Development Of Irrigated Agriculture Research Articles

Water-suitable reclamation can mitigate the amplified agricultural water stress driven by climate change in arid inland basin

The escalation of water scarcity poses a significant challenge to the sustainability of irrigated agriculture in arid regions, with climate change further amplifying the unpredictability of water resources for agricultural purposes. Despite the critical nature of this issue, there is a lack of research identifying effective adaptation strategies and establishing water-suitable thresholds for agricultural development. This study modified a conventional approach for estimating irrigation water use (IWU) in the Heihe agricultural area of Northwest China, integrating the distributed hydrological components of the Soil and Water Assessment Tool (SWAT) model. It modeled IWU and surface water availability across three representative concentration pathways (RCPs) and conducted an extensive analysis of agricultural water scarcity for the period 2021–2050. The study established threshold levels for water-suitable agricultural development based on predicted local water resource conditions. Findings suggested a trend towards warmer and wetter conditions in the Heihe agricultural area over the next three decades. The anticipated average IWU, predicted by five general circulation models (GCMs), was expected to reach 26.785 × 108 m3 (RCP2.6), 26.827 × 108 m3 (RCP4.5), and 26.865 × 108 m3 (RCP8.5). These projections indicated an increase of 0.815 × 108 m3, 0.857 × 108 m3, and 0.895 × 108 m3, respectively, in comparison to the historical period spanning from 1985 to 2014. Streamflow was anticipated to diminish by 0.28 × 108 m3 (RCP2.6), 0.46 × 108 m3 (RCP4.5), and 0.23 × 108 m3 (RCP8.5). The predicted agricultural water scarcity index (WSI) was 1.764 (RCP2.6), 1.789 (RCP4.5), and 1.763 (RCP8.5), indicating a worsening of agricultural water use shortages due to climate change. The study identified controlling the scale of cultivation as the most effective adaptation strategy, recommending that water-suitable agricultural reclamation in the Heihe agricultural area be confined to 25 × 104 ha. This research offers a comprehensive assessment of future water security in an arid inland basin, providing valuable insights into the sustainable development of global irrigated agriculture and adaptation strategies in response to climate change.

Timely monitoring of soil water-salt dynamics within cropland by hybrid spectral unmixing and machine learning models

Soil salinization and water scarcity are main restrictive factors for irrigated agriculture development in arid regions. Knowing dynamics of soil water and salt content is an important antecedent in remediating salinized soils and optimizing irrigation management. Previous studies mostly used remote sensing technologies to individually monitor water or salt content dynamics in agricultural areas. Their ability to asses different levels of crop water and salt management has been less explored. Therefore, how to extract effective diagnostic features from remote sensing images derived spectral information is crucial for accurately estimating soil water and salt content. In this study, Linear spectral unmixing method (LSU) was used to obtain the contribution of soil water and salt to each band spectrum (abundance), and endmember spectra from Sentinel-2 images. Calculating spectral indices and selecting optimal spectal combination were individually based on soil water and salt endmember spectra. The estimation models were constructed using six machine learning algorithms: BP Neural Network (BPNN), Support Vector Regression (SVR), Partial Least Squares Regression (PLSR), Random Forest Regression (RFR), Gradient Boost Regression Tree (GBRT), and eXtreme Gradient Boosting tree (XGBoost). The results showed that the spectral indices calculated from endmember spectra were able to effectively characterize the response of crop spectral properties to soil water and salt, which circumvent spectral ambiguity induced by water-salt mixing. NDRE spectral index was a reliable indicator for estimating water and salt content, with determination coefficients (R2) being 0.55 and 0.57, respectively. Compared to other models, LSU-XGBoost model achieved the best performance. This model properly reflected the process of soil water-salt dynamics in farmland during crop growth period. This study provided new methods and ideas for soil water-salt estimation in dry irrigated agricultural areas, and provided decision support for governance of salinized land and optimal management of irrigation.

