6.1 Introduction

Water is a critical resource to food and energy supply. Demand for water, food, and energy is increasing due to population growth and economic development. The inter-linkage among these three resources is critical to support food and energy security and sustainable development. Understanding and managing these often-competing interests requires an integrated approach to achieve sustainable agriculture and energy production and ensure food and water security. Stakeholders in all three domains are thus focusing on water resources management due to the dependence of energy and food sectors on water. Agriculture is remaining the biggest water consumer, and its water consumption is highly affected by climate, crop patterns, diet, and technologies. Fossil fuel is still a main part of the global energy mix. Its extraction and production process such as fracking and biofuel are highly water intensive. Therefore, water linking to food and energy as well as their nexus relationship are critical to achieve long-term regional sustainability.

6.2 Water Linking to Food

6.2.1 Cropping System

The water resources of the Lancang-Mekong River Basin support the social and economic development of the countries in the basin, provide the suitable planting environment for crops, especially rice, and guarantee nutrition and development of the people. The river connects China with five Southeast Asian countries, Myanmar, Laos, Thailand, Cambodia and Vietnam and covers the entire area of Cambodia and Laos, 30% of Thailand and 20% of Vietnam. The water resources of the basin are vital to the rice cultivation in these four countries, which are also the main source of rice supply in more than 100 countries around the world.

The total agricultural area of Cambodia, Laos, Thailand and Vietnam is estimated to be 41.2 million hectares, of which 16.7 million hectares are allocated to rice fields, accounting for 41% of the total agricultural area. Thailand has the largest agricultural area, estimated at 22.1 million hectares, followed by Vietnam at 10.9 million hectares, Cambodia at 5.8 million hectares and Laos’s 2.4 million hectares. Rice is the main planting system of the basin as the area allocated by each country accounts for 38–42% of the total agricultural area (Cosslett & Cosslett, 2017).

Rice cultivation in the basin has two periods, namely the wet season (May to October) and the dry season (November to April). Furthermore, rice is divided into three types: “lowland rain-fed rice” grown in lowland areas during the wet season; “upland rice” grown in upland areas during the wet season and about 1–2 months earlier than lowland rain-fed rice; and irrigated rice planted in the dry season (Mainuddin & Kirby, 2009). Compared with traditional rain-fed rice (which require 5–6 months of growth time and usually have lower yields), irrigated rice requires an average of 3–4 months of growth time, and thus more than one season can be planted each year and the production is higher. Farmers in Vietnam plant three- seasons of rice each year, while farmers in Thailand, Laos and Cambodia plant two seasons each year.

The basin also has a variety of upland crops, see Table 6.1. Maize (28% of the total area of upland crops), cassava (26%) and sugarcane (22%) are the three main crops, almost all grown under rain-fed conditions in Laos, Thailand and Cambodia. Crops growing areas in Cambodia can be divided into three categories: upland, lowland and flood plain. The main crops on the upland include: upland rice, cassava, corn and soybeans. In the lowlands, rice is the main crop, with some orchards and vegetables. In flood areas, two types of rice are planted, namely flood rice and recession rice. Rice in Laos is mainly produced through rain-fed, and supplementary irrigation is also available in some areas. Other crops include corn (such as sweet corn and animal feed), cassava, sugar cane, rubber and peanuts. Thailand’s rice production can be self-sufficient and is a major exporter of several crops including rice, corn and cassava. Other crops include peanuts, vegetables, rubber and sugarcane. Vietnam is dominated by rice cultivation. Other crops include soybeans, corn, sesame and sweet potatoes. Irrigation in the Vietnam Delta is used to grow rice, upland crops and fruit trees. In the rainy season, the area of irrigated rice is estimated to be 141,684 ha, while in the dry season it is 76,184 ha (Mainuddin & Kirby, 2009; MRC, 2014).

Table 6.1 Main crop types in LMRB countries (adopted from Mainuddin & Kirby, 2009)
Full size table

However, farmers are currently abandoning rice cultivation and are starting to plant other crops such as corn, beans and fruits, which bring more income than rice cultivation. Therefore, the crop production department supports the shift from low-yield rice cultivation to more profitable crops. In 2019, the Mekong Delta provinces planned to convert 124,526 hm2 of rice fields to other crop fields (Wang, 2018).

