| Adaptation | The process of adjustment to actual or expected climate and its effects. In human systems, adaptation seeks to moderate or avoid harm or exploit beneficial opportunities. In some natural systems, human intervention may facilitate adjustment to expected climate and its effects. | IPCC, 2014 |
| Adaptive Capacity | The ability of systems, institutions, humans and other organisms to adjust to potential damage, to take advantage of opportunities, or to
respond to consequences. | IPCC, 2014 |
| Aquifer | Underground layers of permeable rock, sediment or soil filled with water and interconnected, so the water stays within or flows through them. The two major types of aquifers are confined and unconfined. | GWP, 2017 |
| Aridity | Characteristic of a climate relating to insufficiency or inadequacy of precipitation to maintain vegetation (WMO). Aridity is measured by comparing long-term average water supply (precipitation) to long-term average water demand (evapotranspiration). If demand is greater than supply, on average, then the climate is arid (NOAA). | NOAA NCEI, 2017;
WMO, 1992 |
| Available groundwater resource | Volume of water stored in an aquifer which is available for development and use (WMO-UNESCO). It is calculated as the difference between the long-term annual average rate of overall recharge of the body of groundwater and the long-term annual rate of flow required to achieve the ecological quality objectives for associated surface waters (surface waters that are recharged by groundwater) (EC). | EC, 2000;
WMO/UNESCO, 2012 |
| Basin (catchment or watershed) | An area having a common outlet for its surface runoff. | WMO/UNESCO, 2012 |
| Climate change | A change in the state of the climate that can be identified (e.g., by using statistical tests) by changes in the mean
and/or the variability of its properties and that persists for an extended period, typically decades or longer. Climate change may be due to natural internal processes or external forcings such as modulations of the solar cycles, volcanic eruptions and persistent anthropogenic changes in the composition of the atmosphere or in land use. | IPCC, 2014 |
| Crop failure | Abnormal reductions in crop yield such that is insufficient to meet the nutritional or economic needs of the community. | EM-DAT, 2017 |
| Desalination | Water desalination: removal of salt from sea- or brackish water. It is achieved by various methods, for example distillation, reverse osmosis, hyperfiltration, electrodialysis, ion exchange, and solar evaporation followed by condensation of water vapour. Soil desalination: removal of salt from soil by artificial means, usually leaching. | FAO, 2017 |
| Desertification | Land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors, including climatic variations and human activities. | UNCCD, 2019 |
| Disaster | A serious disruption of the functioning of a community or a society at any scale due to hazardous events interacting with conditions of exposure, vulnerability and capacity, leading to one or more of the following: human, material, economic and environmental losses and impacts. | UNISDR, 2017 |
| Disaster Risk | The potential loss of life, injury, or destroyed or damaged assets which could occur to a system, society or a community in a specific period of time, determined probabilistically as a function of hazard, exposure, vulnerability and capacity. | UNISDR, 2017 |
| Disaster Risk Management (DRM) | Disaster risk management is the application of disaster risk reduction policies and strategies to prevent new disaster risk, reduce existing disaster risk and manage residual risk, contributing to the strengthening of resilience and reduction of disaster losses. | UNISDR, 2017 |
| Disaster Risk Reduction (DRR) | Disaster risk reduction is aimed at preventing new and reducing existing disaster risk and managing residual risk, all of which contribute to strengthening resilience and therefore to the achievement of sustainable development. | UNISDR, 2017 |
| Drainage | Removal of surface water or groundwater from a given area by natural or artificial means. | WMO/UNESCO, 2012 |
| Drought | (1) Prolonged absence or marked deficiency of precipitation. (2) Period of abnormally dry weather sufficiently prolonged for the lack of precipitation to cause a serious hydrological imbalance. | WMO, 1992 |
| Drought assessment | Assessment reviewing drought conditions and indicating potential impacts for various economic sectors, such as agriculture and forestry. | NOAA NWS, 2017 |
| Drought forecast | The statistical estimate of the probability of occurrence of a future drought event. | GWP CEE, 2015 |
| Drought impact | A specific effect of drought on the economy, society, and/or environment, which is a symptom of vulnerability. | GWP CEE, 2015 |
| Drought impact assessment | The process of assessing the magnitude and distribution of the effects of a drought. | GWP CEE, 2015 |
