Methodology Used for Comparing Two Locations for the New Lisbon Airport Based on the Impacts on Surface Water - Highway and Urban Environment - page 187

Table 1 Description of the seven characterization indicators for the Ota location
Characterization indicator Description

Catchment impermeabilization (%) 3.5% of the area of the watershed of Ota

River and 25% of the watershed of
the tributary Alvarinho

Length of rivers that are affected (km) Approximately 25 km

Floods Historically flood site; needs huge

constructions to deal with the flood
discharges including one dam

Soil erosion factors Soil uses are not sensitive but there are

steep slopes

Pollution sources Relevant domestic, industrial and

agricultural (arable, cattle and swine)
pollution sources

Water quality and uses Bad water quality reported for the last

10 years. Most frequent parameters
exceeding water quality limits are: total
suspended solids, biochemical oxygen
demand; phosphorus and nitrogen;
faecal coliform . Surface water used for
irrigation

Local availability of water for the airport uses Surface water is not a good source of water

due to its very bad quality

Table 2 Description of the seven characterization indicators for the CTA location
Characterization indicator

Description

Catchment impermeabilization (%) Five percent of the area of the watershed

of Vale Cobrão Stream

Length of rivers that are affected (km) Approximately 26 km

Floods No historical floods reported. Flood

discharge calculations indicate no need
for major constructions to change the
rivers path

Soil erosion factors The factors indicate small soil erosion.

Mild slopes

Pollution sources Only diffuse pollution sources: agriculture

(arable, cattle and sheep)

Water quality and uses Evidences of historical water

eutrophication at a local reservoir, kept
as a reserve for fire combat

Local availability of water for the airport uses Surface water is not a good source of water

due to its scarcity. Groundwater is the
main water source

A Geographical Information System, ArcGis ® , was used to define each water-
shed, therefore allowing different measurements and calculations (e.g., area, perim-
eter and length of the affected rivers).