6.2.2 Irrigation

Agriculture is the biggest water consumption sector in the basin, expansion of irrigated cropland and agricultural intensification has significantly increased the irrigation water demand (Merme et al., 2014). This is especially due to the rice cultivation expansion in the primary rice production bases of the basin. Rapidly increasing irrigation water demand has caused heavy groundwater exploitation, a decrease of river flow and a local water crisis during the dry seasons (Macdonald et al., 2015; Thilakarathne & Sridhar, 2017). In addition, changes in precipitation patterns in the Mekong river basin may also increase supplementary irrigation even during the wet seasons (Yamauchi, 2013). Continuous groundwater overexploitation has led to rapid groundwater depletion and sea water intrusion as sea level rise in the Mekong delta, and potentially threatens crop production and food security under future climate change (Driel & Nauta, 2013; Rahman, 2014).

Nevertheless, it becomes increasingly difficult to maintain the current rice production level due to the intensive irrigation requirement. To solve this problem and achieve sustainable agriculture under projected climate change, water-saving technologies have been introduced to the local agro-ecosystem and guarantee food security in the Mekong river basin countries. Considering the decreasing surface water availability under projected climate, the Alternative Wetting and Drying (AWD) has been proposed and widely accepted as a water-saving technology for the sustainable water use for rice production (Ekkehard & Fiege, 2010; Quynh & Sander, 2015), especially in the major rice production regions of Vietnamese Mekong delta where more than 50% of total rice production and 95% of rice exported from Vietnam are produced (Lovell, 2019). However, AWD requires much higher field water management skills for the local farmers and is difficult to rapidly adopt in the basin (Mushtaq et al., 2006; Yamaguchi et al., 2017). Other agricultural adaptations include shifting the crop calendar, breeding drought-resistant crop cultivars and de-intensification of current multiple cropping systems, such as shifting from triple rice cropping to double rice cropping.

In addition to the agricultural adaptations for water saving and maintaining food production, transboundary water collaboration is also critical to the water management in the basin (Yuan et al., 2019). For example, dams and water diversion for agricultural irrigation in the upstream of the basin (i.e. Thailand) may cause severe water shortage and threaten crop production in the downstream delta, which experienced severe drought in 2016. Meanwhile, increasing population and rapid socioeconomic growth in the basin generate higher water demand and irrigation will also increase under the projected warmer climate. Transboundary collaboration to optimize the water distribution and lower the negative impact of potential drought risk in the Mekong river basin is crucial to water sustainability (Li et al., 2019; Yamauchi, 2013). Therefore, the Mekong River Commission (MRC) and the “Lancang-Mekong Cooperation Mechanism” were established for the water resource cooperation of dams and water diverting facilities in this region. However, this would also significantly impact the local ecosystem and fisheries industry along the river (Yoshida et al., 2020). Tradeoffs between agricultural production and ecosystem conservation should be carefully estimated (Chen et al., 2020).

6.2.3 Water Use in Livestock and Fisheries Sectors

In the basin, farm animals are raised in a conventional extensive way with low inputs. There is a significant discrepancy from lowland areas of the Mekong river to the upland and sloping areas (FAO, 2020). For example, cattle and buffalo are mainly raised in the central areas. While raising pigs and chickens important and common in highland areas. Large-scale farms of pigs and chickens are rare at the village level, and thus would not provide considerable employment opportunities in livestock productions. Meat demands are met mainly due to an ascended production scale instead of the production efficiency increase in the basin. For example, to increase production scale, Cambodians even raise livestock in rice-farming systems (ADB, 2012).

It is of importance to study water resources linking to fisheries in terms of their water availability (Irannezhad et al., 2020) and variety in the basin, in particular aquatic animals (Garrison et al., 2007) such as fish and shrimp. This has attracted attention because the Mekong river basin is the home to the largest inland-fisheries industry worldwide (Fig. 6.1). Specifically, statistical data show there are approximately 1,200 fish species inhabited within the Mekong river basin (second to the much larger Amazon river basin (Schmitt et al., 2019). Wild fish production reaches as high as approximately 2 million tons per year; meanwhile, raised fish production exceeds 2.5 million tons annually. These fish productions are mainly distributed in Laos and Cambodia (WBG, 2018), and support more than 70 million livelihoods in mainland southeast Asia. For example, in the Mekong river basin 96% of the population and 77% of poverty households typically worked in agricultural, forestry and fisheries industries.

