LAKE BANYOLES

An aerial view of the whole lake

Photo.
Photo: Institut Cartografic de Catalunya


A. LOCATION

  • Catalonia, Spain.

  • 42:08N, 2:45E; 175 m above sea level.


B. DESCRIPTION

    Lake Banyoles, the main lake of Catalonia, is located in the northeast of Iberian Peninsula, near the town of Girona (100 km from Barcelona). The lake belongs administratively to the City Council of Banyoles. It is the largest lake in the complex karstic system of Banyoles, with a surface area of 1.12 km2 and a maximum depth of 46.4 m. It is the last remnant of a much bigger lacustrine system developed during Pliocene Quaternary periods, and was formed due to the dissolution of underground gypsum bed and the collapse of overlying layers.
    Lake Banyoles has a complex bathymetry because it is an assemblage of six basins (polje), formed by different episodes of collapse and grouped in three major lobes. In some of these basins, water is incoming from the bottom through different underground sources (up to 12) and maintain marly and argillaceous basement materials in suspension, forming a discrete layer of high density (1,100 1,400 kg m-3). The temperature of this slurry is nearly constant through the year (18 19deg C) and higher than that of the overlying hypolimnetic water. Therefore the lake is continually heated by the incoming groundwater, which considerably decreases the heat budget. The bottom inflow is about 40,000 m3 day 1, accounting for more than 80% of the whole inflow to the lake. From the east side of the lake five channels, constructed during the Middle Ages to canalize water and feed nearby marshes, flow out.
    The basins differ considerably in water quality, physical conditions and mixing dynamics. Whereas the basins C III, C IV are meromictic, the basins C I, C II, C V, and C VI are holomictic. All of them have only one period of stratification during summer. The hardness of the lake water is considerably high, due to carbonates and sulfates loaded by subterranean water. In late summer, the bottom water in the basins of North Lobe becomes completely anoxic, and accumulates sulfide due to sulphate reduction. This process has been increasing in recent years, evidencing the advance of cultural eutrophication caused by excess fertilizer application on crop fields in the lake's catchment area.
    The lake is used as a source of potable water for the town of Banyoles with a population of about 13,000, located to the east of the lake outside its catchment area. Recreation, sightseeing and tourism are also the use of the lake of great importance. Rowing events of 1992 Olympic Games were held here, and works for improving rowing track and restoring reed belt are currently going on in the lake (Q, 7, 9, 10, 11, 14).

C. PHYSICAL DIMENSIONS (6, 18)

    Surface area [km2] 1.12
    Volume [km3] 0.01612
    Maximum depth [m] 46.4
    Mean depth [m] 14.8
    Water level Unregulated
    Normal range of annual water level fluctuation [m] 0.2
    Length of shoreline [km] 9.13
    Residence time [yr] 0.80
    Catchment area [km2] 11.42

D. PHYSIOGRAPHIC FEATURES

D1 GEOGRAPHICAL (18, 28)
  • Bathymetric map: Fig. EUR-56-1.

  • Nnmber of main islands: None.

  • Number of outflowing rivers and channels (name)
    5 (R. de ca n'Hort, R. d'en Teixidor, R. de la Figuera d'en Xo, R. Major, R. de Guemol).
D2 CLIMATIC (12)
  • Climatic data at Limnological Laboratory of Banyoles, 1989 1992

    Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann.
    Mean temp. [deg C] 6.4 7.6 10.9 11.5 16.6 18.8 23.3 23.3 19.9 13.6 10.5 7.7 14.2
    Precipitation [mm] 53 46 46 70 83 79 47 36 64 91 83 106 804
  • Solar radiation: 11.9 MJ m-2 day 1.

    Fig. EUR-56-1
    Bathymetric map [m](Q).

