Zadorra

Zadorra
The Zadorra at Armiñon
Location
Country	Spain
Physical characteristics
Source
• location	Basque Mountains
• elevation	1,045 m (3,428 ft)
Mouth
• location	EbroRiver
Length	78.1 km (48.5 mi)
Basin size	1,361.28 km2(525.59 sq mi)
Discharge
• average	14.1 m3/s (500 cu ft/s) (Ibisate, 2004)
Basin features
Progression	Ebro→Balearic Sea

TheZadorrais a river tributary of theEbroin theBasque Countryat the north of theIberian Peninsula.The river flows acrossprovinceÁlavaall along (with the exception of Burgos' exclaveLa Puebla de Arganzón) till it pours into the Ebro nearMiranda de EbroinBurgos' lands. The river's water volume is the largest in Álava, with its basin being the most extensive in the province. Nowadays it provides by means of the Zadorra Reservoir System (comprising reservoirs Uribarri-Ganboa, Urrunaga and Albina) water supply forVitoriaand half of theBasque Autonomous Community.

The river rises in the slopes of theEntziaPlateau at the spring known as Los Corrales (municipality ofSan Millán/Donemiliaga), meandering thereafter across the Alavan Plains to the west (loops aroundAgurain/Salvatierra) past Vitoria by the north, where it takes a turn to the south heading to the Ebro through La Puebla de Arganzón.

Landmarks

• The village and iconic castle ofGebarasit by the river on its middle stage.
• The Zadorra Reservoir System starting in Uribarri-Ganboa (built as of 1947).
• TheBattle of Vitoriatook place on a stretch extending 18 kilometres (11 mi) on the banks of Zadorra from La Puebla de Arganzon to Trespuentes to Mendoza.
• The site of old Basque-Roman townIruña-Veleiais across the river from Trespuentes.

Pollution

The Zadorra is the most important river in Álavaand is also the mostpolluted.It ranks in the top six polluted rivers in the Basque Country.

More than 2,754wastedisposals have been authorised, 1,783 (65%) of which are urban and 960 (35%) of to which are industrial. From the 960 industries 89 of them are subject integrated environmental authorization. Unauthorized waste disposal also must be taken into account for the pollution. Additionally, waste dumped by industries is often more polluted than it should be.

Theoxygenlevels in the Zadorra are below the standards required for thewildlifein the river. The river's situation is also aggravated by the presence of toxins. The level of toxins is above the amount allowed by the European Union. Fifteen wastewater treatment plants have helped stopping the advance of the pollution in the river. The kind of insects that nest in the river are an indicator of the degradation of the Zadorra. Because the insects show in the top of the river what is happening in the bottom of it. In addition, nitrates have appeared in the river, despite the amount of nitrates being low, there should not be any nitrates.

In 2008 theEbro's hydrographic confederation published a report about some of the rivers around the Ebro, including the Zadorra river. The investigation, which measured pollution in the rivers over four years, started in 2004. The report showed that the amount of pollution found in the river was well over the permitted amount. As a result, the municipalities have started some control programmes for the authorization of waste disposal. The control programmes have brought about some reduction in pollution.