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1. Definition
| Name |
WATER
QUALITY |
| Brief
definition |
Pollutant loads discharged
above permitted limits including toxic and conventional pollutants
such as soluble salts (NaCl, KCl, etc).
 |
A
river with flowing through a montaneous area with high
quality of water (photo by C. Kosmas) |
|
| Unit of measure |
Specific electrical
conductance (dS m-¹), mmol L-¹ |
| Spatial scale |
|
| Temporal scale |
|
2. Position
within the logical framework DPSIR
3. Target and
political pertinence
| Objective |
Contribution
to the measures to combat desertification due to salinization
of soils. |
| Importance
with respect to desertification |
Poor water
quality leads to land deterioration, population sanitation and
health problems, overall environmental deterioration and thus
contributing to desertification processes. |
| International
Conventions and agreements |
A variety of
legislation as well as EU directives exist. |
| Secondary objectives
of the indicator |
Evaluation
of the best available water management practices in combating
desertification. |
4. Methodological
description and basic definitions
| Definitions
and basic concepts |
The presence of even small
concentrations of salts in irrigation water leads to salt
accumulation in soils unless leached away by rain or irrigation
water. Evaporation from the soil surface and transpiration
from the growing plants removes water but leaves salts in
the soil. The salinization problem is associated with arid
and sem-arid climatic conditions.
The criteria for good
water quality for irrigation are: low salinity or low ratio
of Na+ to Ca2+ + Mg2+
to prevent the development of sodicity; and small concentrations
of those ions which may have specific toxic effects. The index
used most often to characterize the quality of irrigation
water with respect to its infuence on the exchangeable sodium
percentage is the sodium adsorption ratio (SAR) which is defined
as follows:
SAR = [Na+] /{([Ca2+]
+ [Mg2+])/2**(1/2).
This is the ratio of the
sodium ion (Na+) concentration to the square root of the average
concentration of the divalent calcium (Ca2+)
and magnesium (Mg2+) ions. The concentrations
are expressed in mmoles per liter.
High salinity water may
have a direct effect on sensitive crops. Salts may concentrate
in the rootzone leading to crop damage unless salts are leached
away by irrigation water. Further impacts of poor quality
irrigation water are expected if water has high concentrations
of Na+. The major hazard is the reduction in infiltration
rate due to soil structural damage.
|
| Benchmarks
Indication of the values/ranges of value |
Electrical conductivity:
- <0.7 ,
- 0.7-3.0,
- >3.0 dS m-¹
for salinity effects
Sodicity effects are determined
by electrical conductivity and sodium adsorption rate (SAR).
|
| Methods of
measurement |
Determination
of electrical conductivity of water by an electrical conductivity
meter. SAR is measured by chemical analysis using flame photometer
and atomic adsorption meter. |
| Limits of the
indicator |
The most important
limitation of water-related indicators is due to data availability
and quality. This may be caused by inaccurate regional resolution,
time fragmentation, units differences, gaps in data on water
status or difficulties in measuring water quality data. |
| Linkages with
other indicators |
Water
availability, Land use type,
Rainfall, Aridity
index (1), Drainage, Population
density. |
5. Evaluation
of data needs and availability
| Data required
to calculate the indicator |
Electrical
conductivity of water during the irrigation period.
|
| Data sources |
Necessary data
are usually available and accessible. |
| Availability
of data from national and international sources |
Data can be
obtained from national agencies, various regional institutions
involved in collecting and elaborating water related data. |
6. Institutions
that have participated in developing the indicator
| Main institutions
responsible |
Agricultural
University of Athens |
| Other contributing
organizations |
Universities
of Lisbon, Murcia and Basilicata |
7. Additional
information
| Bibliography
|
Rowell D.L.
1995. Soil Science, Methods & Applications. Longman Scientific
& Technical., Longam Group Limited, England |
| Other references |
Frederick, Kenneth, D.,
Major, David and Stakhiv, Eugene Z. 1977. Climate change and
water resources planning criteria, Kluwer Academic Publishers.
Mariño, Miguel
and Simonovic, Slobodan, P. 2001. Integrated Water Resources
Management, IAHS publication no. 272, IAHS press, 2001
Mediterranean Commission
on Sustainable Development (MCSD), 2000. Indicators for the
sustainable development in the Mediterranean region, PlanBlue,URL:
www.planbleu.org
OECD (Organization for
Economic Co-operation and Development) 2001. Environmental
indicators, towards sustainable development, OECD, 2001.
|
| Contacts Name
and address |
Dr. Ch. Karavitis
Agricultural University
of Athens, Laboratory of Soils and Agricultural Chemistry,
Iera Odos 75, Athens 11855, Greece
email: lsos2kok@aua.gr
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