Natural Basins Andean Lakes

Most Andean lakes were formed by tectonic activity, vulcanism or glaciers. Tectonic and volcanic events played important roles in lake formation throughout the Andean ranges. However, given that these processes have been more active in arid regions, there are fewer tectonic lakes than glacial lakes. Lake Titicaca is perhaps the best known example of an Andean tectonic lake. Tectonic forces are also responsible for the creation of salt lakes in endorreic areas within the Altiplano (shared by Argentina, Bolivia, Chile and Perú). On the other hand, glaciation has widened, deepened, and dammed many valleys, and created an important lake district in the Andean region of southern South America. In fact, the latter region (between 39° S and 55° S) includes many of the largest and deepest lakes of South America.

Tropical mountain lakes In general, two kinds of systems can be distinguished among tropical mountain lakes:

1. High-elevation lakes from the Andes: these lakes occur in orographic deserts, such as the Puna, at high altitudes (ca. 3500-4000 m.a.s.l.). Because of their occurrence at high elevations, sometimes above the timberline, they are characterized by low water temperatures and rather particular chemo-optical characteristics. High salt and pH values, as well as low dissolved organic matter

(DOC) concentrations and high transparency, characterize these lakes. Moreover, some of the smaller lakes freeze during part of the year. The best known of these lakes is Lake Titicaca (Table 1) in the Andes on the border of Perú and Bolivia. Within high-altitude lakes, Titicaca is the largest and deepest lake in the world. It is one of the few cases in which the lake basin was formed by the uplifting of virtually undisturbed sections of ancient peneplains during the process of the mountain building. In addition, a large number of smaller salt lakes are spread all over the region. 2. Lakes from humid equatorial or seaward facing ranges: in contrast to tropical high altitudinal lakes, the high rainfall in these zones results in low salt concentrations. Overall, the limnological characteristics of these lakes are similar to those described for tropical lowland lakes (see later text). The best studied of these is Lake Valencia (Table 1). It is a graben lake located in the Aragua Valley of Venezuela. It was formed due to faulting and subsequent damming of the Valencia River. The level of the lake has fluctuated widely during the last 10 000 years in response to climatic variations. In recent years, the water level has decreased due to a shift towards drier conditions and to human use of water in the watershed.

Temperate mountain lakes Temperate lakes in the Southern Hemisphere are restricted to the southern tip of South America and New Zealand. Compared to North America, Europe and Asia, the continental southern temperate land masses are relatively small. As a result southern temperate lakes experience strong winds and maritime climates. Thus, large temperate lakes in the Southern Hemisphere are monomictic and do not freeze during winter. Interestingly, thermoclines develop deeper in the Southern Hemisphere than in similar lakes in the Northern Hemisphere. In turn, deeper epilimnia translates into lower chlorophyll concentrations at comparable levels of phosphorus in Southern Hemisphere temperate lakes than their Northern Hemisphere counterparts.

At least three lake types may be recognized in the temperate Andean region of South America:

1. Large, deep, piedmont lakes. These vary in size and depth, but can be as large as 1892 km2 (Buenos Aires lake) and as deep as 836 m (O'Higgins-San Martin). These lakes are mono-mictic, oligotrophic and highly transparent. They tend to occur in transversal valleys running east-west and are therefore well exposed to the dominant winds from the Pacific. These lakes mostly occur in the forested areas close to the

Table 1 Location and morphological features of selected lakes

Ñame

Location

Lake type

Origin

Valencia

10°12'N

Tropical mountain

Tectonic

67°44'W

Titicaca

16°S

Tropical mountain

Tectonic

69°W

Chungará

18°14'S

Tropical mountain

Tectonic-volcanic

69°09'W

Poopo

18°47'S

Tropical mountain

Tectonic

67°7' 30"W

Iberá

28°S

Temperate lowland

Fluviatile

57°W

Mar Chiquita

30°40'S

Temperate lowland

Tectonic

62°40'W

Patos

31°9'S 51°05'W

Coastal lagoon

Marine

Mirim

31°9'S 51°05'W

Coastal lagoon

Marine

Chascomús

35°36'S

Temperate lowland

Eolic

58°00'W

Caviahue

37°53'S

Temperate mountain

Volcanic

71°02'W

Puyehue

40°40'S

Temperate mountain

Glacial

72°35'W

Nahuel Huapi

40°50'S

Temperate mountain

Glacial

71°30'W

Moren ito

41°03'S

Temperate mountain

Glacial

71°31'W

Escondido

41°04'S

Temperate mountain

Glacial

71°35'W

Todos los santos

41°04'S

Temperate mountain

Glacial

72°16'W

Schmol

41°11'S

Temperate mountain

Glacial

71°18'W

Jacob

41°11'S

Temperate mountain

Glacial

71°34'W

Musters

42°22'S

Temperate mountain

Tectonic

69°11'W

Colhué Huapi

45°30'S

Temperate lowland

Tectonic-eolic

68°45'W

Buenos Aires

46°39'S

Temperate mountain

Glacial

72°03'W

Surface area (km2) Max depth (m) Mean depth (m) Altitude (m.a.s.l.) Source

8400

2600

1984

9800 560 30.1

9.22

0.83

178.5

414 810 1892

39 284 34

19 100

51.4

20 2

420 3810 4520 3695

1600 230 764 770 790 189 1950 1550 260 258 230

O'Higgins-San Martin

48°50'S 72°36'W

Temperate mountain

Glacial

1058

836

285

16

Cardiel

48°57'S 71°13'W

Temperate mountain

Tectonic

460

80

49.1

300

1,4

La Tota

5°34'N 72°56'W

Tropical mountain

Tectonic

60

60

30

3015

5

Argentino

50°200S 72°450W

Temperate mountain

Glacial

1466

500

150

187

4

Ofhidro

53°570S 69°38'W

Temperate mountain

Glacial

54

210

16

Blanco Lake

54°04'S 69°03'W

Temperate mountain

Glacial

155

180

16

Fagnano

54°32'S 67°500W

Temperate mountain

Tectonic

590

200

140

1. BaigUn C and Marinone C (1995). Cold-temperate lakes of South America: Do they fit northern hemisphere models? Archive fur Hydrobiologie 135(1): 23-51.

