Le nombre de forages construits dans des régions arides grandit continuellement et provoque une baisse considérable de la nappe aquifère. Il est donc nécessaire d’appliquer une gestion efficace de cette nappe afin de ne pas créer des grands problèmes de tout genre. Nous recommendons donc de se concentrer aussi sur la collecte de l’eau de pluie et sur le stockage de la pluie dans la zone de l’enracinement des plantes (20-30 cm), p.ex. avec le conditionneur de sol TerraCottem.
I have been reading an interesting article on “Managing groundwater for dry season irrigation”, written by I.M. FAISAL, S. PARVEEN and M.R. KABIR (firstname.lastname@example.org). Should you look for the full text, please find it in “id21 natural resources highlights – water – 2006“, an annual publication of the Institute of Development Studies – University of Sussex, Brighton, UK (email@example.com) to which you can easily subscribe.
The article mentioned above tells us first:
“Using groundwater for dry season irrigation has been the preferred strategy of the Bangladesh govenment for many years. For example, the privatisation of irrigation in the 1990s led to huge growth in the number of shallow tube-wells. However, groundwater must be managed carefully: there is not enough information available on national groundwater resources to understand or predict long-term environmental impacts of continued use“.
Having noticed myself the dramatic fall of the groundwater level over the years 1975-2005 in many African Sahel countries, I could not agree more with the statement above. Most probably, this fall is not only caused by the well-known continuous drought in that region, but also to the ever growing number of wells and pumps. It would be wise to ring the alarm bell for any proliferation of the well-intended “humanitarian” projects to drill more and deeper wells to “bring water to people and animals“. On the contrary, it would be wiser to take better care of water harvesting and to look for more efficient water use, like these authors say.
The authors also tell us: “Most water projects in Bangladesh have a narrow focus, such as flood control, drainage or irrigation. Social, economic and environmental factors are largely ignored and there is little monitoring or evaluation. The Barind Multipurpose Development Project (BMDP) consciously tries to overcome these problems to meet the challenges of creating the physical and social infrastructure necessary for groundwater irrigation in a semi-arid area. For example, the project encourages maximum use of carefully spaced deep tube-wells (DTWs), which minimises water wastage.
The BMDP also constantly monitors quality and quantity of groundwater and aquifer levels. Thousands of poorly maintained rainwater collection tanks have been renovated.”
Several positive features of this approach are mentioned:
° Water use groups, consisting of users from many different social groups and institutions, give feedback to BMDP managers to improve project performance.
° A large reforestation campaign and distribution of medicinal plant seedlings are examples of the project’s environmental improvement activities.
According to the authors several problems are encountered, the most significant being when hand wells, used to collect drinking water, began to dry up in DTW target areas. It has highlighted a need to integrate the planning of irrigation projects with drinking water supplies. This phenomenon is also widespread in semi-arid areas in Africa, and probably on other continents too.
It brings me to the following question:
Why are many people so careless about water harvesting and water stockage in the soil?
Rainwater that comes free from the sky runs off, infiltrates deep or evaporates without any human action to stop this. Oh yes, we will construct dams (or even little dikes – diguettes) and we will install expensive tube-wells and pumps. In other words, first we do nothing and then we spend a lot of energy (and money) to bring the water back where it belongs, i.e. in the rooting zone of the cultivated fields.
It would be more logic and more efficient to collect that free rainwater mechanically (in drums or bigger reservoirs/tanks) or chemically (with water stocking substances that can easily be mixed with the soil, let us say 20-30 cm/ 1 foot deep).
Ever heard about the TerraCottem soil conditioner developed at my laboratory at the University of Ghent, Belgium? Please have a look at the website http://www.terracottem.com and learn something about efficient use of rainwater.
Jardin de légumes au Sahara (camp des réfugiés à Smara, Algérie). Le sol est du sable du désert pur sans aucun amendement. Irrigation goutte-à-goutte tous les jours. Production très pauvre.
Le jardin du voisin dans le même camp de Smara. Sable du désert mélangé avec 50 g de conditionneur de sol TerraCottem/25 cm de profondeur. Irrigation goutte-à-goutte tous les 2 jours. Production magnifique.
Instead of letting all the rainwater become groundwater, let us use it for keeping our fields moistened for a longer period. And don’t miss that important information: TerraCottem soil conditioner is only applied one single time ! It stays active in the soil for many years.
You don’t believe it? Give it a try !