Zoning Application of Irrigation Systems in Ajichay River Basin Lands

Water as the most limiting factor in agricultural production plays an important role in providing food for population of the country. Therefore, it is necessary to use optimal water resources of the country and increased its productivity. So to improve irrigation efficiency, as well as the proper use of land and available water resources the best irrigation system should be used to supply plant water requirement. This selection is influenced by various factors such as cultivar type, available water content, water quality, soil characteristics, climatic conditions, selective cultivar pattern, labor force skill, and etc. The mentioned effective parameters depending on the region may change. Therefore, it is necessary to identify the homogenies areas for application of irrigation system. The study area is the Ajichay River Basin in East Azarbaijan Province. This basin is located between 37°  30' to  38 ° '30 northern and  45° 24 '   47°  53' eastern. In this study AHP method and GIS were used for identifying homogeneous zones of irrigated and rainfed areas. Analysis Hierarchical Process method is one of the most comprehensive systems designed for decision making with multiple criteria. This method was first proposed by Thomas El Saaty in 1980, which is based on paired comparisons. This gives managers the opportunity to study different scenarios. In the AHP model, we construct a matrix for comparing two factors. It has two important features, 1- Considering multiple quantitative and qualitative factors in problem solving and 2- The ability to analysis complex issues through hierarchical factors. In this study, to determine the homogeneous irrigation regions, first, the criteria was determined. In AHP method questionnaires were prepared, to score, these questionnaires were provided to the experts of this field. Then using the AHP method the criteria was compared with together. Finally, for each of the criteria, the interpolation maps in the GIS using geostatistical methods were obtained. These maps were divided into different zones using available tables and resources. The maps were combined in their scores in GIS and homogeneous irrigation areas (sprinkler, drip and surface irrigation systems) were selected. In this study, the agricultural lands, including under irrigation lands, dry farming and gardens, were distinguished from non-cultivated lands. In agricultural land of Tabriz plain, applying sprinkler irrigation system has moderate restrictions and some areas face severe restrictions. In the southern parts of Bostanabad plain, the implementation of the sprinkler irrigation system is suitable. The possibility of sprinkler irrigation in dry farming lands was also investigated. Lands that located in the Bostanabad, Heris and Sarab plains will be relatively suitable for sprinkler irrigation. But for the Tabriz plain, the underground water and soil quality are low, applying sprinkler irrigation system has moderate restrictions. However, in Sarab plain, the appropriate area is visible. Implementation of drip irrigation system in the study area, in a large part of the Sarab plain and the southern parts of the plain of Bostanabad were appropriately determined. But in Tabriz plain and lands near the Urmia Lake, the implementation of this system has severe restriction. Like sprinkler irrigation, agricultural land of Tabriz plain has a moderate restrictions. Most areas of Heris, Bostanabad and Sarab plains, for applying this system will be relatively suitable. According to expert, water SAR and land gradients have more effect on the implementation of surface irrigation systems. If we can correct these two parameters with management and planning tasks, the implementation of this system will be appropriate in many areas of the basin. Most agricultural land has a moderate restriction on the implementation of this system. The AjiChay Basin with an equivalent area of 12600 km2 is one of the largest sub basins in Lake Urmia basin. Since agriculture is important in this basin and also the quality of irrigation water in some parts of this basin is low, therefore, it is essential to pay attention to the type of irrigation method. Considering the parameters of water, climate and soil, suitable and unsuitable areas for surface irrigation, sprinkler and drip irrigation systems were determined. Thus, implementing irrigation system in agricultural lands in the margins of Lake Urmia and in some areas, will be severe restrictions. Getting away from Lake Urmia the groundwater quality, which is mainly used for agriculture, using irrigation systems is relatively appropriate.