Evaluation of Irrigation Network Performance of Gavoshan Dam with International Indicators of Water Resources Management

Irrigation is of major importance in many countries. It is important in terms of agricultural production and food supply, the incomes of rural people, public investment for rural development, and often recurrent public expenditures for the agricultural sector. Yet dissatisfaction with the performance of irrigation projects in developing countries is widespread. Despite their promise as engines of agricultural growth, irrigation projects typically perform far below their potential. A large part of low performance may be due to inadequate water management at system and field level. Performance evaluation is an essential part of irrigation systems. Performance of irrigation systems is evaluated for a variety of management objectives. Several researchers have proposed various indicators to assess the performance of irrigation systems. Most of them focused on internal processes of irrigation schemes that relate performance to management objectives such as the area irrigated, crop patterns and distribution and delivery of water. Most of researchers have conducted studies to assess the performance of irrigation management process using financial and physical indicators. Comparative indicators are more suitable than process indicators due to the real evaluation of network performance. Comparison aims to improve the performance of the schemes by identifying shortcomings and benchmarking best practices. In this research the performance of the Gavoshan Irrigation Network in the Kamyaran region of Kurdistan Province was evaluated using some comparative indicators provided by the International Water Resources Management Institute (IWMI) at three groups of comparative performance indicators: agricultural output, water supply and financial indicators.

In this research, the irrigation and drainage sub-system network of B2 construction area of Kamiyaran Bilehvar plain located in the Gavshan reservoir dam in the south of Kurdistan province with an area of 3500 hectares was evaluated. Comparative performance assessment in irrigation schemes is possible through use of comparative indicators. External indicators are those indicators based on outputs and inputs from and to an irrigated agricultural system. In this research Using the indicators of the International Water Management Institute (IWMI) in three groups, agriculture, water consumption and network performance were evaluated. These indicators need data that is available and easily to analyze. The data required includes the crop yield the irrigated area of the plant in the cropping season the water requirement of the plants the cultivation pattern and the information about the amount of water delivered to the network. The indicators of Output per unit command area, Output per unit cropped area, Output per unit irrigation supply, Output per unit water consumed, Relative water supply, Relative irrigation supply, Irrigation ratio, cropping intensity and Water delivery capacity were investigated. The water supply indicators are based on irrigation and water supply/delivery measurements being related to demands or irrigated area.

Irrigation water management is ultimately meant to enhance agricultural production through sustainable water use. Annual relative water supply and annual relative irrigation supply were evaluated for the agricultural system. Annual values of four water supply/demand values were determined. These indicators provide the basis for comparison of irrigated agriculture performance and they relate output to unit land. The performance results of the studied network in terms of water and land efficiency show that the performance of the current state of the network is generally reasonable. The analysis of water consumption performance showed that the values of relative water supply and relative irrigation supply were calculated as 1.3 and 0.94, respectively which means that the water required by the network is supplied by 0.06 less. And the demand for irrigation is slightly more than its supply, which should be made aware of the dangers of excessive demand by educating users. The difference between the values of RWS and RIS is due to the rainfall in the network area during the cropping season. In this study, in general, RWS and RIS values show that the water requirement of crops in the network are supplied. Physical performance was evaluated well in terms of cultivation intensity and irrigation ratio. The water delivery capacity of the main channel of the Gavoshan network is 0.97, which means that the water needs of crops are approximately met for the current cropping pattern. However, in the event of a change in cropping pattern, to avoid water stress first the capacity of the irrigation channel to supply the water needs of the new crop pattern in the peak month of the plant should be checked.