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The Po ( , ; la, Padus or ; grc, Πάδος, Pádos, or , ; Ancient Ligurian: or ) is the longest river in Italy. It is a river that flows eastward across northern
Italy Italy ( it, Italia ), officially the Italian Republic ( it, Repubblica Italiana, links=no ), is a country consisting of a Northern Italy, continental part, delimited by the Alps, a Italian Peninsula, peninsula and List of islands of Italy, se ...
starting from the Cottian Alps. The Po flows either or – considering the length of the Maira, a right bank tributary. The headwaters of the Po are a spring seeping from a stony hillside at Pian del Re, a flat place at the head of the Val Po under the northwest face of Monviso. The Po then extends along the
45th parallel north
45th parallel north
before ending at a delta projecting into the
Adriatic Sea The Adriatic Sea () is a body of water separating the Italian Peninsula from the Balkans. The Adriatic is the northernmost arm of the Mediterranean Sea, extending from the Strait of Otranto (where it connects to the Ionian Sea) to the northwest a ...
near
Venice Venice ( ; it, Venezia ; vec, Venesia or ) is a city in northeastern Italy Italy ( it, Italia ), officially the Italian Republic ( it, Repubblica Italiana, links=no ), is a country consisting of a Northern Italy, continental part, del ...
. It is characterized by its large discharge (several rivers over 1,000 km have a discharge inferior or equal to the Po). As a result of its characteristics, the river is subject to heavy flooding. Consequently, over half its length is controlled with , levees. The river flows through many important Italian cities, including
Turin Turin ( , Piedmontese language, Piedmontese: ; it, Torino ; lat, Augusta Taurinorum, then ''Taurinum'') is a city and an important business and cultural centre in northern Italy. It is the capital city of Piedmont and of the Metropolitan City ...
,
Piacenza Piacenza (; egl, label= Piacentino, Piaṡëinsa ; ) is a city A city is a large human settlement.Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The Social Science Encyclo ...
,
Cremona Cremona (, also ; ; lmo, label=Cremunés, Cremùna; egl, Carmona) is a city and ''comune'' in northern Italy, situated in Lombardy, on the left bank of the Po (river), Po river in the middle of the ''Pianura Padana'' (Po Valley). It is the capit ...
and
Ferrara Ferrara (, ; egl, Fràra ) is a city and ''comune'' in Emilia-Romagna, northern Italy, capital of the Province of Ferrara. it had 132,009 inhabitants. It is situated northeast of Bologna, on the Po di Volano, a branch channel of the main stream ...
. It is connected to
Milan Milan (, , Milanese: ; it, Milano ) is a city in northern Italy, capital of Lombardy, and the second-most populous city in Italy after Rome. Milan served as the capital of the Western Roman Empire, the Duchy of Milan and the Kingdom of Lomb ...
through a net of channels called ''navigli'', which Leonardo da Vinci helped design. Near the end of its course, it creates a wide river delta, delta (with hundreds of small channels and five main ones, called ''Po di Maestra'', ''Po della Pila'', ''Po delle Tolle'', ''Po di Gnocca'' and ''Po di Goro'') at the southern part of which is Comacchio, an area famous for eels. The Po valley was the territory of Roman Cisalpine Gaul, divided into Cispadane Gaul (south of the Po) and Transpadane Gaul (north of the Po).


Geography

The Po has a drainage area of 74,000 km2 in all, 70,000 of those being in Italy, of which 41,000 is in montane environments and 29,000 on the plain. The slope of the Po's river valley decreases from 0.35% in the west to 0.14% in the east, a low gradient. Along its path lie 450 standing lakes.Almost all of the rest of the non-Italy basin is in the Italian speaking Ticino (Tessin) canton in Switzerland, and the outlying extreme south western section (again, Italian speaking) of Grigioni (Graubunden) canton lying to the south of the San Bernardino pass which forms the Po's watershed with the Posterior Rhine. The major tributary in question is the northern source half of the eponymous Ticino river (fed by its Moesa tributary in Grigioni) and the top third of the Alpine lake, Maggiore, formed by it. (The southern two thirds of Lake Maggiore and the southern half of the continuing Ticino River tributary are in Italian territory). A minute section of the Po basin belongs to France in the Valle Etroite (literally, the Narrow Valley) running from Mont Thabor to the Italian ski resort of Bardonecchia. Valle Etroite is so remote it is essentially administered by Italy (telephone network, rubbish collections etc.). Further minuscule parts of the Po's basin (measurable in the hundreds of metres of linear distance) within France are found in the form of small streamheads forced into France by the 1947 post war Peace Treaty of Paris as a punitive measure against Italy. These can be found on the Mont Cenis and Mongenevre passes. The former contains a reservoir dammed at the Po end and so technically constitutes part of its basin, although it contributes little to the water flow as the water is, by definition, retained by the dam. The Po is the longest river in Italy; at its widest point its width is .


