Spatial Multi-Criteria Analysis of Ecological Land Suitability for Irrigated Farming

Agriculture plays a central role in countries' food and economic security, and population growth has increased dependence on it. The Nazluchai basin is one of the important areas for agriculture in Iran, and improper land use has destroyed water and soil resources in the area. One way to improve this situation is land suitability assessment. Land suitability analysis is a multi-criteria decision-making process based on a spatial information system. On the other hand, various systems analyze descriptive and spatial data. However, the Geographic Information System is one of the best methods to acquire, edit, process, and manage data quickly, accurately and simultaneously in large volumes. However, this system also has limitations in decision making. Therefore, the integration of geographical information system with Multi-Criteria Evaluation methods, including Analytical Hierarchy Process, has been proposed as a land suitability assessment method. Therefore, the aim of this study is to investigate the ecological suitability for irrigated farming in a part of Nazluchai with an area of ​​23314 hectares using multi-criteria evaluation within the analytical hierarchy process and geographical information system.

At first, the parameters affecting the ecological land suitability for irrigated farming were identified, and the necessary data were collected and mapped using Geographic Information System. The criteria and sub-criteria were weighed based on expert opinions within Analytical Hierarchy Process. The homogeneous units were prepared by combining the sub-criteria standardized maps. The main limiting criteria in this study, including a slope less than 8% and a water quantity less than 3,000 liter/ha/year, were involved in the Boolean logic analysis. The ecological land suitability map for irrigated farming was generated using the Linear Weight Combination method and was classified into unsuitable, marginally, moderately, and highly suitable classes.

In the current land use map, 46.4% of the area was used for irrigated cultivations, 32.2% for range-dry farming on slopes above 30%, 12.6% for dry farming on slopes of 12-30%, and 0.8% was allocated to dry farming in areas with a slope less than 12%. Rocky and bare lands also cover 8% of the area. The matrix of the main criteria includes the landform, climate, soil, and water resources. Water resources have the highest weight for irrigated farming, and climate and soil are in the next rank. According to experts, the most important sub-criteria for assessing land suitability for irrigated farming are water quantity, temperature, texture, and soil fertility. Therefore, water resources are one of the most important and limiting resources to agriculture development in the basin, affecting other ecological resources. The ecological suitability map showed that 28.2% of the study area is the best area for irrigated farming, i.e., highly suitable class, 16.4% is moderately suitable class and 8% is marginally suitable class. 47% of the study area was classified as unsuitable for irrigated farming. In ecological suitability and current land-use maps, there is about 11% mismatch, and in 89% of the area, current land use is compatible with the ecological suitability of the study area. The results also show that integrating remote sensing, spatial information systems, analytical hierarchy processes, and weighted linear combinations is useful and effective for assessing land suitability and land-use planning.

This study is an important and useful regional guide for agricultural land planning. In order to prevent degradation, land suitability assessment, and optimal management, based on the principles of land-use planning using such new techniques and technologies, can be a fundamental solution for the relevant organizations. It is important to resolve environmental problems and create the conditions for sustainable development.