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7.5 Proportion of total water resources used

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Modified on 2012/11/05 17:46 by MDG Wiki Handbook Categorized as Goal 7
Contents

GOAL AND TARGET ADDRESSED

Goal 7. Ensure environmental sustainability Target 7.A: Integrate the principles of sustainable development into country policies and programmes and reverse the loss of environmental resources Target 7.B: Reduce biodiversity loss, achieving, by 2010, a significant reduction in the rate of loss

DEFINITION AND METHOD OF COMPUTATION

Definition
The proportion of total water resources used is the total volume of groundwater and surface water withdrawn from their sources for human use (in the agricultural, domestic/municipal and industrial sectors), expressed as a percentage of the total actual renewable water resources.

The term “used” in the indicator name refers to “withdrawn” (see section below).

Concepts
Total actual renewable water resources (TARWR) are the sum of internal renewable water resources and the Total actual external renewable water resources. The terms “water resources” and “water withdrawal” are understood here as freshwater resources and freshwater withdrawal.

Internal renewable water resources are defined as the long-term average annual flow of rivers and recharge of groundwater for a given country or region generated from endogenous precipitation.

Total actual external renewable water resources are that part of the country’s annual renewable water resources that are not generated in the country. It includes inflows from upstream countries (groundwater and surface water), and part of the water of border lakes and/or rivers. It takes into account the quantity of flow reserved by upstream (incoming flow) and/or downstream (outflow) countries through formal or informal agreements or treaties and may (if available) include reduction of flow due to withdrawal in upstream countries.

Freshwater withdrawal is estimated at the country level for the following three main sectors: agriculture, municipalities (including domestic water withdrawal) and industries. Freshwater withdrawal includes primary freshwater (not withdrawn before), secondary freshwater (previously withdrawn and returned to rivers and groundwater) and fossil groundwater. It does not include non-conventional water, i.e. direct use of treated wastewater, direct use of agricultural drainage water and desalinated water.

Method of computation
The indicator is computed as the total freshwater withdrawn divided by the total actual renewable water resources and multiplied by 100.

Total freshwater withdrawn is estimated as the volume of water withdrawn by the three main sectors: agriculture, municipalities (including domestic water withdrawal) and industries. It is expressed as km3 (1,000,000,000 m3) withdrawn per year.

The total actual renewable water resources for a country or region are calculated as the sum of internal renewable water resources and the actual external renewable water resources, also expressed in km3 per year. It refers to a long-term annual average. A glossary of water resources terms and the detailed method of calculation of the TARWR can be found at the AQUASTAT water resources page (http://www.fao.org/nr/water/aquastat/water_res/index.stm) and in the water resources balance sheet (http://www.fao.org/nr/water/aquastat/water_res/CountryWaterBalanceTemplate.xls).

RATIONALE AND INTERPRETATION

The purpose of this indicator is to show the degree to which total renewable water resources are being exploited to meet the country's water demand. It measures a country's pressure on its water resources and therefore on the sustainability of its water use.

The indicator shows to what extent water resources are already used, and signals the need for adjusted supply and demand management policies. It can also indicate the likelihood of increasing competition and conflict between different water uses and users in a situation of increasing water scarcity. Increased water scarcity, shown by an increase in the value of the indicator, has negative effects on the sustainability of the natural resources and subsequent negative effects on economic development. On the other hand, very low values of the indicator may indicate that there is still potential for increase in water usage in a sustainable way.

Physical water scarcity occurs when there is not enough water to meet both human demands (agricultural, municipal, industrial) and environmental flow requirements. Physical water scarcity exists if more than 75 per cent of a country's river flows are withdrawn, while figures above 60 per cent are considered to be approaching scarcity. There is little or no physical water scarcity if less than 25 per cent of water from a country's rivers is withdrawn. Economic water scarcity is scarcity caused by lack of investment in water or lack of human capacity to satisfy the demand for water.

SOURCES AND DATA COLLECTION

Data for this indicator are usually collected by national ministries and institutions having water-related issues in their mandate, such as ministries of water resources, agriculture, or environment. Data are mainly published within national water resources and irrigation master plans, national statistical yearbooks and other reports (such as those from projects, international surveys or results and publications from national and international research centres).

DISAGGREGATION

The indicator could be disaggregated to show total freshwater withdrawals for different sectors (e.g., agriculture, municipalities and industry) and use efficiencies for these sectors, in order to be able to also provide consumptive use data for the different sectors in addition to withdrawal data. In general, during data collection disaggregated information is collected and aggregated to produce country totals.

COMMENTS AND LIMITATIONS

Water withdrawal as a percentage of water resources is a good indicator of pressure on limited water resources, one of the most important natural resources. However, it only partially addresses the issues related to sustainable water management.

Supplementary indicators that capture the multiple dimensions of water management would combine data on water demand management, behavioural changes with regard to water use and the availability of appropriate infrastructure, and measure progress in increasing the efficiency and sustainability of water use, in particular in relation to population and economic growth. They would also recognize the different climatic environments that affect water use in countries, in particular in agriculture, which is the main user of water. Sustainability assessment is also linked to the critical thresholds fixed for this indicator and there is no consensus on such threshold.