Po Valley

The vast valley around the Po is called the Po Basin or Po Valley (Italian ''Pianura Padana'' or ''Val Padana''); in time it became the main industrial area of the country. In 2002, more than 16 million people lived there, at the time nearly ⅓ of the population of Italy. The two main economic uses of the valley are for industry and for agriculture, both major uses. The industrial centres, such as
Turin Turin ( , Piedmontese language, Piedmontese: ; it, Torino ; lat, Augusta Taurinorum, then ''Taurinum'') is a city and an important business and cultural centre in northern Italy. It is the capital city of Piedmont and of the Metropolitan City ...
and Milan, are located on higher terrain, away from the river. They rely for power on the numerous hydroelectric stations in or on the flanks of the Alps, and on the coal/oil power stations which use the water of the Po basin as coolant. Drainage from the north is mediated through several large, scenic lakes. The streams are now controlled by so many dams as to slow the river's sedimentation rate, causing geologic problems. The expansive, moist and fertile flood plain is reserved mainly for agriculture and is subject to flash floods, even though the overall quantity of water is lower than in the past and lower than demand. The main products of the farms around the river are cereals including – unusually for Europe – rice, which requires heavy irrigation. The latter method is the chief consumer of surface water, while industrial and human consumption use underground water.


Tributaries

The Po has 141 tributary, tributaries. They include (R on the right bank, L on the left, looking wikt:downstream, downstream): * Pellice (L) * Varaita (R) * Maira (R) * Chisola (L) * Sangone (torrent), Sangone (L) * Dora Riparia (L) * Stura di Lanzo (L) * Malone (river), Malone (L) * Orco (L) * Dora Baltea (L) * Stura del Monferrato (R) * Sesia (L) * Rotaldo (R) * Grana del Monferrato (R) * Tanaro (R) * Scrivia (R) * Agogna (L) * Curone (R) * Staffora (R) * Ticino (river), Ticino (L) * Versa (Po), Versa (R) * Tidone (R) * Lambro (L) * Trebbia (R) * Nure (R) * Adda (river), Adda (L) * Arda (Italy), Arda (R) * Taro (river), Taro (R) * Parma (river), Parma (R) * Enza (R) * Crostolo (R) * Oglio (L) * Mincio (L) * Secchia (R) * Panaro (river), Panaro (R) The Reno (river), Reno (R) was a tributary of the Po until the middle of the eighteenth century when the course was diverted to lessen the risk of devastating floods. The Tanaro is about 50 km (31 mi) longer than the upper Po at their confluence near Alessandria.


Po Delta


Protected areas

The Po Delta wetlands have been protected by the institution of two regional parks in the Regions of Italy, regions in which it is situated: Veneto and Emilia-Romagna. The Po Delta Regional Park in Emilia-Romagna, the largest, consists of four parcels of land on the right bank of the Po and to the south. Created by law in 1988, it was managed by a consortium, the ''Consorzio per la gestione del Parco'', to which
Ferrara Ferrara (, ; egl, Fràra ) is a city and ''comune'' in Emilia-Romagna, northern Italy, capital of the Province of Ferrara. it had 132,009 inhabitants. It is situated northeast of Bologna, on the Po di Volano, a branch channel of the main stream ...
and Ravenna provinces belong as well as nine comune, comuni: Comacchio, Argenta, Emilia–Romagna, Argenta, Ostellato, Goro, Emilia–Romagna, Goro, Mesola, Codigoro, Ravenna, Alfonsine, and Cervia. Executive authority resided in an assembly of the presidents of the provinces, the mayors of the comuni and the board of directors. They employed a Technical-Scientific Committee and a Park Council to carry out directives. In 1999 the park was designated a World Heritage Site by UNESCO and was added to "Ferrara, City of the Renaissance, and its Po Delta." From 2012 the park is managed by the ''Ente di Gestione per i Parchi e la Biodiversità - Delta del Po'', composed by the ''comuni'' of Alfonsine, Argenta, Cervia, Codigoro, Comacchio, Goro, Mesola, Ostellato and Ravenna. The of the park contain wetlands, forest, dunes and salt pans. It has a high biodiversity, with 1000–1100 plant species and 374 vertebrate species, of which 300 are birds.


