Runoff carries mining waste into rivers (Llallagua, Bolivia)
By Kashyapa AS Yapa
There is no life without water. We must be able to survive for a long time without food, but without water, we cannot. This vital liquid constitutes more than half of the human body. We can say, then, that yaku mama (mother water) raises us.
In this changing climate, we must prepare for water shortages in many regions of the world, because the gradual warming of the air forces all living beings (humans, animals and plants) to consume more water. There will also be greater evaporation from land and water. On the other hand, accelerated deforestation in recent decades has stripped and compacted the soil, reducing infiltration of runoff and, therefore, the recharge of aquifers. Serious water pollution, due to industrial, mining, agricultural and urban activities, worsens the situation and we are left with less and less water for consumption.
Infiltration is zero in densely urbanized areas (La Paz, Bolivia)
Our ancestors respected and revered nature, more than we do today, because they depended directly on it for their water supply. They integrated water harvesting into their community life, without waiting for external support. They carried out these activities using local materials, and their own individual and collective physical and mental strength. Likewise, today, we must face this climate crisis alone, because the whole world will be affected and no rescuer will appear.
That is why we propose ancestral water harvesting practices as the best tool to adapt to the water shortages that are coming. We cannot say that every ancestral technology worked everywhere and whenever: however, we have inherited the most appropriate practices for each region. These include techniques for: predicting the weather; procuring water in droughts; harvesting rainwater; collecting groundwater; carefully consuming the water collected; and living with excess water.
Solar halo could indicate freezing nights around the Cotopaxi volcano, Ecuador (Courtesy of: Marco Martinez)
Water harvesting in arid areas
The ancient Andean settlers of the arid Pacific coast managed to capture the water vapor brought by their dense fog, by means of curtains of trees on the coastal hills, and some of these systems still work today. Where there is no more, we must first reestablish vegetation, perhaps by capturing water through artificial nets, raised against the wind. We can also capture pure water from a contaminated pool, condensing its vapor in a closed environment. Using solar energy for its evaporation, as in the old salt mines, one can survive an emergency with the little water that is captured. In the past, people manipulated clouds to convert hail into rain: in Europe, cannons were fired; in the Andean highlands, until now, chains of bonfires of black smoke are used. Now, the wealthy try to force rain by placing chemicals on the clouds by means of rockets or airplanes. Their dubious effectiveness, high cost and serious socio-environmental consequences (Morrison 2009) have slowed the advance of this practice.
Capture rainwater and runoff
Capturing and storing rainwater does not require sophisticated technologies, but rather good planning. Ancient cities collected rainwater at individual homes (Evanari et al. 1982) and in public squares (Matheny 1982) because they avoided dependence on outside water supplies, which were expensive and prone to enemy attack. Modern city dwellers can also use rainwater to reduce consumption of the municipal supply, at least for washing and watering gardens. Some cities, such as Portland, offer incentives to customers for reducing the runoff that enters their sewers from each property, because this lowers the cost of wastewater treatment.
Ancient small stepped reservoirs built on the Mau Ara streams, Walawe River, Sri Lanka
Field runoff can be intercepted with channels and stored in reservoirs. However, infiltrating it into the crop field itself is better because it also prevents erosion. Hopi and Zuni farmers in the US do this simply with rows of stones or branches placed on contour lines. On steep slopes, these traps can be reinforced with terraces, ditches or small dams.
Capturing river runoff and storing it behind a high dam does require advanced technological know-how because the discharge of that water, under a few meters of pressure, can undermine the dam itself, if not properly controlled. Sri Lankan engineers have been using a robust well (Bisokotuwa) for 2000 years.
A cleaning well at Puquio Cantalloc in Nazca, Peru
built of stone blocks (as seen in the Bhu Wewa-Polonnaruwa above; Left: front view, Right: plan) to drain water from these reservoirs, and perhaps had a cork-type gate to control their flow.
However, in rural areas, they used a mechanism that farmers could easily manage: they built many small reservoirs in steps over each stream, instead of installing one large one over the main river.
Groundwater
Ancient farmers on the Santa Elena Peninsula in Ecuador also captured runoff in thousands of small reservoirs (albarradas) at the headwaters of micro-basins. However, their idea was not to store this water superficially in this semi-arid area; almost all the albarradas were located on a porous rock formation, in order to recharge the springs downstream, to survive prolonged droughts (Marcos 2004).