  • Water temperature [deg C](1, 5, 13)
    Station C III, 1980-1990
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 11.0 12.0 12.5 15.9 17.9 20.3 23.9 24.7 23.0 18.8 15.3 11.8
    5 10.9 11.2 11.1 14.9 17.4 17.3 18.9 22.1 21.5 18.3 15.1 11.5
    10 10.9 9.9 10.6 12.3 12.4 13.3 11.6 13.2 14.0 14.8 14.8 11.4
    15 11.0 9.9 9.9 10.8 10.2 11.85 9.2 10.1 10.5 10.8 13.1 11.4
    20 11.1 11.4 11.0 11.5 11.2 11.8 10.4 11.5 11.5 11.6 12.5 12.6
    25 16.0 13.7 12.0 13.2 16.6 15.3 10.8 11.0 12.1 12.0 13.0 15.6
    Station C IV, 1980-1990
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 10.5 9.2 12.3 15.7 19.0 20.3 24.1 14.9 22.4 18.2 16.0 12.5
    3 10.6 9.4 11.7 15.5 17.6 19.7 22.9 24.2 22.0 18.3 15.6 12.4
    6 10.6 9.6 11.4 14.7 15.6 16.0 17.0 20.2 19.6 16.5 15.5 12.5
    9 10.5 9.7 11.2 13.2 14.3 14.6 14.4 16.5 16.9 17.4 14.9 12.0
    12 11.1 9.9 10.9 12.7 13.0 13.0 12.1 14.2 14.3 15.0 14.8 11.9
    15 13.8 12.6 11.9 13.91 14.1 14.25 12.4 14.3 14.3 14.3 14.0 13.9
  • Freezing period: None.

  • Mixing type: Holomictic.
    The whole lake is holomictic but some of the smaller basins with salty underground inflowing water are meromictic.
  • Notes on water mixing and thermocline formation
    Apart from the main thermocline located between 6 and 12 m depths, a second one which covers and area 10% smaller, occurs at about 21 m depth at one of the underground water sources. Although this latter thermocline tends to be instable due to advection and buoyancy force caused by the inflow of hot underground water, it usually persists for some weeks after the disappearance of the main seasonal thermocline. In the meromictic basins, only some part of the monimolimnetic water (approximately 1% of the total lake volume) is mixed with the upper mixolimnetic water during the whole circulation period (Q).

E. LAKE WATER QUALITY

E1 TRANSPARENCY (1)
    Station C III, 1977-1979
    Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    3.22 3.29 3.74 3.23 3.13 2.79 2.80 3.20 3.53 3.01 3.24 3.29

    Fig. EUR-56-2
    Seasonal trends of transparency (Secchi disk depth) at Station C III.

