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The use of waste water for agro-forestry

multipurpose systems in desert Oases

Prof. Paolo De AngelisDr. Sara Da Canal

Dr. M. Cristina MonteverdiDr. Lucia Perugini

”High Relevance” Research Project promoted by the Ministry of Foreign Affair and by the Ministry of University and Research of the Republic of Italy

DISAFRIDISAFRIDepartment of Forest Environment and Resources

Dipartimento di Scienze dell’Ambiente Forestale e delle sue Risorse

Laboratoire de Recherche sur les Systèmes Biologiques et la Géomatique (LRSBG)

Université de Mascara, Algérie

sdwsf Dr. Abdellah NedjahiDr. M. KhemiciDr. L. Makhlouf

Dr. Hocine LarbiDr. Ali Miloudi

Dr. Mohamed BenslimaneDr. Zahira Souidi

INRFInstitut Nationale de Recherche Forestière - Alger

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Algeria

• More than 80% of Algeria is comprised of either arid or semi-arid land, that is about 1.9 million square km.

• 91% of population lives on the coast.

• But about 3.1 million people are scattered on desert lands and survive from the rare but essential oases.

Water stress in Africa – AFRICA: Atlas of Our Changing Environment, UNEP

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Algerian oasis

Climate changes:- Persistence of high temperatures- Low precipitation- The rise in frequency of extreme

events like dust storms

Human pressure: - Demographic growth - Over-exploitation of natural resources- New techniques of agricultural production - pivot - and water/soil management - water retention basin and dam - gradually destroying traditional organization

THE SIMULATANEUS NATURE OF BIOTIC AND ABIOTIC FACTORS CAUSES OASIS DEGRADATION

Ouargla, Algeria - AFRICA: Atlas of Our Changing Environment - UN

•Groundwater depletion•Vegetation reduction•Risk of pollution•Salinity•Soil degradation

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location

Oasis of Brézina 33°6’N, 1°15’E, 800m s.l.

• 12,000 habitants, 75 ha of urban area • 174 ha of palm grove, only 30% is

cultivated.• Arid climate with an annual mean

temperature of 20°C. Diurnal variation of 11°C. Rain rarely exceeds 100 mm, low humidity 40%. High solar radiation of 4.6 kWh/m2 and high wind speed. April dust storm average wind speed grows until 5.9 m s-1

• The Seggueur ephemeral river is the main source of water for the oasis

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Brézina

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challenges

Brezina is facing: » Groundwater depletion resulting

from two combined effects: the increasing urban population and the excessive retention of Seggueur dam upstream of the oasis

» Palm grove death» Risk of groundwater contamination

due to the outflow of untreated wastewater

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proposed solution

Improving of agroforestry plantation:reclamation of marginal degraded landestablishment of a green belt that protects the palm grove protection of soil from wind erosionbringing of economic benefitscarbon sequestration

Development of non-conventional water resources: wastewater harvesting natural treatment systemtreated wastewater reuse

How can we avoid the risk of ground water and soil pollution?

How can we develop the oasis without damaging the palm grove?

MODULAR APPROACH

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non-conventional water resources

• Effective in wastewater treatment• Tolerant of fluctuations in

hydrological and contaminant loading rate

• Relatively inexpensive to construct and operate

• Easy to maintain • Low energy requirements

Natural wetlands act as bio-filters, removing sediments and pollutants from the water, and constructed wetlands can be designed to emulate these features.Vegetation in a wetland provides a substratum (roots, stems, and leaves) upon which microorganisms can grow as they break down organic materials. The plants remove about 70% to 90% of pollutants, and act as a carbon source for the microbes when they decay.

• Requires a large amount of land• Biological and hydrological

complexity • Rise in mosquito population• Evapotranspiration and infiltration

losses

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wastewater treatment module

CELL 1: Preliminary sedimentation, with a water level up to 30cm. Emergent vegetation with a density of 90%

CELL 2: Anaerobic digestion of cell 1 effluent, water level never exceeds 60cm. Vegetation is submerged with a density of 20%.

CELL 3: Completes the water treatment of cell 2 effluent through aerobic process. Water level up to 30cm. Vegetation is emergent with a density of 90%.

