Nature-based Solutions for Water Resource Management in Africa's Arid and Sem-Arid Lands (ASALs): A Systematic Review of Existing Interventions

Olago D.O., Downing T.A., Githiora Y., Borgemeister C., Kamau J., Kuiper G., Koné N.A., Omuombo C.

Nature-based Solutions (NbS) are powerful tools whereby, using nature as the template, societal challenges can be addressed, while simultaneously achieving co-benefits for the environment. NbS have been successfully demonstrated in different ecosystems around the globe, but for savanna ecosystems - the planet's largest terrestrial biome - there is a lingering lack of clarity of what constitutes an NbS. We undertook a systematic review of literature in the savanna belt of Africa - stretching from Senegal to Tanzania. This review examined 3,714 journal articles from 2018 to 2022, out of which 271 papers met the inclusion criteria. Results show that there are a wide variety of nature-based techniques and strategies being used in the savanna-belt. Yet upon greater scrutiny, few qualified as NbS according to the IUCN criteria. Less than 2 % of papers met all the criteria, falling short in the areas of biodiversity gains, economic viability, governance processes, trade-offs, and adaptive management. The geographical and sectoral scopes of these solutions were also limited: 72 % of papers were from just 5 countries, and 80 % were from the agriculture/livestock sectors. Notably, 5 % involved creation of new ecosystems. Author collaborations between countries of the global south with savanna ecosystems were few. Our findings suggest research silos in NbS discourses: the peer-reviewed literature revolves around smallholder farming in just a few countries, where the research is generally driven by the global north. These factors prevent NbS from becoming truly transformational in addressing societal challenges in the savanna belt of Africa.

Adem A.A., Wassie T.M., Gashaw T., Tilahun S.A.

Land degradation is a severe environmental problem in the northern and northwestern Ethiopian highlands. As a response to increasing land degradation, rehabilitation of degraded grazing lands through exclosures (exclusion of farmers and domestic animals) has been undertaken. This study aimed to evaluate the effectiveness of 11 and 8-year exclosures in improving degraded landscapes in the Karita-Wuha and Dengora watersheds. It was assumed that the conditions on communal grazing lands at the time of the investigation corresponded to those at the establishment of exclosures. Vegetation was inventoried, and soil samples were collected and analyzed in 14 and 21 sampling sites selected from exclosures and communal grazing lands in Dengora and Karita-Wuha watersheds, respectively. Sampling plots (20 × 20 m) were established for soil sampling. In the two land uses, 10x10 m and 5x5 m sub-plots were used to survey trees and bushes/shrubs, respectively. Richness, diversity, evenness, and aboveground biomass (AGB) were evaluated using measurements from the vegetation inventory. Organic carbon (OC), total nitrogen (TN), and available phosphorus (AP) and their stocks were used as soil nutrient indicators. The result showed that exclosures aided in restoring vegetation in both watersheds and soil nutrient parameters in the Dengora watershed compared with communal grazing lands. In the Karita-Wuha watershed, there was significantly higher OC, TN, and their stocks in communal grazing land than exclosures (t-test, p < 0.05). These results are generally attributed to the fact that communal grazing lands were significantly degraded before exclosure and have yet to recover. As a result, exclosures of Dengora and Karita-Wuha watersheds were limited in restoring degraded landscapes. There have been differences in the effectiveness of < 11- and > 11-year exclosures in restoring degraded landscapes in the literature. The effectiveness of various aged exclosures in restoring degraded landscapes is likely variable and dependent on local biophysical parameters and land use systems.

Masha M., Bojago E.

