Impacts of climate and land use/cover changes on the sustainability of irrigation water in West Africa: a systematic review

ABSTRACT

Climate and LULC changes have a great influence on the hydrological processes which include evapotranspiration, infiltration, surface runoff, groundwater flow, and stream discharge regime. This study aims to review the existing literature on the impacts of climate, and LULC changes on the sustainability of irrigation water in West Africa. The future of irrigation in West Africa will be driven by strong external factors, such as rapid population growth, climate change, and LULC change. The annual average temperature is between 25.9 and 34°C. Rising temperatures have affected all sectors, including water resources, increased irrigation demand, and the sustainability of agricultural production. Reduction in precipitation will reduce river flows and increase evaporation due to a drier atmosphere, thereby reducing the amount of water available in reservoirs for irrigation. The current demand for freshwater in West Africa for irrigation purposes is expected to triple by 2050. From 1997 to 2018, forest area decreased by 24.6%, while residential and agricultural land areas increased by 140% and 11.7%, respectively, in West Africa. Effective mitigation and adaptation measures are the policy issue for the observed adverse impacts of future climate and LULC changes on the sustainability of irrigation water availability in West Africa.

KEYWORDS:

• Climate changes
• LULC change
• sustainability
• irrigation
• water
• West Africa

1. Introduction

The global hydrological cycle is being hastened by climate change (Bulkeley & Newell, 2023). The effects of climate change are anticipated to be more profound than they are now (Tilahun et al., 2023). Since water is considered the lifeblood of the biosphere, water stress problems directly hinder food, as they are inputs for the process (Anna et al., 2023). Climate change and land use/cover are key factors affecting water yield and availability (Zhu et al., 2023). Climate change can affect water productivity by changing precipitation and evaporation in river basins (Boonwichai et al., 2018). Changes in LULC can alter the water cycle, affecting evaporation, infiltration, and water retention patterns, which in turn can affect water availability (Che et al., 2022). Competition between the irrigation agriculture, hydropower generation, and water supply sectors can increase vulnerability to water scarcity, as can management practices in these sectors (Flörke et al., 2018). Changes in climate and land cover are expected to exacerbate the complex interactions between water security and social development (van der Esch, 2017). Since the 1970s, there has been rapid progress in the development of remote sensing technology and hydrological models (Dong, 2018). To achieve a more rational distribution of water resources, an increasing number of scholars are making efforts to quantify, visualise, and improve the assessment and analysis of regional water supply through model-based simulations (Li et al., 2022).

Changes in climate and land cover have influenced the hydrological cycle in West African countries (Flörke et al., 2018). Land use and climate are two major factors that directly influence irrigation water availability, and understanding their respective impacts is of great importance for land use planning and land management (Neupane & Kumar, 2015). It has been shown that climate change and land use planning have a greater impact on the regulation of seasonal streamflow distribution than the regulation of mean annual streamflow (Liu et al., 2020). Climate change is expected to produce highly variable rainfall and increased temperatures, making water availability uncertain (Kotlarski et al., 2023). In all West African basins, the relationship between rainfall, runoff and streamflow is complex due to land use/land cover change (LULCC) (Obahoundje & Diedhiou, 2022). The Senegal, Niger and Volta basins, where the main irrigation dams are located, are expected to be severely affected by climate change (Shamseddin & Chaibi, 2020). The Niger River basin is likely to experience the largest decrease in river flows in all of Africa due to climate change and the Senegal River basin at a higher risk of LULCC (Zhu et al., 2023). In west Africa and in Ghana, agriculture has been experiencing decline through the decades; whereas the sector once contributed more than 60 percent to GDP in the 1970s, in 2020 agriculture accounted for just 19 percent of GDP (Mensah et al., 2022). Due to the high risks associated with water availability, future irrigation projects may be significantly affected by changes in climatic conditions (Shamseddin & Chaibi, 2020).