Fig. 6.1
A stacked bar graph of fish production versus countries. Vietnam has the highest total production 2016 and 2017, inland water area 2016 and 2017, and maritime area 2016 and 2016. Cambodia has the lowest total production 2016 and 2017, and maritime area 2016 and 2016.

Fish production in the main countries of LMRB during 2016–2017 (FAO, 2020)

Full size image

Therefore, it is critical to investigate the water consumption and variety of the fisheries and livestock industry for sustainable water management. As the Mekong river basin is home to the largest fisheries inland-industry worldwide, its huge water consumption and the competence among fisheries, irrigated agriculture, livestock and hydropower generation for water resources become one of the biggest challenges for sustainable development in this basin. Moreover, water consumption and variety are subject to uncertainty under rapid socio-economic development, trade interaction and sustainability among developing countries within the “Belt and Road initiative”.

Three aspects are stressed and recommended in previous studies: (1) There is a dearth of data in these regions. Water withdrawal and consumption accounting methods and datasets should be localized and suitable to adapt unique local conditions for the LMRB (Zhang et al., 2020). Uncertainty analysis such as inter-comparisons of different data and models should be developed and conducted to improve the reliability of the results and conclusions (Chen et al., 2021). (2) Fisheries and livestock water consumption should be considered for strategic planning at the river basin scale (Ziv et al., 2012). (3) Integrated Water Resources Management and international cooperation were suggested to be conducted and developed, such as the cooperation between Finland and Russia in the Vuoksi river basin (Jormola et al., 2016).

6.3 Water Linking to Energy

6.3.1 Hydropower Development

Hydropower is a renewable and eco-friendly source of energy that makes significant contributions to meet the increasing global power demands. It accounts for 73% of the world’s renewable power supply and has been widely recognized as a crucial component in the fight against climate change (Almeida et al., 2019; Latrubesse et al., 2017; Owusu & Asumadu-Sarkodie, 2016; Zarfl et al., 2019). However, the rapid construction of hydropower-driven dams worldwide has led to disputes over their negative environmental impact (Maavara et al., 2020; Sunday, 2020; Waldman et al., 2019).

The Lancang-Mekong River, which originates in the Qinghai-Tibet Plateau and flows through Myanmar, Vietnam, Laos, Cambodia, and Thailand (Fig. 6.2), is divided into two sub-sections: the mountainous Lancang River basin in China with a low population density and the flat and fertile Mekong River basin with a high population density. The Mekong River basin contributes to about 82% of the river’s annual discharge (MRC, 2010). The Lancang-Mekong River Basin is an ideal location for developing and utilizing hydropower resources due to its strong topographic gradient, rugged terrain, and high flow volumes. Although the Mekong River basin is mainly covered by lowlands and floodplains, it still has considerable hydropower potential estimated at 60,000 MW (MRC, 2011). Pokhrel et al. (2018) estimated that the hydropower potential of the mainstem Lancang-Mekong River is ~53,000 MW with another ~35,000 MW from tributaries. However, only nearly 40% of the hydropower potential has been exploited so far with an installed capacity of around 24,000 MW (WLE-Mekong, 2018). Due to rapid socio-economic development and ascending power demands, the Mekong River basin is undertaking an unparalleled rate of dam construction (Pokhrel et al., 2018).

Fig. 6.2
A map of Cambodia locates existing dams 0 to 100 megawatts, 100 to 1000 megawatts, and greater than 1000 megawatts, river, Lancang Mekong River basin, commissioned, under construction, planned, and canceled, and elevation from negative 1 to 6096 meters.

The location of existing dams in the LMRB. The dam data is from Water, Land and Ecosystems (WLE-Mekong, 2018)

Full size image

According to Pokhrel et al. (2018), the Lancang-Mekong river system is home to several large dam projects, some of which have been completed while others are under construction or planned (Fig. 6.3). The dams under commission are mostly located at the tributaries of the Mekong River. Among those planned are 15 dams in the main stem of the Lancang-Mekong river and several other hydropower dams are being planned in the tributaries of the Mekong River basin, including many in the Seong, Sesan, and Sre Pok basins. These basins constitute the largest sub-watershed of the Mekong and contribute ~17% of the Mekong’s annual discharge with an estimated hydropower capacity of 9500 MW (Xue et al., 2011).

