جستجوی مقالات مرتبط با کلیدواژه « سفره تحت فشار » در نشریات گروه « آب و خاک »

Evaluation of a system needs a combination of indicators that can show their current situation and future. Multilayer aquifers are more complicated due to different recharge and discharge processes of each layer. This paper aims to evaluate sustainability of phreatic and confined layers of an alluvial aquifer in Golestan province. The relevant data includes monthly precipitation of 19 rain gauges, groundwater level of the phreatic layer in 19 observational wells and piezometric level of 19 wells in the confined layer. In this paper combination of eleven indices that selected according to available data in the region, is used to assess sustainability. Results show in spite of detecting no significant trend in the precipitation data, there is descending trend in the water table of phreatic layer and piezometric level of confined one. Aquifer sustainability index of phreatic and confined layers are 0.89 and 1.01, respectively, that means unsustainability of both layers and worse condition of confined layer. Of course unsustainability of the confined layer has been covered by existed non-renewable groundwater resources. According to groundwater abstraction development index equal to 0.26, implementation of water resources development plans is allowed with considering limitations in terms of water quantity and quality. Also 2.82 as the aquifer recovery potential index revealed if driver factors change toward providing sustainable conditions, both layers can be recovered soon. It can be concluded that the region is facing water scarcity that is a limitation to economic development and human health and well-being.

Aquifer overexploitation can cause problems such as salt water intrusion and land subsidence. This condition drives the necessity for the optimal management of aquifers which requires an understanding of aquifer hydrodynamics. In this regard radioisotope dating is one of the useful methods. This paper presents a practical method to determine the age of groundwater using tritium radioisotope. The tritium dating of groundwater includes sampling, initial distillation, enrichment, secondary distillation, measurement of tritium radioactivity, calculation of device parameters, and age of the samples. The electrolytic enrichment method and radioactivity measurement using LSC, which is introduced in this paper, make it possible to measure tritium below 1 TU that means dating water up to 50 years and can overcome the problem of tritium concentration decline in the atmosphere to some extent. The results of a study performed using this method during spring 2012, with interior facilities of the country, showed that the age of the samples were divided into two groups of 5 to 10 years and the mixture of modern recharge and recharged before 1952. Therefore the young parts of aquifer are influenced more readily by qualitative and quantitative climatic and factors. On the contrary, territories with older water reserves are less affected by these changes and have a higher degree of reliability. In the allocation of such resources only the renewable volume should be considered. To achieve this objective imposition of restrictive policies of exploitation seem to be necessary in aquifer management plans.

In many arid and semi-arid regions, groundwater resources exploitation is inevitable to meet water demands for different sectors. This paper aims to study the response of phreatic and confined aquifers in a multilayer groundwater system to climate variability. To achieve this aim, Gorgan plain multilayer aquifer has been investigated using different meteorological (DI, PNI and SPI) and hydrological (GRI) drought indices, involving the correlation analysis method. 19 rain gauge stations and 19 observation wells data with the time period of 38 years and also 14 years data of 19 piezometric wells has been used. The results show that the SPI index has a better performance in monitoring of climate variability and detecting drought events in the studied area. Therefore, the mentioned index has been used in comparing with GRI, to investigate groundwater response. Also, the results indicate difference between aquifers response to meteorological droughts. In this case, long-term 18-month and 48-month SPI indices are the most correlated parameters to the groundwater in both phreatic and confined aquifers and the effect of fluctuations in rainfall remained up to 15 months and 5 months in each zone, respectively. This reflects this fact that, if the principles of sustainable exploitation be followed, confined aquifer has a high reliability and only when prolonged drought or wet condition occurs, it could be affected.

In this paper, the status of groundwater hydrology and hydrogeology plain of Varzaneh was studied. In the hydrology section, the annual average of Zayandehrood river flow in stations of Varzaneh and Cham was investigated. The unit hydrograph of the plain was also illustrated. In hydrogeology section, the software of RockWorks Ver.15 was used and log of wells and also the geological model of Varzaneh plain were prepared according to the logs and material of their layers. The contours lines of underground water level in unconfined andconfined aquifer in the Varzaneh plain were drawn using Surfer Ver.10 software. Also the hydraulic gradient for groundwater flow in the plain area was found. The maximum value of hydraulic gradient was 0.008 from center of plain to the South East. In the past decade, the ten-years unit hydrograph of plain showed that the amount of underground water level was dropped by 1.3 meters, i.e. which the mean of annual loss was 13 centimeters.