Dynamic and harmonious allocation of irrigation water resources under climate change: A SWAT-based multi-objective nonlinear framework

Efficient allocation of water resources in irrigation districts can alleviate regional water shortages and promote sustainable irrigated agriculture development. However, existing research on water resource allocation in irrigation districts does not address the lack of coordination within the “diversion-delivery-irrigation” chain for multiple water sources and users in a changing environment. Hence, poor water supply and demand matching, low efficiency and poor climate change responses pose challenges for efficient water resource allocation in irrigation districts. Therefore, this study couples the SWAT runoff simulation model with a multiobjective nonlinear programming model and proposes a weather-driven dynamic and optimal allocation model for multiple water sources. This model accounts for fluctuations in water supply and fine-tunes the allocation of water resources to different water sources, different channels and different crop fertility periods in the irrigation area. The model is designed to achieve synergistic improvements in water supply and demand, economic efficiency, equity in water distribution and efficiency in water use. The model was applied to the Qindeli Irrigation District in Heilongjiang Province. The results show that an increase in water supply at the head of the channel promotes a synergistic increase in economic efficiency and water supply and demand matching. This model can improve water use efficiency under water scarcity by reasonably optimizing the water use structure of the irrigation district. Compared with the traditional irrigation method, the optimized model saves 4 % of water and increases yield by 399 kg/ha, economic efficiency by 0.2 yuan per cubic meter of water, water use efficiency by 9 %, and water supply and demand matching by >80 % at all stages of fertility. The model ensures that water resources are allocated in an equitable manner at all levels.

Using Film-Mulched Drip Irrigation to Improve the Irrigation Water Productivity of Cotton in the Tarim River Basin, Central Asia

Climate change has significantly influenced water resource patterns in arid regions. Applying effective water-saving measures to improve irrigation efficiency and evaluate their future water-saving capabilities is crucial for ensuring the sustainable development of irrigation agriculture. Based on the daily meteorological data from 15 global climate models (GCMs) in the sixth phase of the Coupled Model Intercomparison Project (CMIP6), this study used the AquaCrop model to perform high-resolution (0.1° × 0.1°) grid simulations of cotton yields and irrigation requirements. The study also investigated the ability of film-mulched drip irrigation (FMDI) to improve future irrigation efficiency under two shared socio-economic pathways (SSP245 and SSP585) in the Tarim River Basin (TRB), Central Asia, from 2025 to 2100. The results showed that the cotton yield and irrigation water productivity (WPI) in the TRB exhibited an upward trend of 13.82 kg/ha/decade (80.68 kg/ha/decade) and 0.015 kg/m3/decade (0.068 kg/m3/decade), respectively, during the study period. The cotton yield and WPI were higher in the northern, northwestern plains, and northeastern intermountain basin areas, where they reach over 4000 kg/ha and 0.8 kg/m3/decade. However, the cotton yield and WPI were lower in the southwestern part of the study area. Therefore, large-scale cotton production was not recommended there. Furthermore, compared to flood irrigation, the use of FMDI can, on average, improve the WPI by approx. 25% and reduce irrigation water requirements by more than 550 m3/ha. Therefore, using FMDI can save a substantial amount of irrigation water in cotton production, which is beneficial for improving irrigation efficiency and ensuring the future stable production of cotton in the TRB. The research results provide a scientific reference for the efficient utilization and management of water resources for cotton production in the TRB and in similar arid regions elsewhere in the world.

Multi-layer multi-objective cooperative regulation of agricultural water resources in large agricultural irrigation areas based on runoff prediction

Reasonable and optimal allocation of irrigation water is of great significance to improve agricultural water use efficiency for large-area agricultural irrigation systems. To solve the problems of large agricultural production scale, unreasonable water distribution structure, many rivers in the region and large changes in runoff volume, this paper takes the Sanjiang Plain in Heilongjiang Province, China, as the research object to develop an efficient and accurate water optimal allocation method. First, the runoff volume of many rivers in the region was obtained through the ARIMA-SVM-BP combined runoff prediction model, based on which a ‘regional-irrigation district-farmland’ multilayer multiobjective water resource cooperative deployment system model was established to achieve the synergistic enhancement of farmers' interests and the economic-social and regional economic-engineering volume of the irrigation district. The joint optimization method, fuzzy mathematical planning, and large system decomposition-coordination coupling were used to solve the multilayer multiobjective regulation system. The results show that the optimal agricultural water allocation volumes for the current year (2020) and the forecast year (2025) of 37 irrigation districts in the Sanjiang Plain are 3.61 × 109 m3 and 3.89 × 109 m3, saving 17% of water and resulting in a 24% decrease in the agricultural water use ratio compared with the actual situation, respectively. In the process of repeated coordination of the large system, the water distribution error is controlled within 1%. The fairness of water distribution in the multilayer system was improved by 34.7% while obtaining high economic benefits. The method proposed in this study helps the coordinated regulation and planning of multiple water sources in large agricultural irrigation areas, improves the ability of water distribution in irrigation areas to cope with different levels of incoming water, and promotes the sustainable development of regional irrigated agriculture.

