Physical Characteristics of the Wetland

In the general hydrology classification of Iran, the Gavkhouni basin is part of the central Iranian plateau catchment area. To the north, it’s bordered by the Lake Namak catchment, to the east by the Daq Sorkh and Siah Kuh desert basins, to the south by the Abarghoo desert basin, and to the west and southwest by the Karun River basin.

Gavkhouni Wetland, registered in the Ramsar Convention in 1975, is among the international natural wetlands. The wetland is located in the southeastern part of the basin, approximately 140 kilometers southeast of Isfahan (following the route: Isfahan, Ziar, Ejieh, Varzaneh, Wetland) and about 30 kilometers from the town of Varzaneh. Its altitude is 1,470 meters above sea level.

Topographically speaking, the western parts of the basin are primarily mountainous, possessing higher elevations and cooler climates. In contrast, the eastern and southeastern areas have lower altitudes, receive less precipitation than the west, and have a warmer climate. The wetland’s size fluctuates based on the incoming water volume. In recent years, with the reduction, especially from the Zayandeh River, flowing into the wetland, its size has shrunk. According to the Comprehensive Water Plan updates, the area of Gavkhouni Wetland was reported as 489 square kilometers.

The National Comprehensive Water Plan’s recent update, focusing on the integrated management of water resources, covered the west basin, Karkheh, Great Karun, Jaraahi, and Zahreh, reporting the balance of water sources and usage. This report, dated September 2012, was provided by Behan Dam Consulting Engineers.

Geological Features of the Wetland

Notable geological formations in the region include the Neogene volcanic complex (12 million years ago) to the north of the Gavkhouni wetland, which is part of the Central Iranian structural zone. The rocks in the area are primarily Neogene andesitic basalt, dacite, andesite, and rhyodacite, which have emerged as lava flows amidst the Eocene volcanic rocks. The andesitic basalts, formed either by melting of metasomatized mantle or by contamination of mantle melt with crust, bring along significant mineralization. Their best appearance in the Gavkhouni wetland can be seen in the Black Mountain, easily distinguishable from other rocks due to their texture and color. Their porous structure indicates that the magma was gas rich. The basalts of the Black Mountain have economic importance for construction, industrial purposes, and evaporative salts for potassium extraction. The central part of the Zayandeh Rood basin, from Isfahan to Gavkhouni, is the continuation of the Urmia-Dokhtar trench located in the geological unit of Sanandaj-Sirjan (Esfandagheh-Marivan). Moreover, the eastern wall of the Gavkhouni basin, made entirely of volcanic material, is the continuation of Iran’s axial volcano and separates the Isfahan-Sirjan water catchment from the Ardistan-Yazd. It’s part of the Central Iranian formations.

The soil condition is directly influenced by sediments carried from the entire basin, mainly from the Quaternary geological period. In addition to that, factors like wind activity, underground saline water, vegetation cover, topography, intense evaporation, and climatic conditions have played crucial roles in the formation and evolution of the soils, mostly leading to increased salinity. The difference in soil salinity across the region is one of its distinct pedological features, due to the varied effects of these factors in different parts of the wetland. Based on this, the region’s soils can be categorized into two main groups:

The first group comprises the soils of the eastern and southern peripheries of the wetland. These areas, benefiting from high groundwater and influenced by the lake’s saline water, intense evaporation, salt wind activity, and salty waterways, exhibit very high salinity levels.

The second group includes soils mostly found on overlooking heights around the wetland or in its north and northwest areas. The soils in the nearby heights, like the Black Mountain, are less affected by the lake’s salinity due to the deeper water table. However, the winds coming from the lake direction do add some amount of salinity to these soils.

Water Sources Feeding the Wetland Most of the waterways leading to the wetland come from the south and southeast. These channels and streams, considering the sudden floods occurring in the region, can somewhat play a vital role in supplying the wetland’s water needs. They are especially crucial in maintaining the wetland’s ecosystem and the habitats for birds and animals in this area.

The climatic appearance of the Gavkhouni watershed is diverse due to its extensive altitude range, which spans from 1,450 meters to 3,974 meters. This range encompasses various climatic examples from very dry to highly humid conditions. The highest point, situated in the western part, lies between the Zagros Mountain range and the Karun River basin, peaking at 3,974 meters above sea level in Mount Karpoush. The lowest point is in the Gavkhouni wetland, sitting at 1,450 meters above sea level.

Plant Coverage

The total number of plants collected from the wetland area that have been identified is about 65 plant species. These belong to 16 families and 54 genera. The spinach (or beetroot) family, with more than 17 plant species, has the highest frequency and diversity, while families like desert screw, ephedra, candelabra, and others each have at least one plant species, showcasing the least diversity.

In general, the plant communities in the area can be divided into several groups:

  • Plant communities established in very saline soils include associations of salicornia, halogeton, and suaeda.
  • Communities that grow on the margins and beds of rivers and waterways leading to the wetlands are dominated by reeds and tamarix.
  • Communities that are established on sandy hills consist of tamarisk and saxaul groups.
  • Communities found on the slopes of the Black Mountain, away from the wetland’s influence, include ephedra, kochia, and astragalus groups.

Registering the International Gavkhouni Wetland in the Ramsar Convention