Determining areas prone to implementing of pressurized irrigation systems using hierarchical analysis (case study: Gorgan city)

The scarcity of water resources is presently regarded as one of the most significant constraints in the agricultural sector. The escalating population growth, expansion of cultivated areas, industrialization, and recurring droughts in recent years have led to an increased reliance on pressurized irrigation systems. Given that the implementation of such systems can pose a substantial financial burden on both the government and farmers, it is essential to approach their design and implementation with precision and principle, minimizing waste and ensuring optimal resource allocation. In this context, utilizing the results of feasibility studies for irrigation system implementation can be a valuable asset for designers in this sector. The primary objective of this research is to identify the most suitable irrigation system for agricultural lands in Gorgan County by employing Geographic Information System (GIS) software and analytical hierarchy process (AHP) methodologies. Methods The focal area of this research is the agricultural lands of Gorgan City, covering an area of approximately 52934 hectares, situated in Golestan Province. To identify suitable regions for the implementation of pressurized irrigation systems, a range of effective indicators were considered, including water quantity and quality, soil characteristics, topography, climatic conditions, labour availability in the area, operating and maintenance requirements, costs, and community acceptance. The irrigation system was examined and evaluated from a cultural perspective using the Analytic Hierarchy Process (AHP).Within the framework of the hierarchical analysis process (AHP), after forming a hierarchical tree and designing questionnaires, criteria and sub-criteria should be compared with each other in pairs. In this study, a customized questionnaire was developed and completed by university professors and experts in pressure irrigation system design for each irrigation system under consideration. To validate the quality of water and soil, the results of laboratory tests conducted on 130 samples of well water and soil from the farms of Gorgan City, as provided by the Gorgan City Organization of Agricultural Jihad, were analyzed. The results of water testing, including pH factors, electrical conductivity, suspended solids, sodium and chlorine concentration, soil texture, permeability parameters and available water content, were investigated. The climate zoning map for the study area in Gorgan City was obtained through the De Martonne method, which categorizes the region into four distinct climate zones: semi-arid, Mediterranean, semi-humid, and humid. Temperature data was gathered from 13 stations, while precipitation data was collected from 29 rain gauge stations in Gorgan City and its surrounding cities. A 20-meter Digital Elevation Model (DEM) was used to generate topographic maps, including slope and elevation information. A wide range of influence status of each parameter was considered in choosing appropriate irrigation methods (especially rain irrigation systems) and the designer can increase his level of accuracy as much as possible. In other words, positive and negative figures or scores that neutralize each other have weight and the intensity of the effect of each parameter (positive or negative) was considered. Following data entry into ArcMap software, normality tests were conducted to verify the integrity of the data. To normalize the data that do not have a normal distribution, the logarithmic function was used, and then the data were interpolated by the Kriging (Gaussian) method. Following the preparation of all the layers in a grid format, the layers were graded from (-3) to (3+) for each of the irrigation methods separately. A rating of (3+) indicates a highly favourable effect, while (3-) represents a severe negative impact on the mentioned index in the relevant irrigation system. The symbol (*) also means a negative effect to the extent of rejecting the recognition of the relevant irrigation system in the project under review. Subsequently, by multiplying the weights obtained from the Expert Choice software for each parameter by the points of each sub-criterion, the final score of the sub-criterion was calculated. The total score for each of the irrigation methods was obtained separately and through the algebraic sum of the final scores of the sub-criteria, and finally, the suitable areas for the implementation of the mentioned systems for each irrigation method were prepared in the form of a map. Results The results showed that for the implementation of rain irrigation systems in the lands of the designated area, 11.09% of the land was characterized as having high restrictions, 38.51% as having low restrictions, 45.08% as having medium restrictions, and 5.32% as being unsuitable for such implementation. Additionally, approximately 5.3% of the land in the region was deemed non-viable for rain irrigation system deployment. Regarding the local irrigation system, it was implemented across all areas of the case study, with high, low, medium, and no restrictions observed in 6.13%, 62.65%, 32.21%, and respective percentages of the land. Furthermore, it was found that low-pressure irrigation systems were not applicable in approximately 6.5% of the land, while high restrictions, low-to-medium restrictions, and no restrictions were present in 8.55%, 69.53%, and 15.41% of the land, respectively. In conclusion, it was determined that approximately 95% of the land (equivalent to 50,899.25 hectares) was suitable for rain irrigation system implementation, while 93% of the land (equivalent to 50, 251.84 hectares) was suitable for low-pressure irrigation system implementation. Notably, all lands under study (equivalent to 53,763.27 hectares) were deemed suitable for local irrigation system implementation.