Document Type : Research Article
Authors
1 Graduated in Master Irrigation and Drainage Department of Water Science and Engineering, University of Zanjan
2 Assistant Professor, Department of Water Science and Engineering, University of Zanjan
Abstract
Introduction: The average of irrigation efficiency is less than the global average due to improper irrigation systems and traditional water management practices in the field. The use of modern irrigation systems is one of the most important ways to cope with the water shortage crisis in Iran. However, it is necessary to evaluate the effective factors on performance of irrigation system. In present study, a zoning map of suitable land for implementation of sprinkle irrigation system was prepared using AHP method with considering the criteria such as chemical characteristics of water, soil properties, topography, climate, social and economic factors in the Zanjan plain.
Materials and Methods: The present study was carried out using collected data from Zanjan plain that located in northwest of Iran and east of Ghezel Ozan River. The total study area is about 4705 km2 and the average rainfall and temperature in region are 259 mm and 10.9 °C, respectively. The first step in the AHP method is to create a hierarchical structure. For this purpose, each of the criteria was rated 1 to 9 based on paired comparisons done by experts and then classification maps were prepared for each of them. In order to provide zoning maps for water and soil factors, data of more than 2000 wells and 111 soil samples were collected, respectively. In addition, data of 13 Meteorological stations were used to prepare zoning maps of climatic factors such as wind speed and temperature. In this research, a topographic map with a scale of 1/25000 was used to investigate the ground slope effect. More than 60 interview forms were completed to produce maps related to socio-economic factors. Zoning maps were prepared using the Kriging interpolation method in ArcGIS software. Finally, the weight of each criteria was calculated according to the scores that obtained in the previous stage and then land classification map was produced by applying the obtained weights on each criteria. In order to evaluate the situation of sprinkle irrigation projects, location of 52 farms equipped with sprinkle irrigation system obtained from the agricultural organization of Zanjan province.
Results and Discussion: Regarding the quality of water resources, 40.3% and 21.0% of area were classified in most suitable and suitable classes, respectively and about 10.4% was evaluated in the inappropriate class in order to implementation of sprinkler irrigation. In terms of the soil physical and chemical properties, about 38.4% of plain were classified as "most suitable", 22.8% as "suitable" and 24.7% as "inappropriate" class. In relation to topographic criteria, it can be stated that about 85% of area are in good condition, so that the ground slope in most of the lands is less than 10%. Based on climate criteria and specifically wind speed factor, about 61% of the plain was classified as "good" and "very good", while about 39% was in medium and low class. In terms of social and economic criteria, most of area were found to have a good rating, so there is no particular limitation in this regard. The results of the paired comparisons between criteria showed that, social and climatic criteria have the lowest and highest weight, respectively. The value of the inconsistency rate was calculated about 0.07, which indicated the acceptability of the gained weights. An examination of land feasibility map showed, about 33.4% of the region is suitable for implementing sprinkle irrigation system. About 29.5% and 25.8% were evaluated without limitation and low limitation, respectively. Also, about 10.3% was not recommended for use of sprinkle irrigation. The assessment of the location of implemented projects showed that 44.2% of the projects were in suitable or perfectly suitable classes of land. The rest of the projects (55.8%) were implemented in medium or unsuitable classes.
Conclusion: The results obtained from the AHP method showed that wind speed factor has the most weight and importance in selecting sprinkle irrigation system. Generally, in most farms of the region, there is no significant limitation on the implementation of sprinkler irrigation system. Due to low water quality and high wind speed in a small part of the study area that located in northern and eastern, the use of these systems is not recommended. The results showed that some of the sprinkle irrigation projects have been implemented in lands with low-class and it is essential to improve or change these systems.
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