Lack of information for decision making

Water problems around the world are increasing; however, information useful for decision makers within the water sector and related to the water sector seems to be decreasing. Solving water problems requires information from many disciplines, and the physical accounts (describing sources and uses of water) are the most important foundation. The information has to be coherent and harmonized in order to provide an integrated picture useful for the assessment of the problems. The current hydrological data democracy does not provide all required data necessary for a proper water consumer communication, which hampers the development of good water stewardship.

Why water accounting?

There is a need to describe water resources in a standard context, using clear terminology and a standard data collection system with known quality standards. Vaporization of water from land into the atmosphere – as well as water in products – produces agro–ecological–economical services. These services should be understood and improved if we want to maintain current per capita water availabilities and water footprints. The water consumption and water pollution needs to be regulated.

Audited Water Accounts are the basis for evidence based decision making and establishing agreements with riparian partners, including those across international borders.

Data integration

Water accounting integrates hydrological processes with land use, managed water flows and the services that result from water consumption in river basins. Its objective is to strive to achieve equitable and transparent water governance for all users and a sustainable water balance Users can provide value assessments of certain process, and more accurate data sets, that replaces the default data collected from open access sources that represent best estimates. Water accounting has been developed originally by Dr. David Molden from the International Water Management Institute (IWMI) and has been modified and upgraded with inputs from the Delft University of Technology.

The current website provides the framework and results of a new Water Accounting methodology (WA+) that is based on global scale public domain datasets. It is a multi-institutional effort from international knowledge centers (IWMI, UNESCO-IHE, FAO, and WWAP) that are neither politically or geographically connected to a given river basin. WA provides independent estimates of water flows, fluxes, stocks, consumption and services, that in the near-future becomes certified.


Atmospheric moisture recycling Describes water that is evaporated from the land surface into the atmosphere and that returns as incremental rainfall within the same physical basin boundaries
Atmospheric boundary layer Lower part of the atmosphere that is under influence of energy, heat, water vapor and carbon dioxide fluxes from the land surface
Available water The total exploitable water minus reserved flows. It represent the water that is available for use at the domain
Baseflow Surface water flow in streams and rivers during dry season that is fed by groundwater discharge
Basin A discrete area being horizontally bounded by a water divide and vertically bounded by an impermeable soil layer (bottom) and the atmospheric boundary layer (top)
Beneficial consumption Water consumed for the intended purpose
Biodiversity The degree of variation of life. This can refer to genetic variation, species variation, or ecosystem variation within an area
Closed basin A basin where utilizable flows are negligible small
Committed flow Water that has been allocated for a special purpose such as an interbasin transfer or cross–boundary flow. Often decrees and acts legally describe the agreed flows between one or more parties
Consumptive use Water withdrawn for an intended process that does not return back into the basin, except from atmospheric recycling; it relates to evapotranspiration, water pollution and water incorporated in products
Demand Amount of extra water needed to supplement naturally available water
Ecosystem services There are four broad categories: provisioning, such as the production of food and water; regulating, such as the control of climate and disease; supporting, such as nutrient cycles and crop pollination; and cultural, such as spiritual and recreational benefits
Effective rainfall Rainfall that is infiltrated and stored into the unsaturated soil and being available for evapotranspiration
Environmental flow Minimum river flow required for maintaining the biodiversity of riverine ecosystem including endangered fish species and the riparian corridor
Evapotranspiration Energy process that converts water from liquid to gaseous phase. EvapoTranspiration (ET) occurs as interception evaporation, soil evaporation, water evaporation, canopy transpiration. ET occurs outdoor
Gross inflow The total amount of water that flows into the domain, this includes precipitation plus any inflow from surface or ground water sources and desalinized water
Groundwater dependent ecosystem In terrestrial GDE systems – such as forests– groundwater contribute to water and nutrients which maintain a rich and unique biodiversity adjusted to these special conditions
Incremental ET Enhancement of evapotranspiration (ET) due to rainfall by supplying additional water resources
Interception Evaporation of a thin water film from wet leaves or other wet impermeable (artificial) surfaces
Landscape ET Water from rainfall that evaporates locally from leaves, litter, soil, and via plants that extract moisture from the unsaturated zone
Managed water use Represents land use elements with anthropogenic regulation of withdrawals and water supplies. It includes water withdrawals for irrigation, aquaculture, domestic use and industries, among others
Modified land use Represents land use elements where vegetation is replaced with the intention to increase the utilization of land resources. Examples are plantation forests, pastures and rainfed crops, among others
Net inflow The gross inflow after correction of storage change (ΔS). It represents water available for landscape ET and exploitable water
Non–beneficial consumption Water consumed for purposes other than the use
Non–conventional ET ET that occurs by non–natural processes such as steam from cooling towers, respiration by humans and animals, sweating and turbine spray, among others
Non–recoverable flow Non–consumed water that is lost to further use, by pollution that exceeds international standards, flows to saline groundwater sinks, deep aquifers that are not economically exploitable or flows to the sea
Productivity of water the physical mass of production or the economic value of production measured against consumptive use water
Protected land use Environmentally sensitive land uses and natural ecosystem that cannot be modified due to protective measures
Recoverable flow Non–consumed water that can be captured and reused in streams, rivers, lakes, reservoirs and aquifers
Renewable water resources Difference between rainfall and landscape ET for a river basin across a certain period. It is essentially the exploitable flow
Reserved flow Surface water that has been reserved to meet committed flows, navigational flows, and environmental flow
Scarcity Difference between supply and demand
Total water stocks represents water being present in reservoirs, rivers, lakes and groundwater that can be used for withdrawals
Sink Area where non–consumed and non–recoverable water ensembles
Supply Provision of water withdrawn from a source to a certain user
Tributary Stream or river that flows into a main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean
Total water stocks Represents water being present in reservoirs, rivers, lakes and groundwater that can be used for withdrawals
Utilized land use Represents land use classes with a low to moderate utilization of natural resources, such as savannah, woodland and mixed pastures
Utilized water Part of available water that is depleted for uses
Utilizable water Water available for additional resources development
Virginal flow River flow without anthropogenic interference, i.e. no withdrawals and no return flows
Water allocation Amount of water that can be withdrawn by licensed holders during a specific period
Water audit Mapping the infrastructure and management of water systems, along with their socio–economics and financial conditions, as well as the legislations and institutions
Water governance Political, social, economic and administrative systems that are in place, and which directly or indirectly affect the use, development and management of water resources and the delivery of water service delivery at different levels of society
Water source Aater available in streams, rivers, drainage, canals, lakes, reservoirs, lagoons, aquifers, the unsaturated zone and desalinized sea water
Water use any water flow related to a specific purpose. It can be related to both withdrawals and consumptive use and is a very broad (and confusing) term
Water withdrawals Water taken away from a water source, either natural (e.g. inundation, leakage) or artificial (i.e. pumping, diversions