Technical Session 5 "Rainfed Agriculture: Financing Smart Agriculture Projects“ Water Harvesting and Supplemental Irrigation - MENA Case Study 1 - Water Productivity Enhancement, Water Harvesting and Supplemental Irrigation. Climate Smart and Efficient Practices, 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
Water Harvesting and Supplemental Irrigation. Climate Smart and Efficient Practices
Prof. Dr. Dieter Prinz, Karlsruhe, SW-Germany (prof. prinz@t-online.de)
HAND OUTS
Water Harvesting: The collection and concentration of rainfall and its use for the irrigation of
crops, pastures, trees, for domestic and livestock consumption.
Supplemental Irrigation: Addition of small amounts of water to essentially rainfed crops during times when rainfall fails to provide sufficient moisture for normal plant growth, in order to
improve and stabilize yields.
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
“Low Cost Techniques of Water Harvesting for Economic Supplemental Irrigation”
The 3 case studies presented show techniques, which are well suited to stabilize yields, to
make best use of available water resources and to adapt to future climatic conditions.
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2. D. Prinz: MENA Case Study 1 - Water Productivity Enhancement (TS 5)
----------------------------------------------------------------------------------------------------------------------------------------Case Study 1A: Increasing Water Use Efficiency of Stored Wadi Water in Jordan
Issue
Large parts of the Jordan’s ‘Badia’ are suffering from low,
erratic winter rainfall (Fig. 1), high evaporation (> 2000
mm/a) and low soil fertility. Surface crusts cause low
infiltration and high runoff with subsequent soil erosion.
About 90% of the precipitation (Ø 200 mm/a; due to climate change in future 150 mm/a) is lost by evaporation
or runoff to salt sinks. Vegetative cover is therefore generally poor. The construction of large dams in the region
is associated with low water use efficiency (WUE) on
agric.
lands.
ICARDA (International Center for Agricultural Research in
the Dry Areas) established, in cooperation with the University of Jordan, a research site in a typical ‚badia‘ area
(in Muaqqar) to investigate the potential use and 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 (Fig. 2 & 3). The reservoirs
are 5 – 6 m deep, maximum 8 meters; freeboard is about
1 meter. They are filled 3 to 5 times per season by floodwater. The stored water is used to irrigate field crops
and trees (Supplemental Irrigation). Various kinds of
floodwater management were tested to arrive at reasonable yields and a high WUE.
Challenges
Main questions were: (1) Is the productivity of water
used for supplemental irrigation of winter crops higher
than that used in full irrigation in summer? (2) Is the
emptying of a reservoir as soon as it is filled (i.e. to store
the water in the soil matrix of the fields) more efficient
than leaving it filled for later use?
Fig. 1: Flooded wadi in winter season
Fig. 2: One of the farm reservoirs
Fig. 3: Spillway: Concrete structure
and gabion step
Innovations
(1) Best yields and highest water use efficiency were obtained, when the stored water was used in
winter (and not saved for the summer season) and the reservoirs emptied as often as possible.
However, there is the risk of not having runoff water to prolong the growing season after an emptying of the reservoir at the end of the winter season. (2) Further-on, sediment removal did not
only extend the lifetime of the reservoirs, but the extracted sediments contribute to an improved
soil fertility when mixed with soil of the agricultural lands.
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
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3. D. Prinz: MENA Case Study 1 - Water Productivity Enhancement (TS 5)
----------------------------------------------------------------------------------------------------------------------------------------Case Study 1B: Using Groundwater Dams for Subterranean Water Accumulation and 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 and
well into the riverbanks (Fig. 4). The dam itself is built from
stone or concrete; the work can be done by manpower or
largely mechanized. Runoff water infiltrates into the wadi
deposits and the bordering riverbanks, creating an artificial
aquifer. Water is extracted through a hand-dug well or tube
well.
Alternatives to groundwater dams are sand dams, which are
constructed in steps, generating accumulation of coarse sand
upstream of the structure (Fig.7). In Niger a groundwater
dam was constructed by local communities under guidance
and financed by an international NGO (Fig.5). The dam was
120 m long and 2 meters high. After a single flood, about
25000 m3 of water had been accumulated (over a wadi length
of 300 m) and were ready to be used for supplemental irrigation and drinking water purposes. 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 (Fig. 6).
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, e.g. very low evaporation, hardly any
pollution, no breeding of mosquitoes and other disease vectors, low maintenance costs and long life. However, a precondition is that the wadi sediments consist mainly of coarse
sand (35 % water content), not of fine sand (5% water content). Upstream-downstream issues might arise, but are normally of low significance as the effects on downstream river
discharge are generally small. The construction of groundwater dams in cascades can improve total water storage. Depending on local conditions (clay layers, geology), groundwater and sand dams will contribute to groundwater recharge.
Fig.4: Groundwater dam
Fig. 5: Groundwater Dam under construction in Niger
Fig. 6: Pumping water from a groundwater dam to a storage pond (Negev)
Fig.7: Sand Dams are built in steps
egev)
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 groundwater 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/
wise
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4. D. Prinz: MENA Case Study 1 - Water Productivity Enhancement (TS 5)
----------------------------------------------------------------------------------------------------------------------------------------Case Study 1C: 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, greenhouse production in the Lebanese mountains flourishes. To optimize the use of available water resources, a ‘Green Plan’
project was started; its special features were (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 slightly below the pond location and
is used there for drip irrigation of ornamental plants
(roses, stocks etc.). The location is NE of Jounieh, Central
Lebanon (Fig. 9), 300 – 350 m asl; precipitation as well as
evaporation are about 1000 mm/year. The size of the
greenhouse complex used for water harvesting is 3500
m2. Assuming 90% ROC, 3150 m3 of rainwater could be
harvested per year. Pond size is 1700 m2; expected lifetime of the pond: 7 – 10 years (Fig. 10).
Fig. 8: Greenhouses in the Lebanese
Mountains cover several hectares of land
Fig. 9: Location of
the case
study area.
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. Expertise and
funds are needed for the rainwater storage; 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. Greenhouse production itself contributes to water conservation as the ET in greenhouses is
significantly lower than in the open.
Fig. 10: Rainwater from greenhouses is
stored in ponds to be used for irrigation
Innovations
The ‘Green Plan’ agency is an autochthonous authority under the Lebanese Ministry of Agriculture,
partially financed by international donors. Green Plan projects aim at utilizing the available water
resources optimally, contributing to economic prosperity in rural, mountainous environments.
Green Plan experts develop together with interested farmers technical and financial development plans
for their enterprises. Farmers receive soft loans and subsidies; the progress is documented. The farmers contribute between 18 and 39% of the total costs only and receive soft loans (annual 1% interest
rate) for it. The farmer pays the loan with easy payments beginning in the 6th year and extending over
10 years. Projects like this one are good examples of ‘sustainable agricultural development’. They are
economically viable, ecologically sound and can adapt well to climate change conditions. Drawback for
wider application is the limited availability of Government funds.
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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