Sustainable Utilization of Water Resources In Agriculture Sector of Sudan

Journal of Environmental and Agricultural Sciences (JEAS). Hussain et al., 2023. 25(1&2):xx-xx.

Open Access – Review Article

Sustainable Utilization of Water Resources in the Agriculture Sector of Sudan, After the Secession of South Sudan 
Amir K. Basheer 1,*, Abubaker B. Ali 2,*, Nazar A. Elshaikh 3, Gamareldawla H. Agbna 2
1 College of Agricultural Engineering, Hohai University, Nanjing, 210098, China
2 Department of Agricultural Engineering, College of Agricultural Studies, Sudan University of Science and Technology, Shambat, Khartoum, Sudan
3 Department of Agricultural Engineering, Faculty of Engineering, University of Sinnar, Sudan

Abstract: Two challenges are facing the sustainable use of water in Sudan i.e., agriculture and the separation of South Sudan. Thus, this article aims to assess Sudan’s water resources, estimate future water demands and shed light on the prospects of sustainable utilization. Irrigated agriculture consumes about 86% of blue water. Rainfall is erratic and concentrates in a short period; groundwater resources require technical and economically feasible means of extraction. Storage capacity facilities are limited to short-term storage. Therefore, integrated water resources management strategies such as surface water and rainwater harvesting techniques should be applied to utilize seasonal streams of water and increase rain-fed agriculture production. The use of groundwater artificial recharge techniques where appropriate could increase storage capacity and maximize utilization.

Keywords: Sudan; Water resources; Utilization; Management; Development.
*Corresponding author:
Amir K. Basheer,; Abubaker B. Ali: 

Cite this article as:
Basheer, A.K., A.B. Ali, N. A. Elshaikh and G.H. Agbna. 2023. Sustainable utilization of water resources in the agriculture sector of Sudan, after the secession of South Sudan. Journal of Environmental & Agricultural Sciences. 25(1&2): XX. [Abstract] [View Full-Text] [Citations

Copyright © Basheer et al., 2023  This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium provided the original author and source are appropriately cited and credited.

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1. Introduction
Water is one of the most critical issues natural resource issues in arid and semi-arid areas especially in the MENA region including Sudan (Allam et al., 2019; Hindiyeh et al., 2023). Irrigated agriculture is the largest consumer of water in the world (Bashir et al., 2019; Sarwar et al., 2021), especially in areas with dry climates, which consume about 50-85 % of total water use. In Sudan, water resources are facing increasing pressure due to rising demand for irrigation water, changing climatic conditions and rapid population growth (Hamdy, 2001). Therefore, it is challenging to meet the agricultural water demand with conventional water resources and without sustainable management of these resources (Mekonnen and Hoekstra, 2016; Ricciardi et al., 2020). Sudan water resources can be classified into conventional and non-conventional water resources. The conventional water resources include rainfall, surface water (Nilotic and Non-Nilotic water) and groundwater, while the non-conventional water resources consist of desalinated water and treated wastewater (Basheer et al., 2023; Djumaet al., 2016; Nasreldin and Elsheikh. 2022).

The River Nile with its main tributaries (White Nile, Blue Nile and Atbara River) is the longest river in the world and is considered as one of the essential components of surface water (Othoche, 2021). It flows 6,600 km, crossing more than 35 degrees latitude and occupying an area of about 3.1 million km2. The River Nile water is a main contributor to agriculture production while most surface water from seasonal streams is lost except on a small scale in some states of Sudan (Abdelkareem and Al-Arifi, 2021; Hamada, 2017).

Moreover, the seasonal streams (Wadis) in Sudan, due to the topographic nature and diversity of the climatic regions, are considered as one of the significant water resources in Sudan, especially in the following areas: basement complex formation, groundwater salinity zones and remote from the Nile system. The diversion and utilities of surface water flow for drinking and growing crops is a technique widely practiced in Sudan (Bushara et al., 2021). This can be seen in most states of Sudan e.g., North Kordofan, River Nile and Blue Nile States where bigger towns and villages depend on harvested surface water in large reservoirs locally known as (Hafirs) as well as traditional farmers who cultivate large areas using small, bounded basins with considerable success. On the other hand, groundwater is also considered as one of the main water resources in Sudan, which plays a significant role in the essential activities of human beings, animal grazing and limited use for agriculture in most parts of Sudan (Amara and Saad, 2014; Bashir et al., 2023).