Soil erosion is a significant environmental problem worldwide, particularly in developing countries agricultural area where it can lead to reduced soil fertility, decreased crop productivity, and even land degradation. This study explores the prevalence of soil erosion in the Wolaita area and the factors that hinder or promote the implementation of soil and water management (SWC) practices by farmers. Despite significant investment by the local government, the adoption rate of these practices remains low. Data from cross-sectional surveys were gathered from primary and secondary sources and analyzed using descriptive and inferential statistics. The study involved 378 sample households, including both adopters and non-adopters of soil and water conservation measures. A multinomial logistic regression model was utilized to investigate the factors influencing the adoption of physical conservation measures. The study found that most local farmers perceived soil erosion rates are high (43.54 %) and increasing. Some respondents had a medium perception (22.96 %) while others had a low perception (17.72 %). The results revealed that education, farm size, family size, livestock ownership, contact with extension workers, farming experiences, and land tenure security all positively and significantly influenced the adoption of conservation measures. The findings highlight the importance of sustainable conservation practices, comprehensive education and training for farmers, and the establishment of strong local institutions for credit accessibility and extension services. Additionally, fostering connections and knowledge-sharing among farm communities can enhance the adoption of soil and water conservation measures. The outcomes of this study will provide valuable insights for policymakers, researchers, and farmers to develop effective strategies to combat soil erosion and promote sustainable agriculture practices in the region. Overall, this study suggests that the local government and stakeholders must prioritize these strategies to address the critical issue of soil erosion in the Wolaita area.

M-Buu File D.J., Nhamo G.

Smallholder agriculture in Northwestern Ghana continues to suffer the increasing threats of climate change and variability. The extant literature has argued that climate-smart agriculture is the way forward for smallholder farmers to reduce the threats of climate change and variability in agriculture production. However, smallholder farmers continue to rely on indigenous knowledge and practices in their day-to-day agricultural activities. Few studies have explored the rationale and factors that explain smallholder farmers choice of local agriculture practices. This study explored the rationale and factors that explain smallholder farmers' choice of indigenous knowledge and agriculture practices. The mixed research method approach involving both quantitative and qualitative methods were employed for data collection and analysis. A survey, involving 305 household heads, 31 in-depth interviews and 18 focus group discussions were held with key participants for the data. The results showed that smallholder farmers' decisions to adopt indigenous practices for climate change adaptation were influenced by socio-demographic characteristics, access to farm capital, landscape and distance to farms, accessibility and reliability of practices, accessibility and cost of inputs, land tenure, access to extension services, and socio-cultural beliefs. These variables were statistically significant at 5 %. The paper concludes that these factors will continue to limit farmers' ability to adopt climate-smart and other improved agricultural practices. This will aggravate smallholder households' vulnerability to food insecurity and poverty. It is, therefore, recommended that climate-smart agriculture practices should be framed within the context of the aforementioned factors influencing farmers choice of indigenous farming practices in mainstreaming them into climate-smart agriculture.

Bilalova S., Newig J., Tremblay-Lévesque L., Roux J., Herron C., Crane S.

Integrated water resources management (IWRM) has been central to water governance and management worldwide since the 1990s. Recognizing the significance of an integrated approach to water management as a way to achieve the Sustainable Development Goals (SDGs), IWRM was formally incorporated as part of the SDG global indicator framework, thus committing the UN and its Member States to achieving high IWRM implementation by 2030 and measuring progress through SDG indicator 6.5.1. This paper examines the extent to which the implementation of IWRM improves the sustainable management of water and the health of water-related ecosystems-a first-of-its-kind in terms of quantitative analysis on a global scale. To achieve this objective, we conducted regression analyses between SDG 6.5.1 (both IWRM (total score) and the dimensions of SDG 6.5.1) and key water-related environmental sustainability indicators: SDG 6.2.1a (access to basic sanitation), 6.3.1 (treated wastewater), 6.4.1 (water-use efficiency), 6.4.2 (water stress), 6.6.1 (freshwater ecosystems, although here the trophic state and turbidity variables were used) and 6.3.2 (ambient water quality). Our analysis covers 124 countries for all these SDGs, with the exception of SDG 6.3.1 and SDG 6.3.2, which cover 112 and 85 countries, respectively. Results show that IWRM-to different degrees-is mainly associated with the good status of water-related sustainability indicators, with the exception of water stress, water quality, and turbidity. We observe a strong impact of control variables such as governance arrangements, economic situation and environmental and geographical conditions. Lagged effects and the scope of the framework may also explain some observed variations in the degree of association. Our study highlights the importance of further uncovering the interlinkages between IWRM implementation and the achievement of water-related environmental sustainability. Overall, the results suggest that although IWRM implementation is primarily linked to sustainable water management and the health of water systems, context-specific factors should be taken into account when evaluating its effectiveness, to enable policy- and decision-makers to make the necessary adjustments to optimize its outcomes.