E2 pH (1, 5, 13)
    Station C III, 1980-1990
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 7.57 7.89 7.85 7.99 7.82 7.89 7.30 7.26 7.63 7.66 7.53 7.52
    3 7.72 7.88 7.89 7.89 7.77 7.71 7.40 7.42 7.35 7.45 7.49 7.51
    6 7.74 7.90 7.93 7.77 7.41 7.42 7.21 7.15 7.33 7.55 7.48 7.47
    9 7.68 7.86 7.93 7.75 7.45 7.45 7.47 7.25 7.25 7.32 7.43 7.46
    12 7.64 7.86 7.94 7.70 7.50 7.41 7.57 7.35 7.10 7.26 7.35 7.43
    15 7.59 7.89 7.92 7.69 7.44 7.39 7.35 7.10 6.95 6.95 7.05 7.43
    18 7.51 7.75 7.87 7.64 7.44 7.38 7.32 7.05 7.01 6.90 6.96 7.40
    21 6.88 7.00 7.83 7.08 6.91 6.87 6.86 6.66 6.84 6.85 6.94 7.25
    24 6.92 7.02 7.05 6.95 9.84 6.91 6.97 6.69 6.92 6.87 6.94 7.05
    Station C IV, 1980-1990
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 7.57 7.86 7.84 7.99 7.85 7.87 7.43 7.53 7.63 7.66 7.65 7.66
    3 7.70 7.90 7.82 7.97 7.74 7.77 7.64 7.58 7.63 7.70 7.73 7.72
    6 7.68 7.86 7.81 7.75 7.39 7.29 7.28 7.29 7.70 7.72 7.71 7.76
    9 7.65 7.89 7.83 7.62 7.34 7.27 7.30 7.27 7.29 7.13 7.60 7.78
    12 7.64 7.75 7.90 7.61 7.32 7.22 7.20 7.14 7.19 6.98 7.55 7.79
    15 7.25 7.05 7.05 7.00 6.92 6.93 7.05 6.51 7.03 6.92 7.10 7.70
E4 DO [mg l-1](1, 5, 13)
    Station C III, 1980-1990
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 8.0 10.0 10.0 10.0 10.0 9.5 8.1 10.0 9.6 10.4 9.5 9.8
    3 10.0 10.5 10.7 11.5 11.2 9.9 8.1 10.1 9.8 10.6 9.5 9.6
    6 10.2 11.6 11.9 12.0 11.0 8.1 7.6 10.0 9.9 10.6 9.2 9.4
    9 10.2 12.4 12.4 12.2 10.8 10.6 11.2 10.4 9.8 6.8 9.0 9.3
    12 9.8 12.0 12.0 12.0 11.2 7.5 7.0 4.3 3.7 1.3 8.7 9.0
    15 8.9 11.7 11.3 10.5 9.5 6.4 3.2 1.2 1.2 0.0 8.5 8.9
    18 8.9 10.8 10.6 10.0 9.0 6.4 3.1 0.5 0.0 0.0 8.3 8.9
    21 0.0 0.0 0.0 8.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
    24 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
    Station C IV, 1980-1990
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 8.7 10.6 10.7 10.0 9.2 8.3 8.6 10.0 10.0 10.2 9.4 9.4
    3 8.5 12.9 12.0 10.5 9.8 9.8 8.9 10.2 9.6 10.0 9.5 9.6
    6 8.0 13.4 12.5 10.5 10.0 8.7 9.4 9.8 9.4 10.1 9.6 9.5
    9 7.5 12.4 12.0 9.2 8.4 6.1 5.5 3.3 3.2 7.0 9.0 9.5
    12 7.0 11.2 11.0 7.4 6.1 5.2 1.5 0.0 0.5 0.0 7.0 9.4
    15 1.5 0.0 5.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 2.0 0.0
E6 CHLOROPHYLL CONCENTRATION [micro l-1](1, 5, 13)
    Station C III, 1980-1990
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 2.96 7.16 12.85 5.80 4.31 2.13 3.97 2.16 2.43 2.74 3.37 4.25
    3 3.47 8.25 11.22 5.98 6.12 2.92 4.24 2.16 2.72 2.01 3.65 4.53
    6 7.36 7.59 10.74 6.18 9.69 10.88 3.53 2.88 4.13 2.45 3.98 5.23
    9 3.48 10.12 13.51 9.33 13.40 8.56 2.51 4.59 7.26 5.26 5.67 5.12
    12 2.38 7.42 12.52 9.27 11.09 8.51 3.52 2.51 4.32 0.00 4.43 5.12
    15 2.56 8.70 12.75 7.83 3.62 5.51 0.00 2.43 3.12 0.00 3.47 5.23
    18 1.20 7.20 12.73 2.48 4.06 4.40 0.00 3.63 0.00 0.00 1.58 2.51
    21 0.97 0.00 12.70 1.44 1.04 1.21 0.00 0.00 0.00 0.00 0.00 0.00
    24 0.00 0.00 2.75 0.46 0.53 1.28 0.00 0.00 0.00 0.00 0.00 0.00
    Station C IV, 1980-1990
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 4.66 10.28 12.2 7.31 5.64 5.10 4.57 4.22 3.86 4.36 4.22 5.98
    3 5.02 12.84 12.6 7.53 6.15 5.47 4.63 4.15 3.47 4.23 4.15 6.80
    6 4.55 5.99 13.7 9.21 8.23 12.38 5.72 4.36 2.44 3.14 4.76 6.41
    9 4.04 5.55 14.9 9.83 8.17 14.57 5.51 4.01 0.00 3.70 5.32 6.42
    12 2.85 8.65 24.6 10.12 1.57 9.75 5.25 3.51 0.00 0.00 2.13 5.28
    15 1.18 1.28 9.37 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4.93
E7 NITROGEN CONCENTRATION (1, 13)
  • NH4-N [mg l-1]

    Station C III, 1980-1990
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
    3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
    6 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
    9 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
    12 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
    15 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.36 0.77 0.00 0.00
    18 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.99 0.90 0.72 0.00
    21 2.16 2.34 0.81 1.80 1.53 1.26 1.35 1.44 1.69 2.25 2.16 2.14
    Station C IV, 1980-1990
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
    3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
    6 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
    9 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
    12 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.18 0.54 1.24 0.09 0.00
    15 0.18 0.00 0.00 0.22 0.54 0.72 0.90 1.29 1.39 1.89 0.81 0.00
  • NO3-N [mg l-1](1, 13)