In addition, groundwater constitutes the main water supply source for drinking and domestic use for more than 80% of the human population and their livestock in the country (Abdalla and Mohamed, 2012). Moreover, groundwater plays a very vital role in maintaining the environment by sustaining stream flows, and wetlands, and supporting vegetation (de Graaf et al., 2019; Mather et al., 2022; Sarwar et al., 2021).

Rainfed agriculture occupies about 15 million ha and plays an important role in the national economy where it contributes, with a big share, to the food security of the country. Mechanized rainfed agriculture is practiced in more than half of the rainfed area of Sudan (Elagib et al., 2019; Mohammed et al., 2010; Rosa et al., 2020).

Separation of South Sudan according to the peace agreement (Machakos Protocol), had several provisions linked with water security and agriculture to address conflicts regarding competition for land and water resources (Carolan, G. 2021; Salman, 2011). Transboundary water utilization from the River Nile and its tributaries is governed by international agreements to ensure fair and equitable use of water resources (Deribe and Berhanu, 2021; Hussein, 2019; Octavianti and Staddon, 2021).

Changing climatic conditions, anomalies and uncertainty of rainfall intensity, duration and frequency, high evapotranspiration losses and poor hydropolitical management may potentially worsen the water crisis of Sudan in the near future (Alriah et al., 2021; Zhang et al., 2012). Standardized precipitation anomaly index of Sudan showed a rapid increase in dryness across the country (Sahoo and Govind, 2022). Models have predicted that anomalies in the hydrological system are expected to further worsen in future (Hamadalnel et al., 2022), which will pressurize excessive utilization of groundwater resources. However, groundwater resources of Sudan need precise assessment, both in terms of quantity and quality of water. Groundwater resources also require technical and economical feasibility for water extraction to meet regional requirements for water use for different purposes (Khan et al., 2021; Scanlon et al., 2023; Widaa and Saeed, 2008). Globally water security is threatened by increasing demand and withdrawals, the degradation of water sources and associated ecosystems due to climate change and pollution, and other threats (Garrick and Hall, 2014; Mullin, 2020; Vörösmarty et al., 2000).

In 2015, the United Nations launched the Sustainable Development Agenda for 2030. This was a plan of action for people, planet and prosperity consisting of 17 Sustainable Development Goals (SDGs). These SDGs cover economic growth, environmental protection and social inclusion for sustainable development (Hák et al., 2016). Several transformations, including priority investments and regulatory challenges, were proposed for achieving SDGs including sustainable water utilization (Sachs et al., 2019).

Targets of different SDGs are interconnected, and linked with water resources (Alcamo, 2019) including (1) Ensuring availability and sustainable management of water for all, (2) improve water quality by reducing pollution, (3) substantially increasing water-use efficiency across all sectors and ensure sustainable withdrawals and supply of freshwater to address water scarcity, (4) implement integrated water resources management at all levels, including through transboundary cooperation as appropriate, (5) protect and restore water-related ecosystems, including mountains, forests, wetlands, rivers, aquifers and lakes, (6)  expand international cooperation and capacity-building support to developing countries in water-related activities and programs, including water harvesting, desalination, water efficiency, wastewater treatment, recycling and reuse technologies (Arora and Mishra, 2022; Hoekstra et al., 2017).

Sudan is lacking systematic water resources management (Dirwai et al., 2021; Pacini and Harper. 2016). Therefore, limited data is available for the assessment of water resources for the present time and future demands. Consequently, under changing climatic scenarios and increasing water scarcity, the national water policy of Sudan needs improved management and serious measures to protect water resources at the national and transboundary levels (Alnour et al., 2022; Hamouda et al., 2009).

