WATER MANAGEMENT ON FARMS.

Water management is often neglected. Therefore, I have devoted a specific section of the RPO-NERPO Code of Best Practice, which I completed in August of this year (see www.rpo.co.za.) to it, and because the principles and practices are also of value to dairy farmers who often farm with more than one species of livestock, I thought it worthwhile to cover the item here as well. The message is: Both in terms of quantity and quality, water will be a declining source in future and therefore requires dedicated management. From a political and social-responsibility point of view, government may become critical since agriculture utilises the major share of South Africa’s water resources.

Agriculture consumes about 75% of the rainfall in South Africa. From this, 60% is utilized by the natural vegetation, 12% by dry land crop production and 3% by irrigation. The natural vegetation (veld) and dry land crop production use only so-called green water, which is rain water that is stored in the soil after precipitation. It is called “green” water because only green plants growing in the soil utilize it. In terms of food production, green water is used for the production of meat and other animal produce under extensive grazing systems.  Veld by and large do not use so-called blue water, which is runoff water to streams, dams and other storage infrastructure, or water stored in underground aquifers and normally recovered from bore holes. Blue water is primarily available for the water requirements of livestock. In terms of management, the objective should be to optimize both green and blue water on the farm.

The effects of climate change is expected to result in a somewhat drier country, the worst off being the Western Cape winter rainfall region and the north-eastern parts of Mpumalanga and Limpopo (Low Veld and bordering Limpopo basin). More rain is expected in the central grassland areas (Free State and Drakensberg region), the Eastern Cape and the Kalahari, the latter due to tropical moisture moving south-east from Angola. “Worst” and “more” however are not dramatic as the difference in total rain compared with today is about 40 mm per annum. What is more important from a management point of view is the frequency and intensity of precipitation and the seasonal shift. Thunder activity is expected to increase resulting in short, heavy down pours, which means more water will flow away unutilized and together with higher temperatures more evaporation. The net effect could be less effective rainfall, even if in total more rain than today, if rain-fed water (both green and blue water) is not well-managed. The following measures become crucial:

• Catchment areas on farm should become storage areas using both mechanical means by for example weir construction, and vegetative means by creating wetlands (vlei, marsh or swamp) in catchment areas by planting reeds and tough grasses which are adapted to the specific region.
• Plant cover in rangelands is probably the most important factor. This primarily is determined by grazing capacity and stocking rate; conservative stocking rates and comparatively long resting periods of camps have the most significant effect on plant cover (even more than the variation in rainfall). Conservative stocking rate refers to the farm in total and does not mean that farmers should not have more animals than the calculated stocking rate in the camp that is presently grazed – in fact, intensive grazing under particular environmental conditions can be a good choice as it would assist in breaking the top soil (trampling) and provide more manure which supports moisture penetration, seeding and seed germination. This results because the organic status of the soil is improved. However, the grazing period should be short and the resting period long to ensure recovery and vegetation thickening. A good plant cover in the rangeland both captures rain water that otherwise would have run away and utilizes it effectively for plant growth. This implies that blue water also then becomes green water.                                                                
• In mixed farming systems where livestock farmers also produce crops, minimum tillage should become the norm rather than the exception. Minimum tillage ensures more organic matter which leads to better water capture and usage.

Seasonal shift refers to the period when rain is expected to occur. Currently, the summer rainfall may start in October and tapers off in March-April, but there is a shift from somewhat earlier in the north–eastern parts of the country to somewhat later towards the south-western parts. With climate change, this trend is expected to shift and in most regions of the summer rainfall areas to shorten, with major effects to the period of active plant growth. For example, in the Drakensberg and central grassland region precipitation is expected to be heavy from November to January but will then cease already in February - early March, which means less moisture availability for fodder production leading into the winter, and therefore major implications to fodder flow and cost of buy-in feeds. Although the example is for this particular region, the trend will apply to some extend to other summer rainfall regions as well. The reason is that the winter high pressure system which is a characteristic of the interior of the country will intensify and lengthen, thereby causing shorter and shifting rainfall seasons.

For the winter rainfall region, less rainfall is expected because the interior high pressure system will shift the rain south-east into the sea. This will have major implications to an already pressurized water storage system and water usage for irrigation from mountain sources. Apart from the wine and fruit industries, major influences to the livestock industries of the Swartland, Overberg and Little Karoo which in some areas depend on water for irrigation of fodder sources, is expected. However, the influence will not be limited to the Western Cape as most of the cold fronts move up the coast to provide water through rain and snow to the Eastern Cape. In fact, many of the storage systems and fountains in the Eastern Cape depend on supplementation by the cold front systems. Thus, apart from the water supply to cities and towns, irrigation-depended livestock production systems of the south-eastern seaboard may be affected, again emphasizing the importance that farmers should take special measures to prevent excessive run-off and make provision for storage.

Apart from quantity, quality of water is important. Yet, quality is often not considered on farms. However, it is important that effective measures be implemented to ensure that water is free from contaminants. Water tests should be done regularly for microbiological and chemical contents to ensure that the water complies with specifications. All water sources such as borehole, river and canal water should be tested. Where water is chlorinated on site, a routine checking procedure must be implemented. Storage tanks and reservoirs for water must be covered to prevent contamination by birds, rodents, organic and inorganic matter. Also, the air vents to these tanks and reservoirs must be insect and rodent proof. Where there may be effluent such as from an on-farm feedlot, it must be appropriately managed to ensure effective disposal with no contamination of water sources. If the effluent is applied to pasture, there must be a lapse of at least 21 days between application and grazing or harvesting of the pasture. In addition, if the effluent is collected and spray-irrigated from a storage system, the homestead and vicinity should not be exposed to spray drift.

Storage facilities for oil, silage spray liquors, fertilizers and other polluting substances must be located in a safe place and precautions must be taken to ensure that accidents do not result in the pollution of farm water supplies.

Measures include:

• Avoiding disposal of agricultural or veterinary chemicals where there is potential of them entering the local environment.

•  Protecting the environment by only using approved agricultural and veterinary chemicals and medicines according to the directives on the label.

•  Ensuring the safe and secure storage of farm chemicals away from the milk storage areas.

• Ensuring the safe disposal of expired and defective chemicals and chemical containers.

•  Applying integrated pest management practices where appropriate.

• Applying fertilizers in a manner that minimizes the risks of off-site nutrient impacts.

• Avoiding usage of fertilizers that contain toxins, heavy metals or other contaminants.

• Ensuring the safe disposal or reuse of empty fertilizer bags.