Fig. 6.3
A flow chart exhibits distribution of dams in China, Myanmar, Laos, Thailand, Cambodia, and Vietnam. Above is a table of 93 dams, greater than 11,747, 10 raise to 9 cubic meter total storage, and installed capacity of 60,687 megawatts.

The quantity and distribution of existing dams in the Lancang-Mekong River basin (WLE-Mekong, 2018)

Full size image

The availability of water resources and hydropower generation are likely to be affected by global warming (Arnell & Gosling, 2013; Hoang et al., 2019), which is projected to cause higher climate variability and more extreme weather conditions. This could have implications for the water-energy-food nexus (van Vliet et al., 2016; Zhang et al., 2017) and alter the positive synergy relationship between hydropower generation and irrigation supply (Zeng et al., 2017). Storage for hydroelectricity generation can improve water supply for irrigation. Dams can be operated to build up a high hydraulic head and then release the water to produce hydropower. At the same time, hydropower dams can provide reliable water resources for irrigation supply during the dry season (Zewdie et al., 2019).

Meng et al. (2021) conducted an integrative analysis to assess the impact of global warming scenarios of 1.5 and 2 °C on the co-benefits between hydropower and irrigation in the Mekong River basin. The study employed a hydrological, techno-economic, and agricultural modeling framework to evaluate the effects of these scenarios. The results showed that the gross hydropower potential in the Mekong River basin is 3,069, 2,936, 2,677 and 2,791 MW under each of the historical period, the scenario of 1.5 ℃ (RCP2.6), 1.5 ℃ (RCP6.0) and 2 ℃ (RCP6.0), for the whole Mekong River basin. The gross hydropower potential is larger under the scenario of 2 ℃ (RCP6.0) than 1.5 ℃ (RCP6.0) although the gross hydropower potential under both scenarios of global warming is smaller than that in the historical period. Most areas in the Mekong River basin show decreasing trends of the hydropower potential under 1.5 and 2 °C global warming scenarios, especially in the grids around the mainstream. The highest hydropower potential during the historical period is located along the Mekong River mainstream where the hydropower potential reduces most under the global warming scenarios, see Fig. 6.4. The study shows that the Mekong River basin’s hydropower generation is expected to decrease under both scenarios. The total production provided by potential hydropower plants for the entire study area is 44.19 × 106, 2.10 × 106, 3.33 × 106 and 1.84 × 106 GWh under each of the historical period, the scenarios of 1.5 ℃ (RCP2.6), 1.5 ℃ (RCP6.0) and 2 ℃ (RCP6.0). The hydropower generation under 2 ℃ (RCP6.0) is less than both scenarios of 1.5 ℃ (RCP2.6) and 1.5 ℃ (RCP6.0). However, when considering the effects of protected areas, the total hydropower generation will be 9.69 × 105, 1.32 × 106, 9.39 × 105 and 6.85 × 105 GWh. The total production decreases by 3.05 and 29.34% under 1.5 ℃ (RCP6.0) and 2 ℃ (RCP6.0), respectively, when excluding the protected areas but increases by 36.66% under the scenario of 1.5 ℃ (RCP2.6) compared to the historical period1. Therefore, policymakers should consider balancing hydropower generation with forest coverage area in nationally determined contributions.

Fig. 6.4
Four maps of Mekong River mainstream at, a, historical period, 1971 to 2010, b, 1.5 degree Celsius, R C P 2.6, c, 1.5 degree Celsius, R C P 6.0, and, d, 2 degree Celsius, R C P 6.0. Hydropower potential and change in hydropower potential values are plotted.

Hydropower potential (GW) during the historical period, and the differences between the historical period and the 1.5 and 2 ℃ global warming scenarios

Full size image

6.3.2 Other Energy Sectors

Water consumption for energy purposes includes thermal plant cooling, extraction of fuels (e.g. oil, gas, and coal), and biofuel crops irrigation. The energy demand in the Mekong river basin increased with rate of 5–6% per year between 1990 and 2010, and this trend was projected to continue in the near future (ADB, 2012). Annual growth rate of electricity demand from 2010 to 2018 was 5%, which is twice the world average. Coal-fired power generation is favored by most countries in the Mekong due to the relatively low costs. Even with rising concerns over emission and pollution, power generated by fossil fuel including coal and gas still represents more than 50% of the total generation (IEA, 2019). Taking the Mekong Delta in Vietnam as an example, there will be 14 new coal-fired power plants in 2030 with a water demand of 79.44 million m3/day, which is about 15 times of the water demand in 2016 (Tuan, 2018) (Fig. 6.5).