Water quality and interaction between groundwater and surface water impacted by agricultural activities in an oasis-desert region

A comprehensive understanding of groundwater dynamics and its interaction with surface water under the influence of agricultural activities is essential for local agriculture, ecology and resident in arid regions, which is poorly understood in arid oasis-desert region. In our study, with emphasis on a comparison of hydrogeochemical characteristics between the oasis (irrigated) and desert (non-irrigated) areas, the water quality and groundwater-surface water interaction of a typical oasis-desert system with a rapid irrigation agriculture development were examined to clarify the effects of agricultural activities on groundwater level and quality using stable isotopic and hydrochemical data of 83 water samples. Results showed that cultivated land area increased by 121.8 % (732.4 km2) during 2000 to 2020, mainly transferring from grassland and bare land. Groundwater EC ranged from 786 to 49,400 μS/cm, with weakly alkaline. Shallow groundwater had a much higher EC than other water components. Stable isotopic and EC values of shallow groundwater in the non-irrigation areas were much greater than those in the irrigation areas, whereas middle groundwater isotopic values were more depleted in the desert than in the oasis. Shallow groundwater EC value was lower in summer, middle groundwater had higher EC in summer. Streamflow and confined water in the study area are suitable for agricultural irrigation, but phreatic water in the oasis is generally not suitable for irrigation at present. The groundwater chemistry was mainly controlled by strong evaporation, dilution, mixing, water-rock interaction and agricultural drainage. Groundwater in the irrigation areas was recharged by ephemeral runoff seepage, irrigation return flow and subsurface lateral inflow. Long-term development of irrigation agriculture (large-scale land reclamation, irrigation and groundwater pumping) in arid region has caused groundwater level decline and salinization, with a strong interaction between phreatic water and surface water. Hence, decreasing irrigation area and groundwater exploitation, carrying out gradual ecological restoration, improving water-saving efficiency and agricultural drainage system would be the viable method to restore groundwater and maintain the oasis-desert ecosystem coexistence in arid regions in the context of climate change.

Human Virtues Revealed in Purananuru

Human race is undergoing various changes as time moves on. Literature is a tool to reflect all these changes. During Sangam period Tamil people were well civilized. Famous text of Sangam period such as Ettuthokai and Pathupaatu shows us the civilization of Tamil people. The writers of those period witnessed the culture, civilization and life styles of that time and distilled it into literature as poems. Irrigation systems, agricultural development, political law, hospitality and faith are very important in these songs. The poetic tradition carried out by Sangam literature is based on Thinai theory. The article overall examines the human virtues in Purananuru.

English

Climate change and inefficient water utilization have led to marked fluctuations of the mean rice crop production in sub-Sahara Africa. In order to improve food security and households’ income, adaptation strategies to climate change such as the adoption of new rice varieties are inevitable. This study examined the farmers’ perception and adoption of climate change friendly New Rice for Africa in Mwea West Sub-county. The study applied the descriptive survey design with questionnaires being administered to a sample of 376 farmers. Key informants included four officers from Mwea Irrigation Agricultural Development and the Ministry of Agriculture. Quantitative data were analysed using Statistical Package for Social Sciences whereas qualitative data were analysed through establishing the categories and themes, relationships/patterns, and conclusions drawn in line with the study objectives. Results indicated a highly significant difference in adoption between farmers affiliated to Mwea Irrigation Scheme and the out-growers (X2= 18.5, df =2, p= 1.67×10-6). The study concluded that the adoption of New Rice for Africa varieties in the Mwea West Sub-county is low and slow. This is mainly caused by inadequate information among the farmers as well as low market demand for the rice varieties. There is a need to enhance these rice varieties by intensifying efforts to sensitize farmers.   Key words: Climate change, new rice for Africa, adaptation strategies.