The active delta

The most recent part of the delta, which projects into the Adriatic between Chioggia and Comacchio, contains channels that actually connect to the Adriatic and on that account is called the active delta by the park authorities, as opposed to the fossil delta, which contains channels that no longer connect the Po to the Adriatic (but once did). The active delta was created in 1604 when the city of
Venice Venice ( ; it, Venezia ; vec, Venesia or ) is a city in northeastern Italy Italy ( it, Italia ), officially the Italian Republic ( it, Repubblica Italiana, links=no ), is a country consisting of a Northern Italy, continental part, del ...
diverted the main stream, the ''Po grande'' or ''Po di Venezia'', from its channel north of Porto Viro to the south of Porto Viro in a channel then called the ''Taglio di Porto Viro'', "Porto Viro cut-off". Their intent was to stop the gradual migration of the Po toward the lagoon of Venice, which would have filled up with sediment had contact been made. The subsequent town of Taglio di Po grew around the diversionary works. The lock of ''Volta Grimana'' blocked the old channel, now the ''Po di Levante'', which flows to the Adriatic through Porto Levante. Below ''Taglio di Po'' the ''Parco Regionale Veneto'', one of the tracts under the authority of the ''Parco Delta del Po'', contains the latest branches of the Po. The ''Po di Gnocca'' branches to the south followed by the ''Po di Maestra'' to the north at Porto Tolle. At Tolle downstream the ''Po di Venezia'' divides into the ''Po delle Tolle'' to the south and the ''Po della Pila'' to the north. The former exits at Bonelli. The latter divides again at Pila into the ''Busa di Tramontana'' to the north and the ''Busa di Scirocco'' to the south, while the mainstream, the ''Busa Dritta'', enters ''Punta Maistra'' and exits finally past Pila lighthouse. Despite the park administration's definition of the active delta as beginning at Porto Viro, there is another active channel upstream from it at Santa Maria in Punta, where the ''Fiume Po'' divides into the ''Po di Goro'' and the ''Po di Venezia''.


The fossil delta

The fossil Po is the region of no longer active channels from the Po to the sea. It begins upstream from
Ferrara Ferrara (, ; egl, Fràra ) is a city and ''comune'' in Emilia-Romagna, northern Italy, capital of the Province of Ferrara. it had 132,009 inhabitants. It is situated northeast of Bologna, on the Po di Volano, a branch channel of the main stream ...
. The ''Fiume Po'' currently flowing to the north of Ferrara is actually the result of a diversion at Ficarolo in 1152 made in the hope of relieving flooding in the vicinity of Ravenna. The diversion channel was at first called the ''Po di Ficarolo''. The ''Fiume Po'' before then followed the ''Po di Volano'', no longer connected to the Po, which ran to the south of Ferrara and exited near Volano. In Roman times it did not exit there but ran to the south as the ''Padus Vetus'' ("old Po") exiting near Comacchio, from which split the ''Po di Primaro'' exiting close to Ravenna. Before 1152 the seaward extension of today's delta, about , did not exist. The entire region from Ravenna to Chioggia was dense swamps, explaining why the Via Aemilia was constructed between Rimini and
Piacenza Piacenza (; egl, label= Piacentino, Piaṡëinsa ; ) is a city A city is a large human settlement.Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The Social Science Encyclo ...
and did not begin further north.