Fig. 6.5
2 graphs. a, a multi-line graph of coal, oil, natural gas, nuclear, hydro, and N R E plotted in M t o e versus years. N R E has the highest and coal the lowest. b, a compound histogram of electricity generation sources plotted on percentage of fossil fuel based and low carbon.

Energy demand (a, adopted from ADB, 2013) and electricity generation by sources (b, adopted from International Energy Agency, 2019)

Full size image

Heat is converted into electricity in the thermal power plant, most of which use steam as the main heat. However, not all the heat is converted, and the “waste heat” requires water to be cooled down and goes back to the system again. Therefore, the amount of cooling water is highly dependent on the cooling methods. There are three typical cooling systems: once-through/open-loop systems, wet-recirculating/closed-loop systems, and dry cooling systems. The once-through method usually withdraws a large amount of water to pass through the heat exchanger, and returns most of the water to the source. The returned warm water is usually concerned with the thermal pollution of the water body. The closed-loop method adopts cooling towers or cooling ponds to cool down the water by transferring the heat to the air. Some amount of water is thus lost due to evaporation, and the rest is reused in the steam condenser. The drying cooling method uses air instead of water to cool the steam and thus consumes the minimum amount of water and has the lowest environmental impact. Tradeoffs among different types of cooling systems are shown in Table 6.2. There is still a lack of a comprehensive assessment of the cooling water use in the Lower Mekong river basin countries due to limited data of power plant cooling methods in these countries.

Table 6.2 Cooling system tradeoffs (adopted from Rodriguez et al., 2013)
Full size table

Mineral resources in the Mekong river basin include gold, copper, lead, zinc, phosphate, potash, oil and gas, coal and gemstones, which remain largely unexploited (MRC, 2021). Oil, gas, and coal are the three main resources for energy production. Fossil fuels are projected to be the dominant energy due to the increasing demand in the lower Mekong countries. There will be an increase in the use of coal, especially Thailand and Vietnam, according to the International Energy Agency (IEA, 2019). In the lower Mekong Basin, the largest thermal generation source is the Mae Moh coal mine in Thailand. Thermal generation sources of Vietnam are mainly located in the northern part. Laos’ coal resources are relatively abundant with for example the Hongsa coal mine in Sainyabuli Province (ADB, 2008). As for the oil and gas, Cambodia and Laos have no significant production, while Myanmar could be a primary gas producer with a reserve of 10 trillion cubic feet in 2012. Thailand is a producer of oil and gas with a proved reserve of 0.3 thousand million barrels and 0.2 trillion cubic meters in 2018, respectively. Vietnam has emerged as an important oil and natural gas producer in the Mekong River basin with a proved reserve of 4.4 thousand million barrels and 0.6 trillion cubic meters in 2018, respectively (BP, 2019). Water withdrawal for fuel extraction is not as intensive as the total industrial water withdrawal and only represents 4% of the basin withdrawal (FAO, 2012). However, detailed water withdrawal data is not available in the Mekong River Basin.

Bioenergy is the mainstay of Southeast Asia’s renewable energy source (IEA, 2019). Traditional biomass products are the main sources of energy and access to electricity in Laos, Cambodia, and Myanmar due to the less-developed infrastructures than Thailand and Vietnam (Soutullo, 2019). Biofuel production increased sharply in the Lower Mekong countries especially in Vietnam and Thailand with an annual increase rate of 30% in Thailand during 2008–2018 (BP, 2019). The planting area of biofuel crops such as cassava and sugarcane thus expanded significantly (FAO, 2021), see Fig. 6.6.

Fig. 6.6
Five area graphs of biofuel and rice plotted in area versus year for Cambodia, Laos, Myanmar, Thailand, and Vietnam.

