The Peruvian Government established the Junín National Reserve with an area of 53,000 hectares bordering Lake Junín and its adjacent territories, through Supreme Decree No. 0750-74-AG on August 7, 1974.
Location, area, and boundaries
Junín National Reserve is located in the Central Andes of Peru, in the Carhuamayo, Ondores and Junín Districts of the Department of Junín and the Ninacaca and Vicco Districts of the Department of Pasco. The area is surrounded by an extensive high plateau known as the Bombón Plateau, as well as small lagoons such as Lulicocha, Chacacancha, Tauli, Cusicocha, Ahuascocha, and Rusquicocha.
The lake is situated in the far northeastern pampas of Junín, at the geographic coordinates of 10º 50’ 50” S - 75º 59’ 25” W and 11º 09’ 55” S - 76º 15’ 40” W (8800000 – 360000 and 8760000 – 400000, UTM coordinates) The elevation of the National Reserve ranges from 4080 to 4125 meters above sea level (masl).
Geology and Geomorphology
The origin of the plateau dates back to the last glaciation (during the Pleistocene Era, 12,000 to 15,000 years ago). In the north, the glaciers converged on both sides of the plateau from the mountains and deposited moraines which formed a dike in this area. In the far south, deposition fans impeded drainage, which led to the formation of Lake Chinchaycocha, also known as Lake Junín.
Although the origin of the lake is not well established, it is possibly related to tectonic phenomena. Another theory maintains that a slight, progressive sinking which occurred once the raising of the Andean Mountains concluded, generating a depression which formed the lake.
The Oriental, Central and Occidental Mountain Ranges converge in Junín, creating the mountain peak known as the Nudo de Pasco to the north. An extensive plateau is formed here, known as the Bombón Plateau, a name which alludes to the ancient people of the region known as the Pumpush, or Pun-Pun. In the reserve there are somewhat deteriorated archaeological artifacts, found near the Upamayo Dam in the northern part of the protected area.
The origin and composition of the geologic strata pertain to continental facies and marine sediments. Continental facies, which are found in deposits on the southern, eastern, and northern shores of the lake, are from Quaternary sedimentary rocks composed of conglomerates and clays formed by moraine and glacial fluvial deposits which settled in depressions. Marine sedimentary deposits from the late Triassic and early Jurassic Periods are seen on the western shore. These are the oldest deposits, which are principally sedimentary limestone rocks corresponding to the beginning of the Mesozoic Era.
The topography of the land surrounding the northern, eastern and southern shores is predominantly flat, with gradients of 1% to 4%, which can be observed from the Upamayo Bridge and from Paucarcoto, points on the border of the pampas of Huampuay and pampas of Vicco, respectively. The topography of the southwestern, western and northeastern shores is totally different, where hills ranging from 50 to 150 meters above the surface border the lake, with gradients of up to 45%.
View of Lake Junín and the surrounding area
The principal soils of the Junín National Reserve are: eutric histosols, which are soils developed from lacustrine sediments, found on slopes of 0 to 2% and permanently hydric conditions; phaezoms, which develop from weathered sandstone, quartz, and occasionally limestone or calcium carbonates; and eutric litosols, soils that develop over intrusive volcanic materials, limestone, calcium carbonates, calcareous sandstone.
The climate of the region is characteristic of the lower puna, where the temperature fluctuates between 3 and 7 degrees Celsius, with the coldest months being between May and September. Annually, there is an average of 940 millimeters of rainfall, mostly in the months from December to April, with the least rainfall during the months between June and September.
Mantaro River Basin
The Mantaro River Basin in Peru contains the greatest number of lagoons of any watershed on the Atlantic slope of the Andes, many of which are larger than 400 hectares. Lake Junín, or Lake Chinchaycocha, is located in this watershed and is second only to Lake Titicaca in area. Its variety of landscapes, size, and biodiversity, make it the characteristic environment of the region.
Lake Junín is located within the Mantaro River basin. The lake drains to the northeast, initially into the Upamayo River, above the Upamayo Dam. This dam, which began operating in 1936, regulates the level of Lake Junín and is used to generate electricity at the Malpaso hydroelectric plant. Below the dam, the Mantaro River begins, which forms one of the principal Andean tributaries of the Amazon Basin.
Twelve rivers and twenty streams gather the water of the humid, wet areas of the region and feed into Lake Junín. These include the Yahuarmayo, the Mararychaca, the Condorcocha, and the Huascán Rivers, all of which are located to the west of the towns of Carhuamayo and Ninacaca. Other rivers of the system include the San Juan, San José, Chacachimpa Rivers.
The lake reaches a maximum depth of 12 meters (10 kilometers offshore of Huayre), with a surface elevation of 4082.7 masl. The temperature of the lake decreases with depth, from 17ºC at 15 cm, to 15.5ºC at 1 meter, 15ºC at 3 meters, and 14ºC at 6 meters.
The lake is extremely contaminated by mining waste in the northeastern section. Also, the decomposition of submerged vegetation and the discharge of wastewater from the towns of Junín and Carhuamayo lower the available oxygen and increase the phosphorous load in the lake. In the center of the lake, oxygen availability is higher due to deeper water and greater aeration. Decomposition of organic matter at depth also increases the ammonium content of the lake water.
Lake Junín is a undergoing a process of eutrophication, and any addition of nitrogenous compounds will accelerate this process. For this reason, wastewater discharged into the lake poses a serious problem.
Iron content and turbidity are higher in the area of the Upamayo bridge as a result of the accumulation of mining waste in the lake. The high iron content of the water also leads to lower dissolved oxygen content. The pH is almost neutral, although it tends to be lower, especially during the dry season and times of drought.(1)
The most common access to the Junín National Reserve is via the Central highway, taking the exit to Tarma in Oroya, and then the exit for Junín. It takes approximately 5 hours to travel to Junín from Lima. In the dry season, there are two alternatives routes to the zone. One is the highway from Canta-cordillera La Viuda to Pasco, which will soon be paved and takes approximately six hours to travel, while the other, lesser-known route goes from Canta-cordillera de La Viuda through (Yactac) Marcapomacocha-Corpacancha-Conocancha-Atocsaico-La Cima to Junín.(2)
1) Plan Maestro de la Reserva Nacional de Junín. INRENA. Junín Perú. 2000. Págs. 8 - 11. Records exist of water quality of the lake and its tributaries for tests conducted environmental consultants working for the mining companies in the exectution of their PAMAs, required by DIGESA. These are summarized in the report “Estado de la Calidad de las Aguas en la Cuenca Alta del Río Mantaro”. Informe final de la Comisión Multisectorial Descentralizada, por Carlos Rojas y Aldo Brigneti.
2) Plan Maestro de la Reserva Nacional de Junín. INRENA. Junín Perú. 2000. Pág.8.