“Laguna del Negro Francisco”的意思、由来-开放百科全书

}}Laguna del Negro Francisco is a lake in the Atacama Region Chile and the southernmost closed lake in the country. It is situated {{convert|200|km}} northeast of the city of Copiapó. The lake is about {{convert|10|km}} long and {{convert|4|km}} wide with a surface area of about {{convert|20.7|km2}} and a depth of about {{convert|1|m}}. A peninsula probably formed by a moraine and subsequently modified by wind-driven accumulation of sand separates the lake into a north-northwesterly and a south-southeasterly half with different colour and water composition.

The lake is of tectonic origin and lies within a basin bordered by mountain ranges to the east and the west and two volcanoes north and south. It formed when the Astaburuaga River was redirected into the lake basin from the east, and this river is also its main source of water. Water levels have fluctuated over the last 6,000 years and the lake is currently in a lowstand period. In 1996 the lake was classified as a Ramsar site and it currently lies within the Nevado Tres Cruces National Park. In the past there were plans to redirect inflowing water into the Copiapó River and presently a mining company holds water rights to the Astaburuaga River.

Geography and geomorphology

Laguna del Negro Francisco lies {{convert|200|km}} northeast of the city of Copiapó in the Atacama Region of Chile,{{sfn|Iriarte|Venegas|2000|p=71}} and can be reached by south-bound roads that diverge from the Copiapó-Tinogasta road close to the Salar de Maricunga.^[1] A National Forest Corporation building is close to the southwestern shore of the lake.{{sfn|Iriarte|Venegas|2000|p=74}} The area has been called a "scenic beauty".{{sfn|UNIDAD DE GESTION PATRIMONIO SILVESTRE|1997|p=17}}

The lake lies at an elevation of {{convert|4125|m}},{{sfn|Grosjean|Valero-Garcés|Geyh|Messerli|1997|p=152}} is {{convert|10|x|4|km}} wide^[2] and has a surface area of {{convert|20.7|km2}}, but a depth of only about {{convert|1|m}};{{sfn|Grosjean|Valero-Garcés|Geyh|Messerli|1997|p=152}} the Ministry of Public Works estimated a mean depth of {{convert|7|m}} in 1941.{{sfn|Niemeyer|1980|p=255}} The water surface can fluctuate between {{convert|17|-|31|km2}} from year to year.{{sfn|Rundel|Kleier|2014|p=3}}

The lake is subdivided into a northern or northwestern and a southern or southeastern part by a^[3]{{sfn|Grosjean|Valero-Garcés|Geyh|Messerli|1997|p=152}} {{convert|20|m}} high peninsula, on which wave action has led to the formation of sand spits.^[4] The peninsula was formed either by wind-driven accumulation of sand as a sandbank or as a moraine left by a former glaciation.^[3]{{sfn|Grosjean|Valero-Garcés|Geyh|Messerli|1997|p=152}} Under present-day water levels, the sandbank separates the lake into two parts with different water composition: The southern part has fresher water and thus has a different colour than the saline northern part, as wetlands formed in the southern part.^[3]{{sfn|Grosjean|Valero-Garcés|Geyh|Messerli|1997|pp=152-153}}

The land around the lake is formed by alluvial fans^[3] and in the eastern sector by alluvial deposits such as gravels, sands and silts.{{sfn|Grosjean|Valero-Garcés|Geyh|Messerli|1997|p=152}} A number of mountains surround the lake, such as the {{convert|6080|m}} high Copiapó and the {{convert|5880|m}} Jotabeche.{{sfn|Niemeyer|1980|p=255}}

The Astaburuaga River enters the lake on its eastern shore;{{sfn|Valero-Garcés|Grosjean|Kelts|Schreier|1999|p=105}} it originates on the mountains east of Laguna del Negro Francisco where it is nourished by snowmelt.{{sfn|Rundel|Kleier|2014|p=3}} Other tributaries are the Quebrada Azufre in the northwest, Rio de la Sal in the northeast and Rio La Gallina in the southwest;{{sfn|Iriarte|Venegas|2000|p=74}} the tributaries of Laguna del Negro Francisco feature wetlands^[2] and marsh vegetation has developed at the mouth of the Astaburuaga.{{sfn|Valero-Garcés|Grosjean|Kelts|Schreier|1999|p=105}}