Hydroelectric production in Akosombo, and the development of irrigated agriculture upstream, a fair balance to be found to reconcile regional energy and food security. - Challenges of the Volta Basin Water Charter

The Volta River is a West African river that flows from Burkina Faso to Ghana where it empties into the Atlantic Ocean. It basin extends over six countries: Benin, Burkina Faso, Côte d’Ivoire, Ghana, Mali and Togo. These states, members of the Volta Basin Authority, have committed themselves to drawing up a Water Charter. One of the challenges of this international agreement is to agree on a reasonable level of abstraction to reconcile food and energy security for the populations, while guaranteeing the minimum needs of the ecosystems. Supported by an appropriation of the needs-resources balance through the use of Lego® bricks, their reflection was supported by a hydro-economic analysis. This analysis consisted in comparing the added value associated with an agricultural abstraction - which leads to a definitive consumption of water upstream of the basin, for example in Bagré in Burkina Faso - and the one associated with the same quantity of water if it had been allowed to flow and turbined in one of the hydroelectric facilities located further downstream, for example in the large Akosombo dam in Ghana. The results show that the agricultural valorisation of a continuous abstraction of one m3/s, i.e. 30 Mm3 per year, allows to irrigate 1,500 ha and generates an added value of 1,300 M FCFA per year, i.e. 44 FCFA/m3. This volume of 30 Mm3, taken upstream of the dam would induce a loss of hydroelectric production of 6 GWh/year, worth 297 M FCFA, i.e. 10 FCFA/m3. The economic value of each m3 withdrawn to develop irrigated agriculture upstream of the basin is thus higher than that of each m3 turbined in the Akosombo-Kpong complex. Within the limit of an acceptable reduction of hydropower production, the economic development of the basin as a whole would thus benefit from the development of irrigated agriculture.

Study on agricultural cultivation development layout based on the matching characteristic of water and land resources in North China Plain

The North China Plain is the main producing area of winter wheat in China. Due to the relatively poor condition of water resources, the competition of water between industry and agriculture is fierce. The increasing shortage of water resources has led to serious overexploitation of groundwater in some areas. Agricultural development is faced with severe challenges. In order to ensure regional food security and sustainable winter wheat planting, 52 cities of North China Plain (NCP), in the following of the paper, use the shorted name NCP，were taken as research units to analyze the matching characteristics of agricultural water and land resources, so as to reveal the direction of irrigated agriculture development and winter wheat suitable planting layout considering their balance in future. The paper firstly analyzed the cultivated area determined by water resource and irrigation development by agricultural available water, and then pointed out the direction of water-suited planting layout of winter wheat. The results showed that: 1) the Gini coefficient showed an increasing trend, which indicated that the area of cultivated land and irrigation area supported by water resources have nearly reached the upper limit. The large-scale extension of both cultivated and irrigation area is impossible under the restriction of water. 2) The amount of agricultural available water resources per unit of effective irrigation area and the effective precipitation increased gradually from north to south in the NCP, but the spatial distribution of water requirement of winter wheat in its growth period changed in the opposite way. This indicated the poor spatiotemporal match between winter wheat planting and water resources, leading to the cost of spending more water to maintain wheat production. 3), The further development of irrigation and the water-suited planting of winter wheat should pay attention to the southern part of the plain with rich water (such as southern Henan Province, Jiangsu Province, Anhui Province, etc.) to ensure the regional agricultural development. That is of great significance to the regional sustainable development, water shortage alleviation and national grain safety.

Spatio-temporal dynamics and eco-hydrological controls of water and salt migration within and among different land uses in an oasis-desert system