In West Africa, rain-fed agriculture is most important for ensuring income and overcoming poverty (Akudugu et al., 2021). Crop production in West Africa is mostly dependent upon rainfed agriculture. Irrigation is a vital need due to uneven distribution of rainfall and seasonality of water resources (Tiamgne et al., 2022). Irrigation is a fundamental strategy for ensuring agricultural production and food security in the developing countries. Irrigated agriculture accounts for about 4% of arable land in sub-Saharan Africa and remains largely underdeveloped due to a lack of sufficient economic resources and political will (Djoumessi, 2021). Irrigation development is high on the agenda of several regional initiatives in West Africa. Over the past decades, drought, population growth, and water shortages have increased water stress in major river basins in West Africa (Dibi-Anoh et al., 2023). According to official statistics, about 1Mha in West Africa are equipped with irrigation, with over 60% equipped for full-control irrigation and 40% in lowlands (inland valleys or bas-fonds). Further, over 1 Mha are reported to be under recession irrigation, primarily in Nigeria, bringing the total area under agricultural water management (AWM) to over 2 Mha (Amali et al., 2021). Irrigation potential is estimated at 9.1 Mha with 55% in just three countries: Nigeria, Ghana and Sierra Leone (de Fraiture, 2014). Most countries in West Africa hardly developed their irrigation potential, with the exception of Mali and Senegal who developed 41% and 29% of their irrigation potential, respectively (Faye, 2023). Irrigation is of importance for local food security, with sustainable irrigation practices having the potential to boost West African agricultural productivity in many areas without adverse environmental impacts on freshwater resources. Previous studies on the impact of climate change on crops in the region have often predicted that yields will even decline by 2050 due to rising temperatures during the growing season and changes in crop variability monsoon rainfall, thereby adding to food insecurity in an already vulnerable region. In West Africa, the sustainability of irrigation water resources has not been thoroughly researched and planned by policymakers and water resources managers. To ensure timely irrigation water sustainability and accessibility in the context of climate and land use change, appropriate planning, optimisation of appropriate investments, and realistic forecasting are required about input and output is a very important task. The main objective of this review is to collect and organise the current scientific literature and research results on the sustainability of irrigation water resources in the context of climate change and land cover in West Africa.

2. Method

2.1. Principles and procedures

In this paper, a systematic review was used to determine how climate and land use/land cover influence the sustainability of irrigation water resources in West Africa. Systematic review steps were used. A systematic review may be used to explore the academic impact of a particular author, groups of authors, or publications on a particular topic (Table 1). The aim is to describe research impacts, knowledge flows, and knowledge networks within a specified body of literature. As emphasised by (Tawfik et al., 2019), the questions that are asked in the systematic review are relevant. The analysis involved an initial reading of each article, which was guided by the desk review of existing literature to respond by answering these particular questions:

1. What are the impact of climate and LULC change on water resource?

2. How are the Climate and LULC change affect the sustainability of irrigation water?

3. Which thematic areas of the publications are included?

Table 1. Results of keyword search terms.

S/N	Keywords- Query	Number of articles
1	Impact of climate on water resource in West Africa	207
2	Impact of LULC on water resource in West Africa	102
3	Coupled Impacts of climate and LULC change on water resource	115
4	Sustainability of irrigation water in West Africa	65
5	Irrigation potential of West Africa	85
Initially screened titles		235
Initially screened abstracts		145
Post-deduplication total		92

To the best of our knowledge, the application of systematic review to examine the contribution of academia to the discourse on Climate change and LULUC change impacts on Water resources, and current available water assessment and future prediction is the first of its kind in the literature. As such, this article makes a significant empirical contribution to the research on Climate and LULC change impact and to the advancement of new methods for development and policy research in general. To ensure there is transparency, structure, and accuracy in the systematic review process, we adopted the general approach to systematic review by (Tawfik et al., 2019) to facilitate the implementation and translation of findings. The general framework adopted in the study is illustrated below (Figure 1):

Figure 1. Inclusion and exclusion criteria.

Identification – The number of published articles on Climate and LULC within the Elsevier database was done using different search terms as described in the search strategy.

Screening – After the identification of relevant published articles within the database, screened was done to remove duplicates and avoid double counting. Then the number of publications screened and selected was documented and included for further analyses.

Eligibility – After the screening, articles were assessed for relevance, and full-text articles that appeared irrelevant were excluded.

Included – An examination of full-text articles was conducted to include those considered to be relevant for qualitative and quantitative synthesis while the irrelevant ones were excluded.

The selected keywords for database are illustrated as shown in Table 1.

