Figure 31: Pumping station regulation with different types of regulation. The main results obtained from this research were:
• The irrigation scheduling applied by farmers is not suitable, but the total volume supplied during the irrigation season is similar to the total requirements of the crops.
• The initial hypotheses of Clement's methodology were rejected. Also, the use of hydrant opening probability, cause up to a 35-40% flow underestimation.
• Discharges around 40-90 l s"1 (6-10% of total discharge) are more frequent than medium and higher discharges. Therefore, optimal economic options are those able to guarantee high efficiency in the case of low discharges. In this study, the best option was the one that consisted of two variable speed pumps running sequentially and the others working as fixed speed pumps. If compared with the current regulation, in which two pumps of variable speed work simultaneously, a saving of around 16.02% could be obtained.
3.4.3 Earth Observation Techniques in Routine Irrigation Advisory Services (DEMETER Project)
One of the main problems that face an IAS are the high economic and labor costs involved to cover each field in extended areas at regular short time intervals. The utilization of Earth Observation (EO) technologies can be of great help in these tasks.
IDR has coordinated the Project DEMETER (DEMonstration of Earth observation Technologies in Routine irrigation advisory services; Contract EVG1-CT-2002-00078) (http://www.demeter-ec.net) funded by the European Commission. This project was designed to assess and demonstrate, in an operational perspective, how the performance and cost-effectiveness of an IAS is substantially improved by the incorporation of Earth observation (EO) techniques. This is done in combination with Geographical Information Systems (GIS), in day-to-day operations. In addition, the latest Information and Communication Technologies (ICT) offer great possibilities to transmit specialized information to users in a personalized manner (Calera et al., 2005).
The main result obtained in DEMETER from a sequence of satellite images are maps of crop coefficient Kc along with the temporal pattern at a given place. Therefore, the EO-derived Kc maps can be introduced directly into the routine IAS information generation flow for irrigation scheduling. Crossing (multiplying pixel by pixel) the Kc map with a map of reference evapotranspiration, ETo, directly provides a map of crop evapotranspiration, which is then used to determine crop water requirements (Jochum et al., 2006).
In order to evaluate and validate the proposed methodology, a group of representative farmers was set up during the irrigation season of 2004. Each farmer received information on a weekly basis via e-mail about crop water requirements. Figure 32 shows an example corresponding to one farm. On the left hand side, a map of actual Kc for the current weekly period is presented together with a color combination (RGB543) image for the same crop area (top panel). The same information is given for the previous week (bottom panel), in order to be able to visualize changes. On the right hand side, a temporal progression of Kc for each of the different monitored plots is displayed. Finally, information about crop water requirements from actual IAS (in this case, SAR) is also displayed in a table, to allow for the comparison with satellite derived crop water requirements.
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