    Station C III, 1980-1990
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 0.34 0.38 0.48 0.68 0.49 0.43 0.49 0.62 0.59 0.57 0.49 0.43
    3 0.29 0.34 0.35 0.63 0.35 0.40 0.48 0.63 0.60 0.58 0.49 0.40
    6 0.27 0.36 0.30 0.56 0.34 0.31 0.41 0.62 0.59 0.58 0.43 0.31
    9 0.24 0.35 0.29 0.54 0.33 0.30 0.50 0.68 0.60 0.57 0.31 0.17
    12 0.21 0.33 0.28 0.53 0.33 0.34 0.51 0.71 0.55 0.50 0.25 0.10
    15 0.22 0.31 0.27 0.52 0.32 0.33 0.50 0.49 0.46 0.39 0.19 0.05
    18 0.25 0.29 0.25 0.50 0.30 0.32 0.40 0.31 0.00 0.00 0.00 0.00
    21 0.00 0.00 0.19 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
    24 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
    Station C IV, 1980-1990
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 0.25 0.42 0.31 0.26 0.19 0.37 0.25 0.14 0.03 0.00 0.25 0.35
    3 0.22 0.40 0.33 0.26 0.19 0.37 0.19 0.09 0.03 0.00 0.25 0.37
    6 0.20 0.40 0.31 0.20 0.15 0.28 0.16 0.09 0.03 0.00 0.28 0.38
    9 0.23 0.40 0.28 0.20 0.09 0.26 0.16 0.06 0.01 0.00 0.25 0.26
    12 0.25 0.37 0.31 0.19 0.06 0.20 0.07 0.01 0.00 0.00 0.19 0.38
    15 0.22 0.28 0.09 0.02 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.35
E8 PHOSPHORUS CONCENTRATION (21)
  • PO4-P [micro l-1]

    Station C II, 1970-1971
    Depth [m] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    0 27.3 2.5 - 5.9 5.0 32.2 1.6 1.2 0.0 4.7 1.2 5.0
    5 20.2 4.3 - 9.9 0.0 31.6 4.7 1.9 9.3 10.2 1.9 2.2
    10 23.6 2.8 - 10.5 28.8 41.2 2.8 5.9 0.6 9.9 0.3 3.1
    15 27.9 3.4 - 8.4 45.3 37.2 3.1 4.7 0.3 7.4 2.2 9.3
    20 9.3 3.1 - 7.4 24.8 33.5 5.0 4.3 0.0 2.8 2.8 7.4
    30 - - - 10.2 53.6 39.1 3.1 2.5 7.1 7.1 2.2 27.3

    Fig. EUR-56-3
    Depth-time diagram of soluble reactive phosphate concentration at Station C III [micro mol l-1].


F. BIOLOGICAL FEATURES

F1 FLORA (21)
  • Emerged macrophytes
    Phragmites australis, Typha latifolia, T. angustifolia, Carex riparia, C. acutiformis, C. hispida, Cladium mariscus, Scirpus littoralis.
  • Floating macrophytes: Nymphaea alba.

  • Submerged macrophytes: Chara sp, Myriophyllum spicatum.

  • Phytoplankton

    • Dinophyceae (Peridinium willei, P. palustre, P. inconspicum, P. pusillum, Ceratium hirundinella); Crytophyceae (Rhodomonas minuta, R. minuta var. nannoplanctica, Cryptomonas erosa, C. ovata, C. curvata, Planonephros parvula); Bacillariophyceae (Cyclotella meneghiniana, C. comta, Synedra acus, S. alnus, Diatoma elongatum, Cocconeis placentula, Achnanthes minutissima, Diploneis elliptica, Navicula cuspidata, N. exigua, N. cryptocephala, Cymbella ventricosa, Gomphocymbella sp., Pinnularia sp., Gomphonema sp., Nitzschia palea, N. acicularis, Amphipleura pellucida, Mastogloia sp.); Chrysophyceae (Chrysococcus rufescens, C. punctiformis, C. tesselatus, Kephyrion sitta, K. doliolum, K. cupuliformis, Ochromonas polychrysis, Erkenia sp., Dinobryon divergens); Chlorophyceae (Chlamydomonas (Chlamydella) sp., C. asymmetrica, Scourfieldia cordiformis, Dictyosphaerium pulchellum, Chlorella vulgaris, Ankistrodesmus falcatus, A. gelifactum, Monoraphidium contortum, M. setiformis, M. minutum, Oocystis sp., Scenedesmus ecornis, S. falcatus, S. quadricauda, Crucigenia tetrapedia, C. irregularis, Cosmarium laeve, Mougeotia sp. Chodatella sp.).
F2 FAUNA (3, 4, 8, 15, 16, 17, 20, 23, 24, 27)
  • Zooplankton

