Oasi La Valle

Oasi La Valle


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General information

How to reach the park
By train, direct railway line Rome - Terontola - Florence with change at Terontola and stop at Magione; railway line Ancona - Foligno - Terontola with stop at Magione.
By car or regular service bus, Motorway Autostrada A1 - exit tollgate Valdichiana and sliproad to clearway E45 - exit Magione direction San Savino - San Feliciano.

The operators of the Oasi
The Oasi has a visit centre where are a didactic room with a slide projector, TV and video recorder, an exhibition concerning the historic-naturalistic aspects area, a documentary centre of the Lake Trasimeno, which places at disposal naturalistic and scientific texts, a ringing station for birds, an electric boat, a wooden gangway and observatories.
The Lake Trasimeno is the biggest lake of the Italian mainland: at 257,50 metres above sea level it has a surface of about 125 square kilometres, a circumference of 54 kilometres, the surface of the drainage basin is 376 square kilometres, the average depth 4,70 metres with a maximum of ,50 metres. As it is a mainly alluvial lake, these data are subject to variations according to an annual higher or lower rainfall. Oasi_La_Valle_16 The water level's dependance on the seasonal precipitations leads to an increasement of it during the rain periods, while in the aridity period it goes down.
This phenomenon has had heavy consequences on the coastal zones, because during the centuries the frequent floodings or the aridity caused the spread of malaria and therefore depopulation. The various governments, which followed on one another during the centuries, handled the regulation of the waters. Someone thinks that under the Roman emperor Claudius in the zone of San Savino was built a subterranean drain, which did not leave any traces except some coins and digging tools. In order to strengthen this thesis they quote the excerpt by the Greek geographer Strabo (60 B.C. - 20 A.D.), which mentions the Lake Trasimeno among the lakes the waters of which flow to the Tiber. But no other antique historian or geographer mentions the drain before 1422, when Giovanni Antonio Campano told the deeds of Braccio Fortebraccio, ruler of Perugia, speaking explicitly of the fact that Braccio let build an artificial drain partly subterranean, called "La Cava", in the same place and probably with the same course as the Roman one, and all that in so little time that the hypothesis that just the antique drain was restored, is quite probable. Pius II, the author of the Commentarii, telling the journey of Pius II from Perugia to Siena in 1450, spoke of the existence of mills of the Cava, which Braccio had built. In other words Braccio did not just build the drain, but he used its water building mills, of which some were still in function at the beginning of the 20th century. The description of Vestrini in occasion of his inspection at the Lake Trasimeno in 740-41: the drain opens in the locality "La Cava", under the hill of San Savino, between San Savino and San Feliciano. The water from the lake did not arrive from the mouth of the drain, but through a channell, which was 200 feet long and 5 feet wide. The channel was crossed with some palisades, which were interwoven with willows and tendrils in order to avoid the getting out of the fish, the exclusive priviledge of which had the tenants of the lake. Armed guards continually patrolled around the shores to repress smuggling and the sale of fish. The mouth of the drain was 5,5 feet high and 5 feet wide. It had a sluice-gate that could be regolated by a caretaker, who had the key of the shed of the mouth. The water was 5 feet and 4 inches high. The subterranean channel is a brick vault in the rock. It is 1.057 metres long, of which 900 run in a tunnel, while the difference in level of the two ends is 1,44 meters. Under the highest point of the hill it is 37,72 metres deep. At the mouth it is 1,46 metres high and 3 metres wide, while at the outpour it is 1,40 metres high and one metre wide. It has breathers or ventilating shafts that serve in case of burial in order to restore the channel and save the lives of the workers. The ventilating shafts are covered with wooden or brick pyramids with a lateral opening, which opens when necessary. Behind the exit of the tunnel (in the locality of Bottino), the water flows in a 300 feet channel up to the place which is called Forcone. Here was a mill, which was the property of the family Oddi of Perugia, demolished by the R.C.A. (Reverenda Camera Apostolica) in order to evitate the block of the ditch. In the place of the mill was built a kind of tank with many holes to keep the fish and let come out the water. The fish was given to the Oddi as reward for the damage incurred through the demolition of the mill. From the Forcone the water flows for 640 feet up to the first mill, which is about one mile and a half from the channel, then it gushes into the Caina, which gushes into the Nestore, and this into the Tiber.
