|
1. Summary Irrigation uses about 80% of
all water diverted for various uses in the Mediterranean. Nevertheless, increased demand
for other uses coupled with water scarcity is putting unprecedented pressures on reducing
the share of freshwater used in irrigation. Given the degree of scarcity in many areas of
the Basin, if irrigation water use could be reduced, it could become a major water source,
thus releasing resources for alternative use. The objective of this project is to evaluate
the concept of deficit irrigation (DI) as a means of reducing irrigation water use while
maintaining or increasing farmers profits. The DI concept will be the subject of
multidisciplinary research at different scales, geographic locations, and with different
perennial and annual crops. The objective will be to develop a workable, comprehensive set
of irrigation (DI) strategies that can be disseminated quickly among the various
agricultural systems of the Mediterranean Region. The project addresses directly the first
topic of the INCO-2002-B1.2 specific measure, ‘research on sustainable irrigation,
including deficit irrigation’. Eleven partners from seven different countries
(Greece, Italy, Jordan, Morocco, Spain, Tunisia and Turkey), including research and water
association institutions will work for three years on the project. Their main activities
will be: a) the development of a general summary model of crop yield as a function of
water supply, b) the validation of the model for the main irrigated annual (wheat,
sunflower, cotton,) and perennial crops (olive, pistachio, citrus), using common research
protocols, c) a survey on physical, socio-economic and cultural conditions for each crop
and irrigated area, and d) scaling up by combining the yield model with economic
optimization modules that will generate optimum DI strategies compatible with the specific
socio-economic characteristics of each area under study. The results of the project will
provide recommendations for reducing irrigation water use while ensuring the
sustainability of irrigated agricultural systems in the Mediterranean basin. Feedback with
project end-users will take place via participation of farmers associations and irrigation
water agencies who will contribute their expertise in managing water scarcity, thus
ensuring that all relevant issues are addressed. 2. Objectives
The ultimate objective is to reduce the consumptive use of water by crops in the
irrigated lands of the Mediterranean Basin and thereby to release water resources for
other uses in the Basin.
Specifically, this project will use deficit irrigation (DI) as a means of
maintaining or increasing farmers’ profits while reducing irrigation water use. The
DI concept will be the subject of multi-disciplinary research with different perennial and
annual crops to develop a workable,
comprehensive set of DI strategies that will be disseminated quickly among various
agricultural systems of the Mediterranean Region. The project has this aim which will be
achieved by meeting the following, measurable objectives:
1.
Development of a simulation model for DI design and for yield prediction in
water-limited situations. 2.
Validation of the simulation model using experiments with the various crops and in
participants countries. 3.
Generation of DI recommendations for farmers and water managers that will reduce
water use for irrigation in participants countries. 4.
Characterization of current DI situations in participants countries and document
farmers’ performance and the limitations of existing irrigation networks. 5.
Assess the economic viability of DI for the various crops, environments, and water
delivery methods in participants countries. For this, the DI simulation model will be
coupled with an optimisation module for economic analysis. 6.
Evaluate the social acceptability of DI and the institutional and cultural features
that are needed for the dissemination and acceptance of DI. 7.
Integrate DI strategies into the management of irrigation water at the watershed,
irrigation district, and farm levels. The field
research program will be carried out in each Country with the following target crops: Annual
Crops:
Experiments in: Cotton
Greece, Turkey Wheat
Italy, Tunisia Sunflower/sugarbeet
Spain, Italy Perennial
Crops: Citrus
Jordan, Tunisia Pistachio
Greece, Turkey Olive
Spain, Tunisia
3.Scientific Background Irrigation
uses about 80% of all water diverted for various uses in the Mediterranean. Nevertheless,
increased demand for other uses coupled with water scarcity is putting unprecedented
pressures on reducing the share of freshwater used in irrigation. Given the degree of
scarcity in many areas of the Basin, if irrigation water use could be reduced, it could
become a major water source, thus releasing resources for alternative use. Where
water is limited, alternatives strategies must be sought to reduce irrigation water use
and do so with the least effect on yield, i.e. to seek greater productivity from applied
water (Seckler, 1996). The application of water below full crop-water requirements
(potential evapotranspiration, PET) is termed deficit irrigation (DI) (English et al.,
1990). In this way, water demand for irrigation can be decreased and the saved water can
be diverted for alternative uses. With careful scheduling, yield under DI need not be
reduced in proportion to the water saved (Howell et al., 1990). In some circumstances
there may be no yield loss, and for some crops product quality may be improved (FAO,
2002). It
is important to identify the mechanisms of water saving that can be generated by using DI
and the scales at which the savings apply. Consider the situation where reduced irrigation
can be compensated by additional extraction of water from the soil profile without
significant crop water stress. In this case, less irrigation is applied but full crop ET
is retained and yields are not affected. If soil water is always fully recharged by
rainfall before subsequent crops, DI will be sustainable and will increase profits to the
extent of savings achieved in the cost of water and its application. Whether such savings
will extend to the irrigation basin as a whole depends upon the contribution of return
flows (runoff and drainage) to water reuse elsewhere (Wallander and Grismer, 2002). If DI in some parts of the basin reduces water
available for reuse elsewhere, then DI cannot be applied at the same level throughout and
the level of water and cost savings are reduced. By contrast, in the situation where
extraction of soil water is insufficient to meet the deficit created by DI, crop ET is
reduced and, normally, crop yields may decrease (Howell, 2001). In this case, however, the
reduction in ET always leads to net water savings at the basin level. There are two general types of Deficit Irrigation. One is the conjunctive use of rainfall and irrigation to meet PET (Stewart and Musick, 1982). The other is a more complex management system which seeks high yield at an appropriately reduced ET (English and Raja, 1996). In both cases, there is a benefit of reduced irrigation water usage and the potential for cost savings. Consequently, it is reasonable to ask why the technique has not been used more widely in the past. The answer is that, with current knowledge and technology, risks increase with DI because the maintenance of yield depends upon more complex management in the face of environmental variability. Such real or perceived risks can only be counteracted by improved irrigation techniques and management and experimental evidence of successful applications. Further research is required before the more general implementation of DI practices in irrigation management is possible. A recent meeting of WASAMED (2003), a network of more than 50 institutions working on water management in the Mediterranean, concluded that little is known about DI in this Region and the potential water savings that could be obtained through its use. Field experimentation is costly and time consuming but its efficiency can be increased and its cost decreased by combining experimentation with simulation modelling.
|
|
||