| Drought index | Computed numerical representations of drought severity, assessed using climatic or hydrometeorological inputs, including precipitation, temperature, streamflow, groundwater and reservoir levels, soil moisture and snowpack. They aim to measure the qualitative status of drought on the landscape for a given time period. Indices are technically indicators as well. | WMO/GWP, 2016 |
| Drought indicator | Variables or parameters used to describe drought conditions. Examples include precipitation, temperature, streamflow, groundwater and reservoir levels, soil moisture and snowpack. | WMO/GWP, 2016 |
| Drought Management Plan | It is a planning tool that can be applied to the basin scale or to other scales. It aims to define mechanisms and a methodology for detecting and predicting droughts, establish thresholds for different stages of drought as it intensifies and recedes, define measures to achieve specific objectives in each drought stage, ensure transparency and public participation in the development of drought strategies. The main objective of drought management plans is to minimize the adverse impacts on the economy, social life and environment when drought appears. | GWP CEE, 2015 |
| Drought vulnerability assessment | It is a drought vulnerability quantification and description that consist in identifying the relevant factors influencing it, from the point of view of exposure, sensitivity and adaptive capacity. The final aim of a drought vulnerability assessment is to identify the underlying sources of drought impact. | Urquijo et al., 2015 |
| Dry spell | Period of abnormally dry weather. Use of the term should be confined to conditions less severe than those of a drought. | WMO, 1992 |
| Early Warning (EW) | The provision of timely and effective information, through identified institutions, that allows stakeholders at risk of a disaster to take action to avoid or reduce their risk and prepare for effective response. | GWP CEE, 2015 |
| Early Warning System (EWS) | The set of capacities needed to generate and disseminate timely and meaningful warning information to enable individuals, communities, and organizations threatened by a hazard to prepare to act promptly and appropriately to reduce the possibility of harm or loss. | IPCC, 2014 |
| El Niño | The term El Niño refers to the large-scale ocean-atmosphere climate phenomenon linked to a periodic warming in sea-surface temperatures across the central and east-central equatorial Pacific (between approximately the date line and 120W). El Niño represents the warm phase of the El Niño/Southern Oscillation (ENSO) cycle, and is sometimes referred to as a Pacific warm episode. El Niño originally referred to an annual warming of sea-surface temperatures along the west coast of tropical South America. | CPC, 2018 |
| El Niño Southern Oscillation (ENSO) | ENSO stands for El Niño/ Southern Oscillation. The ENSO cycle refers to the coherent and sometimes very strong year-to-year variations in sea- surface temperatures, convective rainfall, surface air pressure, and atmospheric circulation that occur across the equatorial Pacific Ocean. El Niño and La Niña represent opposite extremes in the ENSO cycle. | CPC, 2018 |
| Erosion | Wearing away and transport of soil and rock by running water, glaciers, wind or waves. | WMO/UNESCO, 2012 |
| Evapotranspiration | The combined processes by which water is transferred from the Earth's surface to the atmosphere by evaporation from the land and ocean surfaces and by transpiration from vegetation. | WMO, 1992 |
| Exposure | The situation of people, infrastructure, housing, production capacities and other tangible human assets located in hazard-prone areas. | UNISDR, 2017 |
| Famine | Famine exists in areas where at least one in five households has an extreme lack of food and other basic needs. Extreme hunger and destitution is evident. Significant mortality, directly attributable to outright starvation or to the interaction of malnutrition and disease is occurring. | IPC, 2018 |
| Food security | Food security exists when all people, at all times, have physical, social and economic access to sufficient, safe and nutritious food to meet their dietary needs and food preferences for an active and healthy life. The four pillars of food security are availability, access, utilization and stability. The nutritional dimension is integral to the concept of food security. | FAO, 2009 |
| Groundwater | Water within the earth that supplies wells and springs; water in the zone of saturation where all openings in rocks and soil are filled, the upper surface of which forms the water table. | NOAA NWS, 2017 |
