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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 dur-ing 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 Con-servation; (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.

D. Prinz: MENA Case Study 1 - Water Productivity Enhancement (TS 5)

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Fig. 1: Flooded wadi in winter season

Fig. 2: One of the farm reservoirs

Fig. 3: Spillway: Concrete structure

and gabion step

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 cli-

mate change in future 150 mm/a) is lost by evaporation

or runoff to salt sinks. Vegetative cover is therefore gen-

erally 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 Uni-

versity of Jordan, a research site in a typical ‚badia‘ area

(in Muaqqar) to investigate the potential use and im-

proved 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 flood-

water. The stored water is used to irrigate field crops

and trees (Supplemental Irrigation). Various kinds of

floodwater management were tested to arrive at reason-

able 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?

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 emp-

tying 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 Man-

agement in Dry Areas. In: Adeel, Z. (ed.) Integrated Land Management in Dry Areas. United Nations

University, Tokyo, p. 165-182

D. Prinz: MENA Case Study 1 - Water Productivity Enhancement (TS 5)

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Fig. 5: Groundwater Dam under con-

struction in Niger

Fig. 6: Pumping water from a ground-

water dam to a storage pond (Negev)

egev)

Fig.4: Groundwater dam

Fig.7: Sand Dams are built in steps

wise

Case Study 1B: Using Groundwater Dams for Subterranean Water Accumulation and Storage

Fig.: Groundwater Dam

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 irriga-tion 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 vec-tors, low maintenance costs and long life. However, a pre-condition is that the wadi sediments consist mainly of coarse sand (35 % water content), not of fine sand (5% water con-tent). Upstream-downstream issues might arise, but are nor-mally of low significance as the effects on downstream river discharge are generally small. The construction of groundwa-ter dams in cascades can improve total water storage. De-pending on local conditions (clay layers, geology), groundwa-ter and sand dams will contribute to groundwater recharge.

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. Exam-

ples of innovative, low-cost technologies for rain, fog, runoff water and groundwater. Netherlands

Water Partnership, http://publications.cta.int/en/publications/publication/1394/

D. Prinz: MENA Case Study 1 - Water Productivity Enhancement (TS 5)

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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 pro-duction in the Lebanese mountains flourishes. To opti-mize the use of available water resources, a ‘Green Plan’ project was started; its special features were (1) Rainwa-ter 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 life-time of the pond: 7 – 10 years (Fig. 10).

Challenges As there are no springs in the area, there is the need for rainwater harvesting. Greenhouse rooftops offer unpol-luted, good quality water, well suited for crop produc-tion 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 contrib-utes to water conservation as the ET in greenhouses is significantly lower than in the open.

Fig. 8: Greenhouses in the Lebanese

Mountains cover several hectares of land

Fig. 10: Rainwater from greenhouses is

stored in ponds to be used for irrigation

Fig. 9: Lo-

cation of

the case

study area.

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 farm-ers 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). Pro-ject Design Report. Prepared by IFAD (International Fund for Agricultural Development) Updated for Supplementary Financing. Beirut, Lebanon