Water resources in Sudan, and Nile Basin, need strong efforts for development and integrated management for sustainable utilization through improved and efficient water use, water harvesting and transboundary cooperation (Ayyad and Khalifa, 2021; Mumbi et al., 2022; Orme et a., 2015). Therefore, this work aims to shed light on the situation of the conventional and non-conventional water resources after the secession of the south and highlights the water demands in Sudan after separation in 2011. Also, the article will highlight the prospects of planning, development, efficiency, and utilization to reach sustainable water resources in agriculture.

2. Current Status of Water Resources in Sudan
As aforementioned, water resources in Sudan could be classified as Rainfall, surface water (Nilotic and Non-Nilotic), groundwater and non-conventional resources (Table 1).

Table 1. Annual rainfall pattern (BCM/year)

Sudan and Nile Basin are characterized by significant spatiotemporal variability in rainfall patterns (Basheer and Elagib, 2019; Mohamed et al., 2022). Annual rainfall is minimum at the Sudanese-Egyptian border, reaching maximum (>900 mm rainfall) in the southwest of Sudan. Hydrometeorologically Sudan has been divided into four major rainfall zones, (a) The northern part of Sudan (desert zone; lies between 17˚ N and 23º N) with annual rainfall >75 mm. (b) The Red Sea zone in the northeastern part of the country; (between latitudes 23 to 18 º N and longitude 36˚ E, which has the Mediterranean climate with annual rainfall ≥75 mm. (c) The semi-desert zone (between latitudes 15˚ and 17˚ N with an annual rainfall of 75 to 300 mm, the rainy season is limited to 2 – 3 months with the rest of the year being virtually dry.

Fig. 1. Mean monthly rainfall over Sudan (FAO, 2005).

Rainfall usually occurs in isolated showers, which vary considerably in duration, location, and from year to year (Sahoo and Govind, 2022; SMA, 2006). The coefficient of variation of the annual rainfall in this northern half of the country could be as high as 100 percent (FAO, 2005). (d) The Savanna zone; is located between latitudes 9˚ and 15˚ N with an annual rainfall of 300 to 900 mm. The annual rainfall in the northern part exceeds 500 mm, and is concentrated in only four months, from July to October, while the annual rainfall in the southern part exceeds 1000 mm, and is concentrated in only five months, from June to October (SMA, 2006). Rainfed agriculture in Sudan is mainly practiced in this quarter. As the coefficient of variation in annual rainfall in the region is around 30 percent and the dry season extends for about seven to eight months, the cultivated area and productivity vary widely at the interannual scale (Table 1) (FAO, 2005). The mean annual rainfall is estimated around 276 mm (Fig. 1), corresponding to about 519 (BCM/year).

Fig. 2. The discharge of Nile River system (BCM/year) (MOIWR, 2012).

Table 2. Summary of Sudan’s available water resources and associated limitations

2.1.2. Nilotic water resources

The Ethiopian Plateau (Tana Lake) and central Africa great lake region (Victoria) are the major source of Blue and White Nile, respectively. Lake Victoria considers the downstream of the Kegera River that flows from Burundi through Tanzania, and this is the most far distant source of the Nile. Blue Nile has around 59% share in the Nile water, while Tekezaze-Atbara has 12%. This percentage significantly changes during flooding time (July to October). While, the share of White Nile shares around 29% of the Nile water (Table 2), (Fig.2) (Eldaw, 2003)

Fig. 3. The annual discharge of the Nile and tributaries in selected years (BCM) (MOIWR, 2011).

There is significant temporal variation in the water flow of the Nile (Fig. 3). About 24% of the Nile basin lies in Sudan, while 60% of Sudan lies in the Nile Basin (Salman, 2011). Eleven countries (Burundi, Democratic Republic of Congo, Egypt, South Sudan, Eritrea, Ethiopia, Kenya, Rwanda, Sudan, Tanzania and Uganda) share the water resources of the Nile (Salman, 2011). There are certain international agreements controlling the relationships between these countries since 1891 up to 1959. The first Nile Water Agreement between Sudan and Egypt was signed in 1929. It gave Egypt the right to use 48 BCM/year, while it gave Sudan the right to tap only 4 BCM/year. The treaty did not allocate to Ethiopia any rights to use the Nile waters and still bound Uganda, the United Republic of Tanzania and Kenya and barred them from using the Lake Victoria waters (FAO, 2005).

