantages of
virtual water trading are still under discussion. D’Odorico et al. (2010) have reported that virtual water trading is helpful to
counteract food scarcity in the short term but decreases the ability of countries to cope with scarcity in the long term, because the
capacity of trading additional food in times of extremes, e.g., droughts, may be limited.
Improving irrigation efficiency addresses blue water consumption (i.e., the water consumed from surface and groundwater re-
sources). Rather than focusing on this water component only, others have emphasized the importance of green water (i.e., consumed
rainfall) for managing agricultural water use (Rockström et al., 2009). Green and blue water consumption has been calculated to be
135 km
3
yr
−1
for the Nile Basin, with a high percentage of green water of 59% (Sulser et al., 2010). Improving crop production
through use of only green water would play a key role in improving the basin-wide water productivity of the Nile. Multsch et al.
(2016a) have stressed the importance of green water for managing agriculture in the High Plains Aquifer region (USA), one of the
largest groundwater aquifers worldwide, where severe groundwater decline is related to irrigation agriculture. The assessment of
green and blue water resources under the consideration of different irrigation scenarios, as is also acknowledged in the general
guidelines for Integrated Water Resources Management (GWP, 2000), would be a next step for improving agricultural water man-
agement, particularly in the Nile River Basin.
Acknowledgments
This study is a result of analytic work carried out by the NBI Secretariat (Nile-SEC) and the Justus Liebig University (Germany)
and funded by the Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ).
Appendix A
Fig. A1. (a) Climate station from Climwat 2.0 database in North-East Africa and (b) interpolated rainfall in April (mostly average of the years 1971-2000).
S. Multsch et al. Journal of Hydrology: Regional Studies 12 (2017) 315–330
325
Fig. A2. (a) Stream salinity along irrigated areas in Egypt.
S. Multsch et al. Journal of Hydrology: Regional Studies 12 (2017) 315–330
326
Fig. A4. Monthly gross irrigation of Nile riparian countries for planned irrigation schemes in 2050.
Fig. A3. Monthly gross irrigation of Nile riparian countries for existing irrigation schemes.
S. Multsch et al. Journal of Hydrology: Regional Studies 12 (2017) 315–330
327
Table A1
Irrigation efficiency per country and province for gravity (Grav.) and pressurized (Press.) irrigation systems for current conditions (baseline) and scenarios (Sce1, Sce2
and Sce3).
Baseline Sce1 Sce2 Sce3
Country Province Grav . Press . Grav . Press . Grav . Press . Grav .
Egypt Aswan 70% 80% 75% 85% 80% 90% 95%
Egypt Qina 70% 80% 75% 85% 80% 90% 95%
Egypt Sohag 70% 80% 75% 85% 80% 90% 95%
Egypt Asyiut 70% 80% 75% 85% 80% 90% 95%
Egypt Al Fayyum 70% 80% 75% 85% 80% 90% 95%
Egypt Al Jizah 70% 80% 75% 85% 80% 90% 95%
Egypt Al Minya 70% 80% 75% 85% 80% 90% 95%
Egypt Beni Suwayf 70% 80% 75% 85% 80% 90% 95%
Egypt Al Bahayrah 65% 80% 70% 85% 75% 90% 95%
Egypt Al Daqahliyah 70% 80% 75% 85% 80% 90% 95%
Egypt Al Gharbiyah 70% 80% 75% 85% 80% 90% 95%
Egypt Al Minufiyah 70% 80% 75% 85% 80% 90% 95%
Egypt Al Qalyubiyah 70% 80% 75% 85% 80% 90% 95%
Egypt Ash Sharqiyah 65% 80% 70% 85% 75% 90% 95%
Egypt As Ismailiyah 65% 80% 70% 85% 75% 90% 95%
Egypt Dumyat 65% 80% 70% 85% 75% 90% 95%
Egypt Kafr-El-Sheikh 65% 80% 70% 85% 75% 90% 95%
Egypt Matruh 60% 80% 65% 85% 70% 90% 95%
Egypt Al Qahirah 65% 80% 70% 85% 75% 90% 95%
Egypt Al Iskandariyah 60% 80% 65% 85% 70% 90% 95%
Egypt Bur Said 60% 80% 65% 85% 70% 90% 95%
Egypt Shamal Sina 60% 80% 65% 85% 70% 90% 95%
Ethiopia 60% 70% 65% 85% 70% 90% 95%
Kenya 60% 70% 65% 85% 70% 90% 95%
Tanzania 60% 70% 65% 85% 70% 90% 95%
Rwanda 60% 70% 65% 85% 70% 90% 95%
Uganda 60% 70% 65% 85% 70% 90% 95%
South Sudan 65% 70% 70% 85% 75% 90% 95%
Sudan 65% 70% 70% 85% 75% 90% 95%
Table A2
Irrigation efficiency improvements (difference in comparison to the baseline scenario) for scenarios Sce1, Sce2 and Sce3.