Tofu D.A., Wolka K.

This study aimed to evaluate the adaptation efforts of food-aid-reliant smallholder farmers in the drought-prone area of northern Ethiopia. The study involved mixed approaches to collect both quantitative and qualitative data from the randomly selected 398 respondents. The study employed a household survey method to collect quantitative data, while to gather qualitative data focus group discussions and key informant interview methods were used with the help of semi-structured and unstructured questions, respectively. The primary data were gathered focusing on food aid and the opinion of the farmers, perceived causes for food shortage and aid dependence, approaches of improving and sustaining adaptive capacity, options and practice of livelihood diversification, the role of local institutions in building adaptive capacity, and factors influencing the efforts to build adaptive capacity and sustain livelihood. While descriptive statists and econometric models were used to analyze quantitative data, content analysis was used to summarize the qualitative data. The results showed that 100% of the farm households reported that they have been suffering from food insecurity. As a result, about 67% of the respondents were dependent on external support for their livelihood. Climate variability, frequent droughts, low productivity, land degradation, and low technology adoption were the major causes of food insecurity and reliance on aid. To build adaptive capacity and livelihood resilience of the rural poor, implementing integrated watershed management activities was taken as a key approach to improve the productivity of the land, ensure food security, and avoid reliance on external aid coming from abroad. The model was checked for its validity before the analysis. Active community participation, awareness of climate change, social transfer, access to credit service, use of organic fertilizer, and community engagement in off-farm income activities is factors that have a positive and significant influence on adaptive capacity. Therefore, policymakers and planners should focus on improving land productivity, enhancing household income, lessening the vulnerability of households, and increasing the adaptive capacity of aid-dependent poor farmers’.

Wolka K., Uma T., Tofu D.A.

Climate change severely affects smallholder farmers in developing countries such as Ethiopia. To overcome the impacts, the government of Ethiopia has been undertaking a massive adaptation programs including integrated watershed management practices. However, there is a limited understanding of climate change, adaptation strategies, and the effect and acceptance of the implemented techniques. The objective of this study was to assess climate variability, farmers’ climate change adaptation strategies, and the role of watershed management in climate change adaptation. A multi-stage sampling technique was used to select 255 household heads from three rural kebeles (lowest administrative unit of government) in high, mid, and low-elevation areas. The household survey, focus group discussion, and key informant interview record were used to collect data. In addition, long term meteorology record was used. Data were analyzed using descriptive statistics and a multinomial logit model. The results showed that more than 80% of the farmers, in each elevation, perceived climate variability such as increasing temperature and rainfall fluctuations. The perceived variability is more pronounced in the low-elevation areas. The meteorology record also showed fluctuation in rainfall. About 90% of respondents in each elevation area perceived population pressure, cultivation, and deforestation as the major causes of climate variability. About 90% of respondents perceived crop yield decline due to climate variability. In drought years, crop yield and livestock production decline by ∼50% compared to the average year. Adjustment of crop planting time, crop diversification, selling household assets, participating in off-farm activities, and using government aid were practiced as climate change adaptation measures. About 70% of farmers perceived the positive role of watershed management in climate change adaptation. On average, 36–43% of the farmers in the study area participated in watershed management activities such as the construction of bunds and tree planting, which assist in coping with climate variability impacts. Farm size, sex, education, and farming experience positively and significantly affect the adaptation practices of the farmers. Policymakers and practitioners need to consider the issues related to climate variability and watershed management as a strategy for climate change adaptation. Policy intervention by the Federal government on sustainable watershed management and rural livelihood strategies could assist in sustainable environmental management and climate change adaptation.

Eshete A., Teshome S., Edaso A., Yilma G., Furo G.