    • Copepoda (Arctodiaptomus salinus, Tropocyclops prasinus, Diacyclops bicuspidatus, Cyclops abyssorum, C. abyssorum mauritaniae); Cladocera (Diaphanosoma brachyurum, Daphnia longispina, Ceriodaphnia reticulata, Bosmina longirostris, Alona rectangula, Scapholeberis mucronata); Rotifera (Keratella cochlearis, K. quadrata, Kellicottia longispina, Anuraeopsis fissa, Polyarthra longiremis, P. major, P. dolichoptera, P. vulgaris, P. remata, Filinia hofmanni, F. terminalis, F. longiseta, F. imnetica, Mytilina bisulcata, Colurella salina, Lecane luna, L. closterocerca, L. stichaea, Cephalodella gibba, Testudinella patina, Hexarthra mira, H. fennica, Asplanchna girodi, Synchaeta pectinata, Trichocerca similis, Collotheca sp., Epiphanes senta, Brachionus calyciflorus, B. urceolaris, Notholca acuminata).
  • Benthos

    • Sublittoral and profundal zone (5 24 m depth) Nematoda (Daptonema dubium, Dorylaimus stagnalis, D. sp., Ironus elegans, I. cf. tenuicaudatus, Tobrilus gracilis, T. sp., Mermithis sp.); Oligochaeta (Dero digitata, Aulodrilus pigueti, Branchiura sowerbyi, Limnodrilus claparedeianus, L. hoffmeisteri, Potamothrix bavaricus, P. hammoniensis, P. heuscheri, Psammoryctides barbatus); Bivalvia (Pisidium milium, P. nitidum, P. obtusale, P. subtruncatum); Cladocera (Alona affinis, A. quadrangularis, Leydigia acanthocercoides, L. leydigii, Scapholeberis sp.); Ciliatea (Frontonia sp., Cohnilembus sp., Halteria grandinella, Strombidium sp., Coleps hirtus); Copepoda (Cyclops sp., Diacyclops bicuspidatus, Eucyclops serrulatus, Macrocyclops albidus, Paracyclops fimbriatus); Ostracoda (Candona neglecta, Cyclocypris ovum, Cypria ophtalmica, Cyprideis torosa, Darwinula stevensoni, Ilyocypris bradyi, I. gibba, Isocypris beauchampi.); Gammaridae (Echinogammarus pungens); Hydrachnellae (Arrenurus sinuator, Neumania deltiodes, N. imitata, Unionicola crassipes); Ephemeroptera (Ephemera glaucops); Chaoboridae (Chaoborus flavicans); Chironomidae (Tanypus punctipennis, Ablabesmyia sp., Cricotopus sylvestris, Chironomus bernensis, C. plumosus, C. nuditarsis, Cladopelma virescens, Cryptochironomus sp., Cryptotendipes sp., Harnischia sp., Microchironomus tener, Microtendipes sp., Paracladopelma sp., Paratendipes sp., Stempellina sp., Stictochironomus maculipennis, Cladotanytarsus atridorsum). Littoral zone Protozoa (Ophrydium versatile); Porifera (Ephydatia fluviatilis); Hydrozoa (Craspedacusta lacustris); Bryozoa (Fredericella sultana, Lophopus crystallinus, Plumatella repens); Turbellaria (Dugesia tigrina); Gastoropoda (Lymnaea auricularia, L. peregra, L. palustris, L. truncatula, Physa acuta, Planorbis carinatus, Anisus leucostoma, Gyraulus laevis, Armiger crista, Hippeutis sp., H. fontanus, Ancylus fluviatilis, Ferrissia wautieri , Valvata piscinalis, V. pulchella, Theodoxus fluviatilis, Acroloxus lacustris, Bithynia tentaculata, Amnicola similis, Succinea putris, Euconolus fulvus, Zonitoides nitidus, Theba carthusiana, Helix ericetorum, H. aspersa, Buliminus obscurus, Pupa muscorum, Vertigo sp., Gomphroa boisiii); Bivalvia (Unio turtoni, Psilunio littoralis, Anodonta cygnaea, Pisidium casertanum); Cladocera (Alona rectangula, Graptoleberis sp.); Copepoda (Eucyclops speratus, Macrocyclops albidus, Paracyclops fimbriatus); Amphipoda (Echinogammarus pungens); Decapoda (Atyaephyra desmaresti); Ostracoda (Cypridopsis parva, Darwinella stevensoni); Ephemeroptera (Ephemerella sp., Caenis sp.); Neuroptera (Sysira sp.); Megaloptera (Syalis sp.); Trichoptera (Mystacides azurea); Diptera (Chaoborus flavicans, Culex pipiens); Chironomidae (Procladius sp., Tanypus sp. Corynoneura sp., Paracladius sp., Parametriocnemus stylatus, Thienemaniella sp., Chironomus sp., Microchironomus sp., Microtendipes sp., Polypedilum spp., Polypedilum (Tripodura) sp., Cladotanytarsus lepidocalcar, Paratanytarsus bituberculatus, P. inopertus, Stempellina sp., Tanytarsus brundini, T. ejuncidus); Rotifera (Euchlanis parva, Lophocaris salpina, Mytilina mucronata, Trichotria pocillum, Macrochaetus altamirai, Colurella sp., Lepadella sp., Lecane luna, L. crepida, Monostyla sp.).
  • Fish