2.2. Analysis method

Visualising similarities (VOS) viewer software has become increasingly popular in systematic review of literature. This software was developed by (van Eck & Waltman, 2010) to present bibliometric maps visually appealingly. As a result, literature may be efficiently collated, similarities between selected publications identified within the parameters, and significant themes identified among publications (Nobanee et al., 2021). Data obtained from Scopus were used for a performance analysis that included the number of publications, citations, and impact factor, derived using the following equations, respectively:

(1) $\mathrm{Impact}\mathrm{facto}{\mathrm{r}}_Y=\frac{\mathrm{citations}{\mathit{\hspace{0.17em}}}_Y}{\mathrm{publication}{\mathrm{s}}_{\mathit{Y}-1}\mathit{\hspace{0.17em}}+\mathrm{publication}{\mathrm{s}}_{\mathit{Y}-2}}$(1)

where: $\mathit{citationsy}=$ the whole number of citations that journal received in the year ‘y’, publications−1 = the sum of articles that were published in the year (y − 1), $\mathit{publicationsy}-2=$ the sum of articles that were published in the year (y − 2).

A total of Nin tee two (92) articles were discovered in the Scopus database, three articles in the Springer database, eight articles in the Web of Science database, and six articles in Google Scholar. After excluding duplicate articles and non-English publications, 32 articles ready to review. Table 2 shows the research area and software used in these articles.

Table 2. Search result in the databases Scopus, web of science, SpringerLink journal, and Google scholar.

Database
Scopus	Web of Science	Springer	Google Scholar	Area of Research	Analysis Software
✓	5	3	6	Climate and land cover change challenge in West Africa	VOS viewer software
✓	5	6	10	Impact of climate on water resource in West Africa	VOS viewer software
✓	7	6	9	Impact of LULC on water resource	VOS viewer software
✓	5	4	8	Sustainability of irrigation water management	VOS viewer software
✓	2	4	11	Irrigation potential of West Africa	VOS viewer software
✓	2	3	6	Climate smart irrigation in West Africa	VOS viewer software

3. Results and discussion

3.1. Climate and land cover change challenge in West Africa

Climate change exposes millions of people to risks from climate extremes, desertification, land degradation, and the loss of food and livelihood security (Smith et al., 2020). West Africa is experiencing climate change at a faster rate than the global average (Omotoso et al., 2023). The 11 countries that make up West Africa are Benin, Burkina Faso, Ivory Coast, Ghana, Guinea, Liberia, Niger, Nigeria, Senegal, Sierra Leone, Mauritania, Mali and Togo. West Africa is currently facing rising temperatures, changing rainfall patterns, and increased extreme events (Fouque & Reeder, 2019). Climate change will undoubtedly pose one of the most significant risks to Africa’s Sustainable Development Goals over the next decade (Ladan, 2018). In West Africa, the monsoon season accounts for most of the total annual rainfall for several months (Lélé et al., 2015). Agricultural output, water resources and livestock in sub-Saharan Africa are therefore highly dependent on rainfall, which can be strongly influenced by the timing and intensity of irregular monsoons (Turyasingura et al., 2023). Changes in climate and land cover have influenced the hydrological cycle in West African countries (Tiamgne et al., 2022). Climate change and land use planning have been shown to have a greater impact on changing seasonal streamflow distribution as well as water availability and sustainability. Analysis of spatio-temporal changes in land cover in West Africa shows changes from the Guinea-Congolia region to the Sahara region (Palumbo et al., 2011). Figure 2 shows the number of publications and citations from countries from 2011 to 2023. This data could reveal which countries actively Involved in Climate and LULC change and it challenge.

Figure 2. The number of publications and citations from countries from 2011 to 2023.

The growing population has exerted considerable pressure on the land resources, leading to subtle modification (e.g. reduction of woody vegetation in savannas and increase of field trees) as well as more radical conversion (e.g. transition from savanna or forest to agriculture) of land cover. Local-scale studies from the region hint to rural population growth as an important driver for cropland expansion in semiarid southern Burkina Faso and northern Ghana (Figure 3).

Figure 3. Land cover and population trends in the study region. (a) annual population growth rates in the study region (blue line) and globally (orange line) from 1950 to 2018 with projections for 2025, 2050 and 2100, as well as total population of the study region per decade (gray bars). (b) land cover compositions of the six sub-regions in 1975 and 2013. (c) map of the study region is divided into six bioclimatic sub-regions defined by their mean annual rainfall (Herrmann et al., 2020).