WSTR (Water Storage Treatment Reservoir): Designed to store cell 3 effluent during the winter season, with a water level up to 5.5m. The storage could be considered as an auxiliary anaerobic water treatment.

The wastewater treatment module is composed of:

wastewater treated water

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superficial flow constructed wetland

Each module receives about 33,400 m3 of wastewater per year but only about 23,000 m3 per year (66%) are available for agroforestry.

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wetland vegetation

Densely vegetated basin (0.5x0.5m2):

• Phalaris arundinacea• Juncus spp.• Phragmites spp. • Typha spp.

Sparcely vegetated basin (5x5m2):

• Myriophyllum spp.• Typha spp.

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agroforestry project

Agroforestry depends on the availability of treated wastewater from the constructed wetland

A species shortlist has been compiled based on the environmental and economic benefit

Success of agroforestry depends on stakeholder involvement

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specie selection matrix - 1

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specie selection matrix - 2

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international level

1. United Nations Framework Convention on Climate Change (UNFCCC)

2. United Nations Convention to Combat Desertification (UNCCD)

3. Convention on Biological Diversity (CBD)

Afforestation/Reforestation activities under the Clean Development Mechanisms (CDM) of Kyoto Protocol

These are the tools in place at the international level to the mainstream countries’ actions for mitigating the negative effects of the mismanagement of

natural resources.

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carbon credit evaluation

Eligibility verification: • At the national level: ratification of the Kyoto Protocol,

communication of forest definition• At the project level: afforestation and reforestation• At the site: not covered by forest before 1990

Carbon estimation covers 20 years of project lifetime. • null baseline;• null leakage;• carbon stock estimated using the “Gain-loss method”;• GHG emissions estimated using the “bottom up” method.

HYPOTHESES 2 HYPOTHESES 3

41 200 tCO2CER

44 770 tCO2CER

HYPOTHESES 1

41 900 tCO2 CER

Distribution of initial costs

WASTEWATERTREATMENTSYSTEM 58%

FOREST PLAN. 25%

CDM 17%

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preliminary conclusion

Wastewater harvesting and treatment are required in order to guarantee a sustainable development of oases.

Constructed wetland represents an interesting option to match the water quality of restricted irrigation.

The use of non-conventional water resources promote: reclamation of marginal land, reduction of wind erosion, amelioration of soil conditions, economic stimulation for timber and non-timber products and local manpower requirements for new wastewater system management.

Small scale CDMs represent an interesting opportunity to support local development.

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open questions

Due to the low number of constructed wetland realizations in arid land, it is very important to collect real data to tune the chemical model of pollutant removal.

Reality check for side effects like wind and sand storm consequences.

Reality check for agroforestry productivity under extreme conditions.

Long term effect on palm grove depletion.

Real stakeholder involvement.

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What next?

PILOT PROJECT realization

Meeting with local authoritiesand stockholders

Pilot project area

An experimental/pilot project realization

Agroforestry testing plots:

-Species (wood & forage)

-Densities (biomass)

-Genotypes evaluation

The main goal of this project is to face the challenge from two differentperspectives: first introducing a new water management inspired to thecollection, recycle and reuse of urban wastewater and, second, propose a newagroforestry strategy in order to stimulate both alternative economic chains andenvironmental restoration. It is important to note that agroforestry never competeswith human and agricultural needs of fresh water but became an alternativeresource otherwise neglected.

Wastewater treatment system

- The system is composed by two parallel treatment chains

The constructed wetland scheme

The four modules tested in the pilot plantation are:1. Tamarix collection with the objective to compare among

different species and populations.2. Tamarix plantation to estimate biomass production and wood

suitability for bio-ethanol production, in short rotation coppice(SRC).

3. Plantation of different species with a relevant ecological andeconomical value to produce forage, wood and non-woodproducts (Argania spinosa, Pistacia atlantica, Olea europaea).The density is 7 x 6 m with an inter row forage crop of Atriplexspp., Medicago arborea, and Opuntia ficus-indica.

4. Elaeagnus angustifolia plantation to produce wood and forageand to study the capacity of this species to ameliorate theconditions of saline and degraded soils.

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scaling up

The representative condition of the Brézina oasis suggests the replication of the model for several situations in Algeria

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Merci pour votre attention !