Table 3. Water storage reservoirs of Sudan

Sudan’s share of the Nile water (before separation), according to the 1959 Nile Water agreement between Sudan and Egypt is 18.5 BCM/year as measured at Aswan (20.5 BCM/year as measured at Sennar dam), and the corresponding share for Egypt is 55.5 BCM/year (Ali, 1993). Nevertheless, the volume of storage facilities of Sudan is far less than the amount needed. Dams in Sudan were constructed to provide water for irrigation during the low season period and for hydroelectric power. These dams have different and limited storage capacities as shown in (Table 3).

After South Sudan has been separated from Sudan the conflict on water resources is present on the surface, therefore the water issue between the two countries should be discussed in detail. Actually, it has been discussed that agreements relating to the use of international rivers could be included in the category of treaties automatically binding successor states as they are considered as related to the territory. However, newly independent States have often declined to be bound by water agreements concluded by predecessor States such as Tanzania.

2.1.3. Non-Nilotic water resources

Regarding the Non-Nilotic water resources, Sudan has the following watersheds Nuba Mountains (southwest), The Red Sea Hills (east), Angasana Hills (south-east), Jebal Marra (west), Al Botana Hills (central) and the Ethiopian Plateau (Baraka and Gash). Each watershed system of the above is comprised of many Wadis and Khors of various sizes ranging from large ones with annual discharge up to 100 million cubic meters (MCB) to small ones of annual discharge less than one MCB (Abdalgadir et al., 2003). The Gash (Mareb) and Baraka are the largest seasonal streams (Wadis), with an annual average flow ranging from200 to 800 MCM, which occurs between July and September. These Wadis originate from Eritrea and terminate in the continental deltas of Gash, Toker and the Red Sea. Wadis of Azum, Hawar, Kaja, Ebra, Toal, Elkou and Salih are the largest Wadis in western Sudan, with an estimated annual runoff ranging from 120 to 500 MCM (Adam, 1993). The combined total annual runoff of all the Wadis in Sudan is estimated to vary from 5 to 7 BCM (Elteyeb, 2002).

  1. Groundwater resources

Groundwater is available in approximately 50% area of the country (Kheralla, 1984), depth ranged between 40 – 400 m and has total dissolved solids of about (100 to 2000 p.m.). The sedimentary Nubian sandstone, Umm Rawaba formation, Nubian/Basalt and the Alluvial Basin are the main aquifers in Sudan (Eldaw, 2003), which found in a simple form or a complex one, according to their geological formations (Salama, 1979), as shown in Table 4 and Fig.4. The Nubian basin occupies 28.15% of the country area and has high quality water and is suitable for human and animal consumption. The basin is shared with Egypt and Libya (Puri, 2001). The basin storage capacity is 12600 BCM with an annual recharge of about 1008 (MCM). The Nubian basin is divided into the Sahara Nile, Sahara Nubian, Central Darfur, Nuhud, Sag El Na’am and River Atbara Basins. The Umm Rwaba basin is covering a NW-SE trough of a maximum thickness of two kilometers and a surface area of about 400,957 km2. The basin storage capacity is about 3150 BCM and the annual recharge is about 300 MCM. The main recharge is from the White Nile and from the surface flow during the rainy season (Salama, 1979).

The Nubian/Basalt basin covers an area of about 29,016 km2. The basin storage capacity is about 715 BCM with annual recharge of about 325 BCM. The recharge is mainly from the seeping into the sandstone formation from River Setit, (branch of River Atbara) and from surface flow during the rainy season. This basin can be divided into the Gadaref Basin and Shagara Basin. The major alluvial basins are seasonal streams (khors). The runoff from these streams does not exceed three months (June–September) per year. The basin storage capacity is 2.5 BCM and the annual recharge is 1800 MCM. The runoff during this period is substantial, and the aquifers are completely recharged after the rainy season. The alluvial deposits are characterized by high transmissivity values and storability figures. The shallow depth enabled the natives to develop their own technology of abstracting water for irrigation purposes. These basins are the oldest known cultivation centers from groundwater resources (Grigg, 2008; Salama, 1979).