Biofuel crops and rice area in the Lower Mekong River Basin countries (based on data from FAO, 2021)

Full size image

Biofuels consume water mainly through crop irrigation. Take Vietnam as an example, water cultivation for cassava was about 9801 m3/ha/year. In 2015, the total amount of water for cassava cultivation was about 5.55 km3, while water used for processing and ethanol production, 0.086 km3, was relatively small (FAO, 2018). Blue, green, and grey water footprint of sugarcane and cassava in northern Thailand (Kongboon & Sampattagul, 2012) are shown below (Fig. 6.7).

Fig. 6.7
Two compound histograms of green, blue, and gray water footprints. a, Chiang Rai has the highest green, and Lampang has the highest blue and gray water footprints. b, Lampang has the highest green, and all locations have almost equal blue and gray water footprints.

Water footprint of sugarcane (a) and cassava (b) in northern Thailand (adopted from Kongboon & Sampattagul, 2012)

Full size image

6.4 Water-Food-Energy Nexus

6.4.1 The Importance of the Nexus

The United Nations 2030 Sustainable Development Goals prioritize water, food, and energy resources (Liu et al., 2018). However, climate change, population growth, and economic development are putting increasing pressure on achieving food, energy, and water security. By 2050, food demand is expected to increase by 50% due to population growth, urbanization, and personal income increases (FAO, 2017). Similarly, energy demand is projected to increase by a factor of 1.7–2.8 above current usage due to socio-economic developments (Van Vuuren et al., 2019). Climate change exacerbates the situation by making water a growing constraint for food production and energy generation. As a result of climate change, an additional 120 million people are projected to be at risk of undernourishment (FAO, 2017) (Fig. 6.8).

Fig. 6.8
A cyclic chart represents available water resources as water supply security, food security, and energy security. Nexus perspective is beside energy security.

Food, water, and energy nexus (adopted from Hoff, 2011)

Full size image

The Bonn 2011 Conference introduced the nexus approach, which is recognized as an effective way to achieve sustainable management of food, energy, and water resources by integrating management and governance across sectors and scales (Hoff, 2011). Significant progress has been made in understanding the interaction among food, energy, and water systems, which has laid a solid foundation for theoretical research and practical processes of sustainable development (Liu et al., 2020). A case study in the Mekong River Basin highlights the importance of the nexus approach in managing water, food, and energy resources for sustainable development.

6.4.2 Regional Case Study

Mekong River Delta

The Mekong River Delta (MRD) is situated downstream of the Mekong River Basin (Fig. 6.9) in Vietnam, covering an area of 40,500 km2 and home to 17.8 million people in 2018 (WUR, 2020). The delta experiences two seasons: the dry season (November to April) and the wet season (May to October). The average annual rainfall ranges from 1400–2200 mm, and the average monthly flow varies from 6.1 to 69.2 km3 (Tuu et al., 2019). As the primary source of rice production in Vietnam, the delta plays a crucial role in the nation’s food security, accounting for over 56% of rice production in 2015. It is also a significant contributor to food trade in Southeast Asia and globally (WUR, 2020). The Mekong river delta is not solely dependent on hydropower as an energy source. Due to the nation’s high growth power demand, which increased more than 10% per year during 1990–2010, the delta is planned as a thermal power center with 14 new coal-fired plants by 2030 (KEP, 2015; Yoshida et al., 2020).

Fig. 6.9
A map of Mekong River Basin on the left. To the right is the zoomed in map of the Mekong River Delta with marked elevation from negative 0.5 to 8 meters.

The Mekong River Delta

Full size image

The delta is currently facing several challenges due to climate change and socio-economic development. Over the past 30 years, the annual rainfall has increased by 30%, and the average temperature has risen by 0.5 °C. Climate change is expected to cause further temperature increases ranging from 1.1 to 3.6 °C, with projected increases in maximum and decreases in minimum monthly flow (WUR, 2020). Additionally, the planned thermal plants are expected to have adverse environmental impacts and intensify water conflicts among various water-use sectors. Therefore, it is crucial to have a comprehensive understanding of the impacts of climate change and socio-economic development through the Food-Energy-Water nexus to achieve regional resource security and long-term sustainability.

