Agricultural Drought Management in Central Africa: Lessons Learned from the PANAASA Project
Democratic Republic of Congo
Presented by University of Kinshasa
In the project areas of the National Action Program for Climate Change Adaptation in the Agricultural Sector (PAASA Project) in the Democratic Republic of Congo, in partnership with the UNDP, FEM, SENASEM, INERA, SNV, IITA, MTTELSAT, the University of Kinshasa, climate change affects rainfall trends and temperatures, including the occurrence of intra-seasonal droughts. This situation makes agricultural production difficult, and not only has adverse consequences on food and nutrition security, but it also accentuates the poverty of rural populations dependent on agriculture.
This project aims to enhance the resilience of rainfed agricultural production systems of rural and smallholder farmers to the deadly effects of climate variability.
The intervention of this project made it possible to implement sustainable land and drought management practices:
hydro-irrigation schemes, including irrigation systems, to meet the needs of crops and the water resources potential of agro-climatic zones in the DRC have been achieved, inter alia: catchment of rivers in the provinces of Kongo and Kwango (eg Bandundu) and the construction of lateral dams on the kubundula river in the former mining province of Katanga;
different resilient varieties (wheat, cowpeas, groundnuts, rice, beans and cassava) are being tested before scale-up at the farm level;
agro-meteorological information and early warnings are regularly provided to farmers.
A total of 365 rural farmers and 145 government officials, technical support services to agriculture, universities and higher education institutions and agronomic research centers have improved their capacities in resilient techniques for agricultural production and management of soil fertility; and about 225 hectares of resilient seed production are being experimented in agri-multipliers.
The project thus made available the resilient seed by agro-climatic zone (experimental phase), it allowed to profoundly change the standard of living for rural populations, set up a system for the dissemination of agro-meteorological information and alerts, developed endogenous know-how and pooled the supports for the development of income-generating activities.
In 2011, the Sieg River (Germany) has known a vast program to restore the minor bed due to the hydro-morphological context of the site. Indeed, the continuous incision from the bed of the river imposing for this reason to the project of fight against erosion and the scourings, become frequent at every flood. Due to a substrate made of easily erodible materials and without natural vegetation, the banks were fragile.
It was therefore necessary to undertake a renaturation project allowing the development of plant species adapted to the environment in order to renature the environment and protect it against erosion.This project was carried out by Ökon vegetations technik, a German company specializing in protection against erosion and restoration of ecosystems.
For this, work was carried out on 200 ml. Stone rolls, filled with stony material, have been placed on the whole of the minor bed in order to provide an immediately effective solution to the erosion right from the start.Filled with stony materials with a particle size similar to that of the bed of the stream; The stone rollers (also called stone rollers) naturally support the bank and protect it from erosion thanks to the confinement of the pebbles in the envelope of the gabion. The small granulometry favors the clogging of voids by sedimentation, allowing a rapid colonization of vegetation. Cuttings, helophyte plants and seed mixtures can be installed in addition.
The incision of the Sieg River bed was stopped as soon as the stone rolls were put in place. The community wished to wait for a natural and spontaneous vegetation of the herbaceous species. The contribution of the floods allowed the interstices (voids between pebbles) to fill and to serve as substrate for the development of the vegetation.
Rolls of stones are truly an ecological solution. Indeed, following their sedimentation, a diversity of herbaceous and shrub species settled and knew how to colonize the banks naturally. A diversity of invertebrate macros has also been observed at the banks, which are transition zones between the terrestrial and aquatic environments. Indeed, 72 species have been found, whereas on average 48 are found in ecological engineering projects (fascines or willow plaiting).
Adaptation of ancestral techniques to protect the banks
Presented by IRSTEA
Riverbanks are assuming a large number of important ecological functions: biodiversity support, resistance to invasion, ecological corridors, biomass production, water purification, temperature regulation, flood control, and recreation. Besides hard engineering, soil bioengineering techniques for riverbank protection are very old nature based solutions and have been used for centuries throughout the world. First thought of mimicking nature to fulfil the function of erosion control, soil bioengineering techniques are now also formed to assume some of the other important ecological functions of riverbanks.
Using mostly concepts and tools from restoration and functional ecology (but also from engineering and hydraulic), we conducted a set of studies and experiments (in greenhouse and on real works) that aimed at characterising and maximising the contribution of riverbank bioengineering techniques to some of these ecological functions, including biodiversity support, resistance to invasion, resistance to drought and erosion control.
We assessed the capability of several types of managed and mineral riverbank to support both common (terrestrial plants and beetles, macrobenthic communities) and endangered biodiversity (Myricaria germanica and Typha minima). Regarding resistance to invasion, we studied the potential of bioengineering techniques to resist to the pressure of an invasive rodent (Myocastor coypu), and to outcompete Japanese knotweeds. Summer drought should increase with climate change, and is a major threat for bioengineering success; we then studied the resistance of Salicaceae and Tamaricaceae populations to harsh drought. Finally we worked to maximize erosion control function of these techniques by implementing bioengineering works in steep slope rivers (5-10%), and by assessing past shear stress resistance to flood.