The large-scale commercial agriculture, mining, expansion of sedentary agricultural settlements, and overgrazing in Ethiopian pastoral areas have become a major cause of land degradation. Such activities reduce grazing capacities and impoverish already fragile living conditions of the pastoralists. Such an increase in land degradations necessitates urgent calls for interventions. The main objectives of this study were to select the best performing soil and water conservation technologies and native tree species to restore degraded lands of arid and semiarid conditions in Liben District of Guji Zone, Oromia Reginal State, Ethiopia. Four locally grown and locally preferred tree species, namely, Cordia africana, Acacia tortilis, Acacia goetzei, and Combretum molle, were planted in five soil and moisture conservation structures (control, half-moon, spot hoeing, mowing, and trench). The survival rate and height and root collar diameter (RCD) growth of planted tree species were collected two years after planting. A significantly higher survival rate, RCD, and height growth of planted seedlings were recorded from half-moon (52.44 ± 12.48%; 1.66 ± 0.31 cm; 51.57 ± 2.79 cm) and trench (64.00 ± 11.49%; 1.92 ± 0.27; 69.67 ± 2.62 cm) moisture conservation structures, respectively. Acacia tortilis (58.22 ± 12.38%) and Acacia goetzei (42.99 ± 8.81%) had better survival rate than Cordia africana (4.00 ± 1.91%) and Combretum molle (24.22 ± 7.34). Cordia africana attained the largest RCD (2.50 ± 0.34 cm) and height (95.83 ± 17.25 cm) growth, followed by Acacia tortilis and Acacia goetzei. It is concluded that Acacia tortilis and Acacia goetzei are better species to grow in degraded lands. The half-moon and trench moisture conservation structures have a great potential for degraded areas of the arid and semiarid conditions of Ethiopia for better tree establishment, survival, and enhanced growth thereby rehabilitation of degraded lands.

Cyamweshi R.A., Kuyah S., Mukuralinda A., Ngango J., Mbaraka S.R., Manirere J.D., Muthuri W.C.

AbstractAgroforestry is widely considered as a sustainable land management practice with multiple ecosystem benefits that support farmers’ livelihoods. While there is much evidence that the technologies are not being embraced as expected, there is knowledge gap about farmers’ perceptions to help devising extension strategies tailored to farmers’ needs in many countries, including Rwanda. This study determined factors that influence farmers’ perceptions on trees effects on soil fertility, moisture retention and crop productivity in semi-arid and humid regions of Rwanda. Logistic regression was used to analyze household survey data that covered 107 and 146 farmers in semi-arid and humid regions, respectively. Results showed that the proportion of farmers with fertile soil in the humid (92%) and the semi-arid (65%) regions was higher on farms with trees. In the semi-arid region, farmers’ perceptions of trees effect on soil fertility was positively influenced by education (P < 0.05) and negatively influenced by farm size (P < 0.1) whereas in the humid region, it was positively influenced (P < 0.1) by family size. Farmers’ perceptions of the effect of agroforestry on soil moisture were influenced by farmers’ knowledge (P < 0.1) in the semi-arid region and gender (P < 0.05) in the humid region. Farmers reported higher yields of potato, maize and beans on farms with trees in the humid region and beans in the semi-arid region. These factors should be taken into consideration to target agroforestry technologies more efficiently within farmer populations. However, constraints including lack of seedlings, tree-crop competition, droughts, termites and lack of mineral fertilizers for seedlings need to be addressed to increase farmers’ uptake of agroforestry technologies.

Degfe A., Tilahun A., Bekele Y., Dume B., Diriba O.H.

