LOCAL APPLICATION OF THE TECHNIQUE TERRACING SYSTEMS 25

LOCAL APPLICATION OF THE TECHNIQUE

Technique:	TERRACING SYSTEMS
Local name:	Colca Valley, PERU
Site:	Colca Valley, PERU

Location

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Continent: South America
Country: Peru
Site: Colca Valley
Coordinates:
Lat: -15.59
Long: -71.87

Description of the local variant of the technique

The Colca Valley is situated in the Andes, in the west of the Caylloma province, in the Department of Arequipa, between 2200 and 4500 metres of altitude, which represents the highest limit of livestock rearing. Huge mountains dominate the valley which lies in a canyon over 100 km long, and carved by the river Colca. While since the pre-Inca period, the local population cultivated this land on terraces, relying on specific situations found at different altitudes, this technique was abandoned after the colonial period. The remaining terraces are neglected and little irrigated. The DESCO Peruvian ONG has started a rehabilitation of these terraces and their irrigation channels and to sensitize the population on their quality. The results are convincing: the productivity of land and crop yields have increased, erosion and water losses are reduced, the landscape is arranged and attractive to tourists. Lofty mountains dominate the valley which lies in a canyon, over 100 km long, hewn by the Colca river. Long before the Inca period, the local population cultivated their land on terraces, taking into account specific conditions at different altitudes, this technique was abandoned after the colonial period. The remaining terraces are neglected and little irrigated. The DESCO Peruvian ONG has started a rehabilitation of these terraces and of their irrigation canals, informing the population on their importance. The results are positive: soilproductivity and crop yields have increased, erosion and water losses are reduced, the landscape is well organized and made attractive to tourists. The Colca valley was originally inhabited by the Collahuas who had developed a production system based on terraces and particular irrigation methods. Even before the period of the Incas, the local population profited of the different qualities of the land at various altitudes. Approximately 60.000 people fulfilled their needs solely through the resources of the valley (agriculture and animal husbandry), but this technique was abandoned after the colonial period and the population dwindled to only 6000. From the ecological point of view, this area is rich varieties of species: up to 15 different ecosystems have been identified. In terms of agricultural production, there are however three major systems: the area of the high Andes, more than 3800 m high, reserved to the breeding of camelids, the intermediate zone, between 3000 and 3800 m suitable for farming and agriculture associated with animal husbandry, and the lower area, more suitable for the cultivation of fruit. After the colonial period the productivity of the land in the valley of Colca diminished greatly. According to official estimates, 30% of arable land has been lost entirely due to the degradation of terraces and a lack of maintenance of the irrigation system. Poor land management has also contributed to the loss of fertility. In fact, people have abandoned traditional farming techniques, which consisted in enriching the soil through mulching (covering the flower with protective layer), crop rotation, mixed farming or compost. Short term agricultural production, maximizing immediate yields has been given priority to the detriment of sustainable development, and this has exhausted the resources and degraded soils. The felling of trees for the use wood for fuel is another cause of desertification. Mountainous areas are characterized by a severe lack of water, steep terrain and difficult weather conditions (frost, low humidity). The total annual rainfall is 350 mm, 60% of this much occurs between January and March thus allowing only one crop per year. Small properties are widespread and each household owns an average of 1.2 hectares, divided into small parcels distributed along different slopes. Generally the inhabitants grow from eight to sixteen different plant species, the most common are corn, beans, potatoes, barley and quinoa. Traditional techniques to compensate for the difficulties of this environment consist in terracing, irrigation networks and adaptation of crops to the microclimate of each altitude. DESCO has worked out its project in 1992 in the province of Lari, Colca Valley, between 3,200 and 4,500 m of altitude. The objectives were to rehabilitate the terraces, improve irrigation facilities and introduce the practice of agroforestation in the region. The results expected were the improvement of agricultural productivity, public awareness of population and ecological approach to the revaluation of local traditional knowledge. The advantages of terraces go beyond the simple possibility of ploughing a slope. Terraces are effective for controlling erosion and improving water management. They help to break up the moisture in the soil thus reducing the risk of frost. Moreover, they allow to better exploit the microclimatic and ecological peculiarities of various altitudes. The rehabilitation of terraces in the Andes requires the restoration of three fundamental components. First the stone walls , which support the terraces. After digging a trench 50 cm deep along the contour line, large and heavy boulders are laid that form the foundation and give stability to the whole. On the surface, the wall is raised after laying stones of different sizes on top of each other, slightly jutting in the direction of the slope. The height of the wall depends on the width of the terrace. Some smaller stones are then added in the interstices of the larger blocks and behind the wall to reinforce it.The terraces themselves, are essentially created with the earth in the sloping lot which needs flattening. However, some are more elaborate than others and consist of different layers: a base bed consisting of large stones serves as a filter for draining irrigation water, an intermediate layer of small stones covered with sand and clay, and a final top layer of 50-80 cm of fertile land. The terraces are slightly jutting to allow water to seep slowly without causing erosion. Finally, access roads, consisting of small steps that cross-link the terraces. Usually these steps are inserted in the stone wall. Even the irrigation canals have been rehabilitated. Water from springs is collected in a reservoir upstream, then distributed by means of stone gutters from a terrace to another. The agro-forestation is greatly encouraged on the terraces. It consists on growing at the same time the annual species, such as cereals, and persistent species such as fruit trees. This method of production adds to the ecological and economic benefits, since it allows the farmers to diversify their products, thus enriching the soil. For the maintenance of terraces, it is useful to plant woodland species at the foot of the wall in order to support it and act as windbreaks. The species of trees recommended for their properties are thorns and cherry trees, cypresses and pines.