Hydrogen Technologies Research Laboratory at KMG Engineering identified three types of water for Kazakhstan's clean H2 production, namely, 1) available surface water (internal and transboundary waters in eight basins, as shown in Figure 10 in Appendix), 2) flood and precipitation water, and 3) industrial and household wastewater. It currently collaborates with Reiner Lemoine Institut in developing a web Atlas of H2 for four regions in the Zhaiyk-Caspian basin: Atyrau, Aktobe, Mangystau, and West Kazakhstan regions to access water resources through remote sensing in surface water, contract territories of groundwater, and precipitation (Suleimanova, 2024). Water requirements for Kazakhstan's clean H2 production will directly compete with water used for food production, household needs, and other current economic sectors. Due to water scarcity in Kazakhstan, as reviewed in the Introduction, the study assumes that internal surface and groundwater sources and flood and precipitation water will not be used in clean H2 production. Instead, Kazakhstan may need these water resources to ensure its water, food, and economic security in the context of sustainable development. Therefore, Section 4 explicitly reviews Kazakhstan's transboundary water and internal wastewater issues related to clean H2 production. 

Water is needed as a production input and a cooling medium for all types of H2 production. Pink H2 is the most water-intensive due to its water consumption and withdrawal requirements, averaging 294 liters/kg (l/kg) of H2 and 9104 l/kg, accounting for once-through cooling, cooling ponds, and cooking towers (Mahijani & Hersbach, 2004), as shown in Figure 8 (Appendix). Green H2 is considered the most water-efficient among all clean H2 types. For example, proton exchange membrane (PEM) electrolysis has the lowest water consumption intensity at nearly 17.5 liters/kg of H2 (l/kg) compared to blue H2 with steam-methane reforming-carbon capture, utilization, and storage (SMR-CCUS) at 32.2 l/kg, and blue H2 with autothermal reforming (ATR)-CCUS at 24 l/kg (IRENA, 2023) (Figure 9, Appendix). Cooling accounts for 56% (green H2) and up to 92% (blue H2) of the total withdrawal requirement. For every 1% increase in electrolysis efficiency, the water consumption and withdrawal requirements of green H2 lessen by nearly 2%. When considering a full lifecycle analysis, the green H2 (solar energy) average water footprint is about 43 l/kg of H2 in contrast to the water print of oil extraction and refining of 133 l/kg of oil (Woods et al., 2022). Therefore, although blue H2 (SMR-CCUS) is Kazakhstan's most affordable short-mid-term clean H2 option, green H2 might be a better mid-long-term (2030s and beyond) alternative when considering broader sustainability goals and water resource conservation (IRENA, UNECE; 2023).  The following sub-section reviews transboundary water issues in Kazakhstan, which can affect the green H2-water-food-nexus.

Transboundary water issues

Uncertainty of Transboundary Water Supply 

The uncertainty of transboundary water supply and marine pollution associated with the Caspian Sea’s desalination are two main transboundary water issues related to Kazakhstan’s green H2-water-food-nexus. First, the uncertainty of transboundary water supply is connected to its geographic position and the current state of transboundary water cooperation. Regarding geographic position, Kazakhstan has seven transboundary lake and river basins and fifteen transboundary aquifers. These basins are shared with the following countries: China, the Russian Federation, Kyrgyzstan, Tajikistan, and Uzbekistan (UN Water, 2018). Governed by international law, each bordering State, while using its inland waters, can manifest its state sovereignty and the right to development while pursuing its sustainable development. At the same time, since water crosses national borders, the States have the duty to cooperate to share limited resources and solve problems (Hunter et al., 2022; Wouters, 2013a). Since nearly half of Kazakhstan’s freshwater resources are outside its borders, with inflows from the Iri, Irtysh, Ural, Chu Talas, and Syr Darya rivers, drastic changes in withdrawals in any of the upstream countries will significantly impact its water availability. Some government projections indicate that water inflows are expected to decrease from 44.64 km3/year to 31.6 km3/ year due to an increase in the water withdrawals for irrigation and hydroelectricity generation in Central Asian countries and China (Karatayev et al., 2017). Moreover, climate change is expected to impact mountain glaciers, which deliver water to major rivers, since by 2100, the glaciers could decrease by 80%. The expected temperature increase, precipitation decrease, and evaporation increase may also alter water cycle and cause regional drought conditions (Akhmetkaliyeva, 2020). The main rivers providing irrigation and drinking water will have then 20-35% less water in Central Asian downstream countries by 2050 (WEF Nexus, 2024). In sum, as a downstream country, Kazakhstan might face continuous uncertainty about its transboundary water supply. 