In Ethiopia, national wide soil and water conservation is going on since 2010/11in all agro-climatic zones and farming systems. Therefore, this study evaluated the effects of soil bund on soil physico-chemical properties and factors determining farmers' decision on the adoption of SWC technologies in a watershed located in the sub-humid climate of southwest Ethiopia. Two sub-watersheds, namely Nada and Gulufa in the Gilgel Gibe I catchment, were selected for this study. Thirty-six soil samples were collected from non-conserved croplands and croplands conserved with soil bunds (older than 4 years) at three slope positions, namely lower (5–10%), middle (10–15%), and upper (>15%). Both composite and undisturbed top soil (0–30 cm) samples were collected and soil physicochemical properties were determined following standard laboratory procedures. The generated soil physicochemical data was analyzed using one-way ANOVA and the mean separation was carried out by the Tukey test using R-version 3.5.2. To generate survey data, 267 households were randomly selected from the two sub-watersheds and interviewed using a structured questionnaire. The collected survey data was analyzed using a binary logit model using STATA software version 13. The result showed that the implemented soil bund significantly (p < 0.05) improved soil BD, SMC, pH, SOC, TN and CEC at the three slope positions for both the Nada and Gulufa sub-watersheds. The binary logit model showed that personal, socio-economic, institutional, and physical factors influencing the decision of a farmer's adoption. This revealed the need to consider personal, socio-economic, institutional, and physical factors to enhance the willingness probability of adoption. Besides, the improvements in soil properties as a result of conservation practices can help to create awareness.

Babuji P., Thirumalaisamy S., Duraisamy K., Periyasamy G.

Water resources are crucial in developing any area as they serve as a major source of potable, agricultural, and industrial water. Water contamination, caused by natural and anthropogenic activities, poses a significant threat to public health globally. This review synthesizes data from various studies published in national and international journals, as well as reports from governmental and non-governmental organizations. Our primary objective is to understand and review previous research on water pollution, contamination types, and the effects of water contamination on public health. Water pollution studies generally involve a scientific understanding of the biological, chemical, and physical processes that control the movement of contaminants in the underground environment. The nature and severity of health consequences vary based on several factors, including the chemical composition, duration of exposure, and concentration of pollutants. This work highlights the human health risks associated with current research topics such as anthropogenic, geogenic, microplastics, pharmaceuticals, and heavy metals. A section on remedial measures and mitigation strategies is included to emphasize sustainable approaches to water conservation, replenishment, and sustainability. However, there is a lack of comprehensive knowledge regarding the distribution, toxic effects, and human health risks associated with different sources of contamination. This review thus establishes links between multiple sources of pollution, their toxicity to human health, and approaches to health risk assessment.

Araya H.G., Wasonga O.V., Mureithi S., Birhane E.

AbstractLand rehabilitation through exclosures has been recognized as a promising practice in the restoration of degraded drylands. This study evaluated woody species density, diversity, cover, and biomass production from three regeneration approaches (EMTs): (1) Naturally Regenerated (ENR) exclosures, (2) exclosures with Soil and Water Conservation Structures (ECNR), and (3) those enriched with exotic and local plant species in addition to SWC structures (ECP) among which empirical evidence of comparisons are lacking for appropriate decision making of which restoration strategy to promote. Primary data were collected from a total of 72 study plots located across transects laid within exclosures and in adjacent grazing areas with similar ecological condition. Interview with 331 households and focus groups was used to further understand the effects. Regression analysis revealed that the mean difference in herbaceous and canopy cover, herbaceous and woody biomass, and woody species density and diversity of the three EMTs was statistically significantly higher than in the adjacent open grazing areas. Moreover, herbaceous biomass in ECP differed significantly from that of ECNR. The results indicated that ENR and ECP equally enhanced the selected vegetation parameters. This is predominantly attributed to the comparable responsiveness of many degraded areas to natural regeneration as they do to active regeneration approaches. Implementation of natural regeneration is suitable for immediate recruitment of strategy in terms of resources, time, and meeting objectives before decisions are made for assisted models of exclosure that require massive campaigns to construct soil and water conservation structures and huge seedling production in the dryland areas.

Eboi A.A., Amunga H.

Global university ranking is taking place on the background of continental disparities in higher education. A thematic literature review reveals differences in history, political environments, education, and related policies. This chapter documents the position of African universities in global ranking based on the results of three major ranking systems from 2016-2021. It compares performances in North and South universities; examines the factors responsible for poor performance in global South universities; and provides possible solutions for improved performance. The chapter proposes categorizing universities according to regions for fairness; self-evaluation and benchmarking by African universities with globally best-ranked universities; de-linking of African public universities from political sycophancy; more stakeholder appreciation and investment in universities; and more government funding. These can help improve Africa's education, especially staff capacity; infrastructure; curriculum development and implementation; teaching methodologies; research; and community development.