2.1.4. Non-conventional water resources

Desalinization of water is a very recent industry in Sudan. Three are two plants commissioned in the year 2004 in the Red Sea, Port Sudan city to provide it with fresh water. The plants have a total capacity of 10.000 m3 per day (2500 and 7500 m3 per day). The small plant takes the raw water from the Red Sea, where the salt concentration is 42000–45000 ppm. The plant is designed to work with a salt concentration of 45000 ppm. The other plant faced several difficulties because it was placed to take raw water from deep wells where the salt concentration is more than 65000 ppm. Therefore, research studies are highly needed, beforehand, for proper design. Since, there is a good potential for the development of these alternative sources, practically in the future (Eltoum et al., 2002).

Utilization of urban wastewater treatment in agriculture is a century-old practice that is receiving renewed attention with the increasing scarcity of freshwater resources in many arid and semi-arid regions. Previously wastewater was discharged to rivers and onto open areas, but with increasing population disposal in rivers and open areas was environmentally not accepted. This problem increases day by day due to the increase in population and industrial sector in such towns. Recently the authorities of Khartoum state gave more attention to the safe disposal of this water by using it in agriculture, which diverted this amount of water to irrigate Yarmook and Soba projects in the south of the state. Also, there are about eight treatment plants of different capacities distributed across the cities of the state (MI, 2012; IC, 2011). The total capacities of these plants are about 235.887 MCM annually (Table 5).

3. Sudan water use and future demand

It is worth mentioning that, 80% of water consumes by irrigated agriculture for irrigating cotton, sorghum, groundnuts and wheat which consider the main crops grown in Sudan. While, human, animal and industrial consume less than 20% (Fig.5). There are about 1.85 million hectares covered by developed agricultural schemes. The actual cultivated area is more than 1.35 million ha and is expected to rise to 2.31 million ha in the near future (Abdalla, 2001).

For instance, during the season of 2007/2008, irrigated agriculture consumes about 16 BCM with good irrigation efficiency in most schemes in Sudan, which play a very important role in the water use amount. This efficiency is estimated according to present performance and cropping pattern, irrigation water requirements and the high conveyance efficiencies in the Sudan’s clay plains (Abdalla, 2001). The overall efficiency of irrigation in Sudan is generally high for example Gezira scheme which consumes 40% of the present abstraction of the country, has an irrigation water use efficiency of about 85%. Generally, the main problem is siltation and aquatic weed growth in the canals and the deterioration of the condition of the irrigation infrastructure. On the other hand, evaporation and evapotranspiration are generally high, ranging from 1000 to 3000 mm year-1 (Omer, 2008).

Based on the study by the Ministry of Irrigation and Water Resources (MOIWR), irrigation requirements are expected to be about 42.5 BCM in 2027 (Abdalla, 2001; MOIWR, 2011). Domestic use, human and animal needs and other industrial usage are estimated to be around 10.1 BCM (Fig. 6). The total demand will be 59.2 BCM in case of increment of evaporation from proposed hydropower reservoirs (6.6 BCM increment). This will be beyond the reach of the total available water amount including the southern swamps conservation share. This shortage will not fill even if all seasonal stream water is harvested, facilities are available for the entire share of the Nile water and groundwater is pumped to the limit of its recharge.

Potential of Sudan water resources development and Management

Increased resilience of water resources can be achieved through a wide range of water management practices including preservation of wetlands and forests, enhanced storage of surface reservoirs and depleting aquifers, and water transportation (Scanlon et al., 2023).

Rainfall water management

Sustainable management for the rainfed sector can be achieved by: maximizing of infiltration of rainfall and minimization of unproductive losses, maximization of plants water uptake capacity (timeliness) via crop and soil fertility management and bridging crop water deficits during dry spells through supplemental irrigation. Also, the appropriate water harvesting techniques for micro-irrigation combined with supplemental irrigation and conservation tillage.

