Guadiana River Estuary is located in the southeast of Portugal and makes a border between Portugal and Spain. The geographical coordinates of the south most point on the Portuguese margin are 37º10’ N and 7º24’E.
Guadiana is the one of most important rivers on Iberian Peninsula whose total length is 730 km, of which the last 200 make a natural border between Portugal and Spain. Geologically the drainage basin of 67 000km2 is much diversified. The Guadiana Estury is a mesotidal, narrow funnel-shaped body, well mixed for low, summer (XX m3/sec) discharges, but vertically stratified in winter. The mixing zone is within the first 10 kms from mouth but brackish conditions may extend 40 km inland. Winter discharges delivers vital nutrients to shelf sea . More than 40 dams store water mostly for irrigation purposes (mostly in Spain) and decrease severely the water flow. The closing of the Alqueva dam—the largest artificial lake in Europe, with an area of 250 km²—in the Guadiana drainage basin, in Southern Portugal, will affect the river hydrology, by reducing the freshwater input and its inherent characteristics, and will influence the ecology of the estuary and nearby coastal waters. causing eutrophication and sediment starvation along the coast. Forestry and agriculture are the principal activities in the Portuguese part of drainage basin. Industrial pollution is not important in the estuarine area. Domestic sewage discharge at present is important due to the legal halt of water treatment plant constructed in the ecologically sensitive salt-marsh area.
The Human activities on the two margins (East – Spanish, West – Portuguese) of the estuary are at present distributed in an asymmetric way. The real estate development which is much more intense on the Spanish side, added recently, 14 km from the river mouth, a new leisure mega-village named Esuri. Actually Esuri is a small town foreseen mostly for secondary residences, constructed mostly on salt marsh terrains.
The remaining most important activities are paired together with their impacts or with other activities with potential for conflict. I. Agriculture - eutrofication II. Aquaculture - effluents, III. Tourism and recreation – habitat destruction, IV. fisheries – border conflicts, Sewage discharge - water and sediment pollution.
Most recent changes in policies with impacts on the zone :
- Shift from cereal agriculture to the wildlife (birds) sanctuary on Portuguese side of the estuary with subsequent application of NATURA 2000 status
- Construction of major bridge over the estuary which replace the ferryboat transport
- Construction of a jetty which retains most of the drifting sediment on Portuguese side of the estuary