Wolka K., Biazin B., Getachew F., Girma F., Desta G.

Land degradation is one of the contemporary environmental challenges affecting regions inhabited by over one-third of the global population. In response to land degradation, restoration of degraded landscapes through area closure has been implemented through government and bilateral organizations for the last three decades in Ethiopia. Objectives of this study were to: i) explore the effects of landscape restoration on vegetation cover; ii) identify the perceived benefits to local communities; and 3) synthesize the lessons learnt on communities' willingness to sustain the restored landscapes. The study was conducted in project-supported restoration areas including the Dimitu and Kelisa watersheds representing the central rift valley dry lands and the Gola Gagura watershed representing the eastern dry land areas around Dire Dawa. The temporal changes in land use and land cover due to area closure integrated with physical and biological soil and water conservation measures were detected using GIS/Remote sensing techniques. Moreover, eighty-eight rural households were interviewed. The results of the study revealed that landscape restoration activities such as area closure integrated with physical soil and water conservation, and planting of trees and shrubs contributed to the significant changes in land covers of the watersheds in 3-5 years. Hence, barren lands were reduced by 35-100% while there were significant increases in forest lands (15%), woody grasslands (247-785%), and bushlands (78-140%). More than 90% of the respondents in the Dimitu and Gola Gagura watersheds verified that the landscape restoration activities improved vegetation cover and ecosystem services, reduced erosion, and increased incomes. A great majority of farm households (63-100%) expressed their willingness to contribute to different forms of landscape restoration interventions. Encroachment of livestock to closed area, shortage of finance, and the growing number of wild animals in closed area were the perceived challenges. Proper planning and implementation of integrated interventions, creating local watershed user associations, ensuring appropriate benefit-sharing and implementing innovative pathways to reconcile the tradeoffs could be considered to scale up interventions and address potential conflicts of interest.

Oduor O.N., Mucheru-Muna M., Mugwe N.J., Sijali I., Nyabuga G., Mugendi N.D.

Soil moisture scarcity and soil fertility decline in the drylands contribute to declining crop productivity. The possible synergistic effects of integrating soil & water conservation, and soil fertility management practices on soil moisture, and hence water use efficiency (WUE) in the drylands of Tharaka-Nithi County in Kenya was assessed. The experiment was laid in a three by three split plot arrangement, with four replications, for four cropping seasons. Minimum tillage with mulch, tied ridges, and conventional tillage formed the main plot factors. The sub-plot factors included animal manure plus fertilizer at 120, 60, and 30 N kg ha-1. There was significant improvement in soil moisture by 35 and 28% by minimum tillage with mulch and tied ridges, respectively, compared to conventional tillage. Manure plus fertilizer rates of 120 and 60 N kg ha-1 had significantly lower soil moisture by 12 and 10%, respectively than the 30 N kg ha-1 across the seasons. The WUE was significantly enhanced by 150 and 65% under minimum tillage with mulch and tied ridges, respectively, compared to conventional tillage. Compared with 30 N kg ha-1, the 120 N kg ha-1 and 60 kg ha-1 significantly enhanced the WUE by 66 and 25%, respectively. Across the seasons, the best treatment combination for improving WUE was minimum tillage with mulch at 120 N kg ha-1 rate of manure plus fertilizer.

Fazel-Rastgar F., Sivakumar V., Rostami M., Fallah B.

Abstract This study investigates the impact of combined drought and extreme heatwave events on air quality in South Africa during October 2022 (study period). An analysis of meteorological data revealed a sharp increase in surface air temperature and a significant decrease in precipitation, resulting in an extreme heatwave and drought period. The Standardized Precipitation Evaporation Index (SPEI) for October 2022 showed an extreme drought value of -2.01, reflecting increased dryness over the past two decades. Meteorological analysis highlighted the influence of the intensified stationary Angola heat low and Botswana upper ridge subtropical high, facilitating dry and warm air advection into the region, exacerbating an extreme climatic situation with heatwave conditions. Ozone levels exceeded 80 ppb (unhealthy) in northern, central, and eastern regions, particularly on October 13, with concentrations ranging between 88.2 and 93 ppb. Long-term data (1980–2022) showed rising trends in PM2.5 and black carbon concentrations, peaking at 1.48 × 10⁻⁸ kg/m³ and 8 × 10⁻¹⁰ kg/m³ in October 2022, with the highest values in Free State Province. Additionally, the UV Aerosol Index (UVAI) showed significant growth over the last decade, with high values in October 2022, signaling worsening air quality and environmental health concerns. The findings emphasize the important need for mitigation measures to address the compounding effects of extreme weather on air quality and public health.

