Congress Resources: Papers, posters and presentations

< Return to abstract list

Aral Sea Basin: Irrigated Lands And Salt Accumulation Processes Rysbekov Yu.khai Head Of Training Center Of Scientific-information Center Of Icwc Of Central Asia <yusuprysbekov@icwc-aral

Congress: 2015
Author(s): Yusup Rysbekov (Tashkent,, Uzbekistan), Yusup Rysbekov
Scientific-Information Center, ICWC of Central Asia1

Keyword(s): Sub-theme 1: Water supply and demand,
AbstractINTRODUCTION Aral Sea Basin (ASB) is a part of Central Asia and includes territory of Republic of Tajikistan, Turkmenistan, Republic of Uzbekistan, the southern part of the Kyrgyz Republic, and southern part of Republic of Kazakhstan. Some parts of the ASB are located in the Northern Afghanistan and Iran (about 8 %) and in China (less than 0.1 %). ASB comprises watersheds of two great rivers: Amudarya and Syrdarya with their tributaries. Amudarya and Syrdarya rivers lead into the Aral Sea. Salt accumulation processes in arid zone occur under impact of natural (relict salt storage, shallow saline groundwater) and anthropogenic (irrigation, return water, etc.) factors. Relict soil and groundwater salinity is one from most important factors of soils' secondary salinity on most irrigated area, especially in middle and lower reaches. Artificial irrigation forms salt migration and accumulation in root zone that is main reason for soils' secondary salinity and crop yield reduction. In Central Asia more than half of irrigated area is subject to salinity and requires artificial drainage for prevention against salinity. Drainage workability coefficient for 1990-1999 reduced by 30 % and under this trend more than 50 % drainage systems will be out of operation to middle of XXI century. Drainage situation in Central Asian States has a steady tendency to the further deterioration. ASB surface water resources (WRs) are equaled about 116.5 km3/year. More than 70 % of the regional WRs are formed in upstream countries (Tajikistan, Kyrgyzstan, Afghanistan), and more than 80 % are used in the downstream countries (Uzbekistan, Turkmenistan, Kazakhstan). METHODS/MATERIALS Salt accumulation processes in arid zone occur under impact of natural (relict salt storage, shallow saline groundwater) and anthropogenic (irrigation, return water) fac¬tors. Relict soil and groundwater salinity is one from most important factors of the soils' secondary salinity on most irrigated area, especially in midstream and downstream countries (Uzbekistan, Kazakhstan and Turkmenistan). Artificial irri¬gation forms salt migration and accumulation in root zone that is main reason for soils' secondary salinity and crop yield reduction. In the countries of Central Asia more than 50 % of the irrigated lands are subject of salinity. Struggle with soil salinity is one of key problems of the irrigated lands' melioration and requires an artificial drainage. Weak attention to the drainage problems has caused deterioration of agricultural land quality. Below the salt accumulation processes on irrigated areas and drainage problems are considered concerning to the ASB and to five post-Soviet Central Asian republics (Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan). RESULTS AND DISCUSSION Water and Land Resources Average multiyear surface river flow in the ASB is estimated 116.5 km3/year, including 79.3 km3/year for the Amudarya River Basin (RB ) and 37.2 km3/year for the Syrdarya RB. Annual river surface runoff varies within 58.6-109.9km3 for the Amudarya RB and 23.6-51.1 km3 for the Syrdarya RB from dry years (95% probability) to wet years (5% probability). Total regional groundwater supplies amount for 43.5 km3/year, from which 25.1 km3 in the Amudarya RB and 18.4 êì3 in the Syrdarya RB. Total operational supplies are 16.9 km3/year, total water abstraction amounts is 11.0 km3/year. The basic part of groundwater is used for drinking and irrigation needs. Return water is additional sources, but its high salinity is main source of water pollution. Collector-drainage water forms more than 90 % of total return water (RW). During 1990-1999 total volume of RW varies within 28.0-33.5 km3/year. Annually about 13.5-15.5 km3 RWV formed in the Syrdarya RB, and near 16.0-9.0 km3 -- in the Amudarya RB. More than 51 % of RWV is disposed to the rivers, near 33 % - to natural depressions. In the ASB an irrigation consumes about 90% of water. Total land fund of the ASB is about 155Mio ha, of which about 32.6Mio ha are suitable for irrigated agriculture. Area of saline land is 23.9Mio ha, from which area of heavy saline soils is 7.42Mio ha. The poorer irrigated lands are in Turkmenistan and Southern Kazakhstan, where 88 % and 85 % of irrigable lands are saline. As compared to Kazakhstan and Turkmenistan, less saline irrigated lands are in Uzbekistan, where a total irrigable area is 10.7Mio ha, from which 8.03Mio ha (75 %) has propensity to salinity. In 2000, actually 8.07Mio ha was irrigated from 32.6Mio ha of available ASB irrigable land fund, including: Southern Kazakhstan -- 0.79Mio ha; Kyrgyzstan -- 0.43Mio ha, Tajikistan -- 0.72Mio ha, Turkmenistan -- 1.86Mio ha, and Uzbekistan -- 4.28Mio ha. Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan) Quality of Irrigated Lands Last years a steady tendency of irrigated lands degradation is observed. For instance, for 1990-1999 areas with close groundwater level (up to 2m) have increased: - for the Amudarya RB - from 1.29Mio up to 1.57Mio ha (on 22 %); - for the Syrdarya RB - from 0.55Mio up to 0.90Mio ha (64 %). Total area of irrigated lands with medium and strong degrees of soil salinity has sharply increased for the specified period (1990-1999): - for the Amudarya RB - from 1.16Mio up to 1.82Mio ha, or on 0.66Mio ha (57 %); - for the Syrdarya RB - from 0.34Mio up to 0.61Mio ha, or on 0.27Mio ha (79 %). Drainage Infrastructure and its Workability Drainage systems (DSs) in Central Asia were intensively developed during 1960-1990. During last 25 years in results of technical-financial state of farms worsening, machinery ageing, high prices of electric energy, and pumping equipment growth the technical conditions of DSs is aggravating. Drainage workability in the ASB has decreased on 30 % in last decades, and at preservation of this tendency to middle XXI of century more than 50 % of DSs will leave completely out of operation. CONCLUSION At developing situation, the following questions of the drainage management require steadfast attention of decisive persons: - Scientifically grounded water supply limitation for irrigation; - Water losses reduction during its distribution; - Maximum reduction of return water from irrigated fields; - Water users' responsibility for appropriate undertaken actions; etc Inter-farm drainage systems operation should be responsibility of state organizations and on-farm systems -- of the water users associations. Taking into account necessary significant investments in drainage, it is important prioritizing the measures in short, medium and long-term perspective. REFERENCES 1. Bulletin of Interstate Coordination Water Commission of Central Asia (2004) no. 37: 14-19. 2. Drainage in Aral Sea Basin. Progress Report. SIC ICWC of Central Asia (2004).
2011 IWRA - International Water Resources Association office@iwra.org - http://www.iwra.org - Admin