This is the summary of the report of Vestrini. The popes were always very interested in its efficiency. In 1425, only one year after Braccio's death, was made the expense of 512 florins for the Cava of the lake. In 1482 the pope Sixtus IV made divert the course of the two biggest tributary streams to the Chiana, the Tresa and the Rio Maggiore, because of the flooding caused by the lake water on the coastal zones. But the reduction of the drainage basin aggravated the situation and malaria raged in the territory of the Lake Trasimeno. Also Leonardo da Vinci occupied himself indirectly of this problem in a study about the Val di Chiana from 1503, where he recommended to make the Arno communication with the Val di Chiana and the Lake Trasimeno. But the times did not allow agreements between states in continuous belligerance, that is the pontificate, the grand duchy of Tuscany and the republic of Siena, and therefore no conclusion was found. A breve of Clement VII from 1528 ordered the restoration of the drain. In 1568 Pius V gave out a notice which should become the "Magna Charta" of the legislation of the Lake Trasimeno. In the article 89 this notice "orders that Mr. Treasurer, who will be for the time at Perugia, has to let revise every year in May the Cava, and if he should need money for the conservation of it, so that the water of the lake can flow out without obstacle, he has to make the works, of which the R.C.A. is to be charged". The water level continued to be irregular and caused often floodings: the one from 1602 was so abundant that it became necessary to design on the geographical maps also the new shorelines. The cause was attributed not only to the abundant rainfalls, but also to the occlusion of the drain. Clement VIII found it necessary to intervene energically in the face of these events. He nominated a commission, which was composed of the most famous architects and engineers of Perugia, Giovanni Fontana, Paolo Maggi, Carlo Maderno, and professor Livio Esbio was entrusted with the compilation of a new topographic map. Cardinal Maffeo Barberini, supervisor of the waters, presided the commission. The commission visited the Cava, examinated the possibility to drain the lake, conducting the water of the Lake Trasimeno into the Chiana either on the north side near Borghetto or on the south side near La Torre del Pantano, through the Anguillara and the Tresa, which already drained into the Chiana. When they had examinated the different projects, in the end they decided that it was necessary to clean and enlarge the old drain of Braccio, and so it was done. It was a magnificent work at the memory of which was put up a memorial tablet, which still can be seen at the exit of the drain.
Unfortunately it has to be said, that despite of the good intentions of this pope and the material efforts, which were made, this work did not solve the problem. In 1628 the cardinal Barberini (by this time pope Urban VIII) ordered the restoration of the walls of the Cava. In 1720 some of the communities of the Lake Trasimeno made a statement to the governor of Perugia, declaring that nobody had looked after the maintenance of the Cava: the drain was obstructed, the mills stood still, so that for grinding one had to go to the mills at the Tiber, which were many kilometres away. In 1780 a hydraulic agreement was signed between the Papal State and the grand dukedom of Tuscany, which provided for the fact that the water of the Tresa should not pour anymore into the Chiana but into the Lake of Chiusi, where it poured its water first in the case of flooding. In 1790 at Perugia was presented a magnificent anonimous project to dessicate the Lake Trasimeno on the initiative of a Tuscan-Roman society, a project that aroused controversy. The abbot Borghi di Monte del Lago sent his project tending to the same aim, that was to dessicate the Lake Trasimeno with a navigable canal from Livorno to Fiumicino, to Paris, but the French government did not ever take this canal into serious consideration. The scholars in hydrography tended to dessicate the Lake Trasimeno, maybe driven by someone with strong economic interests. In 1833 a Roman society asked for the concession to dessicate the lake, pointing out to the government the big advantage for the national economy deriving from many thousands of hectares of land usable for cultivation. The profiteers magnified the sanitary data of the population of the lake in order to prove the necessity to dessicate it. But the opposition of distinguished inhabitants of Perugia as Dr. Massari saved the lake. Meanwhile the waters of the lake alternate between periods of stability, periods of high water with resulting floodings of the land, and periods of low water. In 1750 happened floodings, also in 1762. In 1810 and in 1820, too, alternating with periods of subsidence of the water level: to the flooding of the land alternated recrudescences of malaria and it was not a rare thing that in the course of few years the range of the waters was even some metres. One of the most exceptional subsidences happened in the years 1832-35, and the documents of the period reported that it was possible to reach many zones just pushing the boat with a pole put into the ground.