| Hazard | A process, phenomenon or human activity that may cause loss of life, injury or other health impacts, property damage, social and economic disruption or environmental degradation. Hazards may be natural, anthropogenic or socio-natural in origin. Natural hazards are predominantly associated with natural processes and phenomena. Anthropogenic hazards, or human-induced hazards, are induced entirely or predominantly by human activities and choices. Hazards may be single, sequential or combined in their origin and effects. Each hazard is characterized by its location, intensity or magnitude, frequency and probability. | UNISDR, 2017 |
| Integrated Water Resources Management (IWRM) | IWRM is a process which promotes the coordinated development and management of water, land and related resources in order to maximize the resultant economic and social welfare in an equitable manner without compromising the sustainability of vital ecosystems. | GWP, 2000 |
| Land degradation | Reduction or loss, in arid, semi-arid and dry sub-humid areas, of the biological or economic productivity and complexity of rainfed cropland, irrigated cropland or range, pasture, forest and woodlands resulting from land uses or from a process or combination of processes, including processes arising from human activities and habitation patterns such as: soil erosion caused by wind and/or water; deterioration of the physical, chemical and biological or economic properties of soil; and long-term loss of natural vegetation. | UNCCD, 2019 |
| Land use | Land use refers to the total of arrangements, activities and inputs undertaken in a certain land cover type (a set of human actions). The term land use is also used in the sense of the social and economic purposes for which land is managed (e.g., grazing, timber extraction and conservation). | IPCC, 2014 |
| La Niña | La Niña refers to the periodic cooling of ocean surface temperatures in the central and east-central equatorial Pacific that occurs every 3 to 5 years or so. La Niña represents the cool phase of the El Niño/Southern Oscillation (ENSO) cycle, and is sometimes referred to as a Pacific cold episode. La Niña originally referred to an annual cooling of ocean waters off the west coast of Peru and Ecuador. | CPC, 2018 |
| Mitigation | Mitigation (of disaster risk and disaster): The lessening of the potential adverse impacts of physical hazards (including those that are human-induced) through actions that reduce hazard, exposure, and vulnerability.
Mitigation (of climate change): A human intervention to reduce the sources or enhance the sinks of greenhouse gases. | IPCC, 2012 |
| Monsoon | Seasonal change of wind direction, from sea to land or vice versa, associated with widespread changes in temperature and rainfall in subtropical regions. | WMO/UNESCO, 2012 |
| Preparedness | The knowledge and capacities developed by governments, response and recovery organizations, communities and individuals to effectively anticipate, respond to and recover from the impacts of likely, imminent or current disasters. | UNISDR, 2017 |
| Prevention | Activities and measures to avoid existing and new disaster risks. Prevention (i.e., disaster prevention) expresses the concept and intention to completely avoid potential adverse impacts of hazardous events. While certain disaster risks cannot be eliminated, prevention aims at reducing vulnerability and exposure in such contexts where, as a result, the risk of disaster is removed. | UNISDR, 2017 |
| Proactive approach to drought management | A proactive approach to drought risk management includes appropriate measures being designed in advance, with related planning tools and stakeholder participation. The proactive approach is based on both short-term and long-term measures and includes monitoring systems for a timely warning of drought conditions, the identification of the most vulnerable part of the population and tailored measures to mitigate drought risk and improve preparedness. The proactive approach entails the planning of necessary measures to prevent or minimize drought impacts in advance. This approach is reflected in the three pillars of integrated drought management. | Vogt et al., 2018 |
| Reactive approach to drought management | A reactive approach to drought management is based on crisis management: it includes measures and actions after a drought event has started and is perceived. This approach is taken in emergency situations and often results in inefficient technical and economic solutions, because actions are taken with little time to evaluate best options and stakeholder participation is very limited. This approach has often been uncoordinated and untimely. In addition, crisis management places little attention on trying to reduce drought impacts caused by future drought events. | Vogt et al., 2018 |
| Recovery | The restoring or improving of livelihoods and health, as well as economic, physical, social, cultural and environmental assets, systems and activities, of a disaster-affected community or society, aligning with the principles of sustainable development and “build back better”, to avoid or reduce future disaster risk. | UNISDR, 2017 |
