Title: Land and Water Development Division Water Resources, Development and Management Service
1Land and Water Development DivisionWater
Resources, Development and Management Service
AQUASTAT
Key water resources statistics
by Karen FRENKEN
International Work Session on Water Statistics,
Vienna, Austria, 20-22 June 2005
2Water resources
Review of world water resources by country
- Internal, external surface water and groundwater
- Country dependency on water from other countries
- Flows reserved by treaties
- Calculation spreadsheets with rules and
guidelines for accounting water resources - Regional overviews of the water resource situation
3Key words
- Presents country-level information
- Deals with renewable water resources
- Concentrates on the physical assessment of
internal and external renewable water resources - Presents of picture of the natural state and
current situation, taking into account existing
uses of water - Combines field-based approaches with modeling
approaches
4Renewable water resources
- Internal Renewable Water Resources (IRWR)
- External Renewable Water resources (ERWR)
- Natural Renewable Water Resources (NRWR)
- Actual Renewable Water Resources (ARWR)
- Exploitable Water Resources
5Internal Renewable Water Resources
IRWR R I (QOUT QIN) R Surface
runoff, generated from endogenous
precipitation I Groundwater recharge,
generated from endogenous precipitation QOUT
Groundwater drainage into rivers (typically,
baseflow of rivers) QIN Seepage from rivers
into aquifers A simple addition of surface water
and groundwater would lead to an overestimation
of the renewable water resources. (Qout Qin),
called Overlap, is the exchange between surface
water and groundwater or the common part of
surface water and groundwater. Humid countries O
? Very arid and coastal areas O ?
6Internal renewable water resourcesin theNile
Basin
7External Renewable Water Resources
ERWRNATURAL SWIN SWPR SWPL
GWIN ERWRACTUAL SW1IN SW2IN SWPR SWPL
SWOUT GWIN SW1IN Surface water entering the
country which is not submitted to treaties SW2IN
Surface water entering the country, which is
secured through treaties SWPR Accounted flow
of border rivers SWPL Accounted part of
shared lakes SWOUT Surface water leaving
country, reserved by treaties for downstream
countries GWIN Groundwater entering the
countries Actual ERWR may vary with
time. Established rules to compute the different
components of the external water resources
8Total Renewable Water Resources
TRWRNATURAL IRWR ERWRNATURAL
TRWRACTUAL IRWR ERWRACTUAL While IRWR can
be added up, TRWR can not
9Dependency ratio
Dependency ratio IRWR/(IRWRIWR)x100 IWR
SW1IN SW2IN SWPR SWPL GWIN SW1IN
Surface water entering the country which is not
submitted to treaties SW2IN Surface water
entering the country, which is secured through
treaties SWPR Accounted flow of border
rivers SWPL Accounted part of shared
lakes GWIN Groundwater entering the
countries The dependency ratio does not consider
possible allocation of water to downstream
countries Indicator varies theoretically between
0 and 100 percent
10(No Transcript)
11Matrix of transboundary flows
12The potential of models
- Relying on country information alone does not
ensure consistency between countries - A model, using available information, presents a
homogenous methodology for computing the water
balance across a continent - The model developed is simple and performed
entirely within the GIS environment - It has been tested on Africa and will next be
used on Asia - Combined use of country-based data and global
water-balance modeling can enhance the overall
reliability of the results
13Assessment of the resultsreflections
14Country information
- Critical analysis is necessary to ensure
consistency between different data collected - Gathering data from different sources highlights
similarities, but also contradictions - Little information available on humid Africa
- Many studies done on arid climates, but access to
information is sometimes restricted for strategic
reasons - No consistency can be ensured at regional level
on period of reference, duration, etc.
15Natural water resources
- Hydrological approach (measurements,
extrapolation, modeling) is not perfect. Natural
versus actual upstream versus downstream - Metadata needed on methods used, validity of
results, etc. - Time reference problem (reference period,
frequency of occurrence) - Spatial reference problem (maps, region, country,
basin) - Water quality problem (definition, classes,
changes during flow)
16Exploitable water resources
Natural resources are quantified exclusively on a
hydrological basis, which is necessary. However,
not all natural water is accessible. Need to
quantify exploitable or manageable water
resources as a function of
- technical-economic criteria affordable cost of
development and exploitation - Environmental criteria exclusion of water that
needs to be conserved for nature - geopolitical criteria sharing of water between
countries
Minimum of consensus between the countries of
each large region in the world needed in order to
have water statistics that are comparable and
respond better to the demands
17Secondary and non-conventional sources of water
- Secondary resources refers to return of primary
water into the system, thus becoming available
for use again. It is the interaction between
resource and use in a same area without
increasing the natural resource. Example
agricultural drainage water - Wastewater reuse refers to the reuse of urban or
industrial wastewater (with or without
treatment), increasing the overall efficiency of
use of water (extracted from primary sources) - Desalinized water refers to the production of
freshwater by desalinization of brackish water or
saltwater - Inter-basin water transfer, transporting water
between different river basins. Examples
Highlands water project in Southern Africa,
importation of water in Israel from Turkey
18Concluding remarks
Adaptation of water statistics to information
needs should be well targeted. Always ask
question for whom and for what use they are
intended
It is advisable to regionalize the efforts to
improve water statistics as a function of the
needs, which are far from uniform in the world
19Thank you
Web site http//www.fao.org/ag/aquastat