Gevorgyan G., Khachatryan G., Varagyan A., Varagyan V., Vaseashta A.

Water quality is a fundamental parameter for assessing the suitability of surface waters. Likewise, the hydrochemical behavior is critically important to understand for rivers used in irrigation. This study aims to evaluate and characterize the surface water quality of the Voghji River catchment basin for irrigation, as it reveals the hydrochemical origins in the catchment basin. Nine key parameters, including EC, Cl−, SO42−, Ca2+, Mg2+, Na+, K+, CO32−, and HCO3−, were measured at seven sampling points in July and September 2017. The ion concentration patterns in July followed the sequence: Ca2+ > Na+ > K+ > Mg2+ and HCO3− > SO42− > Cl− > CO32−, while in September, they were Ca2+ > Na+ > Mg2+ > K+ and HCO3− > SO42− > Cl− > CO32−. The sequences were almost similar between the two months, with minor differences in cation distribution, particularly between Mg2+ and K+. Overall, Ca2+ and HCO3− were the dominant ions in the studied surface water samples. The concentrations of K+, Na+, Mg2+, Ca2+, Cl−, SO42−, and HCO3− were found to be well below the FAO irrigation water standards, indicating that the waters of the Voghji River and its tributaries (Achanan, Vachagan, and Geghi) were generally safe for irrigation. However, the FAO threshold value was exceeded only for CO32− in the Vachagan River in Kapan Town. The chemical analysis of surface waters in the Voghji River catchment basin revealed dominant Ca2+-HCO3− and mixed Ca2+-K+-SO42−-Cl− facies, with key geochemical processes including carbonate and gypsum dissolution, silicate weathering, and cation exchange. Ionic correlations indicated that Na+ and Cl− sources were influenced by both natural (e.g., halite dissolution, weathering) and anthropogenic inputs, while Ca2+ and Mg2+ primarily originated from carbonate dissolution. The Gibbs diagram suggested that rock–water interactions were the primary natural mechanism controlling the water chemistry, with evaporation also playing a significant role. Various indices, including the Kelly index, magnesium adsorption ratio, sodium percentage, sodium adsorption ratio, permeability index, potential salinity, residual sodium carbonate, soluble sodium percentage, and irrigation water quality index, were applied, along with US Salinity Laboratory diagram and Wilcox diagram, to further assess the irrigation suitability. Most indices confirmed the suitability of the waters for irrigation; however, the Achanan River near the mouth and the Voghji River downstream of Kapan Town exhibited moderate salinity levels, underscoring the need for water management to prevent potential soil degradation.

Hirko D.B., Du Plessis J.A., Bosman A.

Abstract This paper examines how machine learning (ML) techniques can enhance the Water Evaluation and Planning (WEAP) model for surface water distribution strategies in the context of climate variability. Recent advancements in ML, General Circulation Models (GCMs), satellite data, and climate projections offer new opportunities for improved water resource management. However, methodological challenges remain in integrating these techniques across scientific disciplines and translating theoretical research into practical applications. The paper evaluates the effectiveness of the WEAP model in scenario planning while identifying uncertainties arising from dynamic socio-economic changes and climate variability. It demonstrates how ML enhances WEAP’s capabilities by improving forecasting accuracy, recognising hydrological patterns, and reducing measurement uncertainties. Furthermore, scenario-based modelling, powered by ML, offers sustainable water management solutions tailored to water-stressed regions facing increasing environmental and demand pressures. By synthesising insights from diverse research, this paper offers actionable recommendations for researchers, policymakers, and practitioners seeking to develop resilient water distribution systems in vulnerable regions.

Nassary E.K.