Geologic history

The Mediterranean Basin#Geology and paleoclimatology, Mediterranean Basin is a depression in the Earth's crust caused by the African Plate slipping under the Eurasian Plate. Typically in geologic history the depression is filled with sea water under various geologic names such as Tethys Sea. In the last period of the Miocene Epoch, the Messinian (7–5 mya (unit), mya), the Messinian salinity crisis, a near drying of the Mediterranean, was caused by the sea level dropping below the sill at the Strait of Gibraltar and the wikt:equilibrium, equilibrium between evaporation and replenishment shifting in favor of evaporation. At that time the Po Valley and the Adriatic Sea, Adriatic depression were a single canyon system thousands of feet deep. On the southwest the Apennine Mountains#Geology, Apennine Mountains bordered a land mass termed Tyrrhenis geologically. Their orogeny was just being completed in the Miocene. On the north the Alpine Orogeny had already created the Alps#Geology and orogeny, Alps. At the end of the Messinian the ocean broke through the sill and the Mediterranean refilled. The Adriatic transgressed into all of northern Italy. In the subsequent Pliocene sedimentary outwash primarily from the Apennines filled the valley and the central Adriatic generally to a depth of to but from to off the current mouth of the Po, with pockets as deep as . At the start of the Pleistocene the valley was full. Cycles of transgression (geology), transgression and regression are detectable in the valley and the Adriatic as far as its centre and in the southern Adriatic. From the Pleistocene alternation of maritime and alluvial sediments occur as far west as
Piacenza Piacenza (; egl, label= Piacentino, Piaṡëinsa ; ) is a city A city is a large human settlement.Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The Social Science Encyclo ...
. The exact sequences at various locations have been studied extensively. Apparently the sea advanced and receded over the valley in conformance to an equilibrium between sedimentation and glacial advance or recession at 100,000-year intervals and to fluctuation of sea level. An advance began after the Last Glacial Maximum around 20,000 years ago, which brought the Adriatic to a high point at about 5500 years ago. Since then the Po River delta, delta had been progradation, prograding. The rate of coastal zone progradation between 1000 BC and 1200 AD was 4 m/yr. Human factors, however, brought about a change in the equilibrium in the mid-20th century with the result that the entire coastline of the northern Adriatic is now degrading.
Venice Venice ( ; it, Venezia ; vec, Venesia or ) is a city in northeastern Italy Italy ( it, Italia ), officially the Italian Republic ( it, Repubblica Italiana, links=no ), is a country consisting of a Northern Italy, continental part, del ...
, which was originally built on islands off the coast, is most at risk due to subsidence, but the effect is realized in the Po delta as well. The causes are first a decrease in the sedimentation rate due to the locking of sediment behind hydroelectric dams and the deliberate excavation of sand from rivers for industrial purposes. Second, agricultural use of the river is heavy; during peak consumption the flow in places nearly dries up, causing local contention. As a result of decreased flow salt water is intruding into the aquifers and coastal ground water. Eutrophication in standing waters and streams of low flow is on the increase. The valley is subsiding due to the removal of ground water.


Human Impacts


Pollution

Always prone to fog, the valley is subject to heavy smog due to industrial atmospheric emissions, especially from
Turin Turin ( , Piedmontese language, Piedmontese: ; it, Torino ; lat, Augusta Taurinorum, then ''Taurinum'') is a city and an important business and cultural centre in northern Italy. It is the capital city of Piedmont and of the Metropolitan City ...
. The city of Milan had no sewage treatment plant(s). Sewage went through channels directly into the Po, for which the European Environment Agency cited the city. Since 2005, all sewage from Milan is treated in plants at Nosedo, San Rocco and Peschiera Borromeo. These treat the sewage from over 2.5 million inhabitants. In 2005, water from the Po was found to contain much benzoylecgonine, excretion, passed by cocaine users in urine. Based on these figures, cocaine consumption was estimated to be about 4 kg daily, or 27 doses per day per thousand young adults in the drainage basin – nearly three times higher than estimated. On February 24, 2010 the Po was contaminated by an Lambro#Pollution, oil spill coming from a refinery in Villasanta through the Lambro, the Agenzia Nazionale Stampa Associata news agency has estimated it to be about 600,000 liters.


Water resource management

Until 1989 water resources were administered regionally or locally. The major authority on the lower Po was the ''Magistrato alle Acque di Venezia'', first formed in the 16th-century Republic of Venice. It made all the decisions concerning the diversion of the lower river. Most part of the delta is still in Veneto. In 1907 under the Italy, Kingdom of Italy the agency became the ''Magistrato alle Acque'' and took responsibility for all the water resources in northeastern Italy. Currently it is a decentralized institution of the Ministry of Public Works, headed by a chairman appointed by the Head of State and the Council of Ministers. Its headquarters are in Venice. Its domain is the management and protection of the water system in Veneto, Mantua, Trento, Bolzano and Friuli-Venezia Giulia. In 1989 in response to the major geologic problems that were developing along the river Law no. 183/89 was passed authorizing The Po Basin Water Board (Autorità di bacino del fiume Po), which would direct operations concerning all the water resources in the Po basin (see under Po Valley). Its headquarters have been in Parma since its inception in 1990. It considers itself a synergy among all the institutions concerned with the preservation and development of the Po basin. It is administered by officials chosen from the administrations of the constituent regions and provinces. In 2009 the water board began its Integrated River Basin Management Plan to meet the European Union (EU) Water Framework Directive, 2000/60/EC. This takes in water management and flood risk plans antecedent. Between 2009 and 2015 the Po Valley Project (the implementation of the plan) took more than 60 measures, notably to: heighten and strengthen levees, increase flood-meadows, resume natural sediment transport and deposition points, enlarge wetlands, afforest, re-nature, promote biodiversity and recreational use.


