Water quality refers to the chemical, physical and biological characteristics of water. For drinking water, high standards of water quality are often applied than for other uses.
For agriculture, key water quality issues include:
Salinization is the build-up of salt in soil and water. It occurs naturally in many parts of the world, but human activities such as irrigation can accelerate the process.. Salinity decreases productivity of agricultural crops.. The cost of salinity to agriculture is estimated conservatively to be about $US 12 billion a year, and is expected to increase as soils are further affected. In addition to this, there are other serious impacts of salinity on infrastructure, water supplies, and on social structure and stability of communities.
The problem is particularly widespread in arid and semiarid environments where crop production requires irrigation. At least 20% of all irrigated lands are salt-affected, with some estimates being as high as 50%. In dry regions where fresh water is becoming a scarce commodity, irrigation of moderately salt tolerant crops with brackish water is feasible.
The main threats to human health from heavy metals are associated with exposure to lead, cadmium, mercury and arsenic. Contamination can occur from naturally occurring deposits (such as arsenic in the Ganges delta) or from industrial waste. IWMI research into cadmium contamination in Northern Thailand illustrates how naturally occurring contamination can be assessed and appropriate action taken to protect public health
Nitrates, phosphates and other compounds
Increased use (and overuse) of pesticides and fertilisers is leading to elevated levels of certain chemicals in many water sources. The long term consequences of this trend on human health and food production are not yet clear.
Millions of urban and peri-urban farmers depend on wastewater to grow crops. But in poor countries this is often contaminated with human waste containing potentially harmful pathogens. IWMI research is looking at how food grown with wastewater can be made safer from farm to fork.