Regarding the current state of transboundary water cooperation, Kazakhstan might need to encourage the non-participating bordering states to join international transboundary water agreements and strengthen its position in bilateral agreements. Transboundary water cooperation is vital for sustainable development, peace, and stability. It is also critical for achieving SDG 6, “Clean water and sanitation.” Transboundary waters connect economic sectors and ecosystems in the basins and sustain population across borders. Conflicting demands over shared waters can cause regional instability and political conflicts (UN Water, 2018). Kazakhstan takes an active role in promoting cooperation over shared resources in the entire Central Asian region, where the impact of climate change and the expected rise in water use due to demographic trends and economic development is a complex background for devising long-term solutions for transboundary water cooperation (EDB, 2024; UNECE, 2010). For example, Kazakhstan is an active Party of the Water Convention (1992 Convention on the Protection and Use of Transboundary Watercourses and International Lakes). Of the five bordering countries, only the Russian Federation and Uzbekistan are other State Parties (UNECE, 2024a).  Furthermore, in January 2024, Kazakhstan joined the 1997 Convention on the Law of the Non-Navigational Uses of International Watercourses. Only Uzbekistan joined the Convention in 2007 (Kazinform, 2024). Thus, Kazakhstan needs to renew the focus on its non-participating bordering states on the duty to cooperate by encouraging them to join international transboundary water agreements. 

Kazakhstan also participates in bilateral transboundary cooperation with China and Russia. Special arrangements exist for the Amu Darya and Syr Darya River Basins and the Chu and Talas River Basins (UN Water, 2018; UNECE, 2023b). As an upstream state with nearly all of its transboundary watercourses, China is a party to several transboundary water agreements, primarily bilateral, following a one-country, one-treaty approach (Wouters et al., 2024; Wouters & Chen, 2013c; Wouters, 2013b). Kazakhstan’s most significant transboundary water inflow (43% of total inflows) comes from China; however, the existing legal framework of transboundary cooperation thus far has proven ineffective in regulating transboundary water resources. Therefore, the current state of transboundary water cooperation can negatively influence Kazakhstan’s water supply. In sum, due to its geographic downstream position and the state of transboundary water cooperation, Kazakhstan faces uncertainty over its water supply, which can affect its green H2-water-food-nexus. The following sub-section describes the effect of marine pollution associated with the Caspian Sea’s desalination on Kazakhstan’s green H2-water-food-nexus.

Marine pollution: Desalination of Caspian Sea 

The marine pollution through the brine, a waste product from desalination, represents another transboundary water issue, which can negatively influence Kazakhstan's green H2-water-food-nexus. The use of desalinated water from the Caspian Sea for Central Asian clean H2 production was advocated during the recent workshop on the Hydrogen-Water Nexus in Central Asia (UNECE, 2024b). The brine is commonly disposed of in seas and oceans, which negatively affects the surrounding biodiversity and marine environment due to the presence of chemicals and the resultant salinity and temperature (Omersphahic et al., 2022).  For instance, to produce 95 million m3 of freshwater, 141.5 million m3 of brine, including toxins like chorine and copper, is also produced. In addition, while typical saltwater is 3.5% sale, brine is 5% salt. Fish and insects can die if the water becomes too salty for them. Brine also lowers the amount of oxygen in the water around the desalination facilities, which is also harmful to sea life (WEF, 2022). 