Nilotic water development and management

  1. Irrigated water management

The main user of Nile water is irrigation, which consumes about 15.9 BCM/year in the last ten years. The irrigated sector produces 100% of the sugar, 95% of the cotton, 36 % of the sorghum, 32 % of the groundnut and all the vegetables and fruits (Farah, 1999). The productivity of the used water is not more than 0.2 kg m-3 as a means for cotton, sorghum, groundnut and wheat while the international statistics indicate the possibility of getting more than 1 kg m-3. Some crops consume huge quantities of water like sugar cane. Although the total sugar cane cultivated area is about 135000 hectares representing about 10% of the cultivated areas of Sudan it consumes about 30 % of Sudan’s water share of the river Nile (18.5 BCM). Abdelhadi and Salih (2012) stated that preliminary trials showed that sugar beet can grow successfully in the Gezira state environment. High root yields and sugar content were obtained resulting in raw sugar yield of 50-55 t ha-1. The total applied water for all the given irrigations measured as average was in the range of 12.852-14.280 m3 ha-1. It was also stated that the crop is very suitable for Gezira Scheme rotation. Also, studies showed that sugar beet needed about 19-20 irrigations with an average of 476.2-714.3 m3ha-1 of water per irrigation, while sugar cane needs almost 42382 m3 ha-1 to produce about 87.14 t ha-1 (Abdelgader et al., 2013). Nevertheless, sugar cane gives 4.2 t ha-1 pure sugar while sugar beet gives 7.5 t ha-1 pure sugar. Regarding water use efficiency sugar beet gives about 0.53 kg m-3 while sugar cane gives about 0.1 kg m-3. Therefore, sugar beet is recommended instead of sugar cane. This has certain implications for the processing of sugar since the current sugarcane factories cannot produce sugar from sugar beet without major adjustments, especially from the energy side point of view.

        Extensive research must be directed to develop field irrigation techniques to increase irrigation efficiency and management practices that increase water use efficiency. The introduction of water stress-tolerant crops and sound irrigation scheduling are some of the techniques to be tried. Irrigation in Gezira Scheme or more broadly in the central clay plains where the potential irrigated agriculture in Sudan is realized. There are very simple facts and rules of thumb that apply when dealing with irrigation water management under the heavy-cracking clay plain. Number one; the cracking clay is self-regulating regarding water uptake due to the cracks and sealing due to swelling. Such soil will not be suitable for sprinkler or center pivot irrigation. Number two; This soil tends to take the same amount of water (because of cracks) bottom-up during each irrigation for example such an amount was found to be about 400 m3 per feddan (4200 m2) every 12-14 days. Delaying or reducing the irrigation interval will not save water but will subject the crop to various water stresses. On the contrary, any over-irrigation tends to stay at the surface (due to the sealing effect) producing an unpleasant situation and more embarrassment to the farmers while the studies of the physical conditions of the soil such as oxygen availability did not indicate shortages since the profile did not practically exhibited full saturation even if the field is flooded for one month (Farbrother, 1996). Finally, it can be said that irrigation water management under the central cracking clay plains as has been represented by Gezira Scheme requires a full understanding of the physical characteristics of this soil leaving few but more viable options to improve water productivity for example in the Gezira Scheme and these could be as follows; (1) Improve timeliness of irrigations not to exceed 12-14 days since any delay after that will introduce the beginning of water stresses for any crop (heavy clay tend to withhold water more strongly when certain amount of available water is depleted). Improve water management infrastructure of the irrigation network in terms of overflow structures and gates and avoid unnecessary and improper digging of minor canals. Water user associations control cannot be implemented without empowering the associations through hands-on training and capacity building in all agricultural production capabilities. (2) Apply without delay all the recommended technological packages resulted from verified on-farm research (this includes type amount and time fertilizer application, sowing of improved varieties, removal of weeds and controlling of insects and diseases using integrated pest management recommended practices). Finally, marketing of the product means fair returns to the farmers and more efforts to improve productivity.            

b. Cooperation between the Nile Basin countries

The Nile Basin encompasses eleven countries: Rwanda, Burundi, Kenya, Tanzania, the Democratic Republic of Congo, Uganda, Ethiopia, Eritrea, Sudan, Egypt and the Republic of South Sudan. In 1997 The Nile Basin countries initiated a dialogue on a long-term cooperative framework. In 1999 the Nile Basin Initiative (NBI) was approved, and the joint program was envisaged to pursue sustainable development and management of Nile waters for the promotion of economic growth, poverty eradication and reversal of environmental degradation. The program is called the Shared Vision Program (SVP) and includes many projects to achieve the set objectives and sharing benefits.