Oasi_La_Valle_17 In August 1862 the Italian Minister of Agriculture resumed the studies for a new dessication and this solution was quite near, but the presented reports proved that the damages would have been higher than the advantages. The paladin of the Lake Trasimeno, he who defended it openly, was Guido Pompili, and to a great extent it is due to him that the lake was not dessicated. Deputy in the parliament, husband of the poetess Vittoria Aganor-Pompili, he played all his cards in this vicissitude and he made it. He published some papers in defense of his thesis.
In 1867 the the "Consorzio per la Bonifica delle Gronde del Trasimeno" and Pompili became a member. The drainage was wanted and it could have been enough to lower the threshold. It was just a little step for the salvation of the lake. The Consorzio studied in depth the problem of the complete and definite drainage. A project for a new drain was presented, which was a second edition of the old one, but increased and corrected. On the 20th March the works for the new drain began and they went on for about two years. The solemn inauguration took place on the 2nd October 1898. The new drain starts at about 30 metres south-east of the old drain at 256,82 metres above sea level and descends to 226,81 metres above sea level on an altoghether lenght of 1.314,25 metres, of which 896,38 metres in the tunnel. It has a regular part, which is almost round and covered with bricks that are 30 to 41 cm thick, some also 60 cm according to the ground. The greatest hight is 3,40 metres, the greatest width 3,60 metres. The offtake of the water is in form of a sluice with an adjustable device. With this work the problem of the flooding was solved, but not that of the subsidence of the water in the years with few rainfall and in spite of the fact that in 1957 the streams Tresa and Rio Maggiore were channelled into the lake. A year after the lowest level was reached under the threshold of 2,63 metres (referring to the "hydrometric zero" at the altitude of 257,33 metres above sea level, therefore it was necessary to bring more water: so an artificial tributary was planned, the canal Anguillara, which lead into the lake also the streams Moiano and Maranzano, allowing so a constant inflow of water, as the new drain allowed a regular reflux. So the Lake Trasimeno has had this exchange, necessary for its survival, for a certain time.
The vicissitudes of the Lake Trasimeno are not finished: since some years the problem of maintaining the water level of the Lake Trasimeno has come up again, because it has lowered slowly. Projects for the amplification of its drainage basin have been presented, and projects to bring through artificial conducts the water of the Tiber (flooded by the Montedoglio) are studied. Today we are still in the phase of projects. We hope that in a short time we can pass from the phase of projects to their being carried out in order to save a good, which is not of just a few but a common good.
The Lake Trasimeno, with its round form and its 124 square kilometers, is the fourth Italian lake for surface and the greatest of the Italian mainland. Originated in the middle-superior Quaternary after the tectonic movements for the reduction in tension, it is a closed laminar lake, with a circumference of 54 km, an average depth of 4,72 metres and a maximum depth of 6,70 metres. Three small islands emerge from the waters, Maggiore, Minore and Polvese. The morphology of the territory, is altogether rather gentle. The greatest heights are assembled in the northern part and they are just a little higher than 800 metres di altitude.
Oasi_La_Valle_18 From there come down small tributaries, small ditches and streams that have brought a minimum of water also in autumn and spring. Therefore and for the reduced dimensions of the hydrographic basin, the quantity of water that reaches the lake depends almost exclusively on the meteoric precipitations that fall on the surface of the lake and, partly, on the groundwater level that is fed by these precipitations. To avoid the floods that often, in past, happened this zone, in the 15th century some natural tributaries were diverted and made to flow into each other on the Tuscan territory. Besides a drain was built, probably already in the Roman period, but rebuilt in the 15th century and at the end of the 19th century, which flows in the river Tiber and which works as floodway for the floods when the water rises over 257,5 metres above sea level.
