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LAGO TRASIMENO (LAKE TRASIMENO)

A view from the southern shore with reed zone

Photo: O. Tiberi

A. LOCATION

  • Perugia, Italy.
  • 43:09N, 12:06E; 257.3 m above sea level.
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B. DESCRIPTION

The formation of Lake Trasimeno began in the Upper Miocene Period following high intensity orogenic movements.

In the later ages, particularly during the Quaternary, other orogenic and epeirogenetic movements caused the formation of the present day basin.

Lake Trasimeno has an extensive surface area, 124 km2 and is only 6.3 m deep. It is the fourth largest lake in Italy. It has a watershed area of 396 km2.

The shores are shallow, marshy and filled by dense submerged and emerged aquatic vegetation. It is rich in both migratory and sedentary avifauna.

There is little industry along the lake; the greater activity (in order of importance) are: agriculture (in a broad sense), fishing (in decline due to fewer fishermen) and tourism (increasing development).

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C. PHYSICAL DIMENSIONS (1)

Surface area [km2] 124
Volume [km3] 0.586
Maximum depth [m] 6.3
Water level Regulated
Length of shoreline [km] 53.1
Residence time [yr] 24.4
Catchment area [km2] 396
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D. PHYSIOGRAPHIC FEATURES

D1 GEOGRAPHICAL (Q)

  • Sketch map: Fig. EUR-29-02.
  • Names of main islands
    Polvese (0.644 km2), Maggiore (0.232 km2) and Minore (0.064 km2).
  • Number of outflowing rivers and channels (name): 1 (artificial channel).

D2 CLIMATIC

  • Climatic data at Monte del Lago (Q)
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann.
Mean temp. [deg C]*1 4.3 5.4 8.8 12.8 16.8 19.7 23.8 23.7 20.6 13.4 10.2 6.0 13.8
Precipitation [mm]*2 52 68 72 56 67 57 32 54 62 94 84 65 763

*1 1926-1970. *2 1973-1987.


    Fig. EUR-29-01
    Seasonal and annual trends of precipitation (Q).
  • Number of hours of bright sunshine: 2,179 hr yr-1 (2).
  • Solar radiation: 11.64 MJ m-2 day-1 (Q).

    Fig. EUR-29-02
    Sketch map (Q).
  • Water temperature [deg C](3)
February 1969-January 1970
Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
S*1 6.9 4.0 6.9 10.2 18.5 18.0 21.8 23.5 22.2 17.8 14.5 5.0
B*2 6.6 3.2 6.9 10.0 16.2 17.7 21.2 22.5 22.1 17.9 14.3 5.0

*1 Surface. *2 Bottom.

  • Freezing period: January (neritic zone)(Q).
  • Notes on water mixing and thermocline formation
    Due to its small depth, the lake is seldom stratified (Q).
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E. LAKE WATER QUALITY

E1 TRANSPARENCY [m](Q)

February 1969-January 1970
Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1.8 5.3 3.0 3.1 4.7 5.0 5.0 3.6 2.7 2.8 1.5 0.7

E2 pH (Q)

Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
S*1 8.20 8.60 8.42 8.55 9.10 9.56 9.74 9.46 8.44 8.87 8.78 8.59
B*2 8.22 8.62 8.40 8.55 9.32 9.57 9.80 9.47 8.40 8.84 8.75 8.50
*1 Surface. *2 Bottom.

E3 SS [mg l-1](4)

May 1973-April 1974
Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
6.0 4.2 6.0 10.0 3.2 1.6 2.0 6.3 10.4 13.8 8.2 52.5

E4 DO [mg l-1](3)

February 1969-January 1970
Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
S*1 12.1 12.7 11.8 10.7 11.3 9.1 10.2 7.6 7.3 9.2 9.5 11.8
B*2 12.0 13.0 11.8 10.7 16.3 9.4 10.8 7.1 6.7 9.0 9.1 12.5
*1 Surface. *2 Bottom.

E5 COD [mg l-1](Q)

Determined by KMnO4 method.
February 1969-January 1970
Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
S*1 5.1 3.6 4.1 5.0 5.2 4.8 7.6 6.5 6.0 8.1 5.6 5.5
B*2 4.3 3.7 4.1 4.7 4.6 5.2 12.7 8.5 7.2 6.4 4.2 4.3
*1 Surface. *2 Bottom.

