The importance of understanding the hydrogeology and geochemistry of karst terrains for safely siting dams

Abstract

Dam site selection in karst regions is an extremely important issue in terms of dam safety and environmental impact. Groundwater in a karst aquifer near a selected dam site is deemed to be impacted greatly by the dam. This study uses the Kangir Reservoir of Iran as an example to illustrate the interrelationships of karst-groundwater condition, lithology of the dam reservoir, future climate changes, and overexploitation of water resources in the area. This study conducted a comprehensive analysis of water balance, groundwater flow, hydrochemistry, characteristics of geologic formations with respect to the quantity and quality of water, distribution of karst and evaporative formations in the catchment, and tectonic setting to highlight the importance of hydrogeological conditions on the water quality and quantity of the Kangir Reservoir. The main findings include, first, a major part of the highland karst aquifer in the Asmari Formation within the dam catchment does not drain into the dam reservoir. Instead, it leaks into the downstream Siahgel Region of the dam mainly along the Zarneh-Siahgel fault zone through the karstic Asmari Formation. Second, selecting the dam site on evaporative Gachsaran Formation causes degradation of water quality in the reservoir. The results of this study demonstrate that considering karst hydrogeological conditions is indispensable for dam site selection from the point of view of groundwater quantity and quality impacted by the dam.

Chemistry of the Karst Sarabkalan Spring, Iran, and Controls of PDO and ENSO Climate Indices on It

“…The higher variations in sulfate are in part due to the mixing between groundwater of different sources, such as the water from Asmari limestone and Gachsaran formations (Karimi et al 2005). Leaching from the Gachsaran can increase the sulfate concentration and destroy water quality because it contains evaporative rocks with high solubility (Karimi et al 2005; Rezaei et al 2017). There are some notable points regarding sulfate concentration.…”

“…The main geologic formations of the area, in decreasing order of age, include Pabdeh (shale and marl), Asmari (limestone), and Gachsaran (marl, gypsum, and halite). The low‐permeability Pabdeh Formation, overlain by the karstic Asmari Formation (Figure 1a), constitutes the core of the Seivan Anticline (SA), SKA, and Charmin Anticline and acts as a barrier to groundwater flow in the Zagros Mountains (Rezaei et al 2017). The evaporative‐rich Gachsaran Formation broadly covers the hillsides of anticlines.…”

Gastropods in Small Water Bodies of the Western Balkans—Endangerments and Threats

“…Even if the areas of springs, small mountain streams (low order streams), and groundwaters of the Western Balkan countries are unevenly explored, they are characterized the great diversity is seen in the freshwater gastropods with 251 species and subspecies belonging in 16 families. The most numerous taxa are in the family Hydrobiidae presented by 153 species and subspecies, followed by families: Moitessieriidae (31 species), Bythinellidae (15), Bithyniidae (11), Planorbidae (12 species), while the rest of families were less diversified (Table 11.1).…”

“…These impacts range from water level loss or gain to lakes, springs or other rivers, unintentional redirection of flows, etc. [14,15].…”