An IWRM-Based Model

An integrated management model (Wang et al., 2019) was used to assess the effects of climate change and socio-economic development on the Food-Energy-Water Nexus. The model, which was developed using system dynamics methodology, captures the interactions among various subsystems at an annual scale. It was designed for Integrated Water Resources Management (IWRM) and includes the main water use sectors: agricultural, municipal, industrial, environmental, and recreational water uses, as well as water supply. These sectors are linked through water allocations and various land, water, and technical management policies. The model simulates water balance by considering water demands, allocation, and consumption, and generates socio-economic and environmental indicators for sustainability assessment at the basin scale.

This study aimed to quantify the changes in the Food-Energy-Water Nexus under different climate change and socio-economic scenarios by analyzing the agricultural, industrial, water use, and supply sectors. Rice cultivation accounts for 80% of surface irrigation withdrawal and is a major driving factor of water competition in the Mekong river delta. Coal-fired power is expected to be the primary energy source, occupying over 50% of power capacity. Therefore, the agricultural and industrial sectors simulate rice yield and thermal power generation, and water withdrawal is used for irrigation and cooling purposes. The water sector connects food and energy sectors through water allocation based on available water each year, and competition between food and energy sectors occurs when their demands cannot be fully satisfied. Various RCP-SSP scenarios (RCP: Representative Concentration Pathway, SSP: Shared Socioeconomic Pathway) are used to drive changes in rice planting area, thermal power demand, available water for allocation, and climate variables such as precipitation. These changes further affect irrigation and cooling water requirements, rice yield, and power generation (Fig. 6.10).

Fig. 6.10
A structural model presents the components of food, water, and energy interconnected to each other with R C P, S S P scenarios in the middle connected to rice area, annual demand change rate, precipitation, and basin available water.

The modified basic structure of the IWRM model used for MRD

Full size image

Scenario Setup

This study comprehensively explored the future conditions of the Food-Energy-Water Nexus by adopting RCP-SSP scenarios from the Coupled Model Intercomparison Project Phase 6 (CMIP6). The scenarios describe socio-economic and climate futures, with SSP representing socio-economic futures and RCP representing climate futures. The integration of these two futures allows for a comprehensive exploration of the future conditions of the Food-Energy-Water Nexus.

To assess the concurrent effects of socio-economy and climate, this study employed five representative SSP-RCP combinations. These combinations are as follows:

  1. 1.

    SSP5-8.5: This combination represents future pathways with high greenhouse gas emissions and a high challenge to mitigation and adaptation.

  2. 2.

    SSP4-6.0: This combination is in the range of medium forcing pathways with a high challenge to adaptation.

  3. 3.

    SSP3-7.0: This combination represents medium–high future mitigation and forcing pathways.

  4. 4.

    SSP2-4.5: This combination is the middle ground, combining intermediate challenges for mitigation and forcing signals.

  5. 5.

    SSP1-2.6: This combination represents the case with low societal vulnerability and forcing level

Main Findings

Figure 6.11 displays the rice yield, power generation, and precipitation of five SSP-RCP scenarios from 2020 onwards. On one hand, the increased yield trends of three rice types in all scenarios were due to technical improvements based on historical data. However, maintaining the yield growth trend is a challenging task, and the Vietnam government recognizes technical improvement, especially biotechnology, as a decisive strategy to achieve long-term food security. On the other hand, yields of all three rice types were vulnerable to future climate and socio-economic changes, which will severely impact autumn rice yields with many extremely low yield events projected by all five scenarios. Finally, winter rice was projected to have many extreme yields, especially in the SSP4-6.0 scenario. The increasing number of low yield events resulting from water shortage could also trigger conflicts with energy and other water use sectors during growing seasons. Therefore, it is recommended to highlight mitigation strategies for the nexus instead of a single sector.

Fig. 6.11
5 graphs. a to c are line graphs of yield versus years, each with an arrow labeled 2016 drought. d, a line graph of power generation versus year. S S P 5, 8.5 and S S P 4, 6.0 and 2 pie charts are plotted. e, A line graph of precipitation versus years. S S P 3, 7.0, S S P 2, 4.5, and S S P 1, 2.6 are plotted.