Trends in water withdrawal show relatively slow patterns of change. Usually, three-five years are a minimum frequency to be able to detect significant changes, as it is unlikely that the indicator would show meaningful variations from one year to the other.

Estimation of water withdrawal by sector is the main limitation to the computation of the indicator. Few countries actually publish water use data on a regular basis by sector.

Renewable water resources include all surface water and groundwater resources that are renewed on a yearly basis without consideration of the capacity to harvest and use this resource. Exploitable water resources, which refer to the volume of surface water or groundwater that is available with an occurrence of 90% of the time, are considerably less than renewable water resources, but no universal method exists to assess such exploitable water resources.

There is no universally agreed method for the computation of incoming freshwater flows originating outside of a country's borders. Nor is there any satisfactory method to account for return flows—water withdrawn which flows back to the river system or is collected by a drainage network— in the computation of water resources and use. In countries where return flow (secondary water) represents a substantial part of water withdrawal, the indicator will tend to overestimate water withdrawal as percentage of renewable water resources.

Other comments and limitations include:
  • scarcity of accurate and complete data;
  • local sub-national variation in water resources and water withdrawal could be considerable, for example, at the level of local or individual river basins;
  • lack of account of seasonal variations in water resources;
  • lack of consideration to the distribution among water uses;
  • lack of consideration of water quality and its suitability for use; and
  • since abstraction can occur from fossil groundwater (non-renewable freshwater) the indicator can, in principle, be greater than 100 percent.

GENDER EQUALITY ISSUES

Women and men tend to have different water-related uses, priorities and responsibilities. There are also trends along gender lines in terms of access and control over water and water rights. Gender differences and inequalities mean that women and men experience and respond to changes in water availability, services or water policies differently. Thus integrated water resources management initiatives should be studied for differential impacts on women and men.

DATA FOR GLOBAL AND REGIONAL MONITORING

The Food and Agriculture Organization of the United Nations (FAO) is the agency responsible for compiling data and calculating this indicator at the international level. This is done through its Global Information System on Water and Agriculture (AQUASTAT) country surveys since 1993. These surveys are carried out every ten years, on average.

Data are obtained through detailed questionnaires filled in by national experts and consultants who collect information from the different institutions and ministries having water-related issues in their mandate. Literature and information at the country and sub-country level are reviewed including national policies and strategies; water resources and irrigation master plans; national reports, yearbooks and statistics; reports from projects; international surveys; results and publications from national and international research centres; and the Internet.

Data obtained from national sources are systematically reviewed to ensure consistency in definitions and consistency in data from countries located in the same river basin. A methodology has been developed and rules established to compute the different elements of national water balances.

Estimates are based on country information, complemented, when necessary, with expert calculations based on unit water use figures by sector, and with available global datasets. In the case of conflicting sources of information, the difficulty lies in selecting the most reliable one. In some cases, water resources figures vary considerably from one source to another. There are various reasons for such differences, including differing computation methods, definitions or reference periods, double counting of surface water and groundwater or of transboundary river flows. Moreover, estimates of long-term average annual values can change due to the availability of better data from improvements in knowledge, methods or measurement networks.

Where several sources result in divergent or contradictory information, preference is given to information collected at the national or sub-national level rather than at regional or world levels. Moreover, except in the case of evident errors, official sources are privileged. As regards shared water resources, the comparison of information between countries makes it possible to verify and complete data concerning the flows of transboundary rivers and to ensure data coherence at the river basin level. In spite of these precautions, the accuracy, reliability and frequency with which information is collected vary considerably by region, country and category of information. Information is completed using models when necessary.

Regional and global level aggregations are done using simple summation. Total water use is divided by total renewable water resources for the region or globe.

AQUASTAT data on water resources and use are published every three years in the United Nations World Water Development Report, or when new information becomes available on the FAO-AQUASTAT website at http://www.fao.org/nr/aquastat.

SUPPLEMENTARY INFORMATION



EXAMPLES



REFERENCES

FOOD AND AGRICULTURAL ORGANIZATION OF THE UNITED NATIONS. AQUASTAT. FAO's Global Information System on Water and Agriculture. Rome. Website http://www.fao.org/nr/aquastat.

The following resources of specific interest to this indicator are available on this site:
AMIT KOHLI, KAREN FRENKEN, CECILIA SPOTTORNO (2012) “Disambiguation of water statistics”, available at http://www.fao.org/nr/water/aquastat/catalogues/Water_Terminology_20120523.pdf.

WORLD WATER ASSESSMENT PROGRAMME. The United Nations World Water Development Report (WWDR) . Paris: United Nations Educational, Scientific and Cultural Organization, and London: Earthscan. Available from http://www.unesco.org/new/en/natural-sciences/environment/water/wwap/wwdr/

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