has resulted in rising groundwater and soil salinization. For instance, nearly half the irrigated lands in Central Asia are affected by salinity (Kijne, 2005). The largest part of saltaffected soils and saline waters exists in the lower reaches of Amu-Darya and Syr-Darya basins, where salinity threatens food production.

2.1.5.2 Water-quality deterioration

Wastewater from household, municipal and industrial activities; agricultural drainage containing residues of pesticides, fertilizers and soil and reaction products of amendments; and overexploitation of brackish groundwater are the major contributors to deteriorating water quality in CWANA (Qadir, Sharma et al., 2007). In addition, drought has a negative influence on aquatic and land ecosystems and on the quantity and salinization of surface water and groundwater. More than half the major rivers in CWANA are seriously depleted and polluted, degrading surrounding ecosystems and threatening the health and livelihoods of the people depending on these rivers.

Wastewater and sludge. Water diverted for household, municipal and industrial activities generates wastewater containing undesirable constituents, depending on the source of the wastewater and its treatment. In most countries of CWANA, domestic wastewater is not segregated from industrial wastewater and other activities (Qadir et al., 2007). The wastewater is often discharged, untreated, into open drains, sometimes getting mixed with storm or fresh water. It is then channeled into natural water bodies or used in agriculture. In some cases, wastewater undergoes treatment.

Most wastewater treatment plants are of simple design or not adequately functioning in the region. Wastewater is diverted to farmers' fields-treated, partly treated, diluted or untreated. It is used by urban and periurban agriculture to grow crops, with vegetables being the most common, across CWANA (Lazarova and Bahri, 2005). Grain, fodders and industrial crops are cultivated as a secondary preference. In addition, parks, sports grounds and road plantings are irrigated with wastewater. Examples of wastewater aquaculture are also found in countries such as Kazakhstan.