Dams

At the village of Isola Serafini in the comune of Monticelli d'Ongina, Piacenza Province, downstream from Piacenza, a long, high gate dam featuring eleven openings gated by vertical lift gates, crosses the Po. Nine gates are high and two are high for sediment-scouring purposes. A spillway to the right passes through a hydroelectric station of 4 generators of 76 MW each operated by a head of water. The spillway connects to a diversionary canal subtending a loop of the Po. A ship lock long and wide next to the station passes some traffic through the canal, but above the dam traffic is mainly barges. The average flow at the dam is 854 m3/s, with a 12,800 m3/s maximum.


Cultural history

The Po is first certainly identified in the Graeco-Roman historians and geographers of the late Roman Republic and the early Roman Empire, long after the valley had been occupied successively by prehistoric and historic peoples: Ligures, Etruscans, Celts, Adriatic Veneti, Veneti, Umbri, and Romans. At that late date the ancient authors were attempting to explain the provenance of the name. Perhaps the earliest of these, Polybius (2nd century BC), uses ''Pados'' (in Greek) and says that it was to be identified with the ''Eridanos'' of the poets. Moreover, the country people call it ''Bodencus''. This implies that a "country" population either remained from prehistoric times or adopted the name in use by that substrate. The name has been segmented as ''Bod-encus'' or ''Bod-incus'', the suffix being characteristic of the ancient Ligurian language (ancient), Ligurian language of northern Italy, southern France, Prehistory of Corsica#Ligurian hypothesis, Corsica and elsewhere. Pliny the Elder has the most to say about the ''Padus'' of his times. Herodotus had expressed doubt concerning the existence of a river in Europe, ''Eridanos'', which flowed into the northern sea, he said, from which amber came. He believed it was a Greek name (there are other Eridanos rivers in Greece), "invented by some poet," but makes no conjectures as to where it might be. Pliny points out that in his own time the Eridanos had become wrongly identified with the ''Padus''. He does not know when or how, but like Herodotus he blames the poets.''Natural History (Pliny), Historia Naturalis'', Book 37, Chapter 11. Amber is supposed to have come from there. Phaethon, Phaëthon, son of the sun, struck by lightning changed into poplars and exuded tears every year, which is the source of amber (a myth of Pausanias (geographer), Pausanias). Expressing surprise at the ignorance of the poets, Pliny says "There can be no doubt that amber is the product of the islands of the northern ocean (Baltic Sea)" and attributes its introduction into the Po valley to the Adriatic Veneti, Veneti, the last link in a trade route to the north through Pannonia and Germany. Pliny (''Hist. Nat.'', iii. 122) also gives the Ligurian name of the Po as ''Bodincus'', which he translates as "bottomless". The root ''bod-'' has been generally analyzed as containing the Proto-Indo-European language, PIE base *''bhu(n)d(h)''- seen in Sanskrit ''budhnah'' and Avestan language, Avestan ''buna''- "bottom", Greek language, Greek ''pythmen'' "foundation", Latin ''fundus'' "bottom", Old Irish ''bond'' "sole of the foot". The word ''Bodincus'' appears in the toponym, place name Bodincomagus, a Ligures, Ligurian town on the right bank of the Po downstream from today's Turin. The Po, along with other rivers in northern Italy, was the scene of numerous military episodes throughout the Middle Ages and all the major cities and coastal lordships were equipped with real river fleets.


Mythology

The Po is often identified with the Eridanos (river of Hades), Eridanos or Eridanus river of Greek mythology. This mythical river is the namesake of the Eridanus (constellation), constellation Eridanus.


See also

* Lunghin Pass (triple watershed: Po-Rhine-Danube) * Witenwasserenstock (triple watershed: Rhone-Rhine-Po)


References


External links

* * {{Authority control Po (river), Po basin, Waterways of Italy Rivers of the Province of Cuneo Rivers of the Province of Turin Rivers of the Province of Vercelli Rivers of the Province of Alessandria Rivers of the Province of Pavia Rivers of the Province of Lodi Rivers of the Province of Cremona Rivers of the Province of Mantua Rivers of the Province of Piacenza Rivers of the Province of Parma Rivers of the Province of Reggio Emilia Rivers of the Province of Ferrara Rivers of the Province of Rovigo Rivers of Italy Braided rivers in Italy