Palustrine carbonates are frequently found with active and dried karstic springs in the foothills of the mountains bordering the Persepolis Basin, southwest Iran. A combination of geological conditions favours their formation, including (i) the presence of karstic limestone aquifers in the limbs of anticlines cut through by fault systems; (ii) very gentle slopes from the spring resurgence point towards the centre of the alluvial plain, creating a flat waterlogged area; and (iii) a semiarid climate with marked precipitation seasonality or significant fluctuations in water discharge and wetland water table. We suggest the term “anastomosing wetlands” or “anastomosing palustrine environments” to denote the studied karstic spring–fed carbonate wetlands, because of similarities with anastomosing river systems in aerial view. The common presence of extended anastomosing wetland carbonates in the Persepolis Basin and adjacent basins in the central and southern Zagros suggests that they can play an important role in the geological records of collision-related basin-and-range settings dominated by karstic limestones. Karstic spring wetlands are a main source of fresh water hosting a rich biodiversity, which attracts human communities, whose impact is visible in the archaeological material imbedded in the wetland stratigraphy. Fresh water availability, through these spring wetlands, partly explains why the semiarid Persepolis region was selected by successive civilizations, from Elamites to Persians until early Islamic entities, to establish regional centres throughout the period from the third millennium B.C. to the first millennium A.D. Only a few of these ecosystems have survived the intensive human activities of recent decades.

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Aggressive recharge water is capable of widening the surface and interior openings of karstic layers that leads to the easy flowing of water in this type of aquifers. The object of this study is to understand if surface karstification is the same as the interior karst development of an aquifer. Surface karstification was analyzed using Geographic Information System and remote sensing techniques, while interior karstification was studied with spring hydrograph analysis. The study area includes seven carbonate aquifers in the Zagros Region of Iran. The surface karstification of these aquifers is controlled by different factors including the thickness of carbonate formations, distance from faults, fracture density, precipitation, temperature, vegetation index, slope, and relief. The most important factors are precipitation and presence and density of faults and fractures; while the least significant factor is the vegetation cover. The spring hydrograph analysis shows that there are different ways of estimating the relative karst development, but each parameter that impacts the specific character of the karst aquifer might be independent of others. Furthermore, comparing the relative surface and interior karst development demonstrates that the possible relationship between them is unpredictable. Consequently, we define a specific and unique numeric method to assess the interior karst development that permits a meaningful concept and comparison among different aquifers throughout the world.

An aquifer test is used mostly to determine the storage coefficient and transmissivity. Although residual drawdown data are widely used in estimating the transmissivity of aquifers, the estimation of storage coefficients with recovery data is controversial. Some researchers have proposed methods to estimate storage coefficients with recovery data by assuming equality of storage coefficients for the recovery and pumping periods (S = S'). The aim of this study is to determine storage coefficients without such an assumption, that is, S≠S'. The method is a modified version of Banton-Bangoy's method without considering drawdown data due to pumping. Drawdown is plotted vs. the logarithmic ratio (t'/t) or time since pumping stopped to the duration of pumping and the ratio of storage coefficient during recovery to the storage coefficient from the pumping period (S'/S). The method is verified with one case study and two synthetic examples. Thus, it is possible to determine storage coefficient of pumping period accurately without any data from pumping period by recovery data.

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