Water Quality Management

Understanding Water Quality Management

In its purest form, water contains only water molecules with the chemical formula of H2O, meaning each molecule consists of two hydrogens (H) atoms and one oxygen (O) atom. Water is however an excellent medium for many other materials, such as salts, to dissolve in. Water is also host to a variety of organisms, and furthermore often carries insoluble and suspended material.

Salts: Salts not only refer to table salt (sodium chloride) but any compound of acids and bases, such as calcium sulphate, potassium nitrate, magnesium chloride, etc. In these salts, calcium, potassium and magnesium base, and salts are formed when acids like sulphuric acid, nitric acid and/or hydrochloric acid are added.

Saline: Water with a high salt concentration, also referred to as high total dissolved salts (TDS), is referred to as saline.

These properties of water cause its quality to be variable and are why it is polluted so easily. All the non-water components dissolved, living or suspended in water are regarded as foreign materials. These foreign materials are responsible for the chemical, physical and biological quality factors of water.

The type and concentration of foreign materials determine the quality of the water.

Managing water quality, therefore, concerns six critical control points, namely:

• Determining the quality of the water received on the farm.
• Identifying the causes of the said quality.
• Being aware of the quality standards of water for crop production.
• Improving the quality of received water where possible.
• Identifying water quality factors that cannot be improved and need to be managed.
• Managing the quality of the water leaving the farm.

In most cases, the water quality manager has little say in the quality of the water received on the farm. The manager has to make the best of what water is available to produce crops profitably. However, the manager can influence the quality of the water leaving the farm, and must take this responsibility seriously.

By maintaining the water delivery infrastructure such as pumps, pipes, dams and boreholes, you are better able to maintain and monitor a consistent level of water quality and quantity.

Water is used in crop production to irrigate fields or trees and to apply nutrients and pesticides to the crop leaves through foliar sprays and soil. Profitable production of permanent crops is not possible in Southern Africa without irrigation, through which an adequate supply of good quality water must be provided to ensure economic yields, the required fruit size and quality.

Orchards are usually irrigated using one of the following methods:

• Micro-sprayer irrigation
• Drip irrigation
• Basin irrigation
• Flood irrigation
• Under-tree-sprinklers

Field crops are usually irrigated using one of the following methods:

• Sprinkler irrigation, quick coupling type or permanent
• Drip irrigation for row crops
• Furrow and short furrow irrigation
• Basin irrigation
• Flood irrigation
• Centre Pivot irrigation