Droughts

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Farmers’ Adaptation to Local Climate Includes Drought Risk-Reduction Strategies

Farmers can take factors like drought risk into account when deciding what to produce and how to produce it. For example, California farmers tend to grow almonds in areas that have access to both surface water and a highly reliable groundwater supply. This allows farmers to substitute groundwater for surface water—one reason that during the recent drought in California, farmers were able to continue producing almonds despite large cutbacks in surface water deliveries. Almond orchards require large capital investments, so locating them in areas with reliable water supplies limits investment risk. In areas of California without reliable groundwater, farmers are more likely to grow annual crops, such as cotton or corn silage, which do not require as large a capital investment and which may be planted on fewer acres or shifted to other crops during a major drought.

Any action that reduces drought vulnerability increases resilience. Farmers can make small but meaningful improvements in their drought resilience through investments and actions that enhance soil moisture-holding capacity. A variety of management practices that increase soil organic matter while reducing soil-moisture loss—such as no-till or reduced tillage, use of cover crops, and conservation crop rotations—may help farms adapt to drought risk. Evidence suggests, for example, that farmers in semi-arid areas like Kansas use no-till, fallow rotations, and cover crops explicitly for such purposes.

Investment in irrigation efficiency may also improve drought resilience. High-efficiency irrigation technologies—such as drip irrigation systems and Low Energy Precision Application (LEPA) sprinklers, whose nozzles drop low to the ground—generally reduce water lost to evaporation or run-off. Such systems make a greater proportion of water withdrawals available for crop use and help stretch limited water supplies. When increased water efficiency at the field level comes from a reduction in run-off or groundwater infiltration, this can reduce availability of water downstream for environmental purposes or for other surface water uses. Due to this potential unintended consequence of investments in irrigation efficiency, some local water management institutions may impose rules to ensure public funding of irrigation efficiency preserves or improves environmental flows.

Soil and water conservation can be approached through agronomic and engineering measures. Agronomic measures include contour farming, off-season tillage, deep tillage, mulching and providing vegetative barriers on the contour. These measures prevent soil erosion and increase soil moisture.

Engineering measures differ with location, slope of the land, soil type, and amount and intensity of rainfall. Measures commonly used are the following:

  • Contour bunds, trenches and stone wallsThese features prevent soil erosion and obstruct the flow of runoff. The retained water increases soil moisture and recharges the groundwater.
  • Check dams and other gully-plugging structuresCheck dams are temporary structures constructed with locally available materials. Types of check dams are the brush-wood dam (Fig. 2 a), the loose-rock dam (Fig. 2 b) and the woven-wire dam.
  • Percolation pondsThese features store water for livestock and recharge the groundwater. They are constructed by excavating a depression to form a small reservoir, or by constructing an embankment in a natural ravine or gully to form an impoundment.

Check dams made out of brush wood

Fig. 2  (a) Check dams made out of brush wood.

Check dams made out of loose rock

Fig. 2  (b) Check dams made out of loose rock.

Water-supply projects can also be implemented for drought mitigation, with a view to strengthen drought preparedness. Activities such as water-use planning, rain-water harvesting, runoff collection using surface and underground structures, improved management of channels and wells, exploration of additional water resources through drilling and dam construction, are implemented as a part of a drought-mitigation plan.

To increase moisture availability, the following in-situ moisture-conservation practices can be adopted:

  • For agricultural crops, measures include ridges and furrows, basins, and water spreading.
  • For tree crops, measures include saucer basins (Fig. 3), semi-circular bunds, crescent-shaped bunds, catch pits and deep pitting.
  • Rainwater harvesting collects rainfall or moisture for immediate or eventual use in irrigation or domestic supplies. Part of the rainwater collected from roofs can be stored in a cistern or tank for later use.
  • Landscape contouring is used to direct runoff into areas planted with trees, shrubs, and turf.

Olive grove in Andalucia, Spain, showing saucer basins to contain precipitation

Fig. 3  Olive grove in Andalucia, Spain, showing saucer basins
to contain precipitation.

Farmers can prepare for drought by developing plans which cover all aspects of farm management and take into account variable climatic conditions. Sustainable strategies include appropriate fencing to control overgrazing, pest-control measures, planting drought-resistant crops and pasture, stabilization of eroded soils, pruning plants to reduce leaf area, removing weak plants and thinning dense beds to reduce competition, and the protection of native plant species.

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