    • Anguilla anguilla, Blennius fluviatilis, Barbus meridionalis, Leuciscus cephalus, Cyprinus carpio, Lepomis gibbosus, Micropterus salmoides, Perca fluviatilis, Scardinius erythrophthalmus.
  • Supplementary notes

    • The phytoplankton biomass reaches the maximum (4,000 6,000 cells ml 1) during the period of spring summer bloom, when the dominant species are Cyclotella glomerata, C. melosiroides and C. comta. The first species are constantly present throughout the year, while the others show distinct seasonal peaks. At the end of summer Chlorella vulgaris begins to increase, culminating after the October rain but without overnumbering Cyclotella spp. Rhodomonas minuta increases in November and becomes dominant in January in the surface water layer (down to 3 m depth). C. glomerata increases simultaneously and remains abundant during winter until the spring bloom. Congeneric forms of planktonic rotifers tend to share the time of appearance or the range of spacial distribution. Many of them exhibit equinoctical maxima of development, and disappear or become hypolimnetic during summer. The distribution of zoobenthos on deep bottom is mainly controlled by dissolved oxygen content. Only one month of DO depletion (at 12 and 20 m depth) in C I basin allows the establishment of diverse benthic communities (31 species) with Oligochaeta as the most important group. In C IV basin, four months of anoxia (at 13 m) limits the benthic fauna to a few species with very low individual densities. The meromictic condition in C III basin allows the occurrence of only Chaoborus flavicans. In the sublittoral zone without oxygen shortage throughout the year, the benthic communities consists of 19 25 species, chironomids being the prevailing components, and sediment particle size becomes an important factor responsible for the distribution of species. Annual production of chironomids ranges between 1 g ash-free dry wt. m-2 yr-1 at 20 m depth and 5 g m-2 yr-1 at 5 m (24). The fish fauna is dominated by rudd (Scaridinius erythrophthalmus) in the limnetic zone and by large mouth bass (Micropterus salmoides, at the surface) and pumpkinseed (Lepomis gibbosus, at 2 m depth )(20).
F4 BIOMASS
    Annual mean values [g C m-2]
    Phytoplankton 1.32 (21)
    Bacterioplankton
    - Phototrophic 1.75 (2)
    - Heterotrophic 1.13 (2)
    Zooplankton 2.60 (16)
    Fish 28.5* (20)
    * [g (wet wt.) m-2]
F5 FISHERY PRODUCTS
    None.
F7 NOTES ON THE REMARKABLE CHANGES OF BIOTA IN THE LAKE IN RECENT YEARS
    Since 1910 two native fish species (Tinca tinca and Gasterosteus aculeatus) became extinct and ten exotic species have been introduced. Among these exotic species, five persist today and dominate the fish community (by importance order: Scardinius erythrophthalmus, Cyprinus carpio, Micropterus salmoides, Lepomis gibbosus, Perca fluviatilis)(19).

G. SOCIO-ECONOMIC CONDITIONS

G1 LAND USE IN THE CATCHMENT AREA (29) (1992)
    Area [km2] [%]
    Natural landscape
    - Woody vegetation 7.3 64
    - Herbaceous vegetation 0.6 5
    - Swamp 1.1 10
    Agricultural land
    - Crop field 0.6 5
    - Pasture 0.2 2
    Residential area 1.6 14
    Total 11.4 100
  • Types of important forest vegetation
    River forest; Mediterranean holm-oak wood mixed with Pinus halepensis.
  • Types of important herbaceous vegetation: Marsh vegetation.