Identifying the eco-hydrological processes associated with water-salt dynamics is important for the sustainable management of water resources and eco-environmental systems in groundwater-dependent ecosystems, especially across different land use types in salt-affected oasis-desert ecosystems. In this study, a typical cropland-shelterbelt-desert site at the oasis-desert system in the Sangong River watershed of northwestern China was selected to investigate the spatio-temporal variations of water-salt dynamics using the Spearman rank correlation analysis and water/mass balance analysis, and to identify the response of vegetation dynamics to water-salt variations based on a model framework for vegetation–salinity–groundwater interactions, within and among these land uses during crop growth period (CGP: April 1–June 28, 2018) and non-crop-growth period (Non-CGP: June 29–October 31, 2018). Results showed that the soil water content (SWC) and soil electrical conductivity (SEC) had clear vertical stratification, horizontal transition and seasonal fluctuation characteristics during both CGP and Non-CGP. Significant differences in groundwater depth and salinity were exhibited between both study periods. The water exchange flux (WEF) and salt exchange flux (SEF) in both the cropland and shelterbelt were closely related to irrigation events and evidently higher than that in desert. The cropland maintained a salt accumulation state (especially at the >60–80 cm soil layer) during CGP. Hydrological links and salt transport processes among adjacent land uses have been weakened owing to the application of water-saving irrigation in cropland and the significantly declined of regional groundwater tables. Groundwater pumping and lateral groundwater flow (LGWF) were the most important media for water-salt exchange in the site. The interactions of vegetation with both the soil water-salt balance and groundwater dynamics may cause a discontinuous and irreversible ecosystem response to changes in land use or environmental conditions. Anthropogenic processes, especially the development of modern water-saving irrigation agriculture with groundwater-fed, are dominating the vegetation-salinity-groundwater interactions and its ecohydrological consequences in this ecosystem. Adaptive management of water and salt migration in soil and groundwater is essential for maintaining the coexistence of oasis-desert ecosystems in arid areas.

Factor Affecting Irrigation Agriculture in Ethiopia

This study reviewed to identify factor affecting irrigation agriculture in Ethiopia. Although Ethiopia has abundant land for irrigation, only a fraction of its potential land is being utilized due to different factors like environmental, social and climate-related, economic and political, the land issue and rural land laws. Related with irrigation agriculture and rural land issue the government of Ethiopia has no visible document. So, as a recommendation since ,the land policy of Ethiopia was, the result of a centralized, top-down approach rather than being developed through consultations with all concerned parties and it impedes the development of irrigation agriculture in the country, it needs to be resolved quickly in order to develop irrigation agriculture based on the irrigation potential of the country.

Understanding the Role of Shallow Groundwater in Improving Field Water Productivity in Arid Areas

Soil water and salt transport in soil profiles and capillary rise from shallow groundwater are significant seasonal responses that help determine irrigation schedules and agricultural development in arid areas. In this study the Agricultural Water Productivity Model for Shallow Groundwater (AWPM-SG) was modified by adding a soil salinity simulation to precisely describe the soil water and salt cycle, calculating capillary fluxes from shallow groundwater using readily available data, and simulating the effect of soil salinity on crop growth. The model combines an analytical solution of upward flux from groundwater using the Environmental Policy Integrated Climate (EPIC) crop growth model. The modified AWPM-SG was calibrated and validated with a maize field experiment run in 2016 in which predicted soil moisture, soil salinity, groundwater depth, and leaf area index were in agreement with the observations. To investigate the response of the model, various scenarios with varying groundwater depth and groundwater salinity were run. The inhibition of groundwater salinity on crop yield was slightly less than that on crop water use, while the water consumption of maize with a groundwater depth of 1 m is 3% less than that of 2 m, and the yield of maize with groundwater depth of 1 m is only 1% less than that of 2 m, under the groundwater salinity of 2.0 g/L. At the same groundwater depth, the higher the salinity, the greater the corn water productivity, and the smaller the corn irrigation water productivity. Consequently, using modified AWPM-SG in irrigation scheduling will be beneficial to save more water in areas with shallow groundwater.

Optimizing irrigation and drainage by considering agricultural hydrological process in arid farmland with shallow groundwater

