System Users – Residential, Industry and Agriculture:
These users need to determine the best of practice option for each site in an endeavour to be as water efficient as possible and as a consequence result in more effective use and conservation of precious water resources.
Irrigation water saving practice falls into three basic categories:
• Field practices:
These involve keeping the irrigated water in the field by distributing it more efficiently and to encourage retention of the soil moisture against evaporation. Methods to achieve this is to reduce extreme soil compaction which promotes water penetration to root zones, runoff prevention by forming intermediate and peripheral dikes, leveling the land to promote even water distribution and mulching to reduce evaporation.
• Management strategies:
Strategies revolve around soil moisture monitoring, measuring rainfall, pumping efficiency and then collating this information to determine efficient irrigation scheduling of water distribution.
• System modifications:
System design should not be regarded as being fixed but rather be approached dynamically. This concept will allow for the improvement of the design on an ongoing basis as more efficient pumps, distribution equipment, installation of more water measurement meters, soil monitoring instruments and the recovery of excess tail water systems evolve.
Water Reuse and Recycling:
Approximately 40% of total water demand nationwide is attributable to agricultural irrigation. This represents a significant portion of total water available and therefore irrigation practices such as reuse and recycling would result in substantial water conservation.
Therefore an agricultural water reuse program should include:
• Identify opportunities for water re-use.
• Determine the applicable water quality requirements for any give use of re-used water.
• Sources of waster water, that are able to meet the water quality requirements, need to be then identified.
• Determine how to transport the re-used water to the proposed usage area.
• Measure the amount of water that is being re-used.
• Integration with Urban reuse opportunities
In addition to incorporating best practice water behaviour habits is the need to develop methods that optimise the amount of water needed to irrigate a given crop efficiently. This includes water scheduling decisions based on data collected from soil monitoring stations, weather conditions and careful choice of irrigation application rates for the given crop. Additional factors that irrigators need to be taken into consideration:
• Uncertain rainfall and crop water demand
• The water retention characteristics of the irrigated soil.
• Pumping capacity being equal to the task.
• Impact of increased energy costs resulting in increased pumping cost.
Agricultural extension services need to be included in the irrigation design so that their extensive knowledge base is incorporated. This expertise would include information on solar radiation levels, weather variables obtained from weather stations, resistance blocks, tensiometers, and neutron probes to monitor soil moisture conditions to assist in determining when and how much water should be applied.