  • Main kinds of crops: Cereals.

  • Levels of fertilizer application on crop fields: Moderate.

  • Trends of change in land use in recent years: Crop fields decreasing.

G2 INDUSTRIES IN THE CATCHMENT AREA AND THE LAKE (30) (1993)
    Gross product per year [$] No. of persons engaged No. of establishments Main products or major industries
    Primary industry
    - Crop production 53,000 24 6 Oat
    - Animal husbandry 65,000 24 6 Cattle, swine
    Secondary industry 7.5x1.0E+6 58 4 Pumps, jewelry
    Tertiary industry - 25 6 Tourism, camping, hotel
  • Numbers of domestic animals in the catchment area
    Cattle 230, sheep 550, swine 2,310, poultry 10,300.
G3 POPULATION IN THE CATCHMENT AREA (30) (1993)
    Population Population density [km 2] Major cities
    Urban - Porqueres
    Rural 350
    Total 350 32

H. LAKE UTILIZATION (30)

H1 LAKE UTILIZATION
    Source of water, sightseeing and tourism (150,000 visitors in 1992), recreation (swimming, sport-fishing and rowing).
H2 THE LAKE AS WATER RESOURCE (1993)
    Use rate [m3 day 1]
    Domestic 6,000
    Irrigation 5,850
    Industrial 5,000

I. DETERIORATION OF LAKE ENVIRONMENTS AND HAZARDS (30)

I1 ENHANCED SILTATION
  • Extent of damage: None.
I2 TOXIC CONTAMINATION
  • Present status: None.

I3 EUTROPHICATION
  • Nuisance caused by eutrophication: None.

I4 ACIDIFICATION
  • Extent of damage: None.


J. WASTEWATER TREATMENTS (30)

J1 GENERATION OF POLLUTANTS IN THE CATCHMENT AREA
    (b) No sources of significant pollution.
J2 APPROXIMATE PERCENTAGE DISTRIBUTION OF POLLUTANT LOADS
    [%]
    Non-point sources (agricultural, natural and dispersed settlements) 90
    Point sources
    - Tourism 10
    Total 100
J3 SANITARY FACILITIES AND SEWERAGE
  • Percentage of municipal population in the catchment area provided with ade-
    quate sanitary facilities or public sewerage: 86%.
  • Percentage of rural population with adequate sanitary facilities: 10%.

  • Municipal wastewater treatment systems
    No. of secondary treatment systems: 1.
    No. of primary treatment systems: 1.

K. IMPROVEMENT WORKS IN THE LAKE (30)

K1 RESTORATION
    Restoration of reed belt and riparian vegetation.

L. DEVELOPMENT PLANS: None.


M. LEGISLATIVE AND INSTITUTIONAL MEASURES FOR UPGRADING LAKE ENVIRONMENTS (30)

M1 NATIONAL AND LOCAL LAWS CONCERNED
  • Names of the laws (the year of legislation)

    1. RAE (1992)
  • Responsible authorities

    1. City Council of Banyoles
M3 RESEARCH INSTITUTES ENGAGED IN THE LAKE ENVIRONMENT STUDIES
  1. Department of Ecology, University of Barcelona
  2. Institute of Aquatic Ecology, University of Girona