E6 CHLOROPHYLL CONCENTRATION [micro g l-1](5)

May 1963-April 1964
Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
S*1 2.4 3.9 1.4 1.8 6.0 2.7 8.5 3.8 1.8 3.1 2.7 1.9
B*2 2.6 4.3 2.5 1.7 4.6 3.8 10.1 11.4 5.8 4.6 5.0 3.7
*1 Surface. *2 Bottom.

E7 NITROGEN CONCENTRATION (3)

  • Total-N [mg l-1]
February 1969-January 1970
Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
S*1 0.67 0.30 0.44 0.40 0.32 0.16 0.28 0.22 0.27 0.26 0.25 0.78
B*2 0.68 0.30 0.34 0.28 0.46 0.24 0.28 0.58 0.28 0.29 0.29 0.80
*1 Surface. *2 Bottom.

E8 PHOSPHORUS CONCENTRATION (Q)

  • Total-P [mg l-1]
February 1969-January 1970
Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
S*1 0.031 0.027 0.039 0.052 0.061 0.087 0.065 0.022 0.109 0.087 0.057 0.035
B*2 0.031 0.031 0.035 0.052 0.083 0.083 0.031 0.035 0.096 0.083 0.105 0.057
*1 Surface. *2 Bottom.

E9 CHLORIDE CONCENTRATION [mg l-1](Q)

February 1969-January 1970
Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
S*1 130.3 138.2 132.0 132.6 126.3 139.9 133.1 135.4 134.8 132.6 134.8 132.0
B*2 128.6 138.2 132.0 129.2 128.6 137.7 130.9 135.4 136.5 133.6 134.8 132.6
*1 Surface. *2 Bottom.
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F. BIOLOGICAL FEATURES

F1 FLORA (3)

  • Emerged macrophytes:
    Phragmites communis, Typha angustifolia, T. latifolia.
  • Floating macrophytes:
    Lemna gibba, L. minor, Nymphaea alba.
  • Submerged macrophytes
    Potamogeton perfoliatus, Ceratophyllum demersum, Vallisneria spiralis, Chara delicatula.
  • Phytoplankton
    Chlamydomonas, Ankistrodesmus, Cosmarium, Scenedesmus, Phormidium, Anabaena, Microcystis aeruginosa, Achnantes, Synedra, Navicula.

F2 FAUNA (3)

  • Zooplankton
    Codonella, Asplanchna, Keratella, Polyarthra, Synchaeta, Pedalia, Cyclops, Daphnia galeata, Diaphanosoma, Leptodora, Bosmina.
  • Benthos:
    Nais, Tubifex, Branchiura sowerbyi, Physa, Limnaea, Plumatella.
  • Fish
    Anguilla anguilla*, Lepomis gibbosus*, Atherina boyeri*, Perca fluviatilis*, Cyprinus carpio*, Cyprinus carpio var. specularis*, Scardinius erythrophtalmus*, Tinca tinca*, Esox lucius*.
    * Economically important.

F4 BIOMASS: Fig. EUR-29-03 and 04 (4).


    Fig. EUR-29-03
    Trend of phytoplankton density [10,000 cells l-1].

    Fig. EUR-29-04
    Trend of zooplankton density [1,000 cells l-1].

F5 FISHERY PRODUCTS (6)

  • Annual fish catch [metric tons]
    1980: 629.5.

F6 PAST TRENDS: Fig. EUR-29-05 (Q).


    Fig. EUR-29-05
    Past trend of fishery production [metric tons yr-1].
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G. SOCIO-ECONOMIC CONDITIONS

G1 LAND USE IN THE CATCHMENT AREA (7)

1976
Area [km2] [%]
- Natural landscape
Woody vegetation 65.80 23.3
Bush 6 1.8
Grazing ground 3 1.1
Uncultivated or unproductive lan 23 8.1
- Agricultural land
Ordinary and industrial crops 126 44.5
Grape 14.50 5.1
Olive 45.60 16.1
- Total 283.90* 100

* The data are based on an area not exactly the same with the catchment area.

  • Natural woody vegetation
    • Quercus pubescens, Q. ilex, Q. cerris, Pinus pinaster.
  • Tree plantation: Pinus pinea, Populus nigra, Olea europaea, Vitis vinifera.
  • Hydrophilous vegetation: Salix alba, Alnus glutinosa, Ulmus minor.
  • Main kinds of crops
    • Wheat, maize, barley, lucerne, clovers, white lupine, tobacco, sugar beet, sunflower.
  • Levels of fertilizer application on crop fields: Heavy.

