What is the Freshwater Harvest for?

Trees and forests help retain water. What happens between the tree and the soil to retain water? The observations shared with the farmers give us to understand that the integration of biological, physical and chemical phenomena occurs in the harvest of freshwater.

The influence of trees on the water cycle

Since childhood, we have known that the simple leaf of a plant, the branches of trees, the shoots, the stems, among other aerial parts of plants, collaborate in stopping the blows provided by the precipitation of raindrops. These are distributed throughout the structure and shapes of the different trees. Those with small leaves lose the minimum of water through evaporation, trees with broad, lance-shaped, long leaves and with small theticas (stomata), with little surface area and fibrous roots, form a sponge of water around and inside them.

We call the mechanism that uses water, which at some point is trapped or retained between the different parts of the trees, interception. Approximately 100ml of water that falls on a tree, 10 to 20% slowly drains to infiltrate or percolate between the soil profiles, increasing the fertilization of the water table.

Another part of it runs over the earth's surface and will contribute to increasing the flow of the rivers, which will flow into the sea, where the water evaporates and when it condenses it precipitates on the surface of the earth and in this way it is fulfills the hydrological cycle of water.

Water quality, like stream flows, will be affected by soil and vegetation cover conditions. A forested soil retains water between 5 to 8 times more than a grassland cover soil and between 10 to 15 times more than a bare soil or an eroded soil.

The freshwater harvest

As evidenced in the previous paragraph, trees and forests help retain water. Due to the structure and composition, many forest-covered soils have a high capacity to retain water. What happens between the tree and the soil to retain water?

The observations shared with the farmers give us to understand that the integration of biological, physical and chemical phenomena occurs in the harvest of freshwater. We have learned a first biophysical phenomenon in the role played by leaf litter and humus (decomposed organic matter, biochemical process) coming from the decomposition of leaves, branches and fruits, which accumulates on the ground.

In some forests it reaches 6 to 20 cm deep. As the leaf litter opens and decomposes, nutrients are released, enriching the surface layer of the soil. Leaf litter and humus protect the soil from the direct impact of water, helping to maintain water infiltration without disturbing the soil.

After infiltrating, some of the water runs off, another part percolates into the soil. Here and depending on the diversity of crops and their biomass (total weight of organic (living) matter of the trees) and their different levels of water interception, water harvesting begins. An association of crops by difference in biomass will retain more water than a monoculture.

These watercourses constitute the most important water resource, since they form rivers, streams, spaces of humidity for crop production, streams, for the formation of rain and the maintenance of hydrographic basins.

Venezuela and its Hydrographic Basins

The natural area, limited by watersheds, where both rainwater and water from snow-capped mountains are deposited and flow towards a main drainage that generally functions as the axes of a region, we call hydrographic basins. The basins or receiving slopes are part of the basins of the valleys, plateaus and mountains affected by the runoff that feeds the main drainages.

Any portion of land can be considered an integral part of a hydrographic basin. For example, almost the entire Venezuelan territory is made up of hydrographic basins. Five of them are international, which are part of other countries. Among them we have The Lake Maracaibo Basin; The Orinoco River Basin; The Black River Basin of the Amazon; The Cuyuní Basin towards the Essequibo and the Paraguachón Basin (Venezuela and Colombia); The Black River Basin (of the Amazon) (Venezuela, Colombia and Brazil); The Cuyuní Basin towards the Essequibo (Venezuela-Guyana).

Other important basins in Venezuela are: in the east of the country, the Unare, Neverí, Manzanares, San Juan and Guarapicjhe basins. In the Center: the Basins of Tuy, Guapo, Lago de Valencia and in the West: the Basins of Hueque, Tocuyo, Aroa, Yaracuy, Chama and Motatan; The rivers of all of them flow into the Caribbean Sea, except those of Lake Valencia.

These large areas could be observed, in turn, as a kind of puzzle made up of smaller basins. As management units, we sometimes talk about micro basins on several farms, and on the same farm we can have mini basins or small areas for freshwater harvesting.

In Venezuela, in most of the western states of the Andean foothills and various mountain ranges, there are a good number of farms with shared micro and mini basins, which indicates that we cannot work in isolation since the management of one affects the others.

Production in freshwater harvest

We have noted the importance of freshwater harvesting in maintaining watersheds. It is understood that the different formations, such as the arrangements of trees and plants in the agro-biodiversity of a production system, regulate the different water sources that drain into it. We cannot maintain a hydrographic basin without its agro-biodiversity and, this , without the vital resource of water for its existence. There is an exact synergy and complementarity between ecosystems.

Let's understand what the producers and farmers of the states of Mérida, Barinas and Portuguesa in western Venezuela have taught us by producing and harvesting water. The attached figure (#18 Page 82 of the Book Proposal for Sustainable Rural Development of MANúñez 2002) presents the:

The family production unit of the Venezuelan Andean foothills considers the humidity gradient (water harvest) and the preservation of the slope, where crop associations are also established in each of the specificities indicated.

Peasant knowledge demonstrates the arrangement of agrobiodiversity where at least 26 crops stand out for different productive uses, they teach us that this production is achieved according to the natural physical limitations expressed in the different degrees of slope. They instruct us that above a slope of 30 degrees we must maintain the forests to obtain the water harvest produced there and provide us with the different humidity spaces that are considered in their production systems.

These cultivation arrangements are given according to their seasonality, perenniality and short cycle crops. Agricultural production systems, typical of countries that have supported sustainable tropical agriculture for millennia.

The farmer is also instructing us that he has dense and extensive agronomic knowledge of the different types of soils, agro-climatic conditions and eco-technologies, which together collaborate sustainably with the environment. There is efficient use of water based on the synergy and complementarity between the physical, chemical and biological properties of the agro-productive system, which is not very well known by academia and university students. It is demonstrated that agrobiodiversity in its water harvest acts as an antidote to the preservation of the environment of the micro hydrographic basin evaluated.

The other contribution of water harvesting.

Understanding the meaning of being able to easily harvest water implies that the knowledge that this experience provides us, we must necessarily have the participation of farmers and producers who, in the end, are the ones who truly have the most genuine and instructive knowledge.

Here where with pride and dignity we have demonstrated it. It is about knowing how to obtain the ideas, criteria and different forms of wisdom that they have possessed throughout their centuries of existence. It is also about respecting the different rationalities between the cultural, social and religious values ​​that we Latin American peoples possess. Knowledge that has not disappeared, is maintained and is waiting to be valued and recognized.

In the production systems of tropical latitudes, we recognize that for their understanding and interpretation it is necessary among farmers to apply participatory methodologies that help us organize and systematize the knowledge that through the different processes of reflection and action allow us to value more objectively. the knowledge and wisdom of our farmers. We affirm that the most appropriate environmental education is that which is received on the basis and interaction of environmental and cultural rationality expressed among the actors themselves who develop it.

This accumulation of knowledge that we have presented here should call us to reflection because an endless number of criteria and ideas must be derived from them, and more knowledge of extreme usefulness, which must be valued and assumed by the academy, the universities and research institutions.

For example among others we have; the way in which sustainable use of water can be produced and maintained; the comprehensive management of forest resources, the implications of agrobiodiversity and the different eco-technologies in productive systems. Bases for agroecological practice in the new face that our agriculture demands. Which must become the most dynamic part of our local economies, helping the new types of sustainable environmental societies that we must create and reorganize for the future of the new generations that are coming and to substantially improve the quality and reason for life of our rural and urban sectors.

Miguel Angel Nunez
IPIAT
Barinas, Venezuela