Hydrology and biology

The lake is polymictic,{{sfn|Grosjean|Valero-Garcés|Geyh|Messerli|1997|p=152}} meaning that the water in the lake is usually layered but mixes over several times in the year. In sediments remnants of characeae, diatoms, ostracods and Ruppia have been found;{{sfn|Grosjean|Valero-Garcés|Geyh|Messerli|1997|p=153}} today only one ostracod species persists in the lake.^[10] Flamingos exist in the area and the lake is an important site for birds.{{sfn|Rundel|Kleier|2014|p=4}}

The watershed of Laguna del Negro Francisco covers a surface area of {{convert|930|km2}}.{{sfn|Grosjean|Valero-Garcés|Geyh|Messerli|1997|p=152}} The Astaburuaga River is the principal inflow; other creeks that enter the lake and groundwater play only a minor role.{{sfn|Grosjean|Valero-Garcés|Geyh|Messerli|1997|p=153}}{{sfn|Iriarte|Venegas|2000|p=71}} The mean discharge of the Astaburuaga is about {{convert|0.888|m3/s}},{{sfn|UNIDAD DE GESTION PATRIMONIO SILVESTRE|1997|p=27}} but it varies strongly over time, including at different hours of the day as the water of the river freezes and remelts.{{sfn|Niemeyer|1980|p=256}} In addition, some water from the Astaburuaga River flows into the Cíenaga Redonda basin rather than Laguna del Negro Francisco;{{sfn|UNIDAD DE GESTION PATRIMONIO SILVESTRE|1997|p=27}} presently, an alluvial cone separates the Astaburuaga River in the Valle Ancho gorge from the Salar de Maricunga/{{sfn|Niemeyer|1980|p=249}} Cíenaga Redonda watershed.{{sfn|UNIDAD DE GESTION PATRIMONIO SILVESTRE|1997|p=27}}

The lake has no outlet{{sfn|Grosjean|Valero-Garcés|Geyh|Messerli|1997|p=152}} and is the southernmost closed basin in Chile;^[11] however during former lake level highstands the lake overflowed at {{convert|4236|m}} into the Salar de Maricunga.{{sfn|Grosjean|Valero-Garcés|Geyh|Messerli|1997|p=153}} The lake was once considered to be the source of the Copiapó River.^[2]

Geology

Geologically, the lake is located in a {{convert|200|km2}}{{sfn|Iriarte|Venegas|2000|p=71}} north-south trending depression between the Andes in the east and the Cordillera Domeyko in the west;{{sfn|Valero-Garcés|Grosjean|Kelts|Schreier|1999|p=104}} subduction of the Nazca Plate beneath South America os responsible for the formation of these mountain ranges.{{sfn|Valero-Garcés|Grosjean|Kelts|Schreier|1999|p=102}} On these sides normal faults border the depression which is closed to the north and the south by the Quaternary volcanoes Copiapó and Jotabeche, respectively. Oligocene to Pliocene andesites of the Negro Francisco Formation and Quaternary sediments cover the depression, the latter especially in the east.{{sfn|Grosjean|Valero-Garcés|Geyh|Messerli|1997|p=152}} The depression extends past these volcanoes to the Salar de Pedernales and the Salar de Maricunga;{{sfn|Valero-Garcés|Grosjean|Kelts|Schreier|1999|p=104}}

Climate and life

There is little information on the climate of the lake, but average temperatures are {{convert|1|-|2|C}} and precipitation mostly falls during winter from cold fronts and cutoff lows probably subordinate summer precipitation;{{sfn|Grosjean|Valero-Garcés|Geyh|Messerli|1997|p=152}} the total amount of precipitation is about {{convert|250|mm/year|in/year}}.{{efn|Between 1943 and 1945, an annual precipitation of {{convert|118|mm/year|in/year}} was measured.{{sfn|UNIDAD DE GESTION PATRIMONIO SILVESTRE|1997|p=23}}}} Evaporation is about six times larger than precipitation.{{sfn|Valero-Garcés|Grosjean|Kelts|Schreier|1999|p=104}} The region is windy^[3] and is considered to be a cold desert.{{sfn|UNIDAD DE GESTION PATRIMONIO SILVESTRE|1997|p=23}}