Where springs do not discharge sufficient flows, our ancestors bored deep into the mountains to capture more water from the aquifers, and brought it to the surface under gravity. These filtration galleries are known as qanat in the Middle East or puquios in Nazca-Peru. The famous 'Nazca Lines', according to one hypothesis, follow the numerous geological faults in the area and thus indicate possible sources of underground water in this extreme desert (Proulx 2008?).
Huachaque Grande, a sunken field in Chanchan, Trujillo, Peru
Inca engineers in Cuzco, Peru captured groundwater and stored it there, using terrace-type walls built between two impermeable rock edges that delineate an intermittent stream. In this way, they provided clean water, with a steady flow and sufficient for human consumption or irrigation (Fairley 2003). Today, a similar technique is used in the semi-arid northeast of Brazil, constructing curtain-type walls submerged in the bed of intermittent streams (UNEP 1997). If we incorporate a filtration gallery upstream of such a wall, it will be easy to extract that water and perform maintenance.
Instead of bringing groundwater to the irrigation surface, as they normally do, some ancient farmers decided to lower the cultivation floor! Some of these sunken fields on the Peruvian coast were continuously cultivated (Schjellerup 2009) at least since the Chimú kingdom (1300 AD), when they reached their peak, by purposely irrigating the fields upstream.
How to make better use of captured water
First, we must reduce consumption and eliminate leaks in the supply system. To reduce human consumption without sacrificing modern conveniences, we can use low-flow toilets, male urinals or dry latrines. In the field, low-water consumption crops can be chosen without losing profitability, as demonstrated by farmers in southeastern Turkey who switched from cotton to saffron (Drynet 2008?). Water leakage in conveyance and storage can be reduced by using pipes and/or casings. But to eliminate water waste in distribution, especially in irrigation, a detailed analysis of: seed type, agricultural calendar, soil, climate and irrigation mode is required. The need for frequent irrigation can also be reduced by minimizing soil moisture loss, through the use of windbreaks, ground covers, organic compost, etc.
Second, let us not unnecessarily pollute the water in order to recycle it. By recycling grey water in an urban house, the owner and the municipality would win. In marginal urban and rural areas, it will be more economical in the long term if we manage to recycle the liquid component of the septic tank as well. On farms, biogas can be produced by discharging stables (Pedraza et al. 2002), which accelerates the composting process of solids and also allows the recycling of the liquid.
Channels that connect the lowlands with the river, Momposina depression, Colombia (Plazas et al. 1993)
This article is a preview of this topic. With the support of UNDP/SNGR – Ecuador, we have prepared for free distribution the complete document as A FIELD GUIDE and a complementary document MEMORIES OF THE WORKSHOP ON THE EXCHANGE BETWEEN PEASANTS. Thanks to the support of a dear Colombian friend, Germán Bustos, you can download these books from his website: http://germanbustos.com/Libros-Crianza-del-Agua.)
Literature:
- Cachiguango, Luis Enrique “Katsa” and Julián Pontón (2010) “Yaku-Mama: The raising of water – the ritual music of the Hatun Puncha Inti Raymi in Kotama, Otavalo” Ministry of Culture, Ecuador, June.
- CHUYMA ARU (2007) “Signs and secrets of raising life” Chuyma Rural Support Association, Puno, Peru.
- Drynet (2008?) “Saffron flowers and sunken gardens”, http://www.dry-net.org/uploaded_files/109.pdf
- Evanari, Michael, Leslie Shanan and Naphtali Tadmor (1982) “The Negev: the challenge of a desert” 2nd ed., Harvard U Press, Cambridge.
- Fairley Jr., Jerry P. (2003) “Geologic water storage in pre-Columbian Peru”, Latin American Antiquity 14(2): 193-206.
- Marcos, Jorge G. (2004) “Las Albarradas on the Coast of Ecuador: Rescuing ancestral knowledge of biodiversity management”, Coordinator, CEAA/ESPOL, Guayaquil, Ecuador.
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- Proulx, Donald A. (2008?) “Nasca Puquios and Aqueducts” http://www-unix.oit.umass.edu/~proulx
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- Uragoda, C.G. (2000) “Traditions of Sri Lanka”, Vishva Lekha, Ratmalana, Sri Lanka.
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