The impact of the climate change on the Nile River, which is projected to virtually be affected in the future, which will lead to a decrease/increase in water resources in the Nile Basin countries, particularly Sudan (Elshamy et al., 2009; Basheer et al., 2016). Sudan’s share in the Nile water may be increased by acting with Egypt and South to reduce evaporation losses from the swamps. This requires working with South Sudan as an independent country now. Whereas a large amount of water can be saved from the White Nile system as suggested by the Nile Basin Initiative (NBI). Some studies suggested digging canals to collect water from some rivers and deliver it to the White Nile, which will produce about 19 BCM/year (Ganadi, 2006). Although the capability of these projects, it should seriously consider the social and environmental impacts. These projects could be considered as a solution to reducing water shortage and increase Nile water discharge. Sudan, Egypt and South Sudan should cooperate between them to implement these projects. Further, all these projects may help to solve the issue of water in the near future between Sudan and South Sudan. The amount of available water from these projects in the future can be predicted from the different sources as shown in Fig. 7.

  1. Protection of River Nile water against pollution

Nile water agreement in 1959 between Sudan and Egypt did not mention or include the protection of river Nile water against pollution, although it is one of the main factors which decrease the water quality and quantity of this resource. The river Nile experiences increasing deterioration in water quality. This is due to increasing pollution loads arising from high population and economic growth in the region (Alnail et al., 2013). According to the carried out by UNEP, (2007).

Post-conflict environmental assessment of Sudan indicates that the wastewater contains an elevated biochemical oxygen demand (BOD), which can reach 800−3000 ppm (UNEP, 2007). A prior investigation carried out at Assalaya, one of the sugar cane processors in the Sudan, had revealed that the factory’s discharge into the river had chemical oxygen demand (COD), BOD, and TSS of 2160, 1200, and 2080 mg L-1, respectively. Pollution can be controlled by prohibiting the spillage of industrial waste, sewerage and agricultural drainage in the river and establishing cooperation between the Nile basin countries to protect the river Nile water from pollution (UNEP, 2007).

Seasonal streams water harvesting

The major categories of water harvesting are classified as follows: excavation of reservoirs (Hafirs), contour bunds, rill bunds, micro catchment basins, diversion and groundwater recharge dikes and earth or concrete dams. These techniques were adopted to increase the year-round availability of water, for human and animal consumption, in different parts of Sudan. Also, these techniques are expected to provide water for both irrigation and domestic use, reduce crop yield fluctuation, reduce risk of investment in rainfed agriculture, improve pastures, reduce the use of groundwater in agriculture, save soil fertility, and increase groundwater recharge. Optimal design and hence sustainable development of seasonal streams requires reliable and properly analyzed data. Long-term monitoring of discharge is essential for the determination of capacity and choice of hydraulic constructions, other information, including meteorological, topographic, structural and soil test are required for completion of design. Despite the good chemical quality of the Wadi water, to avoid negative environmental impacts, social economics study is a prerequisite for the assessment of the environmental situation down and upstream before any development.

1.2. The groundwater management

Sudan has huge groundwater resources in many different parts, which are used for domestic and agricultural practices. Therefore, a wise look for groundwater resources should be established, by achieving sustainable groundwater resources management. To accomplish sustainable development and management, more studies to determine the water quantities in the basins and water quality by making integrated maps explaining the groundwater places. Additionally, determine the annual quantity required for domestic, industrial and agricultural uses.