3.2. Water resource and irrigation potential of West African countries

Irrigation development is critical to ensuring food security and reducing climate vulnerability in Sahelian countries (Ibrahim et al., 2021). However, ‘irrigation’ encompasses many different systems and activities, some of which are little known to policymakers and scientists (Higginbottom et al., 2021). About 1 million hectares in West Africa are equipped with irrigation systems, of which more than 60% are equipped with fully controlled irrigation systems and 40% are in the lowlands (de Fraiture, 2014). In addition, more than 1 million hectares will be subject to flood irrigation, mainly in Nigeria, bringing the total area under agricultural water management (AWM) to more than 2 million hectares (Wendimu et al., 2023). The estimated irrigation potential is 9.1 Mha, of which 55% is located in just three countries: Nigeria, Ghana, and Sierra Leone. Most West African countries have marginally developed their irrigation potential, with the exception of Mali and Senegal, which have developed 41% and 29% of their irrigation potential, respectively (Richards, 2023). Overall, less than 12% of West Africa’s irrigation potential is available (Table 3).

Table 3. Water resources by country.

Country	Average rainfall in depth (mm/yr)	Average rainfall inVolume (10^9 m^3/yr)	Ground water(10^9m^3/yr)	Surface water (10^9 m^3/yr)	Total water resource (10^9 m^3/yr)	Water resources per capita (m^3/inhabitant/yr)	Reference
Benin	1,039	117	2	26	26	3,144	(Odeloui et al., 2022)
Burkina Faso	748	205	10	8	13	849	(Idrissou et al., 2022)
Cote d’Ivoire	1,348	435	38	78	81	4,032	(Soro et al., 2017)
Gambia	836	9	1	8	8	4,950	(Séne et al., 2023)
Ghana	1,187	283	26	52	53	2,326	(Agodzo et al., 2023)
Guinea	1,651	406	38	226	226	23,505	(Mohamed et al., 2023)
Guinea-Bissau	1,577	57	14	27	31	20,117	(Marcolla et al., 2019)
Liberia	2,391	266	45	232	232	63,965	(Koon et al., 2023)
Mali	282	350	20	90	100	8,059	(Diancoumba et al., 2023)
Mauritania	92	95	0	11	11	3,632	(Faye, 2023)
Niger	151	191	3	31	34	2,380	(Abdou Mahaman et al., 2023)
Nigeria	1,150	1,062	87	279	286	1,937	(Ozegin et al., 2023)
Senegal	686	135	4	37	39	3,262	(Sambou et al., 2023)
Sierra Leone	2,526	181	25	150	160	29,520	(Kamara & Kamara, 2014)
Togo	1,168	66	6	14	15	2,333	(Yomo et al., 2019)
Tota1		3,859	317	1,270	1,315	4,638

In Burkina Faso conflicts over water resources due to overdrawing by pump owners were observed (Hutton & Chase, 2017). African countries spend 10% of their national budgets on agriculture to create an annual agricultural growth rate of 6% (Varela et al., 2020). In West Africa, very few countries have a strong strategic, legal and regulatory policy framework that provides the basis for economically efficient distribution of water among different users, making it possible to access the potential of water (Grönwall & Danert, 2020; van Koppen & Schreiner, 2014). The country’s productivity becomes more equitable and sustainable. West Africa has 10 major river basins (Figure 4). In Senegal, Gambia, central Niger, northern Volta, and northern and southern Chad, rainfall decreased. In the Sahelian basins, such as Senegal, Gambia, Niger, Chad and to some extent in the Volta, reductions are limited to about 10 to 30% (Sylla, Pal, et al., 2018). However, in smaller basins located in the Gulf of Guinea (such as Sassandra, Bandama, Comoé, Mono and Ouémé), the reductions were significantly larger, ranging from 35% to 65%, with the largest and highest reductions recorded in Bandama and Ouémé (Imorou et al., 2019). West Africa’s 10 major river basins are likely to face significant challenges in meeting future water demands under global warming, with the Gulf of Guinea basin experiencing major water shortages (Sylla, Pal, et al., 2018). While irrigation demand is likely to require increased water consumption and will strongly affect the sustainability of irrigation water sources in the region (Table 4).

