Water Security and Transboundary Waters

Introduction

Water security concerns the availability, accessibility, quality, and sustainable management of water for people, economies, ecosystems, and societies. Water is essential for drinking, sanitation, agriculture, industry, energy production, public health, and biodiversity. When water supplies become unreliable or polluted, the consequences can extend into economic development, public health, social stability, and international relations.

Water security is particularly important in regions where rainfall is variable, groundwater is declining, populations are growing, or several countries depend on the same rivers and aquifers. These conditions require effective domestic water management as well as cooperation between neighbouring states.

Transboundary waters are rivers, lakes, and aquifers shared by two or more countries. Decisions taken in one country can affect water availability, quality, ecosystems, and livelihoods in another. UN-Water emphasizes that transboundary waters account for a substantial share of global freshwater flows and that cooperative arrangements remain incomplete across many shared basins.

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Core Concepts

Water security: The capacity of a population to safeguard sustainable access to adequate quantities of acceptable-quality water for livelihoods, human well-being, socioeconomic development, and ecosystems, while managing water-related risks.

Water scarcity: A condition in which available water resources are insufficient to meet demand, taking account of quantity, quality, timing, and access.

Physical water scarcity: A situation in which natural water availability is insufficient to meet demand under prevailing conditions.

Economic water scarcity: A condition in which water exists but infrastructure, investment, institutions, or affordability prevent people from accessing it reliably.

Water stress: Pressure on available water resources relative to demand. Indicators can measure withdrawals against renewable supplies, but results depend on methodology and local circumstances.

Water quality: The physical, chemical, and biological characteristics of water that determine its suitability for different uses.

Water governance: The institutions, rules, policies, and decision-making processes that determine how water is allocated, used, protected, and managed.

Integrated Water Resources Management (IWRM): A coordinated approach to managing water, land, and related resources to maximize social and economic welfare equitably without compromising the sustainability of ecosystems.

Water resilience: The ability of water systems and the communities that depend on them to withstand and recover from droughts, floods, contamination, and other disruptions.

Water equity: Fairness in access to water, the distribution of water-related costs and benefits, and participation in water decisions.

Dimensions of Water Security

Drinking-water security: Reliable access to sufficient and safe water for drinking, cooking, and other essential domestic needs.

Sanitation security: Access to safe sanitation services that protect health and prevent contamination of water and the environment.

Agricultural water security: Reliable water access for crops, livestock, and agricultural livelihoods.

Industrial water security: Access to water of suitable quantity and quality for industrial production and related activities.

Energy-water nexus: The relationship between water and energy systems. Water is needed for many energy activities, while energy is needed to pump, treat, transport, and desalinate water.

Water-related ecosystem security: Maintaining the water flows, quality, and ecological conditions needed to sustain wetlands, rivers, lakes, and other ecosystems.

Flood security: The capacity to reduce exposure and vulnerability to damaging floods through planning, infrastructure, warnings, and preparedness.

Drought security: The ability to prepare for, manage, and recover from periods of prolonged water shortage.

Sources and Forms of Water

Surface water: Water found in rivers, lakes, reservoirs, wetlands, and other surface bodies.

Groundwater: Water stored beneath the Earth’s surface in soil, rock formations, and aquifers.

Aquifer: A geological formation capable of storing and transmitting groundwater in usable quantities.

Recharge: The process through which water enters an aquifer, often from rainfall, rivers, irrigation return flows, or other sources.

River basin: The land area from which water drains into a common river system, including its tributaries.

Drainage basin: The geographical area that contributes water to a river, lake, or other drainage system.

Transboundary river basin: A river basin that extends across the territory of two or more countries.

Transboundary aquifer: An underground water-bearing formation that crosses an international boundary or is hydraulically connected across borders.

Renewable water resources: Water supplied or replenished through natural processes over a specified period, particularly precipitation and associated runoff and recharge.

Non-renewable groundwater: Groundwater whose replenishment is negligible relative to extraction on relevant human timescales.

Environmental flow: The quantity, timing, and quality of water flows needed to sustain freshwater ecosystems and the human livelihoods and well-being that depend on them.

Transboundary Water Politics

Transboundary water governance: The institutions, rules, agreements, and cooperative processes through which countries manage shared water resources.

Riparian state: A state located along or sharing a river, lake, or other water body.

Upstream state: A country located nearer the source or higher along a river system, whose water-management decisions may affect downstream countries.

Downstream state: A country located farther along a river’s flow, potentially affected by upstream withdrawals, dams, pollution, or changes in flow.

Water allocation: The distribution of water among users, sectors, regions, or countries.

Equitable and reasonable utilization: A principle of international water law requiring shared watercourses to be used fairly and reasonably, taking relevant circumstances and interests into account.

Obligation not to cause significant harm: A principle requiring states to exercise appropriate care to prevent significant harm to other states in the use of shared watercourses, interpreted alongside other applicable international legal rules.

Prior notification: The provision of information to potentially affected states about certain planned measures that may have transboundary effects.

Joint water commission: A bilateral or multilateral body established to facilitate cooperation over shared water resources.

