Evaluation of furrow irrigation practices in Fergana Valley of Uzbekistan
Highlights
► Average application efficiency of 54 irrigation events was 49%. ► Average runoff was 39% indicating problem with selection of appropriate flow rate. ► Farmers did not follow the suggested irrigation norms. ► Mismatch between root zone soil-moisture deficit and volume of water applied. ► Supply flow rates fluctuated considerably during and between irrigation events.
Introduction
Furrow irrigation is the dominant method of irrigation in Uzbekistan, and this method of irrigation is practiced over more than 95% of the irrigated area. Recently, the area under drip irrigation has been slowly increasing, particularly for growing fruit and vegetable crops. The total irrigated area in Uzbekistan is close to 4 million hectares, most of which has been developed during the last century. In 1960 the total irrigated area in Uzbekistan was 2.5 million hectares. Starting from 1970, there was a rapid increase in irrigated area, and by 1990s the total irrigated area reached a maximum of 4.3 million hectares. As early as late 1970s, the twin problems of waterlogging and salinity were spreading within the irrigation schemes, indicating that there were problems with the management of the irrigation schemes. By 1994, close to 50% of the total irrigated area was affected by waterlogging and salinity. These problems are unevenly distributed within irrigation schemes: only 10% of the irrigated area is under waterlogging and saline conditions in the upper reaches of the two river basins (Amu Darya and Syr Darya), and close to 90% of the irrigated area is under waterlogging and salinity in the lower reaches of these two river basins. The prevailing waterlogging and salinity conditions are a result of excessive seepage and operational losses from canal networks (mostly earthen canals), and losses at field level combined with poor performance of drainage systems.
In order to address the issues associated with irrigation systems, one has to understand the way the irrigation systems are operated in Uzbekistan. With the collapse of the Soviet Union, the State Agricultural Cooperatives disintegrated, and the agricultural land was distributed to individuals. The agricultural land is still owned by the Republic of Uzbekistan. The farmers lease the land, typically for 50 years, from the Government. In year 2000, through an Agricultural Reform Act, Water User Associations (WUAs) were formed. Today, there are close to 66,000 farmers grouped into 1486 WUAs. On about 80% of the leased land, farmers are mandated to grow only cotton and winter wheat, and on the remaining 20% of the land, farmers grow fruit crops. On about less than 10% of the irrigated area, farmers are given the freedom to grow ‘kitchen gardens’. At the beginning of the irrigation season, based upon the planned cropping pattern, an operational plan for each irrigation system is prepared. Then, based upon the projected availability of water during the given irrigation season in any river basin, these operational plans are adjusted, if necessary, and this information is communicated to farmers through Water Users Associations (WUAs). Every WUA is expected to have a copy of the proposed operational plan for the entire irrigation season. The operational plan is based upon the cropping pattern, historical average climatic data, soil conditions (including salinity), and groundwater conditions. The operational plan basically specifies the magnitude and duration of flow rate to be supplied to each farmer within each decadal period (10-day period) during the irrigation season.
The Government provides bulk water supply to WUAs, and then it is the responsibility of WUAs to supply this water equitably to individual farmers. Because of lack of adequate infrastructure to control water, and lack of skilled personnel to distribute water within each WUA, there are issues with equity in water distribution within WUAs. In addition to equity, the flow rates received at fields fluctuate considerably during each irrigation event, affecting the performance of field application systems. Water is provided to WUAs and, subsequently, to farmers free of charge. The volume of water delivered to each WUA is measured and recorded. However, WUAs charge a service fee to supply irrigation water to farmers. This charge is typically based upon area irrigated, and not based upon the volume of water used by each farmer. Hence, farmers do not have any incentives to save water.
Furrow irrigation is the dominant method of irrigation used in Uzbekistan. The irrigation technology used at field level is very simple and labor intensive (Fig. 1). Though there is no published data on average field application efficiency, field observations indicate that the efficiencies are low. Bos and Nugteren (1990), from their world-wide survey of data on irrigation efficiencies, reported field application efficiency values ranging from 17% to 88%. The higher values of reported application efficiencies refer to drip and sprinkler irrigation systems, whereas the application efficiencies of surface irrigation systems in developing countries are reported to be, on average, less than 40%.