Figure 4. West African major river basin.

Table 4. Irrigation statistics for West Africa.

Country	Irrigation Potential (Ha)	Area Equipped for full-control irrigation	Equipped Low land areas	Total area equipped for irrigation	Percentage of Irrigation Potential equipped	Total AWM (including recession irrigation)	Percentage of irrigated by ground water	Reference
	‘000 ha	‘000 ha	‘000 ha	‘000ha	%	‘000 ha	%
Benin	322	11	1	12	3.8	19	20	(Snezhko et al., 2023)
Burkina Faso	165	19	6	25	15.2	46	3	(Yabre et al., 2023)
Cote d’Ivoire	475	48	25	73	15.3	89	18	(Dossou-Yovo & Saito, 2021)
Gambia	80	2	0	2	2.7	15	23	(Boussouga et al., 2023)
Ghana	1,900	31	0	31	1.6	31	11	(Tuffour et al., 2023)
Guinea	520	20	75	95	18.3	95	2	(Terán-Chaves et al., 2023)
Guinea-Bissau	281	9	14	23	8.0	52	6	(You et al., 2011)
Liberia	600	11	2	13	6	57	4	(Nkiaka et al., 2023)
Mali	566	98	138	236	41.7	296	1	(Birhanu et al., 2023)
Mauritania	250	45		45	18.0	109	10	(Higginbottom et al., 2023)
Niger	270	14	60	74	27.3	85	6	(Odofin et al., 2023)
Nigeria	2,331	238	55	293	12.6	972	9	(Ugalahi et al., 2016)
Senegal	409	102	18	120	29.3	150	10	(Higginbottom et al., 2023)
Sierra Leone	807	1	28	29	3.6	155	8	(Moinina et al., 2021)
Togo	180	2	5	7	4.1	7	2	(Gadédjisso-Tossou et al., 2018)
Total	9,156	640	425	1,065	11.6	2,122

West Africa is enriched with numerous surface water resources (rivers, estuaries, lakes, reservoirs), including major rivers such as the Niger, Senegal, Gambia, and Lake Chad. These rivers take their sources in tropically wet major groundwater basins and regions with considerable amount of annual rainfall. But with climate change disrupting the frequency, timing, and intensity of the rainfall patterns across the continent, extended droughts and intensified flooding have become the new normal (Ndehedehe, 2019).

According to official statistics, about 1 Mha in West Africa are equipped with irrigation, with over 60% equipped for full-control irrigation and 40% in lowlands (inland valleys or bas-fonds). Further, over 1 Mha are reported to be under recession irrigation, primarily in Nigeria, bringing the total area under agricultural water management (AWM) to over 2 Mha. Irrigation potential is estimated at 9.1 Mha with 55% in just three countries: Nigeria, Ghana and Sierra Leone. Most countries in West Africa hardly developed their irrigation potential, with the exception of Mali and Senegal who developed 41% and 29% of their irrigation potential, respectively. Overall, less than 12% of the irrigation potential is developed (Richards, 2023).

3.3. Impact of climate change on sustainability of irrigation water availability in West Africa

Irrigation plays a crucial role in promoting sustainable growth, ensuring economic stability, and providing employment stability (Mondejar et al., 2021). It has helped certain areas recover from droughts and acted as a protective measure during their occurrence. Irrigation plays a role in boosting agricultural production and ensuring consistent yields and productivity, despite its indirect benefits. Supplying water to meet the plant’s requirements enhances the production of food, reduces hunger, and fosters the development of high-quality plants. The future of irrigation and agriculture is unpredictable due to the limited, inconsistent, and unexpected rainfall caused by climate change. It serves as a foundation that helps farmers and reduces their dependence on weather conditions, enabling them to enhance their overall agricultural output. This is determined by the presence of water, which greatly affects irrigation, agricultural output, and manufacturing. Furthermore, it plays a vital role in promoting higher agricultural productivity per unit of land area and in expanding agricultural reach. According to the (Malek & Verburg, 2018) Over 70% of the world’s irrigation water is abstracted and used annually for irrigation purposes.

