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UNESCO-IHE Institute for Water Education, Delft (2011)

Optimization of land and water productivity of agriculture areas in arid regions of emerging and least developed countries

Rahman W.U.

Titre : Optimization of land and water productivity of agriculture areas in arid regions of emerging and least developed countries

Auteur : Rahman W.U.

Université de soutenance : UNESCO-IHE Institute for Water Education, Delft

Grade : Master of Science 2011

Résumé
The main goal of this research was to improve land and water productivity of the irrigated area and identify options for improving the level of irrigation service in emerging and least developed countries of arid regions to meet their growing food demand. The key elements of growing food demand, population growth, urbanization, undernourishment, economic growth and food price have also been reviewed. Several ways to satisfy future food demands with the world’s available land and water resources have been introduced by different researchers and scholars e.g. expanding rainfed croplands or enhancing rainfed agricultural management, expanding irrigated area, improving irrigated area management and promoting agricultural trade, etc. The best solution for improving food production in emerging and least developed countries (especially Afghanistan and Uzbekistan) located in the arid regions is to improve the level of irrigation service. Due to the low level of service in surface irrigation systems of selected countries production of crops is quite below their potential. The practice of surface irrigation is thousands of years old. It collectively represents perhaps as much as 95 % of common irrigation activity today. Around 90 % of irrigated area in Afghanistan and 99.9 % of irrigated area in Uzbekistan is under surface irrigation. It is so widely utilized because it is relatively easy to operate and maintain, minimal capital investment, control and regulation structures are simple, durable and easily constructed with inexpensive and readily-available materials, like wood, concrete, brick and mortar, etc. In this research two countries, Afghanistan among least developed and Uzbekistan from emerging countries, located in an arid region, have been selected, one irrigation system from each country was selected. Current levels of irrigation service in these irrigation systems were analyzed and compared with that in case of developed countries. Pashdan Irrigation System in Afghanistan and Mashal Irrigation System in Uzbekistan were selected in this study. Pashdan Irrigation System is fully managed by farmers at the farm level and Mirab (Mirab is an experienced farmer, elected by farmers for one year) is in charge at secondary and main canal level, but Mashal Irrigation System is managed by farmers and a water users association (WUA) at the farm and secondary canal level and the main canal is managed by a water board and main canal authority. Around 90% of irrigation systems in Afghanistan are informal irrigation systems ; the reason for selecting Pashdan Irrigation System is availability of data. Also it is a good representative of informal irrigation systems in the area. Mashal Irrigation System is also a good example of surface irrigation systems in Central Asia. Both of the selected schemes are located in the arid region. In both countries irrigation water use right is clearly defined. As per the water law, use of water for agriculture is free but water delivery service charge has to be paid. In Afghanistan land and water owners are the farmers, and have the right to sell the land or water temporary and permanently. But in case of Uzbekistan is reverse, the government is owner of land and water ; farmers do not have the right to sell land or water. Also the water use right is not transferable. vi Irrigation policy makers in the Pashdan Irrigation System are not well organized, most of responsibility of the system is on farmer and Mirab’s shoulders. Also there is no proper control from government side on the system activity, but in Mashal Irrigation System all the stakeholders are engaged in irrigation activities that are well organized, Irrigation scheduling in Pashdan Irrigation System is based on tradition rule. Water delivery duration and frequency (10 days) are fixed and the rate dependent on water availability in the river, but the water delivery in the Mashal Irrigation System is on request, it has to be 10 days before irrigating the farm, which is a long procedure and labour consuming job. This long procedure of water request has a negative impact on the yield. In Colorado water delivery is on request with 48 hours notice in advance. In Pashdan Irrigation System Mirab is in charge of overall management (operation, maintenance, water distribution up to secondary canal and solving conflicts related with water), of main and secondary canals, in Mashal Irrigation System, Mirab is a part of WUA, who has the responsibility to bring water from secondary canal up to farm and deliver it to the farmer, and the WUA is responsible for overall management of the system. In Pashdan Irrigation System farmers contribute a fixed amount of