Because of the limited depth of its waters and its nature of closed laminar lake, that is subject to strong yearly and long-term oscillations of the level, the water is very warm in summer and very cold in winter (in some years it is even completely frozen). The little depth of the water and the concentration of nourishing substances make it a mesotrophic basin and therefore very rich of animal and vegetable life. The area of the Valley between S. Feliciano, S. Savino and S. Arcangelo, in the commune of Magione, probably is the most interesting part of the whole Lake Trasimeno from the naturalistic point of view: a great damp zone with extended cane thickets and many faunistic species of high scientific value.
Oasi_La_Valle_19 The whole circumference of the Lake Trasimeno, which is characterized by a modest depth of its water, is covered by a dense cane thicket, which reaches its maximum development in the zone of the Valley: in some points it extends for about one kilometre between the fields and the open water of the lake. A huge number of animal species, mainly birds, which represent the most important component of the zoocenosis, find shelter and food here. The Lake Trasimeno, in fact, is situated in a strategic position along the migration routs of many species that live in the damp zones and that stop here for the restoration of the energetic reserves necessary for the continutation of their flight. Protected Oasis from 1989 on, in 1996 the Valley is endowed by the Province of Perugia with the equipment that make accessible to the public and entrusted to the management of Legambiente, allowing a naturalistic, didactic, touristic and scientific use. Today it is part of the Regional Natural Park of the Lake Trasimeno.
Didactic activities
With the aim to discover the extraordinary emergencies of the territory of the Park of the Lake Trasimeno, the Naturalistic oasis "La Valle" proposes some activities of environmental education for all kinds of schools.
The exploration of the territory begins with the observation of the lake ecosystem on a route, which goes partly on a wooden gangway, that leads beyond the cane thicket into hide, from which it is possible to observe the water fowl population. Afterwards one can learn something about bird ringing and visit the channel of the antique drain. The vision of slides and other material not only allows in-depths studies of the birds' migration, but also, in general, on the historical, physical, geological and geomorphological peculiarities of the territory.
Duration: circa three hours.
Period: all the year.
Besides the visit of the oasis (see above), that of the Fishing Museum, where the ancient methods of fishing are reconstructed, becomes a journey to the secrets of a secular tradition that risks to be forgotten.
Duration: circa four hours.
Period: from April.
After the visit of the oasis and that of the Fishing Museum (see above) the visit of the island Polvese goes on an itinerary that shows the most important environmental characteristics: the natural environment with the charming ilex grove and the remarkable evidences left by man: the medieval castle, the monastery of the Olivetans and the Garden of aquatic Plants of Pietro Porcinai.
Duration: all day
Period: from the Easter week to the end of September.
The laboratories of experiences constitute an important element for the development of the pragmatic and cognitive dimension. Through a series of games the children should make some practical-maunal experiences with the aim to sharpen their abilities of observation and annotation of informations using suitable tools, to understand relations, to make hypotheses and to verify them, to interpret and assign the collected data. A didactic guide has the purpose to furnish ideas for subjects of study and to give suggestions for the practical activities to carry out in the laboratory and on the field.
Botanic laboratory
The children are divided in groups and assigned an exercise (planned with the teachers). Therefore they are led to the territory of the oasis (together with teachers and operators) to pick up the necessary material for the research (samples, photographs, sketches, informations), and to make annotations in a a special field notebook. When they come back to the didactic classroom the children analyze this material using guides and manuals, comparing the samples with the herbarium of the oasis. It will be used by the children to prepare the picking of vegetable species (herbarium) for scholastic use, in order to carry out small manufactures like stamps for drying leaves and compositions.