Vegetation is scarce at these altitudes{{sfn|Niemeyer|1980|p=257}} ans is classified as steppe vegetation. Animals found in the region include guanacos, pumas, vicuñas and vizcachas, while birds include Andean goose and three flamingo species.^[14] The area is a protected area{{sfn|Iriarte|Venegas|2000|p=71}} as part of the Nevado Tres Cruces National Park{{sfn|Rundel|Kleier|2014|p=3}} and was declared a Ramsar site in 1996, a site of international importance to waterbirds.{{sfn|UNIDAD DE GESTION PATRIMONIO SILVESTRE|1997|p=1}}

Lacustrine history

In the past, the Astaburuaga River did flow to the Salar de Maricunga; tectonic subsidence of the Negro Francisco Basin eventually led to a river capture involving a former tributary of the Astaburuaga reversing into the Negro Francisco basin and finally capturing the Astaburuaga itself.{{sfn|Valero-Garcés|Grosjean|Kelts|Schreier|1999|p=104}} This event is responsible for the formation of Laguna del Negro Francisco within the basin as without the Astaburuaga's input there would not be enough water to sustain a permanent lake.{{sfn|Valero-Garcés|Grosjean|Kelts|Schreier|1999|p=123}}

Older shorelines testify to higher water levels in the past^[3] exceeding the present-day water level by {{convert|100|m}} (at spillover point); other shorelines are found at {{convert|1|m}}, {{convert|5|m}} and {{convert|25|m}} above sea level.{{sfn|Grosjean|Valero-Garcés|Geyh|Messerli|1997|p=153}} The maximum surface area of the lake reached {{convert|30|mi2|km2|order=flip}}.{{sfn|Stoertz|Ericksen|1974|p=53}} A wet period occurred in northern Chile, northwestern Argentina and the Bolivian Altiplano during the so-called "Lake Tauca phase", and in the Mediterranean parts of Chile it ended together with the Pleistocene for not yet clear reasons.{{sfn|Grosjean|Valero-Garcés|Geyh|Messerli|1997|p=152}} Underwater shorelines also exist, indicating that at times the lake level was lower than today.{{sfn|Stoertz|Ericksen|1974|p=63}}

During the Holocene, the lake at times turned into a salt pan which only occasionally filled with water, such as between 6,000 and 3,800 years before present.{{sfn|Grosjean|Valero-Garcés|Geyh|Messerli|1997|p=156}} Starting 3,600 years ago, a large wet period in the region made the lake grow in size and become less saline, with brackish conditions established between 3,000 and 1,800 years ago. During this wet period, glaciers in the region expanded due to the increased availability of moisture and peat bogs formed in valleys.{{sfn|Grosjean|Valero-Garcés|Geyh|Messerli|1997|p=158}}

After 1,800 years before present the lake became saltier again, either because of salt accumulation or because the lake shrank; the latter possibility is more likely. More recent fluctuations have occurred as well; a dry period may be associated with the little ice age.{{sfn|Grosjean|Valero-Garcés|Geyh|Messerli|1997|p=158}} In 2012-2015 environmental degradation in the area has become apparent, accompanied by a shrinkage of water surfaces and dropping groundwater levels.^[16]

Human use

In prehistory, first pre-ceramic hunter-gatherers and later ceramics-using people who also engaged in horticulture were active in the area of the Astaburuaga River and the Laguna del Negro Francisco.^[17] The Inca were active in the valleys south and southwest from Laguna del Negro Francisco{{sfn|Gaete|1999|p=225}} and also on the Copiapó and Jotabeche.{{sfn|Gaete|1999|p=225,234}}

A 1921 publication mentioned a project to divert waters of the Astaburuaga River for irrigation purposes;^[18] later devised projects envisaged capturing the discharge into the lake in a canal and transfer the water through a tunnel into the Figueroa River,{{sfn|Niemeyer|1980|p=257}} one of the headwaters of the Copiapó River;{{sfn|Gaete|1999|p=224}}) or to divert the Astaburuaga River into the Salar de Maricunga and from there into the Copiapó River catchment.{{sfn|Niemeyer|1980|p=257}} In 2009, a mining company held rights to divert about {{convert|0.34|m3/s}} from the Astaburuaga River.^[19] The lakes of the water itself are not suited for either drinking or irrigation purposes.{{sfn|Niemeyer|1980|p=257}}