The yield of spring (a), autumn (b), and winter (c) rice, power generation (d), and precipitation (e) in different climate and socio-economic scenarios

Full size image

SSP5-8.5 was the most resource and energy-intensive scenario, with a power demand projection that was about 10 times higher than the generation in 2010. SSP1-2.6, on the other hand, was oriented towards low energy and resource consumption, and thus had the lowest projection, which was about 2 times higher than the generation in 2010. The other three scenarios fell between SSP1-2.6 and SSP5-8.5 in terms of power generation. The Electricity and Renewable Energy Authority in Vietnam estimated that national energy consumption would increase by about four times from 2017 to 2050, which is in the middle range of the five scenarios in this study. It is worth noting that coal-fired power plants will generate more power in the future, increasing from 15% in 2010 to 55% in 2030, as Mekong river delta will be Vietnam’s thermal power center and the coal-fired plant is favored by the national government. However, this growth of coal-fired power plant generation will inevitably increase water use for cooling purposes and intensify conflicts with irrigation use during growing seasons.

Figure 6.11e illustrates the effects of five scenarios on precipitation during growing seasons. While SSP1-2.6 predicted a downward trend, the other four scenarios projected an increase in precipitation, with several years of extreme wetness, such as the SSP4-4.6 scenario. Overall, future precipitation is expected to increase, but more extreme high and low events are also anticipated. As a result, the Mekong River Delta is expected to face an increasing risk of flooding during the wet season and water shortages during the dry season.

Figure 6.12 displays the total water withdrawal, rice irrigation, and coal-fired power plant withdrawal. On one hand, the growth of power generation and the ratio of coal-fired plants will lead to an increase in total water withdrawal (Figs. 6.11d and 6.12a). The average value of total water withdrawal in 2050 is expected to be more than three times higher than the average withdrawal during the 1995–2010 period, with a 40% increase from the 2016 drought year withdrawal. On the other hand, climate change is expected to result in increased precipitation during growing seasons, which might reduce irrigation water demand in wet years and provide more available water for expanding coal-fired plants. However, high cooling water demand in dry years could trigger conflicts between the food and energy sectors. All existing and planned plants in the Mekong River Delta assume once-through cooling method. Therefore, it is suggested to use water-saving technologies such as air cooling and non-surface water instead of the once-through method for new thermal power plants to mitigate the impacts of climate change and socio-economic development on the nexus system.

Fig. 6.12
a, A line graph of total water withdrawal versus year. S S P 5, 8.5, S S P 4, 6.0, S S P 3, 7.0, S S P 2, 4.5, and S S P 1, 2.6 are plotted. b, A cllustered stacked bar graph of water withdrawal versus year. 2050 has the highest coal fired plant withdrawal, and 2010 has the highest rice irrigation withdrawal.

Water withdrawal of the MRD (a) and rice and coal-fired plant withdrawal (b)

Full size image

Figure 6.13a illustrates the relationship between rice yield, coal-fired power generation, and water withdrawal under five climate change and socio-economic scenarios in the Mekong river delta. The trends in the three-dimensional relationship of the five scenarios reveal a strong connection among food, energy, and water systems in the Mekong river delta. Figure 6.13b shows a clear linear trend between coal-fired power generation and water withdrawal under five scenarios. This trend indicates that water is a constraint of the coal-fired power plants, and water withdrawal is also affected by the amount of power generated by coal-fired plants. The strong connection between the water and energy sector also implies possible pressure on the local water system due to power plant development, which has already received significant attention. Figure 6.13c shows that rice yield in the Mekong river delta increases with water withdrawal when it is lower than 8000 MCM (million cubic meters), indicating that rice cultivation in the region heavily relies on irrigation and is vulnerable to water availability. However, when water withdrawal exceeds 8000 MCM, yield seldom increases as energy generation accounts for most of the water withdrawal, particularly under SSP5-8.5 and SSP4-6.0 scenarios. The relationship between the food and energy sectors is relatively weak. The linear trend observed between coal-fired plant generation and water withdrawal is due to water availability, which affects both rice yield and coal-fired plant generation. Therefore, water plays a key role in the Food-Energy-Water Nexus as it connects both the food and energy sectors in the Mekong river delta.

Fig. 6.13
4 graphs. a, a 3 dimensional dot plot of water withdrawal and coal fired power generation versus rice yield. 3 line graphs of, b, coal fired power versus water withdrawal, b, rice yield versus water withdrawal, and, d, coal fired power versus rice yield.

FEW nexus (a), food-energy (b), food-water (c), and energy-water (d) relationship in the MRD

Full size image