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| Lake name: | Mondego (St2-Euhaline) | Country: | Portugal | GIG Region: | NEA |
|---|---|---|---|---|---|
| GIG Type: | TW | Site code: | ---- | Altitude(m a.s.l.): | ---- |
| Area (km²): | 8.6 | Mean depth (m): | 2-10 | Mixing regime: | ---- |
| Alkalinity (m eq/l): | ---- | Retention time (days): | 2-5 | Chlorophyll a (µg/l): | ---- |
| Total phosphorus (µg/l): | ---- | Eutrophication status: | NOx 1 - POx 1 | Hydromorphological status: | 3 - High |
Description
The Mondego estuary is a transitional water body, located on the south eastern Atlantic coast of Europe near Figueira da Foz. This is a touristic city, with 30,000 inhabitants' (doubling the population during summer), surrounded by the sea, the river and forested hills. The Mondego estuary is a warm-temperate polyhaline and mesotidal system, with an annual average river flow of 79 m3s-1. The north arm is 21 km long, with an area of 5.87 km2 (20% intertidal), and a 2 days' residence time. The south arm is 7 km long, with an area of 2.71 km2 (70% intertidal), and a residence time of more than 5 days. Average depth at high tide varies between 2 and 10 m. Concerning the bottom, the small-sized sediment particles (clay and silt) and higher organic matter content dominate at the inner areas of the south arm, with coarse sand sediments being found mostly in the north arm.
The main activities found at the lower estuary are shipping activities (fishing and mercantile harbours), shipyard and other small industries, fish farming, salt production and tourism. The upper part of the estuary is inserted in a flat and low altitude alluvium area, intensively used for agriculture production (mainly rice, maize and vegetables). Due to this use, nutrients constitute an important pressure on the estuary which, in addition to modifications on the topography of the river bed and the hydrodynamics of the system, stimulated the eutrophication symptoms that were observed in the past (1990s) at the south arm. Presently, the main pressures along the Mondego estuary are: (i) high temporal and spatial variability in salinity (natural), (ii) nutrients and organic matter enrichment (anthropogenic); and (iii) harbours and dredging in downstream areas.
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