Irrigation efficiency improvements in the Aral Sea Basin

Optimizing irrigation efficiency improvements in the Aral Sea Basin (Central Asia)

Inefficient use of water resources in irrigated agriculture is the primary reason for reduced environmental flows as well as waterlogging and land salinization processes in the Aral Sea basin of Central Asia.1

Under current water management practices, water, energy, and food security goals of the riparian countries cannot be met. Increasing the efficiency of irrigation canals and introducing improved irrigation technologies, such as drip irrigation and alternate dry or short furrow irrigation, could substantially enhance water release to downstream ecosystems (particularly to the Aral Sea), improve food security, and increase farm incomes.

However, given the differences in cropping patterns, agro-climatic conditions, financial capability and technology adoption costs across the irrigation sites in the basin, the optimal levels of irrigation efficiency improvements and required investments across irrigation sites need to be assessed.

A recent study2 used a basin-wide hydro-economic model to determine optimal investment levels and areas for improving water application and conveyance efficiency across irrigation sites in the Aral Sea Basin. The model considered surface and groundwater sources, their use across various irrigation sites and resulting economic effects along the Amu and Syr Darya rivers. Detailed accounts of water diversions, losses, impacts on groundwater levels and drainage flow were included. The model maximizes economic benefits from agricultural and hydropower production through allocation of water and irrigation technology investments across the sites with different climatic and soil conditions and cropping patterns.

Model results suggest that downstream regions where sandy soils are common and return flows largely feed saline lakes in tail-end depressions would greatly benefit from conveyance efficiency investments. Meanwhile, alternate wet and dry irrigation or even drip irrigation is recommended for rice-producing systems in the lower reaches because rice is a very water consumptive crop despite its high profitability. Drip irrigation is more efficient and advisable in the cotton-producing areas in the mid-stream reaches of the Syr Darya Basin (Ferghana Valley) because higher cotton yields in this region make expensive irrigation technologies economically feasible.

Ultimately, modernizing irrigation networks and improving water application at the field level could substantially reduce wasteful water use and generate large net benefits from crop production (US$ 600 million in a climate-normal year2). The value of these efficiency improvements increases with reduced water availability. The implementation of an optimal set of investments in irrigation efficiency improvements could increase net benefits from crop production by 20% (from US$ 2.8 to 3.4 billion) under normal water availability and by 40% (from US$ 2.2 to 3.1 billion) under dry conditions (80% of normal supply).

Given expected higher temperatures and thus crop water demand under climate change, the net value of these improvements is likely increasing.3 Since water for agriculture has a higher value than water for direct ecosystem benefits (as considered in the model) water savings from irrigation improvements can be used for further irrigation expansion or increased water consumption in some irrigation sites. This rebound effect as a result of increased access to irrigation technologies may constrain the use of the saved water for increasing environmental flows. However, according to the study by Bekchanov et al.2 water savings from irrigation modernization surpass area and consumption increases as further expansions are too costly and thus do enhance environmental flows and downstream conditions.

Investment requirements to achieve these improvements are considerable. More than US$60 million would be required for conveyance efficiency improvements in addition to more than US$210 million for water application improvements (see Figure 1). If funds are insufficient, the focus should be on those locations and technologies with highest payoff in terms of US$ per unit of water saved.

Figure 1. Optimal annualized investment costs of improving conveyance and water application efficiency (US$ million per year) under normal water supply.

Sharing the costs and benefits of irrigation efficiency improvements is a challenging task. The present lack of maintenance of irrigation networks, which exacerbates their deterioration and increases losses, and the growing number of silted up and damaged canals, broken gates and outdated pumps reflects bank lending constraints as well as a lack of incentives and required institutional platforms for such investments.

It seems likely that the widespread adoption and effectiveness of water saving technologies, particularly at the field level, could be enhanced through reforms of irrigation water pricing and reduced differential crop support.4

Introducing tradable water use rights is an alternative water allocation institution that not only allows redistributing water rights from less efficient sites to those with higher efficiency but also may encourage water savings through wider adoption of improved irrigation technologies.5 Yet, high transaction cost of introducing market-based water allocation systems in developing regions with poor infrastructure and governance can be a serious obstacle for institutional reforms. More secure land use rights would also be essential for the required capital investments that require long-term planning and management.

In addition to this, conveyance efficiency improvements would depend on both public sector support and collective action among farmers. Government support and financing is also essential to improve the institutional framework that incentivizes water users to modernize irrigation systems and reduces free-riding, helping farmers to secure both environmental and economic benefits.

Source: Global Water Forum

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Taxonomy

• Irrigation
• Irrigation Design
• Irrigation Energy Efficiency Audits