La Revista Digital 1 Versión Final Revista No. 2 - Prueva | Page 49

Water, Silt and Dams: Prehispanic Geological Storage in the Cordillera Negra, North-Central Andes, Peru
Figure 8. Plan of Pa 5 – Tsaquicocha, Collapampa River.
between 1.1 m and 1.83 m, with a maximum height 1.3 m
(Figure 8). If a sluice existed, it would have been located
on the central section of the structure. The dam was triple-
stepped on its exterior face and the upper level is very
deteriorated. The bofedal thus created covers 1027 m 2 .
The south-eastern end of the dam is anchored to bedrock,
while the north-eastern one abuts the natural earthen
slope. Given the characteristics of the site and its height,
it is possible that this structure started as a water dam that
then dried-up and was used as a small silt dam – the prefix
tsaqui means “dry”, and cocha means “lake”, in the local
Quechua language.
m). Oriented southeast-northwest, the structure is very
well constructed and solid, with a double-faced wall and
compacted fill stones and earth. The dam measures 75
m in length, and its width varies between 1 m – at the
extremities – and 3.6 m at the center, with a maximum
height of between 1 m and 4.7 m (Figure 11). The structure
is anchored onto the earthen slopes of the valley. There was
no sluice to the dam, with water currently filtering from
beneath the wall. Behind the dam, a 16,000 m 2 bofedal is
forming.
Huancacocha [Rac 1] Silt Dam
Located in the upper section of the Racratumanca side-
valley adjacent to the town of Pamparomás, the silt dam
of Huancacocha lies at 4425 m (Figure 9). The site itself
is set in a natural terrace or platform – much like Cho 2
above – surrounded by steep, rocky hills. Behind the wall
there is an extensive area of bofedal covering 17,500 m 2 .
This silt dam, double-walled and infilled with packed earth
and stones, lies directly downstream from Huaytacocha
(4500 m) to the northeast. The height of the structure varies
between 0.3 m and 1.4 m, while its maximum width is 3
m. The wall zigzags over 50 m, making best use of the
available rock outcrops (Figure 10). A single sluice 0.4 m
wide by 0.6 m high drains excess water. The masonry is
rough, with no evidence for repairs or reconstruction of the
dam. Both extremities of the dam are anchored on bedrock.
Tsaquicocha [Uc 3] Silt Dam
Tsaquicocha is a large silt dam, located at 4300 m in
the upper end of Uchpacancha Valley, directly below the
large Agococha/Negrahuacanan [Uc 1] water dam (4525
Revista de Glaciares y Ecosistemas de Montaña 2 (2017): 41-50
Figure 9. Photograph of Rac 1 – Huancacocha,
Racratumanca Valley. Photo: K. Lane, 2002.
Conclusion
This study shows that silt dams are an intrinsic feature
of the Andean hydraulic landscape, capturing water, silts
and sediments, ameliorating the effects of erosion and
landslides, while providing a fertile platform for animal
foraging. The five examples presented here are probably
just a few of the many such structures that exist across the
Cordillera Negra and most likely throughout the entire
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