Agricultural production in arid and semi-arid area faces a global problem of water resources shortage and land salinization. Irrigation and drainage are the important measure to enhance crop yield and control soil salinity. Generally, at field scale only irrigation is optimized to pursue the higher water use efficiency and crop yield, while drainage is difficult to optimize owing to controlled by dynamic groundwater levels. Here, we develop a new collaborative optimization model of irrigation and drainage to improve irrigation water use efficiency and to control soil salinity. The model is formulated by integrating simulation of physical processes of field water - salt balance and a genetic algorithm-based optimization model. The new model is to search optimized irrigation and drainage strategic decision for enhancing field economic benefit with the condition controlling salinity with limited water resources. Then, a case study on optimally allocating irrigation and drainage water to different growth stages of maize field in the Hetao Irrigation District, arid area of northwest China shows enhanced applicability of the developed model. Five groundwater depth levels (1 m, 1.5 m, 2 m, 2.5 m and 3 m) and five groundwater salinity levels (2 g/L, 2.25 g/L, 2.5 g/L, 2.75 g/L and 3 g/L) are provided to show and compare the solutions of the optimal irrigation and drainage water allocation. Results indicate the developed model can supply reasonable field monthly irrigation and drainage decision with considering field hydrology, especially contribution of groundwater to crop water demand and groundwater role to soil salt accumulation. The contrary relationship between system benefit and irrigation water use efficiency was described successfully by the developed model. And compared with traditional single irrigation optimization model, the developed irrigation-drainage collaborative optimization model can enhance drainage function to keep the optimal groundwater levels and improve the system benefit by 0–8%. Overall, the developed model can provide more applicable irrigation water and drainage strategies to the sustainable development of irrigation agriculture.

A sustainable irrigation water management framework coupling water-salt processes simulation and uncertain optimization in an arid area

Field irrigation water management depends on interactions among crop yield, soil water/salt and groundwater/salt in arid irrigation area with shallow-saline groundwater. This paper presents a novel uncertainty simulation-optimization framework for irrigation water allocation and sustainable agricultural environment, which integrates simulation of physical processes of soil-groundwater water and salt balance into an uncertainty-based optimization model. The impacts of crop evapotranspiration, soil water and salt and groundwater levels are interactively involved in the simulation model. Uncertainties (economic and crop parameters, available water amount) presented as fuzzy boundary intervals and probability distribution functions are considered in the optimization model. This field irrigation water allocation framework emphasizes the role of field soil water and salt movement processes to decision-making of irrigation water allocation. Then, the proposed simulation-optimization framework was applied to a case study in the Hetao Irrigation District, an arid area of northwest China where soil salinity is a serious environmental problem induced by irrigation and shallow groundwater. Therefore, optimal irrigation water allocation solutions can be generated for providing decision makers with reliable decision options where the maximum system benefits resulting from sustainable agricultural production are desired. Furthermore, the results can support analysis of interrelationships among system benefits, water allocation planning and groundwater depth, soil salt content constraints. Scenario analysis (groundwater table depth (GTD) = 1, 1.5, 2, 2.5, 3 m and no groundwater exchange consideration) showed that the maximum net benefit could be [27469, 44818] Yuan with the groundwater table depth of 1.5 m. Also, the irrigation water allocation changed when the salt constraint was considered, which indicates that the results obtained by the developed framework can alleviate soil salinization to a certain degree. Therefore, this framework can provide more effective information for the irrigation water management and soil salinization control, which is meaningful for the sustainable development of irrigation agriculture.

Pastoral livelihood transition via divergent pathways: A case study in northern Xinjiang, China

This study explored the process of pastoral livelihood transition and driving factors from 1987 to 2017 in northern Xinjiang and analyzed the internal determinants of grazing and nonfarm participation in 2017. Based on the classification tree method, livelihood strategies were classified into six types. The livelihood change rate accelerated over time, and livelihoods displayed different characteristics over the three decades: pastoralist livelihood with high mobility, mixed agro-pastoral livelihood with reduced mobility, and diversified livelihood around settlements. The transition occurred principally because of the increased support of the pastoralist sedentarization policy and the development of irrigation agriculture and secondary and tertiary industries. Contemporarily, households with rich natural capital and livestock tended to adopt grazing; a lack of these assets and higher level of Mandarin proficiency enhance the propensity for nonfarm participation. Future pastoral policy should emphasize the synergistic development of agriculture and non-agriculture to facilitate livelihood diversification.