With a view to improve application efficiencies at field level, the Government of Uzbekistan has been encouraging use of improved methods of furrow irrigation such as alternate furrow irrigation, zig-zag furrow irrigation, short furrow irrigation, and laser land leveling, etc. Alternate furrow irrigation has definite advantages in terms of saving water on light to medium textured soils. Water savings in alternate furrow irrigation result from reduced deep percolation losses due to reduced wet surface area of furrows. Field studies by Eisenhauer and Youth (1992), Graterol et al. (1993), Khan et al. (1999), Samadi and Sepaskhah (1984), Sepaskhah and Kamgar-Haghighi (1997), and Unlu et al. (2007) suggested water savings of as much as 40% using alternate-furrow irrigation compared to every-furrow irrigation. Based upon experimental data, Horst et al. (2005) reported on the potential for water savings in furrow irrigation systems in the Fergana Valley of Central Asia, and recommended the use of alternate-furrow irrigation rather than every-furrow irrigation. Alternate-furrow irrigation does not have any advantages in clay or heavy textured soils. Conversely, every-furrow irrigation, including zig-zag furrows, is more desirable in the case of heavy textured soils because every-furrow irrigation provides more wetted surface area for water to infiltrate into the crop rootzone. Similarly, short-furrow irrigation has the advantage of providing irrigation water more uniformly along the length of a field, particularly on light to medium textured soils. Today, alternate-furrow irrigation and short-furrow irrigation are widely practiced by farmers in Uzbekistan. However, there is no real field data on the performance of alternate-furrow and short-furrow irrigation systems under farmer-managed conditions in Uzbekistan. Therefore, during the summers of 2009 and 2010, field studies were undertaken to evaluate the performance of furrow irrigation systems in Uzbekistan. This kind of information is crucial for developing future strategies for improving irrigated agriculture in Uzbekistan. This paper presents the results of this study, and provides recommendations for improving performance of furrow irrigation systems. These recommendations have wider implications throughout Central Asia and beyond.
Section snippets
Description of the experimental sites
All sites selected for research are located in the command area of South Fergana Canal, Uzbekistan. These sites are located in two different Provinces – Andijan and Fergana – of Uzbekistan. Altogether, nine different field sites were selected for this research (Fig. 2). The same field sites were used in 2009 and 2010. Initially, as a part of the Integrated Water Resources Management Project of Fergana Valley (IWRM-FV), several WUAs were selected for strengthening their capacity to manage
Methodolgy for irrigation performance evaluation at field level
The performance of furrow irrigation systems was evaluated in terms of application efficiency of water applied to several selected fields, where application efficiency is defined as (Jensen, 1980):in which Ea = application efficiency, in percent; Vwsrz = volume of water stored in the rootzone (m3); Va = volume of water applied to the field (m3). In addition to Ea, additional parameters such as water requirement efficiency (ER) and runoff ratio (RR) were used to describe the performance
Results and discussion
Cotton is typically planted during the first decade of April, and harvested after mid-September. In a normal year, the first irrigation is not applied until the last decade of May. As shown in Table 2, the seasonal irrigation norms for cotton during the vegetation period (April–September) vary from 4000 m3/ha to 7000 m3/ha depending upon the soil type and groundwater depth, and the farmers are expected to apply an irrigation amount that is close to the specified water requirement for each
Summary and conclusions
The performance of furrow irrigation systems in terms of application efficiency, runoff ratio, and water requirement efficiency were evaluated in nine different cotton fields covering a total of 54 individual irrigation events during the growing seasons of 2009 and 2010 in the Fergana Valley of Uzbekistan. Data shows that the farmers did not follow the specified irrigation norms for their locations. The average application efficiency of the 46 irrigation events in 2009 was 48% with an average
Acknowledgement
The funding for this research was provided by the Swiss Agency for Development and Cooperation (SDC) Tashkent office, Uzbekistan, as part of the Water Productivity Improvement at Plot Level (WPI-PL) project. Their financial support is highly appreciated.
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