Feasibility Assessment of Cloud Seeding Technology for Water Enhancement in Iran’s Watersheds

Introduction

Water scarcity has become one of the most critical environmental and socio-economic challenges in arid and semi-arid regions worldwide, particularly in Iran. Recurrent droughts, declining precipitation trends, and increasing pressure on conventional water resources have intensified the need for alternative approaches to water resource management. Cloud seeding, as one of the most widely studied weather modification techniques, has been employed in several countries to enhance precipitation and improve water availability. However, the success of cloud seeding operations strongly depends on regional climatic conditions, cloud microphysical characteristics, and atmospheric dynamics. Due to the diverse climatic regimes and physiographic conditions across Iran, a comprehensive assessment of cloud seeding potential is required before implementing operational programs. The present study aims to evaluate the feasibility of cloud seeding for water enhancement in the thirty major watersheds of Iran by identifying suitable spatial and temporal windows and determining watershed priorities based on climatological and cloud microphysical indicators.

Materials and Methods

The methodology was developed based on the guidelines of the World Meteorological Organization’s Precipitation Enhancement Project (WMO-PEP No. 3) and adapted to the climatic conditions of Iran. Long-term meteorological observations from synoptic, climatological, and rain-gauge stations covering the period 1981–2010 were utilized. In addition, gridded Climate Forecast System Reanalysis (CFSR) datasets with a spatial resolution of 0.5° were employed to estimate precipitable water and cloud liquid water content.

Nine key indicators influencing cloud seeding potential were selected and objectively scored, including: (1) terrain homogeneity, (2) mean monthly precipitation, (3) precipitation regime, (4) ratio of solid precipitation to total precipitation, (5) frequency of low-level clouds, (6) cloudiness percentage, (7) precipitable water, (8) frequency of convective clouds (Cumulus and Cumulonimbus types 2 and 3), and (9) cloud liquid water content (LWC). Each indicator was assigned a weighting factor according to its relative importance in cloud seeding effectiveness. Spatial analyses were conducted using GIS techniques, and final scores were calculated for each watershed on a monthly basis. The resulting values were used to classify and rank watersheds according to their cloud seeding suitability.

Results and Discussion

The results reveal substantial spatial and seasonal variability in cloud seeding potential across Iran. Northern and northwestern watersheds exhibited the highest suitability, particularly during the cold season when frontal systems dominate atmospheric circulation. The Lake Urmia and Aras watersheds consistently achieved the highest scores due to favorable precipitation regimes, higher cloud occurrence, significant proportions of solid precipitation, and elevated cloud liquid water content.

The Caspian Sea watersheds, including Talesh, Gorgan, Haraz, and Sefidrud, also demonstrated considerable cloud seeding potential, especially during late spring and summer, owing to persistent moisture supply from the Caspian Sea and orographic lifting processes. In contrast, central and southern watersheds generally showed lower suitability because of limited atmospheric moisture, reduced cloud occurrence, and unfavorable cloud microphysical conditions.

Monthly prioritization indicated that Lake Urmia and Namak Lake watersheds were among the most favorable regions during winter, while Talesh, Gorgan, and Haraz watersheds exhibited higher suitability during summer and early autumn. The findings are consistent with international studies conducted in China, Australia, and India, which emphasize the effectiveness of cloud seeding in mountainous regions influenced by frontal weather systems. The analysis also highlights that cloud seeding success depends not only on cloud presence but also on cloud microphysical properties and atmospheric moisture availability.

Conclusion

This study provides a comprehensive climatological and microphysical assessment of cloud seeding feasibility across Iran’s thirty major watersheds. The results indicate that the northwestern, western, and northern regions of Iran possess the highest potential for precipitation enhancement, particularly during the cold season. Among the evaluated watersheds, Lake Urmia, Aras, Talesh, Gorgan, Haraz, and Sefidrud emerged as the most promising candidates for operational cloud seeding programs.

The findings suggest that cloud seeding can serve as a complementary tool for water resource management in Iran, provided that seeding strategies are carefully adapted to the specific cloud microphysical characteristics and climatic conditions of each watershed. Nevertheless, successful implementation requires real-time atmospheric monitoring, numerical weather prediction support, and rigorous operational evaluation. Future studies should integrate high-resolution atmospheric modeling, radar observations, and economic assessments to further quantify the effectiveness and cost-benefit ratio of cloud seeding operations under changing climatic conditions.