Notes

References

1. ^¹{{cite journal|last1=Desplanque|first1=Samantha Amstein|title=Los humedales y su protección en el Derecho Internacional|journal=Revista de Derecho Ambiental|date=4 July 2017|issue=7|pages=114–140|url=https://revistas.uchile.cl/index.php/RDA/article/view/46451|language=es|issn=0719-4633}}
2. ^¹{{cite book|last1=Scheffers|first1=Anja M.|last2=Kelletat|first2=Dieter H.|title=Lakes of the World with Google Earth: Understanding our Environment|date=2016|publisher=Springer|isbn=9783319296173|page=113|language=en}}
3. ^¹{{cite web|last1=Risacher|first1=François|last2=Alonso|first2=Hugo|last3=Salazar|first3=Carlos|title=Geoquimica de aguas en cuencas cerradas: I, II y III regiones - Chile|url=http://documentos.dga.cl/CQA1921v1.pdf|accessdate=17 November 2018|page=9|language=es|date=1999}}
4. ^¹{{Cite journal|via=Academia.edu|language=es|last1=PERALTA|first1=Paulina|first2=Carlos|last2=GONZÁLEZ|first3=Catherine|last3=WESTFALL|first4=Gabriela|last4=SANTANDER|year=2010|title=Primeras aproximaciones sobre la arqueología de Pampa Austral: Explotación y tecnología lítica al interior de la Región de Atacama (Chile)|journal=En Actas del XVII Congreso Nacional de Arqueología Chilena|volume=2|p=304}}
5. ^¹{{Cite journal|url=http://publicaciones.mnhn.cl/668/w3-article-70596.html|language=es|journal=Boletín del Museo Nacional de Historia Natural, Chile|volume=61|year=2012|title=Nuevos registros de poblaciones de Chinchilla de cola corta, Chinchilla chinchilla, (Rodentia: Chinchillidae) en la cordillera de la región de Atacama, Chile|first1=Nicolás|last1=Lagos|first2=Rodrigo|last2=Villalobos|first3=Agustín|last3=Iriarte|p=193}}
6. ^¹{{cite journal|last1=Schwalb|first1=Antje|last2=Burns|first2=Stephen J|last3=Kelts|first3=Kerry|title=Holocene environments from stable isotope stratigraphy of ostracods and authigenic carbonate in Chilean Altiplano Lakes|journal=Palaeogeography, Palaeoclimatology, Palaeoecology|date=April 1999|volume=148|issue=1–3|pages=153–168|doi=10.1016/S0031-0182(98)00181-3|language=en|issn=0031-0182}}
7. ^¹{{cite news|title=Volcán sigue aumentando reservas|url=http://www.mch.cl/reportajes/volcan-sigue-aumentando-reservas/|accessdate=17 November 2018|work=Míneria Chilena|date=9 June 2009|language=es}}
8. ^¹{{cite journal|title=Agriculture, Industry and Commerce|journal=Bulletin of the Pan American Union|via=Hein Online|date=1921|page=71|url=https://heinonline.org/HOL/LandingPage?handle=hein.journals/bulpnamu52&div=12&id=&page=|accessdate=17 November 2018}}
9. ^¹²³{{Cite book|url=https://archive.org/details/jeografiadescri00munogoog|title=Jeografía descriptiva de las provincias de Atacama i Antofagasta|last=Muñoz|first=Santiago|date=1894|location=Santiago de Chile|language=es|p=45|publisher=University of California}}
10. ^¹{{cite web|last1=Gonzalez|first1=Fernando P.|title=Estudio geologico preliminar sobre los recursos minerales de la hoja Laguna del Negro Francisco|url=http://tienda.sernageomin.cl/TiendaVirtual2/ProductDetail.aspx?pid=1268|website=SERNAGEOMIN|accessdate=16 November 2018|page=6|language=es|date=1978}}
11. ^¹²³⁴⁵⁶{{cite web|last1=Wilkinson|first1=M. Justin|title=Laguna del Negro Francisco|url=https://earthobservatory.nasa.gov/images/89348/laguna-del-negro-francisco|website=NASA Earth Observatory|accessdate=16 November 2018|date=18 March 2010}}