N. SOURCES OF DATA

  1. Questionnaire filled by Dr. Maria Rieradevall, Department of Ecology, University of Barcelona, and the Secretariat, Institut d'Ecologia Aquatica, Girona.
  2. Abella, C. (1980) Population dynamics compared of planktonic photosynthetic bacteria. Ph.D. Dissertation, Univ. of Barcelona.*1
  3. Abella, C., Montesinos, E. & Guerrero, R. (1981) Stratification and dynamics of phototrophic bacterial populations in a meromictic basin of Lake Banyoles. Bull. Soc. Cat. Biol., V VI: 11 27.
  4. Alfonso, M. T. (1985) Zooplankton study in a meromictic basin of Lake Banyoles and an anoxic lagoon in the same karstic system. Ph.D. Dissertation, Univ. of Valencia.*1
  5. Altaba, C. R. (1985) Recent freshwater bivalves from Paisos Catalans . Master Thesis, Univ. of Barcelona. 237 pp.*2
  6. Borrego, C. (1992) Studies on Phototrophic Sulphur Bacterial Growth in Lake Banyoles. Progress Report. Institute of Aquatic Ecology, Univ. of Girona.*2
  7. Brusi, D. (1993) Travertine formations in Banyoles depression. Ph.D. Dissertation, Autonomous Univ. of Barcelona.*2
  8. Canals, M., Got, H., Julia, R. & Serra, J. (1990) Solution-collapse depressions and suspended in the limnocrenic lake of Banyoles (NE Spain). Earth Surface Process and Landforms, 15: 243 254.
  9. Casadevall, M., Vila, A. & Moreno-Amich, R. (1985) Approach to Lake Banyoles malacological fauna by rests analysis in the sediment. Scientia Gerundensis, 11: 73 80.*2
  10. Casamitjana, X. & Roget, E. (1988) Effect of suspended sediment on the heating of Lake Banyoles. Jour. Geophys. Res., 93 (C8): 9332 9336.
  11. Casamitjana, X. & Roget, E. (1993) Resuspension of sediment by focused ground water in Lake Banyoles. Limnol. Oceanogr., 38 (3): 643 656.
  12. Casamitjana, X., Schladow, G. & Roget, E. (1993) The seasonal cycle of a groundwater dominated lake. Jour. Hydraul. Res., 31 (3): 293 306.
  13. Colomer, J. (1992) Study of the thermal and mass fluxes in Lake Banyoles. Master Thesis, Auton. Univ. of Barcelona.*2
  14. Garcia, Gil, L. J. (1990) Phototrophic bacteria and iron cycle in Lake Banyoles. Ph.D. Dissertation, Institute of Aquatic Ecology, Auton. Univ. of Barcelona.*2
  15. Julia, R. (1980) Catchment area of Banyoles-Besalu. Ph.D. Thesis, Centre d'Estudis Comarcals de Banyoles. 275 pp.*2
  16. Miracle, M. R. (1974) Population dynamics and structure in zooplanktonic community of Lake Banyoles. Ph.D. Dissertation, Univ. of Barcelona.*1
  17. Miracle, M. R. (1978) Specific composition of zooplanktonic communities in 153 Pyrenees lakes and their biogeographical interest. Oecol. aquat., 3: 167 192.*1
  18. Miracle, M. R. (1976) Spatial and temporal distribution of zooplankton species in Lake Banyoles. Monografias Icona, 5: 1 270.*1
  19. Moreno-Amich, R. & Garcia-Berthou, E. (1989) A new bathymetric map based on echo-sounding and morphometrical characterization of the Lake of Banyoles (NE Spain). Hydrobiologia, 185: 83 90.
  20. Moreno-Amich, R., Vila, A. & Garcia-Berthou, E. (1991) Fish introduction in a Mediterranean karstic lake. Abstracts, Seventh International Ichthyology Congress.
  21. Moreno-Amich, R., Vila, A., Boix, D. & Garcia-Berthou, E. (1992) Spatial distribution of native and introduced fish of Banyoles Lake (NE Spain). Abstracts, XXV SIL International Congress.
  22. Planas, M. D. (1973) Productivity, composition and cycle of phytoplankton in Lake Banyoles. Oecol. Aquat. 1: 3 106.*2
  23. Riera, P. & Roca, A. (1992) A diverse economy. El Pla de l Estany (ed. Caixa de Catalunya).*2
  24. Rieradevall, M. & Busquets, J. M. (1990) Bryozoans of Banyoles Lake (NE Spain). Limnetica, 6: 137 146.
  25. Rieradevall, M. (1991) Ecology and production of benthos of Lake Banyoles. Ph.D. Dissertation, Univ. of Barcelona (some chapters in English).*2
  26. Roget, E., Colomer, J. & Casamitjana, X. (1993) Bottom currents induced by baroclinic forcing in Lake Banyoles (Spain). Aquatic Sciences, 52 (2) (in press).
  27. Roget, E., Salvado, G., Llebot, J. E. & Zamboni, F. (1993) Internal waves in a little lake with a thick metalimnion. Verh. Internat. Verein Limnol. (in press).
  28. Traveset, A. (1985) Contribution to the knowledge of freshwater sponges of Iberian Peninsula: 1 87. Master Thesis, Univ. of Barcelona.*2
  29. Vila, X., Torrent, C., Moreno-Amich, R. & Abella, C. (1987) Evaluation of physical and chemical pollution indicators in the outflowing channels of Lake Banyoles. Scientia Gerundensis, 13: 53 65.*2
  30. Vilar, L., Dept. Biology, Univ. of Girona: Personal communication.
    *1 Printed in Spanish.
    *2 Printed in Catalan.