Book of Abstracts

26
Platform, June 2012). Large quantities of water are needed to produce any agricultural product--food, feed, fiber,
fuel-- and any additional savings allow us what we need most – getting more with less input.
By mid-century, the world will need 100% more food than is produced today. It is estimated that about 70% of the
increase in food production is expected to come from higher yields. Drip irrigation is, then, not an option but a real
need. Our mission is to leverage the potential of drip and micro-irrigation to efficiently employ the world’s most
precious resources--arable land, water and energy--and by doing that, to ensure greater food security for the global
population while preserving the environment. More than 80% of the global agricultural land is not irrigated (less
than 20% is irrigated, supplying 40% of the world's food). Disappointingly, just 4%-5% is irrigated efficiently with
drip-irrigation systems. We know that irrigation is a key component in the required water revolution. Drip-irrigation
is, therefore, a key component in sustainable water management solutions. This is the moment to introduce the 2 nd
drip-irrigation revolution – the nano-irrigation system.
Study of evapotranspiration for estimation of harvested water storage efficiency
G. Carmi, B. Rewald, and P. Berliner; The French Associates Institute for Agriculture & Biotechnology of Dryland;
The Jacob Blaustein Institutes for Desert Research; Ben-Gurion University of the Negev; Sede Boqer, Israel;
genadi@bgu.ac.il
Water is a primary limiting factor to agricultural development in arid and semi-arid areas. In these regions, much of
the annual rainfall occurs as a result of a few intensive convective storms. A technique of runoff collecting, known
as runoff harvesting, may be used for food and fuel production and flood and erosion control, as well as for
landscape development. The efficiency of runoff generation is an important issue in water harvesting schemes, but
the critical component is the water availability to the tree/crop planted in the runoff receiving area. The area in
which the runoff water is collected is usually a depression located in the immediate vicinity of the runoff generating
area. Evaporative losses play a major role in determining the amount of water that will be available to the plants
and/or trees planted in the shallow depressions. We hypothesize that when water is collected in deep trenches, it
infiltrates through the trenches’ bottom and into the surrounding walls as well, and the evaporative losses will be
smaller than those that can be expected for shallow depressions. The experiment was carried out in Sede Boker,
Israel from January 2011 to January 2012. The effects of water collection in i) deep trenches and ii)
microcatchments were investigated; each treatment was replicated three times. Three olive trees were planted at the
bottom of the 12 m long, 1 m deep and 1 m wide trenches. Microcatchments had a cross-sectional area of 9 m 2 (3x3
m) with one olive tree planted in the middle. The trenches and microcatchments were flooded simultaneously in
April 2011 with 1.5 m 3 water per tree; the soil water content was continuously monitored through the access tubes
using a neutron probe. To estimate transpiration, stem sap-flow was measured by a Granier system.
Evapotranspiration for each trench and microcatchment was calculated by the mass balance method. Transpiration
was deducted from the resulted evapotranspiration. Total evapotranspiration in the trenches was 50% of the water
amount applied by flooding, while microcatchments lost 132% (flooded water plus additional soil water left after the
rainy season). The results show that water losses from microcatchments were significantly higher than those from
the trenches, and that evaporation of the collected water in trenches was more effectively prevented.
Estimating precipitation and actual evaporation from precision lysimeter measurements
Wolfgang Durner; Institute of Geoecology; TU Braunschweig; Braunschweig, Germany;
w.durner@tu-bs.de
Lysimeters are excellent tools for obtaining reliable data about seepage water quantity and quality. Large weighable
lysimeters, furthermore, permit the quantification of the water balance of the soil and the precise measurement of
water exchange at both the soil-atmosphere interface, by rain, dew, fog, and rime, and the flux below the root zone
toward the groundwater. If well embedded into a similarly vegetated environment, they avoid errors made by
traditional measurement systems, such as the wind error of Hellman rain samplers, or the island error of class-A
pans, or the heterogeneity error that affects any readings from in situ instrumentation of soil water state variables. If
the amount of seepage water is recorded separately, the time series of the lysimeter mass represents the other parts
of the water balance equation: increasing mass shows precipitation amount, decreasing mass is the effect of
evapotranspiration, the mass difference in the evaluation period indicates the change of stored water volume.