WHAT-IF: an open-source decision support tool for water infrastructure investment planning within the water–energy–food–climate nexus

Abstract. Water infrastructure investment planning must consider the interdependencies within the water–energy–food nexus. Moreover, uncertain future climate, evolving socio-economic context, and stakeholders with conflicting interests, lead to a highly complex decision problem. Therefore, there is a need for decision support tools to objectively determine the value of investments, considering the impacts on different groups of actors, and the risks linked to uncertainties. We present a new open-source hydro-economic optimization model, incorporating in a holistic framework, representations of the water, agriculture, and power systems. The model represents the joint development of nexus-related infrastructure and policies and evaluates their economic impact, as well as the risks linked to uncertainties in future climate and socio-economic development. We apply the methodology in the Zambezi River basin, a major African basin shared by eight countries, in which multiple investment opportunities exist, including new hydropower plants, new or resized reservoirs, development of irrigation agriculture, and investments into the power grid. We show that it is crucial to consider the links between the different systems when evaluating the impacts of climate change and socio-economic development, which will ultimately influence investment decisions. We find that climate change could induce economic losses of up to USD 2.3 billion per year in the current system. We show that the value of the hydropower development plan is sensitive to future fuel prices, carbon pricing policies, the capital cost of solar technologies, and climate change. Similarly, we show that the value of the irrigation development plan is sensitive to the evolution of crop yields, world market crop prices, and climate change. Finally, we evaluate the opportunity costs of restoring the natural floods in the Zambezi Delta; we find limited economic trade-offs under the current climate, but major trade-offs with irrigation and hydropower generation under the driest climate change scenario.

Impacts of water level changes in the fauna, flora and physical properties over the Balkhash Lake watershed

AbstractThe water level variations of the Lake Balkhash, the Kapshagay Reservoir and the Ili River and the linkage with salinity and biological conditions are investigated in this work using different techniques: satellite radar altimetry, in situ gauges, historical archives of fish population counting and field works. We show that it is possible now to monitor, over decades, in near real time, with high precision, the water level changes in the Lake Balkhash from satellite altimetry, over the reservoir and also along the Ili River. The vulnerability of the lake fauna and flora populations is enhanced by the morphometry of the lake: shallow and separation of the eastern basin from the western basin through the narrow Uzun‐Aral strait. Water policy of the Ili River also plays a fundamental role in the evolution of the Balkhash Lake. The Ili River that provides 80% of the surface water of the lake is a transboundary river. Development of intense irrigated agriculture in the upstream part of this river, located in the Chinese territory, could lead in the future to high hydrological stress in the downstream regions with potentially high damage in the delta and for fishery production. We show here the recent evolution of the Lake Balkhash basin from satellite data. Some interannual oscillation of 6–8 years over the last decade has been highlighted, with a water level of the lake still at a high value, but prediction on increasing irrigation is also highlighting the vulnerability of this lake. Linkage between water level change along the river and the downstream waters is also investigated. It shows that the role of the reservoir is not fundamental in the understanding of the Lake Balkhash water level changes which is in contrast highly correlated to upstream river level changes.

Do separated taxa react differently to a long-term salinity increase? The meiobenthos changes in Bay Sivash, largest hypersaline lagoon worldwide

In the world's largest hypersaline lagoon Bay Sivash, its ecosystem twice transformed from a previous state to a new one due to human intervention. Before the North Crimean Canal construction, it was hypersaline (average salinity of 140 g l−1). The canal was built between 1963 and 1975, which resulted in intensive development of irrigated agriculture discharging drainage water into the bay. Between 1988 and 2013, salinity gradually dropped to average of 18–23 g l−1; a new ecosystem with a different biotic composition formed. In April 2014, the supply of Dnieper water into the North Crimean Canal ceased. This resulted in a gradual salinity increase in the bay to an average of 52 g l−1in 2015. The start of second ecosystem shift was observed in 2015. In 2018, TSS, DOM and meiobenthos were studied in a salinity gradient from 30 to 88 g l−1. There was an increase in TSS and DOM with increasing salinity. The meiobenthos structure was significantly different in the bottom community and floating mats of filamentous green algae. No correlation was recorded between the number of meiobenthic macrotaxa in the sample and salinity. From 2013 to 2018, changes were seen in the taxocene structure of Nematoda and Harpacticoida. Changes in Nematoda were more dramatic and prolonged than in Harpacticoida. The structure of the Harpacticoida and Ostracoda taxocenes are less variable and more stable than that of the Nematoda taxocene. One of the reasons may be more mobility of Harpacticoida/Ostracoda than Nematoda and/or better osmoadaptation mechanisms.

Technology Selection for Small-scale Irrigated Agriculture Development of Malawi in International Cooperation

Technology Selection for Small-scale Irrigated Agriculture Development of Malawi in International Cooperation