Climate change has a notable impact on the availability of water for agricultural purposes and irrigation, which poses potential risks to food security at both domestic and global levels (Kumar & Sharma, 2022). The changes in time and space of the main elements of the water cycle greatly affect hydrological processes. The area most affected by climate change is irrigation, as it utilises a larger amount of water compared to any other industry. On the other hand, climate change has an opposite effect as it leads to an increase in evaporation, which in turn boosts the need for water in irrigation. This demand is particularly high as irrigation already consumes the majority of the available water in the present surroundings (Egbueri et al., 2023; Hamududu & Ngoma, 2019).

West Africa’s climate depends on the variability of the West African monsoon, the southward movement of the Intertropical Convergence Zone (ITCZ), and the location and intensity of the East African jet and thermal jet eastern zone (Biasutti, 2019). The ITCZ is the region where the Sahara’s warm, dry harmattan air mass to the north (northeast trade winds) meets cool, moist monsoon air (southwest winds) from the South Atlantic (Augustin et al., 2023). From December to February, the ITCZ moves towards the Gulf of Guinea, and from March to November it moves from the Gulf to higher latitudes, even passing through some areas twice (Bahrami et al., 2017). Therefore, in southern West Africa (i.e. the Guinea coast) there are two rainy seasons (March-June and August-November) and two dry seasons (December-February). The northern part of West Africa (i.e. the Sahel) experiences a rainy season from July to September and a long dry season starting in October (Orimoloye et al., 2021).

Surface temperatures in West Africa have increased over the past 50 years, between 0.5 ◦C and 0.8 ◦C between 1970 and 2010 (Riede et al., 2016), with higher over the past 50 years in the past 20 years compared to previous decades. Temperature increases in the West African region are expected to be larger than average global temperature increases, and heat waves are expected to occur more frequently and last longer (Sylla, Faye, et al., 2018). Rising temperatures have affected all sectors, including water resources, increased irrigation demand and the sustainability of agricultural production (Cai et al., 2015). River flows are expected to decrease by 20 to 40% by 2050 (Obahoundje & Diedhiou, 2022). In transboundary basins such as the Niger, Senegal, and Volta, river flows are expected to decline between 5% and 34%, depending on time period and location (Aziz et al., 2019). At Lake Guiers in Senegal, it was found that climate change and population growth will put pressure on available water resources, leading to greater competition between irrigation and municipal demand (Aina et al., 2023).

In the Volta basin, not all water needs (urban and irrigation) can be met simultaneously with current and future needs. In Ghana, agricultural production frequently fails during periods of rainfall deficit due to low water levels of the Tono irrigation dam (Agodzo et al., 2023). Reduced rainfall will reduce river flows and increase evaporation due to a drier atmosphere, thereby reducing the amount of water available in reservoirs for irrigation. Rising temperatures will increase evaporation, which can contribute to reduced water levels in reservoirs and negatively affect irrigation sustainability (Figure 5). Current demand for freshwater in West Africa for agricultural, industrial, and domestic irrigation purposes is expected to triple by 2050 (USAID 2013). Therefore, it is important to carefully consider the impact of upstream socioeconomic development on reservoirs while also assessing the impact of climate change on the sustainability of irrigation water resources in West Africa (Baratto et al., 2022).

Figure 5. West African Irrigation Dam.

3.4. Impact of land use/land cover change on sustainability of irrigation water availability in West Africa

The impacts of land use change and climate change on water resources pose a major threat in semi-arid environments, especially in sub-Saharan Africa. West African basins are facing rapid changes in land use and land cover and have lost or are losing large areas of natural landscape, which are being replaced by large tracts of land largely influenced by humans due to agriculture, forest fires, and logging (Obahoundje & Diedhiou, 2022). From 1975 to 2013, forest area decreased by 24.6%, while residential and agricultural land areas increased by 140% and 11.7%, respectively, in West Africa (Obahoundje et al., 2021). The size of vegetated areas continues to decrease as rainfall decreases and temperatures increase, especially in arid regions. The hydrological response to changes in LULC varies by region (Koffi et al., 2023). In the Black Volta sub-basin, LULC development between 2000 and 2013 contributed to increases in surface runoff and lateral flow by 27% and 19%, respectively, while the groundwater contribution to runoff River flow decreased by 6% due to land use climate change, as well as 4.6% increase in evapotranspiration due to rising temperatures (Kayitesi et al., 2022). At all scales in the Sahelian region, runoff coefficients generally increase with river flow, driven by reduced vegetation cover (Descroix et al., 2018).

