poster - International Conference of Agricultural Engineering

total area is about 13,700 km2. The two larger basins of region are the Pinios River
and the Lake Karla basins. Thessaly plain is the most productive agricultural region
of Greece with an area of about 4,000 km2. The main crops cultivated in the plain
area are cotton, wheat and maize whereas apple, apricot, cherry, olive trees and
grapes are cultivated at the foothills of the eastern mountains. Lake Karla occupied,
until 1962, most of the eastern part of Thessaly plain in central Greece. It was one of
the most important wetlands in Greece and a natural reservoir, which provided
significant water storage and recharge to groundwater. The basin surface runoff and
the overflowing floodwaters of the Pinios River sustained Lake Karla. The lake area
fluctuated from 40 to 180 km2 due to the very gentle land slope and the inflow–
outflow balance. For this reason, significant area of the surrounding farmland was
often inundated facing soil salinity problems
3.2. Water needs
Evapotranspiration is a key indicator for water management and irrigation
performance. The agricultural water demand for irrigation per sub-basin was
estimated as follows. Firstly, data of the irrigated agricultural areas per crop and
municipality for the year 2008, provided by the Cooperation of Agriculture Farmers of
Larisa, were used to estimate the irrigated agricultural areas for each sub-basin and
each crop. The major crops in the study area were cotton, wheat, legumes, and
orchards. The monthly reference evapotranspiration for each crop (ETo) was
estimated using the Blaney–Criddle method (Blaney and Criddle 1950) and the
monthly crop coefficients proposed by FAO (Allen et al. 1998) for Mediterranean
climate conditions. Fig. 1 presents the potential evapotranspiration of main crops and
the relative water needs.
1000
Evapotranspiration / water needs, mm/year
900
800
700
600
500
400
300
200
100
0
Sugar beat Corn Vineyiards Orchands Vegetables Wheat Tomato Legumes
Crop
FIGURE 1: Potential evapotranspiration (blue) and water needs (red) of basic crops
in the region of Karla basin
Taking into account the total area of each crop in the area the maximum water needs
for irrigation are 165.943.916,24 m3/year (based on climate date for the reference
year 2008). Here we should state that practical (actual) water needs maybe vary from
what has been calculated since the above calculation did not take into account the
potential water losses during the transfer of water from the water both from irrigation
channels to the fields and also the application or irrigation method used in the field.
The efficiency of the system of water transfer and distribution depends on the type of
network. For example the open channel surface distribution networks (mainly used in
the studied area) have efficiencythat ranges from 0.20 to 0.75 (Papazafiriou 1999).