| Reservoir | Body of water, either natural or man-made, used for storage, regulation and control of water resources. | WMO/UNESCO, 2012 |
| Resilience | The ability of a system, community or society exposed to hazards to resist, absorb, accommodate, adapt to, transform and recover from the effects of a hazard in a timely and efficient manner, including through the preservation and restoration of its essential basic structures and functions through risk management. | UNISDR, 2017 |
| Response | Actions taken directly before, during or immediately after a disaster in order to save lives, reduce health impacts, ensure public safety and meet the basic subsistence needs of the people affected. Disaster response is predominantly focused on immediate and short-term needs and is sometimes called disaster relief. | UNISDR, 2017 |
| Runoff | That part of the precipitation which flows towards a river on the ground surface (surface runoff) or within the soil (subsurface runoff or interflow). | WMO/UNESCO, 2012 |
| Soil degradation | The decline in soil quality caused by natural processes or, more commonly, improper use by humans, resulting in a diminished capacity of the ecosystem to provide goods and services for its beneficiaries. | FAO, 2017 |
| Soil moisture | Moisture contained in that portion of the soil which lies above the water table, including the water vapour contained in the soil pores. Sometimes it refers strictly to the humidity contained in the root zone of the plants. | WMO, 1992 |
| Teleconnection | A linkage between weather changes occurring in widely separated regions of the globe. Most commonly applied to variability on monthly and longer timescales, the name refers to the fact that such correlations suggest that information is propagating between the distant points through the atmosphere. | AMS, 2017 |
| Vulnerability | The degree to which a system is susceptible to, or unable to cope with, adverse effects of climate change, including climate variability and extremes. Vulnerability is a function of the character, magnitude, and rate of climate variation to which a system is exposed, its sensitivity, and its adaptive capacity. | UNFCCC, 2014 |
| Water banking | A water management strategy that temporarily transfers water from those who are willing to lease it to those who are willing to pay to use it. | NDMC, 2017 |
| Water consumption | Water abstracted which is no longer available for use because it has evaporated, transpired, been incorporated into products and crops, consumed by man or livestock, ejected directly into sea, or otherwise removed from freshwater resources. Water losses during transport of water between the point or points of abstractions and point or points of use are excluded. | EEA, 2017 |
| Water demand | Quantities of water scheduled for delivery to consumers during specified periods for identified uses at given prices. | WMO/UNESCO, 2012 |
| Water governance | The political, administrative, economic and social systems that exist to manage water resources and services and is essential in order to manage water resources sustainably and provide access to water services for domestic or productive purposes. | GWP, 2017 |
| Water scarcity | An imbalance between supply and demand of freshwater in a specified domain (country, region, catchment, river basin, etc.) as a result of a high rate of demand compared with available supply, under prevailing institutional arrangements (including price) and infrastructural conditions. | FAO, 2012 |
| Water security | The availability of an acceptable quantity and quality of water for health, livelihoods, ecosystems and production, coupled with an acceptable level of water-related risks to people, environments and economies. | GWP, 2017 |
| Water shortage | A shortage of water supply of an acceptable quality; low levels of water supply, at a given place and a given time, relative to design supply levels. The shortage may arise from climatic factors, or other causes of insufficient water resources, a lack of, or poorly maintained, infrastructure; or a range of other hydrological or hydro-geological factors. | FAO, 2012 |
| Water stress | The symptoms of water scarcity or shortage, e.g. widespread, frequent and serious restrictions on use, growing conflict between users and competition for water, declining standards of reliability and service, harvest failures and food insecurity. | FAO, 2012 |
| Water supply | The share of water abstraction which is supplied to users (excluding losses in storage, conveyance and distribution). | GWP, 2017 |
| Water withdrawal | Extraction of water from a surface reservoir or an aquifer. | WMO/UNESCO, 2012 |
| Weather | State of the atmosphere at a particular time, as defined by the various meteorological elements. | WMO, 1992 |