Runoff has increased in the Sahelian basins despite a 20–25% increase in rainfall recorded between 1997 and 2017 (Descroix et al., 2018) and an increased number of dams built in the basins (Efon et al., 2023). This increase in runoff and runoff despite decreased precipitation is known as the ‘Sahelian paradox’ and was first observed in small catchments in Burkina Faso by (Yonaba et al., 2021). In contrast, a 15% decrease in rainfall in Sudan resulted in a more intuitive reduction in annual runoff and streamflow (Hector et al., 2018). In the latter region, the decrease in flow rate is two to three times greater than that of precipitation (Massazza et al., 2021). In the southern region of West Africa, reduced vegetation cover may also contribute to reduced soil water holding capacity and infiltration rates, leading to reduced water tables and sustainability (Obahoundje & Diedhiou, 2022). Reduced groundwater recharge capacity or water table levels can drastically reduce dry season flows, which, in addition to increasing evaporation due to rising temperatures, can also seriously affect reservoir water availability for irrigation (Mendoza-Grimón et al., 2021).

The potential impact of changing land use and land cover on the Bui Hydropower Project in the Black Volta Basin under climate change was studied using the WEAP model from 2000 to 2040 (Obahoundje & Diedhiou, 2022). Evaluation using the WEAP model in wet and dry climates shows that the combined impact of changing land cover/land use and climate will reduce water availability for all sectors in need water demand (Mensah et al., 2022). Wet conditions are seen as a 14% increase in precipitation and dry conditions as a 15% increase in precipitation between 2012 and 2040 (Obahoundje et al., 2017). Consequences of human-induced land-use change on irrigation water has received little attention from political decision makers and dam managers in the West Africa, while integrating this information about changes on earth, is important for strategic planning, for effective national and regional adaptation policies and for sustainable development (Asenso Barnieh et al., 2020).

3.5. Best irrigation system for agriculture under water stress dry land of Africa

Irrigation agriculture is an essential sector in West Africa, providing food, employment, and income for millions of people. However, the sector is facing numerous challenges, including limited access to water, unreliable rainfall patterns, and climate change, among others. Irrigation systems play a critical role in addressing these challenges and improving agricultural productivity and food security (Baratto et al., 2022). The effects of irrigation on livelihoods are particularly high in areas where agriculture is the main source of livelihood (Akudugu et al., 2021). Sprinkler irrigation: Sprinkler irrigation is the most common type of irrigation system used in West Africa, especially for large-scale cultivation. It uses a system of sprinklers to distribute water over crops. It plays a vital role in the Maximizing water use efficiency and minimising evapotranspiration Büyükcangaz et al. (2017).

4. Conclusion

The future of irrigation water resources and sustainability in West Africa remains uncertain. Large areas are experiencing new dynamics, especially in Senegal and Mali, through private agricultural sectors and small private and individual systems, either spontaneously or with the support of government. The future of irrigation in West Africa will be driven by strong external factors, such as rapid urban growth, climate change and land acquisition. Achieving food security, reducing poverty and adapting to climate change are among the major challenges facing irrigated agriculture in West Africa. Farmers’ ability to adapt to this landscape will depend on the agricultural, energy and land policies their governments implement. Land use/cover changes interact with the warmer temperatures affect water availability for irrigation by increasing evapotranspiration and surface runoff and decrease in water yield. As population and urbanisation intensify and economies grow, increasing municipal and industrial water demands are likely to amplify the overall water demands in West Africa. Land and water management practices have great potential to mitigate the impacts of future climate and land use/cover changes on water resource, thus increasing its availability. In addition, these management practices will potentially reduce the stress caused by the decline in available water resource due to climate change. Land and water management practices namely filter strips, terracing and contouring and grassed waterways have to be effective mitigation and adaptation measures for the observed adverse impacts of future climate and land use/cover changes on sustainability of irrigation water availability. Adoption of climate-smart irrigation for climate change adaptation, improved food security, and environmental sustainability in the West Africa.

Disclosure statement

No potential conflict of interest was reported by the author(s).