Handbook for Irrigation of Wine Grapes in South Africa

FIGURE 7.44. When strong winds prevail during daytime, it is advisable to irrigate during the night.

Dams used for catching and/or storage of irrigation water should also be considered as part of the irrigation infrastructure. In many cases, silt sediments can accumulate in dams over time, thereby reducing the storage capacity. The amount of sediment that accumulates will depend on the nature and usage of soils in the catchment, or the quality of the water obtained from irrigation schemes. The sediments need to be excavated from time to time in order to restore the storage capacity of dams. As water is becoming scarcer, growers should consider increasing dam capacities to increase the volume of stored winter water where possible (Fig. 7.45A). It must be noted that the enlargement of dams is subject to limitations as laid down by the authorities. Substantial volumes of irrigation water can be lost via seepage losses through water permeable dam floors. If the latter occurs, dams must be lined with impermeable material (Fig. 7.45B).

228 CHAPTER 7 – IRRIGATION STRATEGIES