Zoological laboratory
It will primarily beconcentrated on the study of the birds. According to the methods seen before the children will go onto the territory of the oasis to look for data and information (using direct observations, photographs, sketches, video and audio recordings .), which will be elaborated together with the teachers and operators inside the structures of the oasis. In the case of the gathering of biological samples is planned a macroscopic control of them, mainly of morphological and functional nature (guides for the recognition, for the attribution of the species) without ever making anatomical investigations.
These meetings examinate the subjects that concern the peculiar aspects of the territory of the Lake Trasimeno and the connected antropical activities.
• Geological and geomorphological aspects of the basin: the causes that have determinated the formation of the lake, the different kinds of stone of the zone, the modelling of the landscape...
• Geographical aspects: the characteristics of the territory (the heights, the inflow and outlet of the lake, the oscillations of the water level), particularities of the basin (depth, size...); the different kinds of maps (geographic, geologic, cadastrali...) and their use.
• Vegetation of the Lake Trasimeno: analysis of the herbaceous, shrubby and arboreal species in the different environmental typologies (damp zone, forest areas, cultivated areas); what are the ecological successions and the vegetational belts; carrying out of herbariums.
• Fauna of the Lake Trasimeno: analysis of the vertebrate species with particular reference to the water fowl; the food chains.
• The migration of the birds: the ringing of the birds as research technique in order to discover the secrets of the migrations.
• The Parco del Trasimeno: what is a Park, what is it for, the appointing laws, why the Lake Trasimeno has become a protected area.
• Informative file of the subjects for the teachers
• Informative file for the pupils
• Didactic material It is possible to compile didactic packages for the work in the classes, which go hand in hand with the guided visits described above. FOR INFORMATION AND RESERVATION: Centro visita Oasi "La Valle", San Savino di Magione - Phone and fax 075/8476007; Legambiente Umbria, Perugia - Phone and fax 075/5722083 :: E-Mail: oasilavalle@libero.it

Scientific activities
The Oasi Naturalistica -"La Valle" collaborates with the Province of Perugia (Faunistic programmation and management service - Department for the management and the development of the fauna) for activities of scientific research concerning the study of the avifauna of the Lake Trasimeno and consisting in scientific ringing and winter census of the water fowl.
by Francesco Velatta
Faunistic programmation and management service - Department for the management and the development of the fauna
As it is a consolidated practice, last January the provincial administration of Perugia has organized, within the program International Waterfowl Census and coordinated in Italy by the I.N.F.S. (National Institute for the Wild Fauna), censuses of the aquatic birds wintering in the principal damp zones of the territory of own competence: Lake Trasimeno, pits of Pietrafitta, marsh of Colfiorito, bight of the Ornaris. Afterwards the results related to the Lake Trasimeno are exposed.
At the field survey have paricipated operators dependent from the province, operators of the Oasi Naturalistica "La Valle" and qualified volunteers.
Daytime censuses
All species of birds, for which the National Institue for the Wild Fauna has asked the census were object of the gathering.
Considering the great dimensions of the area, which do not allow an effective exploration of the lake surface from the shore, the calculations have been carried out combining more techniques:
1. censuses on land, carried out through the use of a series of stations distributed along the whole circumference of the lake;
2. censuses from the boat, carried out according to navigation programs, which allowed to cover the entire shore belt, the islands included;
3. aerial photos of the flocks and counting of the individual birds on the photo. Particularly the Great Crested Grebe, the Little Grebe, the Cormorant have been censused with method 1., the Eurasian Coot with method 3., the Great Heron and the Marsh Harrier with method 2., the ducks, geese and swans and the Northern Lapwing with a combination of method 1. and 2., comparing critically the data gathered with the two different techniques.
It has to be underlined that for some species, which are difficult to census due to their evasive habits or their mobility, has just been annotated the date of their presence without providing the number. This had to be applicated to the Common Moorhen, the Common Snipe and the Black-headed and the Yellow-legged Gull.
Census in the roost (Cormorant)
For the Cormoran have been carried out in addition to the daytime censuses with the above described methods evening censuses of the birds in the roost in the territory of the Lake Trasimeno (Island Minore).
The calculations have been carried out waiting near the roost for the arrival of the birds and counting them.