Therefore, brine from Central Asian countries' additional desalination plants used for green H2 production, might be interpreted as a direct threat to transboundary water and food security. Like the phenomenon of acid rain, which highlighted the potential for airborne pollution to affect water supplies in other countries negatively, the rise of desalination highlights how brine, as a pollution in the marine environment, has become a novel area of concern for transboundary water supply (Katz, 2020). Furthermore, the decline in the water level of the Caspian Sea can also be related to existing desalination efforts undertaken by Iran, Kazakhstan, Turkmenistan, and Azerbaijan (Amangeldina, 2024). Thus, Central Asian countries' adherence to the principles of the right to development and the state sovereignty related to their green H2 productions might clash with the duty to cooperate and the obligation not to cause environmental harm in the context of sustainable development. 

Regarding the obligation not to cause environmental harm, Kazakhstan adheres to the Convention on Biological Diversity, which protects genetic, species, and ecosystem diversity (Hunter et al., 2022). Recent fires and floods have propelled nature to the top of the political and societal agenda, spotlighting the urgency of the required balance between nature and people. Besides spearheading some notable biodiversity projects, Kazakhstan has established the Caspian Sea's first marine protected area to protect unique species, including the Caspian seal (Wawiernia, K, 2024). The country adheres to the Convention on the Legal Status of the Caspian Sea, where Article 15 states that "any activity damaging the biological diversity of the Caspian Sea shall be prohibited" (PR, 2018, p. 5). Since brine can be definitively designated as a pollutant (Hutson & Taganova, 2023), desalination aspirations related to Kazakhstan's green H2 production contradict its biodiversity plans and promises. Thus, the country's transboundary water issues, related to the uncertainty of transboundary water supply and marine pollution in the Caspian Sea, may negatively influence Kazakhstan's green H2-water-food-nexus. Lastly, the next sub-section reviews the country’s internal wastewater opportunities. 

Internal wastewater opportunities  

At the intersection of the water and energy industries, wastewater has an “untapped potential as a renewable – and arguably infinite - energy source” (Naylor & Gidda, 2022, p. 2), which can positively affect the green H2-water-food nexus. Wastewater can be described as industrial, domestic, and atmospheric (Mussaev et al., 2024). The present practices for reuse and disposal options of various kinds of wastewater comprise, composting to utilize as a fertilizer, brick production, filler material, and bioplastic production as well as anaerobic digestion for biogas production (Kumari et al., 2023). Nearly a third of Kazakhstan’s cities do not have proper wastewater treatment facilities (BI, 2024). Moreover, the efficiency of the existing facilities is very low, with the volume of wastewater increasing yearly, which increases the load on wastewater treatment facilities (PMK, 2022). Therefore, Kazakhstan is committed to investing in developing wastewater treatment plant (WWTP) infrastructure, intending to match or exceed the progress seen in other nations (Mussaev et al., 2024). For example, the government plans to invest an annual average of $530 million in Kazakhstani water management during 2021-2030 (ITA, 2022). In 2022, Kazakhstan announced that from 2023 to 2028, the government plans to construct and modernize WWTPs in 68 cities (PMK, 2022). Some notable recent projects include the European Bank for Reconstruction and Development (EBRD) financing of replacing the current facility in Kazakhstan’s fourth largest municipality, Aktobe, with modern wastewater treatment technologies, which will improve the quality of liquid waste discharge, called effluent, in line with the European Union and Kazakhstan’s standards (BI, 2024). Asian Development Bank and EBRD will allocate $686 million for the modernization and construction of sewage treatment facilities in Kazakhstani’s 53 cities starting in 2021 (ITA, 2022). Lastly, Metito and Econet will be involved in significant WWTP projects, while Atyrau Oil Refinery Plant JSC plans to modernize its wastewater treatment facilities (Econet, 2024; SWM, 2023; ITA, 2022). Thus, internal wastewater opportunities might positively influence the green H2-water-food-nexus. Section 5 presents innovative policies for future Kazakhstani sustainable green H2 hubs.