DIS4ME DIS4ME Homepage | DESERTLINKS Homepage | © DESERTLINKS 2004
English-EN | Español-ES | Italiano-I | Ελληνικά-GR | Portuguese-PT
Desertification Indicator System for Mediterranean Europe


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

Type of Indicator State

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