Historical and Current Perspectives of AKST | 41

The use and disposal of partly treated or untreated wastewater has environmental and health implications, but despite some governmental restrictions in CWANA countries and potential health risks, farmers use it (Keraita and Drechsel, 2004). In Central Asia, wastewater is discharged into streams, rivers, lakes and natural depressions, significantly polluting the ecosystem and threatening human health through waterborne diseases such as typhoid fever and bacterial dysentery (Fayzieva et al., 2004). Except for a few national assessments, only scattered information exists on the volume of raw or diluted wastewater currently produced and used in agriculture in CWANA (Qadir, Wichelns et al., 2007). Although water-quality management is reported to be a high priority and a major concern of governments in the CWANA region, most countries do not have sufficient resources to avoid polluting water bodies. However, with increased investment and awareness, the safe use of recycled wastewater can be increased (Karajeh et al., 2004).

Much of the operating cost of wastewater treatment plants involves handling and disposing of the sludge. This sludge is rich in organic materials but may also contain heavy metals and pathogens. Sludge needs to be treated and its environmental effect reduced. Sludge may be treated using pasteurization, aerobic thermophilic treatment, thickening with lime and composting. In Morocco, sludge from drying beds was tested on Italian ray grass crops. Heavy metals in the soil or in the vegetation did not accumulate (Jamali and Kefati, 2002). In Jordan, anaerobic pond sludge of stabilized waste could be used as fertilizer in agriculture after drying for three months, when pathogens numbers were reduced enough to meet safety standards (Hindiyeh, 1995).

Saline and sodic water. Under irrigated agriculture, increases in cropping intensity, excessive use of agrochemicals, inappropriate irrigation methods and salt-affected soils for crops contribute to increased salt in drainage water (Skaggs and Van Schilfgaarde, 1999). This water is collected in artificial or natural drainage systems or penetrates through the soil to become groundwater. Water scarcity in several countries of CWANA has led to reusing drainage water and overexploiting groundwater to produce food, fodder and wood (Qadir, Sharma et al., 2007).

Changes in river runoff directly affect river water quality. In Central Asia, the rivers Amu-Darya and Syr-Darya are the major source of irrigation. Long-term monitoring of these rivers shows that, in the 1950s, the salinity varied around the year within the range of 0.33 to 0.72 g L−1. Other river water-quality parameters, such as major cations and anions, organic compounds, pH and pesticide levels, were also within safe limits during 1950s. Since the 1970s, salts in river water have increased steadily as a result of a decrease in the flow of Amu-Darya and Syr-Darya and increased discharge of return water, particularly drainage water from irrigated schemes. Consequently, there has been a significant increase in river water salinity since the 1980s.

Although return flow of water to the rivers is an additional reserve for use, it has become a source of environmental pollution in Central Asia (Altiyev, 2005). About 95% of return water is drainage water, containing elevated salts and pesticides, herbicides, fertilizer and other agricultural chemical residues. It is estimated that annually about 140

 

106 tonnes of salt are discharged into the drainage water, 75% brought in by irrigation water. About one-quarter of the salt in drainage water is from the subsoil by mineral dissolution while some estimates reveal the average of mobilized salts at 40% of the total salt discharged (Kijne, 2005). About 51% of the total return flow goes into rivers, about 33% into depressions and 16% is reused in irrigation. As a result of returning water to natural depressions, hundreds of water bodies have been formed. Since these water bodies do not have an outflow, their water quality has deteriorated every year because of massive evaporation.

The Aral Sea, which is fed by two main rivers, Amu- Darya and Syr-Darya, is in the center of the Central Asian deserts and functions as a gigantic evaporator. This sea, which was the fourth largest inland lake in the world before 1960, is now the largest inland salty reservoir. It has become synonymous with environmental catastrophe, representing one of the world's worst ecological disasters. In the Soviet era, massive quantities of water from Amu-Darya and Syr- Darya were diverted for irrigating cotton, which decreased river water inflow to the Aral Sea. This led the sea to shrink dramatically. This seemingly irreversible process has continued, as irrigated agriculture has expanded and hydropower generation increased.

The disposal of agricultural drainage water containing many salts and agrochemicals into freshwater canals and rivers disperses salts and potentially toxic substances on a large scale. For instance, in the Euphrates Basin within Syria, about 1 109 m3 of saline drainage water are put back into the Euphrates River, doubling the salinity in the river water (from ~ 0.5 to 1.0 dS m-1) when it enters Iraq downstream. Inappropriate water management in the lower Euphrates Basin affects land and water quality in Iraq. In Jordan, water quality in the Amman-Zarqa Basin and Jordan Valley has been affected over the past few decades, with consequences for the downstream irrigated agriculture (McCormick et al., 2003). Anticipated increases in the basin's population and economic growth are expected to further affect the situation. Understanding the past dynamics and developing scenarios for the future that affect water quality for downstream users have been facilitated. National agencies have gathered extensive datasets, including water-quality data, for several years from strategic locations.

2.1.6 Agriculture and carbon sequestration

2.1.6.1 Soil organic stock and the potential of carbon sequestration

In CWANA, soil organic content is low, ranging from 0.2 to 0.8% in relation to aridity (Lal, 2002) for soils of Pakistan (Rashid, 2000), Iraq (Aziz et al., 1988) and elsewhere in the region (Ryan and Matar, 1988; ICARDA, 1991). However, when rainfall is high, soil humidification allows better nutrient status, and some soils may have a higher organic content, around 1.5 to 2.0% (Yurtserver and Gedikoglu, 1988).

The organic pool of most soils has been and is being depleted by soil degradation, erosion and subsistence and exploitative farming (Albergel et al., 2005). The historic loss of a soil organic content pool for CWANA may be 6 to 12 Pg. Assuming that 60% of the historic loss can be resequestered, the total soil carbon sink capacity of the region may