Definition: Water scarcity arises when water availability is insufficient to meet the demands of economic activities, human well-being, and environmental health.

Variability in Scarcity: Scarcity can manifest continuously or sporadically, fluctuating with seasons and over extended periods of time.

Primary Causes: Water scarcity intensifies due to excessive consumption and degradation of both surface and groundwater. Notably, irrigated agriculture consumes the largest portion of water resources through the process of evapotranspiration.

Consequences of Scarcity: Water scarcity often leads to, or is caused by, over-exploitation of available water resources. This can result in consequences like aquifer depletion, harm to aquatic ecosystems and associated ecological services (e.g. fishing; drinking water quality), increased competition between diverse water users, and adverse social and economic outcomes.

Degradation of Quality: Over time, the continuous degradation of water resources can become irreversible, leading to deterioration in water quality. In some instances, human activities degrade the water quality to such an extent that it exacerbates the impacts of water scarcity.

Challenges in Reallocation: Addressing water scarcity becomes increasingly difficult as societies and economies grow reliant on unsustainable water consumption patterns. This dependency creates resistance to necessary change.

Long-term Implications: Overexploitation is, by its very nature, unsustainable. Prolonged disregard for sustainable water management can culminate in crises that demand challenging re-allocations of water resources among various stakeholders and the environment.

Between 1975 and 2010, the region's population living under high or severe water scarcity grew dramatically, from 1.1 billion to over 2.6 billion. Similarly, those experiencing green-blue water scarcity (Green-blue water scarcity refers to a situation where there is insufficient water to meet both the environmental (green water) and human (blue water) demands within a given region) increased from around 0.2 billion to nearly 1.5 billion. Seasonal water scarcity is a significant issue in countries with monsoonal climates and wet tropical and sub-tropical regions.

Agriculture in the region is highly dependent on freshwater for irrigation, a crucial component of Asia's food production accounts for up to 95 percent of the region's freshwater water consumption and is increasingly faced with competition from other water use. This dependency considerably strains local water systems, especially given the region's rapid economic growth and increasing competition for water resources. Water scarcity in the Asia-Pacific manifests in different forms, ranging from absolute scarcity in arid and semi-arid regions to seasonal or inter-annual shortages in the monsoonal tropics. Scarcity is characterized by challenges such as insufficient water availability, over-utilization, variability in water supply, or poor water quality, which pose risks to the region's developmental progress.

In 2019, FAO launched the Asia-Pacific Water Scarcity Programme (WSP) in response to these challenges. The WSP aims to help countries maintain water consumption within quantified sustainable limits while preparing them for a productive, food-secure future with less water. The WSP promotes practical water accounting and the development of transparent, rational, and evidence-based water allocation processes. It seeks to embed these activities at a high level and represent the interests of all water stakeholders, improving policy coherence between water-using sectors. The WSP is also undertaking fieldwork to understand water tenure and set a framework for the transparent and equitable inclusion of all water users. Additionally, the WSP facilitates high-level regional buy-in and south-south cooperation across technical and governance issues through the Regional Cooperative Platform (RCP).