poster - International Conference of Agricultural Engineering

Measuring of resources employed for crop irrigation in general, and for lettuce in particular,
will let to set the fundaments for the quantification of the environmental impact of their
exploitation, and advance in the knowledge about the sustainability of resources employed in
crop production.
This paper is focused in the evaluation of water and energy use to produce lettuce in
alternative countries during the winter season in Europe. The case study is located in a farm
in the Southern of Spain, a warm country where there are zones in which is possible to
cultivate lettuce in winter. The main objective was to evaluate the efficiency of water and
energy used in the irrigation of lettuce crops during a typical season.
2. Materials and Methods
The analysis of water and energy efficiency was performed during the 2010-2011 season in
a commercial Iceberg lettuce orchard (Lactuca sativa, L. cv. ‘Capitata’) under trickle
irrigation, located at Cartagena, Murcia (Spain).
2.1. Description of the irrigation system of the experimental farm.
The irrigated surface of the experimental farm is around 98.93 ha. Irrigation water comes
from Tajo-Segura transfer and close wells, and it is stored in a private regulation reservoir at
the East of the irrigation station of the farm. The capacity of the reservoir is 13,975 m 3 .
Irrigation water is supplied by gravity from the regulation reservoir to the irrigation station. In
this irrigation station energy is consumed by a horizontal pump where water is distributed to
several plots under trickle irrigation. Moreover, the pump supplies the adequate pressure to
different plots of the irrigation system. Additionally, the pump incorporates a frequency speed
drive in order to adapt the operation point to the demand of the system along the operational
period of the pump. The pump level is under the water level of the reservoir (around 5
meters). Water must be raised approximately from a level of 25 meters over the sea level,
where the pump is located, to a maximum level of 45 meters over the sea level (at the most
unfavourable point of the farm), what supposes an elevation of around 20 meters. Due to the
operation pressure of the trickle emitters, an additional pressure of 10 meters has to be
added to this geometric level. Moreover, in specific times (e.g. in the beginning of the
seedling phase in lettuce crops) is necessary an adicional pressure for sprinklers. If some
additional losses (friction and located losses) are also considered, a maximum total pressure
of 44 to 56.7 meters of water column (mWC) is required. The unitary flow of the pump
installed is 90 m 3·h -1 . In the studied farm, an autoclean mesh filter and a fertilized dosage
system are installed after the pump.
The only meter that registers the volume that is flowing in the irrigation system network is
located at the exit of the irrigation station. Due to the flow and store capacity of the reservoir
are not enough for irrigating all the plots at the same time, a rotational scheduling water
distribution network is needed to be used. For this reason, water distribution network is
sectored and every sector irrigates a plot by means of manual opening valves.
2.2. Methodology and equipment for data adquisition.
The study was partially based in the methodology employed for Water Users Associations
(WUA) (Abadía, et al., 2008a), but adapted to the specific conditions of a concrete farm.
Concretely in this case, the irrigation station is considered as an independent hydraulicfunctioning
sector with an independent energy contract. Some energy parameters (Abadía,
et al., 2008b) were calculated and monthly energy bills along the season 2010-2011 were
collected. During the study, the following parameters were simultaneously measured:
Flow: it was measured by using an ultrasonic flowmeter, with a nominal diameter from
12.7 mm to 7.6 mm and a measure error of ±1% to 2%.
Energy consumption and other energy parameters: a net analyser that measures
voltage, intensity, active and reactive power, power factor and frequency was used. All
the obtained values had a precision level minor or equal to 1%.