Techn. Session 5 "Rainfed Agriculture: Financing Smart Agriculture Projects“ Water Harvesting and Supplemental Irrigation - MENA Case Study 1 - Water Productivity Enhancement, By Prof. Dr. Dieter Prinz, Karlsruhe, SW-Germany, Land and Water Days in Near East & North Africa, 15-18 December 2013, Amman, Jordan

1. FAO Near-East & North Africa Land & Water Days, Amman, 15 – 18 Dec. 2013
Techn. Session 5 „Rainfed Agriculture: Financing Smart Agriculture Projects“
Water Harvesting and Supplemental Irrigation MENA Case Study 1 - Water Productivity Enhancement
Prof. Dr. Dieter Prinz, Karlsruhe, SW-Germany (prof.prinz@t-online.de)
EXECUTIVE SUMMARY
Water Harvesting: The collection and concentration of rainfall and its use for the irrigation of crops,
pastures, trees, for domestic and livestock consumption.
Climate Smart Practices: (a) Fitting to the local climatic conditions; (b) Well suited for future climatic
conditions (Climate Change Adaptation)
Efficient Practices: (a) Catching the rain optimally, (b) High water-use efficiency / Water Conservation;
(c) High economic / financial efficiency (‘Water Productivity’)
Case Study 1.A: Increasing Water Use Efficiency of Stored Wadi Water in Jordan’s Badia
Issue
Large parts of the Jordan’s ‘Badia’ are suffering from low, erratic
winter rainfall, high evaporation (> 2000 mm/a) and low soil
fertility. Surface crusts cause low infiltration and high runoff with
subsequent soil erosion. Vegetative cover is therefore generally
poor. ICARDA established, in cooperation with the University of
Jordan, a research site in a typical ‚badia‘ area (in Muaqqar) to
investigate improved management options of small farm reservoirs. Three small earth dams were constructed across the upstream part of a wadi, creating farm reservoirs of 25,000 to
40,000 m3 volume. The stored water is used to irrigate field
crops and trees (Supplemental Irrigation), aiming at a high WUE.
Challenges
Main questions are: (1) Is the productivity of water used for supplemental irrigation of winter crops higher than that used for full
irrigation in summer? (2) Is the emptying of a reservoir as soon
as it is filled more efficient than leaving it filled for later use?
Flooded wadi and a reservoir
Innovations
(1) Highest water use efficiency was obtained, when the stored water was used in winter and the reservoirs emptied as often as possible. (2) Further-on, sediment removal did not only extend the lifetime of
the reservoirs, but the extracted sediments contributed to an improved soil fertility.
Literature: Oweis, T. & Taimeh, A. (2002). Farm Water Reservoirs: Issues of Planning and Management in Dry Areas. In: Adeel, Z. (ed.) Integrated
Land Management in Dry Areas. United Nations University, Tokyo, p. 165-182
Case Study 1.B: Using Groundwater Dams for Subterranean Water Storage
Issue
The use of floodwater flowing in wadis is well established,
but the benefits of constructing ground-water dams are
not as well known. To establish such a dam, a trench is
dug into the wadi sediment across a wadi bed, down to
the bedrock. The dam itself is built from stone or concrete; the work can be done by manpower or largely
mechanized. Alternatives to groundwater dams are sand
dams, which are constructed in steps, generating
accumulation of coarse sand upstream of the structure.
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2. In Niger a groundwater dam was constructed by local
communities under guidance and financed by an international NGO. The dam was 120 m long and 2 meters high.
After a single flood, about 25,000 m3 of water had been
accumulated (over a wadi length of 300 m). The water is
used for irrigation and domestic purposes.
Challenges
The above-surface flow in wadis lasts for hours or days,
whereas the groundwater flow within the wadi bed lasts for weeks. The dams can be extended above
the sediment level at time of construction to serve the purpose of slowing down the runoff flow and to
facilitate infiltration. These dams offer numerous advantages of water storage e.g. very low evaporation,
hardly any pollution, no breeding of mosquitoes. However, a precondition is that the wadi bed consists
mainly of coarse sand (35 % water content), not of fine sand (5% water content), silt or clay. There are
numerous groundwater dams in the Near and Middle East, e.g. in the Negev, where the extracted water
is stored in large ponds for irrigation.
Innovations
In spite of being a very ancient technique, the potential of groundwater and sand dams is largely untapped. The (material) costs are generally low (500 Euro). There are modern tools available to identify
suitable wadis (e.g. radar satellite images), the location of most suitable sites for a ground-water or sand
dam (e.g. using Google Earth), the size of the catchment (by DEM and Google Earth).
Literature: van Waes, B., Bouman, D. & Worm, J. (2007). Smart Water Harvesting Solutions. Examples of innovative, low-cost technologies for
rain, fog, runoff water and groundwater. Netherlands Water Partnership, http://publications.cta.int/en/publications/publication/1394/
Case Study 1.C: Rooftop Water Harvesting in Greenhouse Production in Lebanon Mountains
Issue
Due to the high demand for vegetables and cut flowers in the
densely populated coastal areas, green-house production in the
Lebanese mountains flourishes. To optimize the use of available
water resources, a ‘Green Plan’ project was started; its special
features are (1) Rainwater is harvested from the tops of plastic
greenhouses and directed into a pond, which is lined with PVC
sheets and geotextiles. (2) The pond water is flowing by gravity
into other greenhouses and is used there for drip irrigation of
ornamental plants (roses, stocks etc.). The location is NE of
Jounieh, Central Lebanon, 300 – 350 m asl, precipitation as well
as evaporation are about 1000 mm/year.
Challenges
As there are no springs in the area, there is the need for rainwater harvesting; greenhouse rooftops offer unpolluted, good
quality water, well suited for crop production within the greenhouses. Karstic underground asks for sealing of ponds to store the water. The rainwater storage needs
expertise and funds; the lifetime of a pond is limited to max. 10 years. A high water use efficiency can be
achieved by applying drip irrigation in the greenhouses.
Innovations
The ‘Green Plan’ agency is an autochthonous authority under the Lebanese Ministry of Agriculture, partially financed by international donors. Green Plan experts develop together with interested farmers
technical and financial development plans for their enterprise. Farmers receive soft loans and subsidies;
the progress is documented.
Literature: Republic of Lebanon (2012). Hilly Areas Sustainable Agriculture Development (HASAD). Project Design Report. Prepared by IFAD
(International Fund for Agricultural Development) Updated for Supplementary Financing. Beirut, Lebanon
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