Hydrology
A. Shemshaki; Gh. H. Karami
Abstract
The water level of Urmia lake during the last twenty years has been significantly declining. Along with changes in quantity, water quality has also substantially changed. In this article, attempts has been made to identify the relationship between water quality and quantity to have a better understanding ...
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The water level of Urmia lake during the last twenty years has been significantly declining. Along with changes in quantity, water quality has also substantially changed. In this article, attempts has been made to identify the relationship between water quality and quantity to have a better understanding of the changing history of the lake during the geological past. This can help to better explore the risk factors influencing the drying process of the lake. This understanding can therefore be employed to appropriate planning and management procedures in order to revive this lake effectively. Based on this study, the lake water in the levels higher than 1286 meters (MSL) is brackish to fresh and is not of saline type. Thus, it seems that, in the late Pleistocene, the lake water was of a fresh type where the water level was higher than 1297 meters. The study revealed that the lake become to a playa-type environment in water level of about 1273 MSL. The present water level of 1270 meters suggests that the lake has a dominantly playa-type environment. In this environment, increase in precipitation and inflows will lead to a rapid increase in reservoir volume; and vice versa, a stop or decrease in the precipitation and inflows with an increase of temperature and evaporation will lead to a rapid reduction in reservoir volume. This study estimates that a volume of over 9.5 billion cubic meters of water is necessary to revive the Urmia Lake.
A. Shemshaki; Y. Mohammadi; M. J. Bolourchi
Abstract
Based on recent research by geological survey of Iran (GSI), an extensive subsidence area was observed in Hashtgerd plain (Tehran province). The geographical position of this area is 35° 47' 45" to 35° 03' 05" N and 50° 29' 05" to 50° 54' 28" E. The maximum and mean rates of this subsidence ...
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Based on recent research by geological survey of Iran (GSI), an extensive subsidence area was observed in Hashtgerd plain (Tehran province). The geographical position of this area is 35° 47' 45" to 35° 03' 05" N and 50° 29' 05" to 50° 54' 28" E. The maximum and mean rates of this subsidence are 16 and 8.4 cm per year. In general, the main aquifer of plain is composed of Kahrizak and Tehran formations. These formations are alluvium type. The Kahrizak formation consists of gravel, sand and silt. This formation scatters in north of plain. Tehran formation is composed of pebble, gravel, sand and clay in fluvial cone form. Toward the center and south of plain the amount of fine material increases. The subsidence is shown in Tehran formation only. Based on geoelectrical and well-logs data, the confined to semi confined aquifer area is recognized in south and west of Hashtgerd plain. This area is in accordance with subsidence area. In the upper part of confined aquifer we can find an unconfined aquifer. The whole of penetrated water from surface of plain recharges the unconfined aquifer. The extortion of water from confined aquifer and unconfined aquifer in north of plain has caused subsidence phenomena. The unique recharge resources of confined aquifer is unconfined aquifer in north of plain. To take notice of the position and properties of confined and unconfined aquifers in this place is very important in suitable planning and management to prevent and mitigate subsidence occurrence in future.