Our results show that soil bioengineering techniques can be definitely thought as a nature based solution for assuming both erosion control and main ecological functions of riverbanks, and are thus promising in the achievement of these complex human goals in a context of global change.
In 2009, the construction of the ‘Dragonfly Zone’ in Saint-Just (34) reflected the need for specific design of the vegetated discharging areas to be adapted to the ecological services: elimination of pollutants or the reception of biodiversity. A 3-year follow-up revealed promising results in terms of purification performance. In this context, the ZHART project was developed to make sufficient progress in the knowledge of the physical, chemical and biological mechanisms existing within the vegetated discharging areas and allowing the abatement of pollutants in water.
How can the design and the sizing of a vegetated discharging area affect the treatment of pollutants? What are the mechanisms, naturally occurring in wetlands, which make it possible to eliminate certain pollutants from phase water? How to guarantee purification efficiency over time? Several problems were solved during the ZHART project surveys between 2013 and 2016. Through audits carried out at five sites, microcosm tests carried out under experimental greenhouses and a consolidation of interpretations by the state of the art scientific literature, the fate of several pollutants within the ZHART project has been studied. The results obtained for each of the 33 molecules monitored (chemical analyzes in water, sediment and vegetation) revealed the elimination processes, their importance and the limiting conditions. Thus, the association of purification guarantees with proposals for design and design in ecological engineering has been made possible.
Investigations carried out during the ZHART project confirmed the concept of vegetated discharging areas composed of habitats typical of wetlands. This specificity allows the mechanisms of elimination targeted beforehand and the colonization of faunistic / floristic species subservient to these spaces. The floristic procession is chosen according to the purifying capacities of the plants but their autoecological characteristic has priority in the decision tree.
The ZHART project also developed a methodology for studying the social and territorial integration of a vegetated discharging area. This method allowed highlighting the high added value attributed to the purification process and the relative questioning concerning the ecological surplus value among the inhabitants.
The results also show that it is necessary to identify the main local issues from the start of a new vegetated discharging area project.
This new concept of vegetated discharging area is suggested, with various services and quantifiable thanks to the tools and the methodology developed. To ensure the reality of these services, they must be defined, even before the design phase, during a first stage of consultation and data collection, allowing identifying the client’s need and integrating the main constraints to the implementation of the project.
For the treatment aspect, this solution is for example applicable to the removal of certain pharmaceutical or metallic pollutants. However, depending on the effluent flows to be treated, it may require a rather large area, which is not compatible with large urban wastewater treatment plants (> 50 000EH). For a similar cost, there are solutions for intensive treatment (eg Ozonation) which also eliminate organic micropollutants. However, if their ground grip is lower and their performance is higher for certain substances, these intensive solutions do not provide the services offered by these vegetated discharging areas.
Reducing run-off: Evaluation of long term infiltration capacities
Presented by AREAS
Rainwater infiltration buffer zones are gradually developing. They are widely used in Normandy to combat soil erosion, mudslides and pollution of water resources. References and the question of the sustainability of long-term infiltration capacities according to the local context have little scientific response. This lack of reliable data limits the generalization of these developments on the territories.
AREAS leads various research programs to acquire data on the performance evaluation of infiltration capacities of valleys, infiltration ponds and hedgerows in Normandy. These results are essential for the design of structures, their design, watershed management and urban areas.
The valleys in urban areas:
The program includes the implementation of measures on infiltration valleys and basins in the suburban zone, aged between 2 and 10 years, either at a specific point in the development or at global level when they test the entire area. The measurements were carried out by successive fillings or by monitoring in natural conditions over several months. 13 sites were tested: 4 sites of valleys per filling, 6 basins of infiltration and 3 sites with infiltrometer. The results indicate saturation infiltration capacities of silt soils between 1 10-6 and 2.3 10-5 m/s, even after several years. No significant clogging values were observed. The presence of a draining trench beneath the valleys allows a higher permeability to be maintained.
Hedges and fascines in rural areas:
Buffer zones are recommended in the management of agricultural run-off and soil erosion. They can be used to reduce runoff by infiltration and trap suspended matter. Shrub and fence hedgerows with weak rights-of-way are the most widely used in the field.
To measure their efficiencies, measurements were made on 7 fascines and 3 hedges using a runoff simulator at flow rates of 0.5 to 12 l/s/m wide. In terms of infiltration, the results obtained under well-developed hedges range from 260 to 540 mm/h under saturated conditions (runoff rates of 0.5 to 2.5 l/s/ml). As for fascines, half of the values range from 0 to 100 mm / h and the remainder varies from 100 to 500 mm/h.
These results make it possible to establish technical recommendations for the realization of efficient, coherent developments and to indicate the situations in which these arrangements are most effective.