Protection of groundwater resources from pollution should be implemented, especially in those areas with limited rainfall. Cooperation between the countries which share with Sudan’s any basin for development of that basin by; develop regional agreements and implementation mechanisms. In addition, enhance institutional collaboration, joint decision-making regarding pumping policies and encourage joint studies and research for better understanding of the aquifer mechanism. Furthermore, strengthen monitoring networks and data information bases, and establish data exchange programs.

Precipitation represents the main source of aquifer recharge, besides stream and lake or pond seepage, irrigation return flow, inter-aquifer flows, and urban recharge play an important role in groundwater recharge (Valdivielso et al., 2022). Application of the direct methods of artificial groundwater recharge (surface spreading techniques and sub-surface techniques), and indirect methods (such as induced recharge method) in the Sudan aquifers will lead to sustainable management of this resource (Saha et al., 2022; Sherif et al., 2023). The most important purposes of artificial recharge are the storage of freshwater, raising the declining water table, water reclamation, flood control, water quality preservation and improvement, prevention of saline and low-quality water intrusion, subsidence abatement, raising artesian pressure, disposal of cooling and wastewater (O’Hare et al., 1986).

The most suitable artificial groundwater recharge method is the one that can maintain a high infiltration rate at the economical level and with the sustained desirable quality of water (Wadi et al., 2022). Site specific best suited method in Sudan will require more detailed investigation on the quantity and quality of the available source of recharged water and overall characteristics of the aquifer and the overlying formation (Ismael et al., 2021). The possibility of application of these methods, especially in the valleys and seasonal streams will save large amounts of water which is currently being lost by evaporation and runoff. In general, these methods should be seriously considering for the social and environmental impacts.

Use of smart information and communication technology (ICT) techniques, e.g., integrating remote sensing (RS), geographical information systems (GIS), can be utilized for better assessment of water resources, improved protection and utilization (Amarnath et al., 2018).

3. Conclusion
This study aimed to assess Sudan’s water resources, the current situation of the utilization of these resources, the future demands, and explore the prospects of sustainable development. Water security in Sudan is highly vulnerable and dependent on conventional water resources, with a negligible contribution from unconventional water resources. However, the country has not exploited the full potential of conventional water resources. Efforts should be directed to better manage and utilize conventional water resources and increase the use of unconventional water resources, such as wastewater and seawater desalination. In light of climatic changes, the use of water for surface irrigation, the expansion of growing sugarcane crop, and the separation of South Sudan are considered the major challenges facing sustainable water resource development in Sudan. Therefore, the conventional water resources in Sudan should be accurately assessed for proper utilization, sustainable development, and management. The agricultural sector is considered to be the main consumer of water resources in Sudan. Therefore, any conservation strategy should focus on reducing these quantities. Therefore, high-efficiency irrigation systems are required to ensure sustainability. On the other hand, introducing modern irrigation systems, increasing the efficiency of existing surface irrigation systems, and adopting supplemental irrigation in the rainfed agriculture sector are needed. In fact, Sudan needs to cooperate with other Nile Basin countries to develop the basin and the volume of storage facilities, especially in the eastern Nile Basin countries (Egypt and Ethiopia) and South Sudan. Groundwater resources require assessment, monitoring, development, protection from pollution, and artificial recharge, where appropriate. Development of databases and monitoring stations for rainfall and streams (Wadis) is recommended for the design and implementation of efficient water harvesting methods and development of the seasonal streams.

Competing Interest Statement: All the authors declare that they have no competing interests.

List of Abbreviations: BCM: Billion Cubic Meters. MCM: Million Cubic Meters.

Author’s Contribution:  A.K.B. planned and conducted this research, collected data, wrote, and revised the manuscript under the supervision of A.E.M., while N.A.E. and A.B.A. revised the manuscript and produced all tables and figures. All the authors read and approved the manuscript.

Acknowledgment: We would like to thank the Ministry of Irrigation & Water Resources and Electricity for support in providing us with the data. Our thanks are extended to the Ministry of Agriculture and Forests, Sudan Meteorological Authority and Nile basin initiative for data. Also, authors are thankful to anonymous reviewers for giving constructive comments to revise the manuscript.

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