G2 INDUSTRIES IN THE CATCHMENT AREA AND THE LAKE (7)

Gross product during the year [mill. Lire]*1 No. of persons engaged No. of establishments Main products or major industries
-- Primary industry*2 8,851 N.A.
- Agriculture
Cereal and vegetable 3,964 1)
Permanent orchard 5,709 2)
Industrial crop 1,635 3)
Livestock breeding 13,896 4)
Forestry 286 5)
- Fisheries N.A. 251 7 6)
-- Secondary industry*3
- Manufacturing N.A. 3,147 706 7)
- Others N.A. 1,176 232 8)
-- Tertiary industry*4 N.A. 2,577 N.A. 9)
*1 $=881 Lire (1977)
*2 1977
*3 1971
1) Wheat, barley, maize, sorghum and vegetables. 2) Wine, olive oil, fruit, etc. 3) Sugar beet, sunflower, tobacco, etc. 4) Cattle, sheep, swine, equine and poultry. 5) Timber, firewood, etc. 6) Tinca tinca 27%, Anguilla Anguilla 18%, Lepomis gibbosus 18%, Esox lucius 12%, etc. 7) Machine, textile, clothing and foodstuff industries. 8) Construction, etc. 9) Wholesale retail, service, transportation, banking, public service, etc.
  • Numbers of domestic animals in the catchment area
    • Cattle 8,570, sheep 12,480, swine 32,700, poultry 1,069,000, others 380.

G3 POPULATION IN THE CATCHMENT AREA (9)

1986
Population Population density [km-2] Major cities (population)
Rural 45,562 67.1 None

    Fig. EUR-29-06
    Trend of population in the catchment area communities.
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H. LAKE UTILIZATION (10)

H1 LAKE UTILIZATION

    Source of water, navigation and transportation, sight-seeing and tourism (no. of visitors in 1975: 38,700), recreation (swimming, sport-fishing, yachting) and fisheries.

H2 THE LAKE AS WATER RESOURCE

1977
Use rate [m3 day-1]
Domestic 4,400
Irrigation 8,200
Industrial 3,800
Total 16,400
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I. DETERIORATION OF LAKE ENVIRONMENTS AND HAZARDS

I1 ENHANCED SILTATION (7)

  • Extent of damage: Not serious.

I2 TOXIC CONTAMINATION (7)

  • Present status: None.
  • Main contaminants, their concentrations and sources
Concentration [ppm (wet wt.) basis]
Name of contaminants Water (1970-1972) Fish* (1972-1973)
Hg N.D. 0.29
Cr N.D. 0.24
Pb N.D. 0.47
Zn N.D. 6.6
* Mean value of Tinca tinca, Cyprinus carpio and Esox lucius.
  • Water pollution control for the effluent (National Law No. 319-1976)
Maximum permissible limits
pH 5.5-9.5
BOD5 40 [ppm]
COD 160 "
SS 80 "
Mineral oil 10 "
Animal and vegetable fat 40 "
Phenols 1 "
Cu 0.4 "
Zn 1 "
Fe 4 "
Cr 2 "
Coliform group 20,000 [MPN 100 ml-1]
Pesticides (P-deriv.) 0.05 [ppm]
Pesticides (Cl-deriv.) 0.10 "

I3 EUTROPHICATION

  • Nuisance caused by eutrophication (7)
    Unusual algal bloom Phormidium spp. (1985-87), Ceratium hirundinella (since 1972), Microcystis aeruginosa (since 1955).
    Foul odour of tap water: Seldom.
    Harms to fishery products: Due, sometime, to parasitism or anoxia.
  • Nitrogen and phosphorus loadings to the lake [t yr-1](10)
Soureces Industrial Breeding Domestic Agricultural Natural Total
T-N 2.34 47.21 66.05 300.89 16.46 432.95
T-P 0.16 11.14 18.79 11.28 0.82 42.19

I4 ACIDIFICATION (7)

  • Extent of damage:
    None.
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J. WASTEWATER TREATMENTS (Q)

J1 GENERATION OF POLLUTANTS IN THE CATCHMENT AREA

c) Limited pollution with wastewater treatment.

J2 APPROXIMATE PERCENTAGE DISTRIBUTION OF POLLUTANT LOADS

N[%] P[%]
- Non-point sources
Agricultural and natural 84.2 55.1
- Point sources
Domestic 15.3 44.5
Industrial 0.5 0.4
- Total 100 100

J3 SANITARY FACILITIES AND SEWERAGE

  • Percentage of municipal population in the catchment area provided with adequate sanitary facilities (on-site treatment systems) or public sewerage: 100%.
  • Percentage of rural population with adequate sanitary facilities (on-site treatment systems): ca. 100 %
  • Municipal wastewater treatment systems
    No. of secondary treatment systems: 5.
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K. IMPROVEMENT WORKS IN THE LAKE (Q)

K1 RESTORATION

Dredging is sometimes carried out along the lake shore.

