Spain has a land area of 505,950 km2 and a population (1986) of 39.0 million. It is bounded on Portugal to the west and by France to the north. The eight largest Spanish river systems drain approximately 362,000 km2 or 72 per cent of the total land area. The Miño, the Duero, the Tajo, and the Guadiana rivers run from east to west either through or as a boundary river to Portugal before discharging into the Atlantic; the Guadalquivir also discharges into the Atlantic, while the Segura, the Júcar and the Ebro run from west to east and discharge into the Mediterranean. There are only a few big natural lakes in Spain and a modest number of small alpine lakes in the Pyrenees and the other mountain ranges. The greater part of the land area lacks natural lakes, although estuarian wetlands are of great ecological importance. Spain has, however, many reservoirs. On nearly all large rivers reservoirs have been constructed. Spain has around 1,000 large reservoirs with a surface area exceeding 8 km2. The coastline of the Spanish mainland is around 3,900 km long, 20 per cent bordering on the Bay of Biscay, 30 per cent bordering on the Atlantic Ocean and the remaining half bordering on the Mediterranean.

Monitoring of inland waters

Spain is divided into ten hydrometric areas. Seven hydrometric areas are situated at the large river systems of the Duero, the Tajo, the Guadiana, the Guadalquivir, the Segura, the Júcar and the Ebro and three areas consist of several smaller river systems. The administration, control and surveillance of water quality are under the responsibility of the Water Commissioner within the different hydrographic areas.

Spain has a long tradition for national assessment of the chemical and physical quality of surface water (primarily rivers). In 1962 La Dirección General de Obras Hidráulicas (the Executive for Water Works) established a water quality monitoring network (Red COCA/R1) based on 50 sampling sites at which 18 variables were measured monthly.

In 1972 the monitoring network increased by 221 sampling sites. The chemical analyses of water samples are undertaken by los Laboratorios de las Comisarías de Aguas (the laboratories of the Water Commission). In 1979 la Sección de Control Analítico de las Aguas de la Comisaría Central de Aguas (Central Commission for Water, Department for Analytical Water Control) was established with a view to analyzing the results from the monitoring network, and the results are stored in a database in la Secretaría General Técnica del Ministerio (the Department for Data Management).

In 1981-82, a revision of the monitoring programme was conducted resulting in coordination and harmonization of the work undertaken by the various institutions co-operating in the monitoring programme. The sampling sites were classified into three groups: special sites, preference sites and basic sites and the sampling frequency was regulated according to the importance of the sampling sites and based on former water quality results.

Reporting of information and data storage

Since 1972/73 the Ministry of Public Works, Transportation and Environment (Ministerio de Obras Públicas Transportes y Medio Ambiente (MOPTMA)) annually edit a statistic yearbook (anuario estadístico) with the results of the analyses from all the hydrographical areas. The results of the analysis are stored in a database kept by the Dirección General de Calidad de las Aguas del MOPTMA.

Network and variables measured

In 1994 the network consisted of 448 sampling sites in 226 rivers and 55 river systems. About 60 per cent of the sampling sites are located in the five largest river systems. More than 70 per cent of the sampling sites have catchment areas greater than 500 km2. Monthly sampling for basic variables such as temperature, pH, and organic pollution indicators, are performed at 75 per cent of the sampling sites, while samples for analysis of nutrients, specific ions (Na, Ca, K, etc.), heavy metals and organic micropollutants generally are collected less frequent. These variables are, however, determined at monthly intervals on 25-30 percent of the sampling sites.

Biological monitoring of river water quality

In 1980 the Centro de Estudios y Experimentación de Obras Publicas (CEDEX) del MOPTMA initiated a biological monitoring and classification programme (ES-R2) including all main Spanish rivers. A total of 847 sampling sites are classified according to macroinvertebrate indices. Sampling is made four times annually and water quality maps are drawn annually.

Table 3.13: Spanish national surface water monitoring programmes.

No. Name Responsible institution Variables Period of operation & Sampling Frequency SF Geographical
Data & national
Rivers and streams
ES-R1 Assessment of physico-chemical river quality MOPTMA Chemical and physical variables Since 1962
SF: 1-12/yr
448 sampling sites in all main Spanish rivers
Database: MOPTMA
Reporting annually
ES-R2 Biological classification of river water quality MOPTMA
Macroinvertebrates Since 1980
SF: 4/yr
847 sampling sites in all main Spanish rivers.
160 sites/yr
Database: MOPTMA
Reporting annually
Lakes and reservoirs
ES-L1 National survey on eutrophication in reservoirs MOPTMA
Physical, chemical and biological variables Since 1972

SF: 4/yr

350 reservoirs
Database: MOPTMA
Reporting annually
ES-L2 National survey on eutrophication in reservoirs by remote sensing MOPTMA
Temperature, transparency, chlorophyll Since 1984
SF: 4/yr in summer
496 reservoirs, 1 river basin each year
Database: MOPTMA
Reporting annually

MOPTMA: Ministerio de Obras Públicas e Urbanismo, Dirección General de Obras Hidráulicas; CEDEX: Centro de Estudios y Experimentaciónde Obras Públicas del MOPTMA.

Lakes and reservoirs

Some reservoirs are monitored according to the R1 programme, but no specific lacustrine monitoring programme exists. A national survey on eutrophication in 350 reservoirs (ES-L1) was initiated by the CEDEX in 1972, recording physical, chemical and biological variables. Furthermore, 496 reservoirs have been surveyed by remote sensing since 1986 (ES-L2) and data on temperature, transparency and chlorophyll have been recorded. Sampling frequencies in both programmes are four times a year.

Marine waters

No information about monitoring of marine areas has been reported by Spain. Spain participates in the Mediterranean Pollution Monitoring and Research Programme (MED POL/UNEP), both in the monitoring of coastal waters and in related research activities.


Geographic coverage


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Filed under: surface water
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