Handbook for Irrigation of Wine Grapes in South Africa

FIGURE 7.41. Vigorous reed growth in a dam will cause unnecessary water losses via transpiration.

7.2.11.3 PREVENTING IRRIGATION SYSTEM LOSSES Large volumes of water will be wasted if leaks occur in any of the components in the irrigation system, i.e. between the water supply and the sprinklers or drippers. To avoid unnecessary leaks, continuous inspection and maintenance are essential. Make sure that micro-sprinklers are on the upright position, i.e. on laterals or pegs, to prevent uneven wetting patterns. Remove any weeds or down growing shoots that can disturb the distribution pattern of micro-sprinklers (Fig. 7.42). Sagging dripper lines will also cause uneven wetting along the grapevine row. Make sure that the dripper lines are attached to the wires. It is critical that irrigation systems operate at the design pressure. Therefore, water filters should be cleaned regularly to avoid a decrease in pressure and water flow in the laterals. On the other hand, excessive pressure in micro-irrigation systems will cause a fine mist that will result in substantial evaporation losses as the water droplets travel through the air (Fig. 7.43). Furthermore, water losses due to excessive pressure in the irrigation system will increase under windy conditions. Figur 7.42

A

B

FIGURE 7.42. The water distribution of micro-sprinklers should be uninterrupted (A) and not be interrupted by weeds or cover crops (B).

226 CHAPTER 7 – IRRIGATION STRATEGIES

Figure 7.43