Basin-wide cooperation: Coordinated management involving relevant states and stakeholders across an entire river basin rather than isolated sections.

Hydro-diplomacy: Diplomatic engagement over water allocation, infrastructure, water quality, and shared-water management.

Hydropolitics: The political relationships and power dynamics surrounding water resources.

Water-sharing agreement: An arrangement setting out rules for water use, allocation, data exchange, infrastructure, or dispute management.

International Water Law and Institutions

Convention on the Law of the Non-Navigational Uses of International Watercourses: A 1997 UN convention addressing the use, management, and protection of international watercourses for purposes other than navigation.

Convention on the Protection and Use of Transboundary Watercourses and International Lakes: A 1992 convention developed under the UN Economic Commission for Europe, designed to promote cooperation in protecting and managing transboundary waters. It has also been opened to accession by UN member states outside the UNECE region.

International water law: The body of international legal principles, treaties, and customary rules governing shared water resources.

Customary international law: International law arising from general state practice accepted as law, where the applicable requirements are met.

International Court of Justice (ICJ): The principal judicial organ of the United Nations, which may hear disputes between states where jurisdiction is established.

UN-Water: The United Nations coordination mechanism for water and sanitation-related issues.

UNESCO: The UN agency involved in water sciences, hydrology, education, and related international cooperation.

International river basin organization: An institution established by countries to coordinate management of a shared river basin.

Water Scarcity and Conflict

Water conflict: A dispute involving access to, use of, control over, or management of water resources.

Water weaponization: The deliberate use of water supplies or infrastructure as an instrument of coercion or warfare. The legality of particular conduct depends on the circumstances and applicable international law.

Hydro-hegemony: A concept describing situations in which a powerful actor shapes shared-water arrangements through its economic, geographic, military, or political influence.

Hydraulic infrastructure: Structures such as dams, canals, reservoirs, barrages, and water-transfer systems used to store, regulate, or distribute water.

Dam diplomacy: Diplomatic bargaining and political engagement involving the construction, operation, or management of dams and related infrastructure.

Water nationalism: Political rhetoric or policy that emphasizes national control over water resources, sometimes limiting the scope for compromise over shared waters.

Water cooperation: Joint action by states or communities to manage water resources, exchange data, prevent disputes, and distribute benefits.

Water peace dividend: Benefits generated when cooperation over water reduces tensions, supports livelihoods, or creates shared economic and environmental gains.

Climate Change and Water Security

Hydrological cycle: The continuous movement of water through evaporation, condensation, precipitation, infiltration, runoff, and groundwater flows.

Hydrological drought: A period in which river flows, reservoirs, lakes, or groundwater levels fall below normal conditions.

Meteorological drought: A period of unusually low precipitation relative to the expected conditions of a region.

Agricultural drought: A shortage of soil moisture that adversely affects crops or agricultural production.

Glacial meltwater: Water released as glaciers melt, which can contribute to river flows and seasonal water supplies.

Saltwater intrusion: The movement of saline water into freshwater aquifers or other freshwater systems, often associated with coastal groundwater extraction and sea-level rise.

Desalination: The removal of salts from seawater or brackish water to produce water suitable for specified uses.

Water reuse: The use of treated wastewater or other previously used water for suitable purposes.

Rainwater harvesting: The collection and storage of rainwater for later use.

Key Distinctions

Key Terms at a Glance

• Water footprint: A measure of water use associated with a person, product, organization, or activity.

• Virtual water: Water used in producing goods and services that are traded across regions or countries.

• Water productivity: The amount of economic or agricultural output produced per unit of water used.

• Non-revenue water: Water supplied by a utility that is not billed because of physical losses, unauthorized use, or metering and administrative issues.

• Water treatment: Processes used to make water suitable for drinking or other specified purposes.

• Watershed management: The coordinated management of land and water within a drainage area.

• Water diplomacy: Negotiation and cooperation over water-related interests and disputes.

• Transboundary impact: An effect originating in one jurisdiction that affects another jurisdiction.

• Environmental flow requirement: The water-flow conditions needed to sustain ecosystems and associated livelihoods.

• Water conflict prevention: Measures designed to address grievances, improve cooperation, and reduce the risk of disputes over water.

Related Glossaries

• 6.1 International Law: Core Concepts

• 6.2 Treaties, Conventions and International Agreements

• 9.2 Human Security and Non-Traditional Security

• 12.4 Chokepoints, Corridors and Strategic Locations

• 17.7 Food, Health and Human Security

• 18.1 Climate Change and Global Warming

• 18.2 Climate Security and Climate Diplomacy

• 18.4 Environmental Security and Resource Conflicts

• 18.7 Biodiversity and Global Environmental Governance

Conclusion

Water security encompasses much more than the physical supply of water. It includes safe access, affordability, ecosystem protection, disaster preparedness, and effective governance. Where water resources cross national borders, cooperation becomes especially important. Shared data, equitable arrangements, functioning institutions, international law, and sustained diplomacy can help countries manage common waters while reducing the risk of conflict.