https://lirias.kuleuven.be/retrieve/78844

Deficit irrigation as an on-farm strategy to maximize crop water productivity in dry areas

Irrigation management under water scarcity

A variety of indices for characterising hydrological drought have been devised which, in general, are data demanding and computationally intensive. On the contrary, for meteorological droughts very simple and effective indices such as the Standardised Precipitation Index (SPI) have been used. A methodology for characterising the severity of hydrological droughts is proposed which uses an index analogous to SPI, the Streamflow Drought Index (SDI). Cumulative streamflow is used for overlapping periods of 3, 6, 9 and 12 months within each hydrological year. Drought states are defined which form a non-stationary Markov chain. Prediction of hydrological drought based on precipitation is also investigated. The methodology is validated using reliable data from the Evinos river basin (Greece). It can be easily applied within a Drought Watch System in river basins with significant storage works and can cope with the lack of streamflow data.

Assessment of Hydrological Drought Revisited

http://www.cropscience.org.au/icsc2004/pdf/1018_passiourai.pdf

Increasing Crop Productivity When Water is Scarce - From Breeding to Field Management

The Mediterranean region is undergoing rapid local and global social and environmental changes. All indicators point to an increase in environmental and water scarcity problems with negative implications towards current and future sustainability. Water management in Mediterranean countries is challenged these pressures and needs to evolve to reach the target of increasing population with reliable access to freshwater established by the Millennium Development Goals. This paper first reviews and evaluates current and future social and environmental pressures on water resources, including climate change. The results show that pressures are not homogeneous across the region and sectors of water use. Second the paper evaluates the adaptation strategies to cope with water scarcity, including technology, use of strategic groundwater, and management. Finally, the paper proposes a framework for managing the risk of water scarcity based on preparedness rather than a crisis approach. The importance of local management at the basin level is emphasized, but the potential benefits depend on the appropriate multi-institutional and multi-stakeholder coordination.

Challenges to Manage the Risk of Water Scarcity and Climate Change in the Mediterranean

Tools for Drought Mitigation in Mediterranean Regions

Preparedness measures to cope with droughts and water scarcity in semi-arid climates in irrigated agriculture include the identification of irrigation scheduling strategies that minimize the water demand with acceptable impacts on yields. Those strategies may be produced by simulation and focus on different levels of water demand. The irrigation scheduling simulation model ISAREG, validated for Tunisia, is used to simulate those strategies. The generated irrigation scheduling strategies are applied to deficit irrigation of winter wheat, tomato and potato crops under semi-arid conditions in Central Tunisia. The alternative schedules are evaluated through the combined use of indicators relative to the reduction in demand for irrigation water, the consequent yield reduction and the impacts on farmer’s income. The economic evaluation of those strategies is performed with the help of a linear programming model. Results indicate that, when there is limited water availability, each crop reacts differently to the water restrictions applied in terms of yield decrease and gross margin per unit surface and unit of water applied. For average demand, the adoption of deficit irrigation is generally feasible for all crops considered. However, for the tomato crop, there is a trend to restrict the cultivated surface when water scarcity increases. Under high and very high demand conditions, the gross margin per unit of water applied decreases for the potato and the tomato crops but increases for the wheat crop. Then, adopting deficit irrigation is not feasible for the tomato and potato crops, the option being to decrease the cultivated surface. On the contrary, the wheat crop responds well to deficit irrigation, with a good water valorisation, including under drought conditions.

Coping with drought: deficit irrigation strategies for cereals and field horticultural crops in central tunisia

The identification of deficit irrigation strategies that provide for a reduced water demand with acceptable impacts on yields is part of preparedness measures to cope with drought and water scarcity. The irrigation scheduling simulation model ISAREG, which has been prior calibrated and validated in several Mediterranean regions, is used to simulate various irrigation schedules under average, high and very high climatic demand conditions to cope with diverse water supply restrictions. The study applies to the Vigia irrigation project in Alentejo, Portugal, which is taken as case study for similar areas in the region. The study concerns the supplemental irrigation of wheat and deficit irrigation of maize and sunflower under center-pivot sprinkler irrigation. The alternative irrigation schedules are evaluated taking into consideration the reduction in demand for irrigation water, the consequent decrease in yield, and the respective impacts on farmers income. Results show that deficit supplemental irrigation strategies for wheat are generally feasible. On the contrary, deficit irrigation strategies for maize are only feasible when the irrigation deficit is limited and water restrictions are low to moderate. Otherwise, the best practice is to limit the area cropped and apply there near optimal irrigation. Results for the sunflower show the feasibility of deficit irrigation because the crop is subsidised, which compensates for the yield losses.

A. Zairi

Papers

Irrigation management under water scarcity

Tools for Drought Mitigation in Mediterranean Regions

Coping with drought: deficit irrigation strategies for cereals and field horticultural crops in central tunisia

Feasibility of Deficit Irrigation with Center-Pivot to Cope with Limited Water Supplies in Alentejo, Portugal

Irrigation scheduling strategies for horticultural field crops under limited water availability.