Previously were counted the birds already present near the roost.
At the Lake Trasimeno have been censused more than 42.000 birds (96% of the provincial number) of 25 different species.
The total number of the wintering contingents is circa 22% higher than in January 1998.
For the fourth consecutive year has been exceeded the threshold of 20.000 aquatic birds, which means according to the RAMSAR CONVENTION BUREAU (1990) a sufficient criterion for a damp zone to be assigned among the internationally important ones. The species most numerous on the lake is the Eurasian Coot, that with more than 34.000 birds has further increased its number(+30%) in comparison with the already elevated numbers observed in the three year period 1996-98.
The Wigeon, that also if circa 2.700 were counted results in sensitive diminution in comparison with the record number of more than 3.500 bird counted in January 1998 (-25%);
The Gadwall, until now present in insignificant numbers (max. 31 birds in 1997) has experienced an unexpected increase reaching circa 1.600 birds;
The Cormorant, that (according to the daytime censuses) appears notably diminished in comparison to the preceding winter (948 birds against 1.564, equal to a 39% diminution).
An analogous diminution (- 35 %) characterizes the dynamics of another ichthyophagous diver, the Great Crested Crebe, that continues the negative trend observed on local level for some years by now.
A further increase of the duck population has been observed with more than 5.500 birds against about 5.000 in 1998 (+ 10%).
After the Wigeon and the Gadwall the species with more birds (more than 100) result in the order:
Mallard (754 birds, highest number reached in the period of 1988-99, +63 % in comparison with 1998), Common Teal (268), Northern Shoveler (115).
The Great Herons, altogether quite few (circa 150 birds censused), have been found just a little more numerous than in 1997-98. As usual, the species most numerous is the Gray Heron (116 birds).
The Little Gull (one bird) deserves to be mentioned, as it is unusual to find it on the Lake Trasimeno.
FOR INFORMATION AND RESERVATION: Centro visita Oasi "La Valle", San Savino di Magione - Phone and fax 075/8476007; Legambiente Umbria, Perugia - Phone and fax :: E-Mail: oasilavalle@libero.it
A walk in the Oasis
The route begins at the house of the Visit Centre. Inside one can visit an exhibition concerning the historical-naturalistic aspects of the valley: one part is dedicated to the medieval drain; the naturalistic section exposes some of the results of the scientific ringing of the birds and of the censuses of the wintering birds.
A few metres from the building, on the other side of the modern channel, is the medieval drain: inside the tiny 15th century shed, where was kept the lock mechanism of the channel, is the original "door" from the same period. Outside a wooden stair leads inside the channel, which in part can be visited.
Again on the principal path one is in front of the farmhouse, which is today the provisional centre of the ringing station. Once a week it is possible to watch the extraordinary work of the ornithologists.
Going along the modern channel of the drain one arrives at the shore of the lake. Here a big "ruler", put near the sluice gates, comes out of the water. This is the "hydrometre", a tool that measures the water level.
Having crossed the bridge over the locks one arrives at the wooden gangway. It is almost 400 metres long, runs along the cane thicket and finishes in an observatory, which pushes out onto the lake and is equipped for bird-watching.

On board of the boat
From the Visit Centre leads a path along the drain channel which conducts to the lake.
The route begins at the small wooden landing stage near the hydrometre. "Il CIGNO", the swan, glides slowly and silently along the wooden gangway towards the open lake: when it has reached the open water it veers to the left and following the external edge of the cane thicket it directs toward the channel of Pietrafitta, not far away from the built-up area of Sant'Arcangelo, on the south-eastern shore of the lake, where an observation tower allows to watch from above the cane thicket in order to discover its inhabitants.
Along this itinerary a great part of the territory of the Lake Trasimeno can be seen: the island Polvese in the foreground and behind the islands Maggiore and Minore; Castiglione del Lago in the distance seems to emerge from the water; nearer the built-up area of San Savino, which dominates the area of the Oasis with its castle.
From the boat it is easy to observe the enthralling show of the great number of birds, in the winter period, when they gather to winter, more than 50.000.

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