wheat per/ha to the Mirab for his services and also pay tax per ha to the government. In Mashal Irrigation System, farmers have to pay fee per ha (fee is dependent on type of crops) to the WUA for their service, also they have to sell all the cotton and a fixed amount of wheat/ ha to government (based on the contract). Quality of irrigation service from farmers’ perspective (flexibility, adequacy, reliability and equity) in Pashdan Irrigation System is poor, because it is dependent on water availability in the river. In rainy season quality of irrigation service is at the desired level but at the time of high water demand flexibility of system is significantly decreases, because there is no storage. On the other hand, lacks of lined canals, structures and farmers knowledge are the main causes. In Mashal Irrigation System level of irrigation service is stable but in the time of high water demand it is reducing, it is because of old structures which do not have the capacity to supply water for many farmers at the same time. Use of high technology for the irrigation system in Colorado has made the level of irrigation service maintained at desired level. Crop water requirement has been calculated by using Cropwat 8.0 model. In existing condition Pashdan Irrigation System farmers use their experiences to estimate crop water requirement and they are receiving water after 10 days. Two scenarios have been considered for calculating crop water requirement : a) if existing irrigation scheduling is in practice 86 Mm (million cubic meters) of water per year is required which is more than available water for agriculture, and crops loss a significant part of their yields, and b) in the second scenario by considering irrigation at the critical depletion it is possible to irrigate 9,000 ha by 76 Mm. It was found that the existing irrigation scheduling is not useful anymore. Soil moisture content has to calculated frequently (using modern methods) based on crop sensitivity to water shortage, and accordingly irrigation scheduling need to be arranged. In Mashal Irrigation System farmer use the crop water requirement estimates (norm), prepared by the government, and farmers are by field observation request for water. Estimates of crop water requirements using CropWat were compared with the current practice and were found to largely the same. However more water supplied for some of vii the crops and for some of the crops less than requirement. In the norm they are considering ground water effect. We could not consider this due to the lack of data (it means they are irrigating more than requirement). In Mashal Irrigation System also soil moisture has to calculated frequently and accordingly arranges irrigation scheduling. In existing condition water distribution between main canals, can be arranged in such a way that when the water is available in the river, the downstream canals will receive full allocation and the extra water can be diverted by upstream farmers and divided proportionally between themselves. This will require a clear division between boundaries of irrigated areas between upstream and downstream. It is also possible that the upstream and downstream farmers agree for a fixed irrigation rotation, but the best option will be to Share water proportionally. Under this arrangement each canal shares the burden of water shortages proportionally. After construction of Pashdan Dam it is strongly recommended that the water delivery to farmers is based on crop water requirement on volumetric base. Construction of more water measurement structures and also adopting new irrigation technology can improve flexibility in the system. By providing more flexibility more water loss may occur but it can be solved if volumetric water pricing is adapted in the system. Proper maintenance and cleaning of the sediments of canals, calculating water availability in the storage, strengthening the Forecasting Department and for cultivating crops according to water availability will improve adequacy and reliability up to desired levels. Equity will improve if water delivery will be volumetric. However more water measurement structures will be required, but this investment will solve many social and economic problems of farmers in Pashdan and Mashal Irrigation Systems. The Mirab does not have the organizational and institutional capability to manage the irrigation system up to the desired level. Existing Mirab needs to be transformed into a legal entity and formal institution with greater efficiency and organizational capability in Pashdan Irrigation System. In Mashal Irrigation System capacity building for WUA and farmers is essential. Beside that government must financially support WUA to become sustainable. Delivering water free to the farmers is not a good idea any more. By charging fee per m of water, loss of water will reduce ; efficiency of water use will improve. Fee collection can improve the level of irrigation service and also make the WUA financially sustainable.

Mots clés : land productivity ; irrigated agriculture ; food production ; arid areas ; Afghanistan ; Uzbekistan

Présentation

Page publiée le 26 février 2015, mise à jour le 18 octobre 2018