Sce1 Sce2 Sce3
Gravity Pressurized Gravity Pressurized Pressurized
Egypt 5% 5% 10% 10% 15%
Ethiopia 5% 15% 10% 20% 25%
Kenya 5% 15% 10% 20% 25%
Tanzania 5% 15% 10% 20% 25%
Rwanda 5% 15% 10% 20% 25%
Uganda 5% 15% 10% 20% 25%
Sudan 5% 15% 10% 20% 25%
South Sudan 5% 15% 10% 20% 25%
Note: Pressurized systems for Egypt vary by district −on new land we assume pressurized irrigation techniques and on old land surface irrigation and remain like that in the
future.
S. Multsch et al. Journal of Hydrology: Regional Studies 12 (2017) 315–330
328
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Table A3
Gross irrigation (IRR
gross
) of gravity and pressurized systems in 2011 and 2050 grouped by country and scenario.
2011 2050
Scenario Country Gravity Pressurized Gravity Pressurized.
(km
3
yr
−1
)
baseline Egypt 54.06 10.25 11.26 0.00
sce1 Egypt 50.67 9.97 10.51 0.00
Sce2 Egypt 47.95 9.81 5.78 4.56
Sce3 Egypt 0.00 48.92 0.00 8.48
baseline Ethiopia 0.47 0.01 10.06 0.18
sce1 Ethiopia 0.33 0.09 7.11 1.81
Sce2 Ethiopia 0.31 0.08 6.60 1.71
Sce3 Ethiopia 0.00 0.31 0.00 6.49
baseline Kenya 0.08 0.00 0.00 0.00
sce1 Kenya 0.04 0.03 0.00 0.00
Sce2 Kenya 0.03 0.03 0.00 0.00
Sce3 Kenya 0.00 0.05 0.00 0.00
baseline Rwanda 0.01 0.00 0.00 0.00
sce1 Rwanda 0.01 0.00 0.00 0.00
Sce2 Rwanda 0.01 0.00 0.00 0.00
Sce3 Rwanda 0.00 0.00 0.00 0.00
baseline South Sudan 0.00 0.00 3.05 0.00
sce1 South Sudan 0.00 0.00 2.11 0.54
Sce2 South Sudan 0.00 0.00 1.96 0.51
Sce3 South Sudan 0.00 0.00 0.00 1.93
baseline Sudan 18.18 0.89 13.80 0.67
sce1 Sudan 13.32 3.66 10.12 2.78
Sce2 Sudan 12.44 3.45 9.44 2.62
Sce3 Sudan 0.00 13.09 0.00 9.94
baseline Tanzania 0.13 0.00 0.00 0.00
sce1 Tanzania 0.09 0.02 0.00 0.00
Sce2 Tanzania 0.08 0.02 0.00 0.00
Sce3 Tanzania 0.00 0.08 0.00 0.00
baseline Uganda 0.04 0.01 0.00 0.00
sce1 Uganda 0.03 0.01 0.00 0.00
Sce2 Uganda 0.03 0.01 0.00 0.00
Sce3 Uganda 0.00 0.03 0.00 0.00
S. Multsch et al. Journal of Hydrology: Regional Studies 12 (2017) 315–330
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