2. Baker PA, Fritz SC, Garland J, and Ekdhal E (2005) Holocene hydrologic variation at Lake Titicaca, Bolivia/Peru, and its relationship to North Atlantic climate variation. Journal of Quaternary Science 20(7-8): 655-662.

3. Brachini L, Cozar A, Dattilo AM, Picchi MP, Arena C, Mazzuoli S, and Loiselle SA (2005) Modelling the components of the vertical attenuation of ultraviolet radiation in a wetland lake ecosystem. Ecological Modelling 186: 43-45.

4. Calcagno A, Fioriti MJ, Lopez H, Pedrozo F, Razquin ME, Rey C, Quiros R, and Vigiliano P (1995) Catalogo de Lagos y Embalses de la Argentina, Direccion Nacional de Recursos Hidricos, Buenos Aires, Argentina.

5. Cordero RD, Ruiz JE, and Vargas EF (2005) Determinación espacio-temporal de la concentración de fosforo en el Lago de Tota. Revista Colombiana de Química 34(2): 211-218.

6. Díaz M, Pedrozo F, and Baccala N (2000) Summer classification of Southern Hemisphere temperate lakes (Patagonia, Argentina). Lakes and Reservoirs: Research and Management 5: 213-229.

7. Dorador C, Pardo R, and Vila I (2003) Variaciones temporales de parámetros físicos, químicos y biologicos de un lago de altura: el caso del lago Chungará. Revista Chilena de Historia Natural 76: 15-22.

8. Lewis W Jr (1983) Temperature, heat and mixing in lake Valencia. Venezuela. Limnology and Oceanography 28(2): 273-286.

9. Mulhauser H, Hrepic N, Mladinic P, Montecino V, and Cabrera S (1995) Water quality and limnological features of a high altitude Andean lake, Chungaré!, in northern Chile. Revista Chilena de Historia Natural 68: 341-349.

10. Niencheski LFH, Baraj B, Windom HL, and Franca RG (2004). Natural background assessment and its anthropogenic contamination of Cd, Pb, Cu, Cr, Zn, Al and Fe in the sediments of the southern area of Patos Lagoon. Journal of Coastal Research. 39: 1040-1043. (Special issue).

11. Pedrozo F, Kelly L, Diaz M, Temporetti P, Baffico G, Kringel R, Friese K, Mages M, Geller W, and Woelfl S (2001) First results on the water chemistry, algae and trophic status of an Andean acidic lake system of volcanic origin in Patagonia (Lake Caviahue). Hydrobiologia 452: 129-137.

12. Spivak E (1997) Cangrejos estuariales del Atlantico sudoccidental (25°-41° S) (Crustacea: Decapada: Brachyura). Ivest. Mar. Valparaiso 25: 105-120.

13. Taborga J and Campos J (1995) Les resources Hydriques de L'Altiplano. Bull. Inst. Fr. Eludes Andines 24(3): 441-448.

14. Vincent W, Wurtsbaugh W, Vincent C, and Richerson P (1984) Seasonal dynamics of nutrient limitation in a tropical high-altitude lake (Lake Titicaca, Peru-Bolivia): Application of physiological bioassays. Limnology and Oceanography 29(3): 540-552.

15. Zagarese HE, Díaz M, Pedrozo F, and Úbeda, C. (2000) Mountain lakes in orthwestwen Patagonia. Verhandlungen Internationale Vereinigung fu r theoretische und angewandte. Limnologie, 27: 533-538.

16. Ziesler R and Ardizzone GD (1979) COPESCAL, Doc. Tec./COPESCAL Tech. Pap., (1): Las Aguas Continentales de America Latina. http://www.fao.org/docrep/008/ad770b/AD770B00.HTM

Refer to * Soto (2002), ** Morris et al. (1995), *** Marinone et al. (2006) in Further readings section.

Andes, but some of them also occur in (or extend into) the Patagonian steppe.

2. Small to medium size, piedmont lakes. They share many characteristics with the previous type, the main difference being their relatively shallowness (less than 15-20 m) and as a consequence, polymic-tic thermal regimes. Least exposed lakes freeze during winter. They tend to be more productive and less transparent, partly due to the lack of permanent stratification (i.e., epilimnetic water is periodically in contact with the sediments), and partly because of higher levels of colored dissolved organic matter (CDOM) from the surrounding forests.

3. Small to medium size mountain lakes. These lakes are similar in size and depth to the previous group of lakes, but they occur at higher elevations, some even above the timberline. Given that the soils in their watersheds are poorly developed and the dominant rock, granite, is highly refractory, these lakes are typically oligo-trophic or ultraoligotrophic. Conductance may be as low as 10-15 mScm-1, CDOM concentrations are close to the lower limit reported for lakes, and transparency to PAR and ultraviolet radiation is only slightly lower than that of the most oligotrophic oceanic waters (e.g., Lake Schmol). Most of these lakes freeze from late fall until late spring or early summer. Summer stratification is also unstable, since these lakes frequently mix completely due to their relative shallowness and high exposure to strong winds. Most, if not all, of these lakes lack fish and have extremely simple food webs.

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