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L. DEVELOPMENT PLANS (Q)

Provincial Council 1981: "Trasimeno Lake Project", concerning professional and sport fishery, tourism, agriculture, environment protection, etc.

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M. LEGISLATIVE AND INSTITUTIONAL MEASURES FOR UPGRADING LAKE ENVIRONMENTS (Q)

M1 NATIONAL AND LOCAL LAWS CONCERNED

  • Names of the laws (the year of legislation)
    1. Regulations for water protection against pollution, Law No. 319 (1976)
    2. Integrations and modifications of the Laws No. 176-16 (1973) and No. 319 (1976) in the matter of water protection against pollution, Law No. 650-10 (1979)
    3. Art. 30 of D.P.R. (Decree of the Republic President) No. 915-10 (1982); it regards the implementation of the C. E. E. (European Economic Community) directives: a) No.75/403; wastes: b) No. 76/406; polychlorodiphenyl and polychlorotriphenyl waste disposal: c) No. 78/319; toxic and harmful wastes.
  • Responsible authorities: National government.
  • Main items of control
    1. Toxic substances: Cd, Pb, Hg, Cr, As, Cu, Ni, Zn, etc.
    2. Pollutants: N, P, BOD, COD, 55, pH, phenols, fats and mineral oils, surfactants, pesticides, coliforms, etc.

M2 INSTITUTIONAL MEASURES

Trasimeno Lake Project

M3 RESEARCH INSTITUTES ENGAGED IN THE LAKE ENVIRONMENT STUDIES

  1. U.S.L. (Local Sanitary Unity)
    a) Physical and chemical laboratory - Perugia
    b) Bio-medical laboratory - Perugia
  2. Hydrobiology Institute: University - Perugia
  3. Botany Institute: University - Camerino

N. SOURCES OF DATA

Questionnaire filled by Prof. O. Tiberi, Istituto di Idrobiologia, Perugia, Italy.

  • Carollo, A. (1969) Carta batimetrica e note geomorfologische sul bacino del Lago Trasimeno. Mem. Ist. Ital. Idrobiol., 25: 144-159.
  • Baltadori, A. & Pitzalis, M. (1978) La radiazione globale a Perugia dal 1931 al 1977. Ecologia Agraria, 14 (3).
  • Tiberi, O., Taticchi, M. I. & Giovanni, M. V. (1971) Ragguagli sulle condizioni fisiche, chimiche, planctonologiche e bentoniche del Lago Trasimeno (Feb. 69-Feb. 70). Riv. Idrobiol., 10 (3): 37-233.
  • Di Giovanni, M. V., Gianotti, F. S., Mantilacci, L. & Tiberi, O. (1974) Prime informazioni su nutrienti N, P e produttivita del Lago Trasimeno. Riv. Idrobiol., 13 (2/3): 281-360.
  • Gianotti, F. S., Mantilacci, L., Mearelli, L. & Tiberi, 0. (1982) Physionomie physique et chimique du Lac Trasimene pendant la periode 1969 79. Guide-itineraire: Excursion Internationale de Phytosociologie en Italie Centrale (2-11 Juillet 1982). Edizione Universita di Camerino (Macerata).
  • Mearelli, M. (1985) Considerazioni sulla produzione ittica del Lago Trasimeno dal 1956-1961. Provincia di Perugia: Atti del Convegno: La tutela dell'ambiente lacuale il Lago Trasimeno. Perugia, 8-9 Mar.
  • Ministero Agricoltura e Foreste (1977) Studio per la tutela e la valorizzazione del patrimonio naturalistico del bacino del Lago Trasimeno. Italconsult, Vol. 1, 2, 3, 4. Roma.
  • E. S. U. (Ente Sviluppo Umbria: Umbrian Expansion Body)(1977) Rapporto informativo sull'andamento della produzione lorda vendibile agricola in Umbria nell'anno 1977. Servizio Piani e Programmi Maggio.
  • ISTAT (Statistic Institute)(1986) Ban a dei dati territoriali. Roma.
  • Mearelli, M., Lorenzoni, M. & Rufini, F. (1981) Determinazione dello stato trofico del Lago Trasimeno attraverso la valutazione indiretta dell'azoto e del fosforo. Riv. Idrobiol., 20 (3): 571-587.
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