Foroud Sharifi
Abstract
This paper has focused on the application of hydro- geochemical techniques in conceptualizing of groundwater and to estimate recharge/discharge and the renewability of aquifer in Hashtgerd Watershed, Iran. At first, the aquifer boundary was defined based on data of existing wells and basin morphologic ...
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This paper has focused on the application of hydro- geochemical techniques in conceptualizing of groundwater and to estimate recharge/discharge and the renewability of aquifer in Hashtgerd Watershed, Iran. At first, the aquifer boundary was defined based on data of existing wells and basin morphologic conditions. Estimation of recharge rate at different depth intervals by using tracer mass balance was done for 291 representative groundwater samples which includes 195 samples from soil and water of unsaturated zone in depths of 30 to 90 m (sampling in each meter), 10 samples were taken from rainfall, five samples from Qanats and 21 samples from wells and 60 samples taken from surface water in the study area. Based on water balance technique applying to a 7 year measured data and evaluation of hydrological and hydro- geological processes in the Watershed, average groundwater depletion was calculated at 0.37 m/year that indicated annual recharge rate of 245 million cubic meter (mcm) and over use of storage capacity of the aquifer. The groundwater studies showed that the natural recharge from direct rainfall is about 2% of total recharge. The annual recharge rate over an area of 752 km2 varies from 2.3 to 15.1 mm/yr. The required time for aquifer recharge from rainfall for the aquifer of 30 m thickness in the southern part of the aquifer is 1200 years while for aquifer of 90 m thickness in the north, recharge time is around 1100 years. On the other hand, in north and south of the aquifer, transitivity rates are 2500 and 300 m2/day, respectively with the groundwater renewability of 2.92 years which shows the importance of renewability of groundwater via concentrated/linear recharge from fractured zones. Studies of direct recharge in other parts of the world have shown that direct recharge rates may vary from zero to around 40% of mean rainfall volume. The results of this study revealed that around 98% of aquifer recharge occurs via concentrated/linear recharge from fractured zones with the average renewability of three years. Then it is recommended to consider the above mentioned geologic features in concentrated recharge of aquifer in saturated zone by watershed management, floodwater spreading and vegetation cover improvement projects.
H. Saadati; F. Sharifi; M. Mahdavi; H. Ahmadi; M. Mohseni Saravi
Volume 62, Issue 1 , June 2009
Abstract
The main structure of this study includes; isotopic tracer evaluation and measuring, to identify and origin of groundwater recharge, contributions determine of diffused recharge (DR) and concentrated recharge (CR) as well as determine drought and wet periods in Hashtgerd plain. The hydrochemical study ...
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The main structure of this study includes; isotopic tracer evaluation and measuring, to identify and origin of groundwater recharge, contributions determine of diffused recharge (DR) and concentrated recharge (CR) as well as determine drought and wet periods in Hashtgerd plain. The hydrochemical study which involved collection and analysis of water samples from the deep and dug wells, springs, tap water and rainwater showed that the rainwater is little source of groundwater recharge. The isotopical study aimed to determine the origin of the groundwater bodies and to offer support for the hydrochemical analysis. To achieve this purpose samples analyzed for H2 and O18 and data was quoted from literature about the isotopic composition of precipitation. The study shows that the isotopic composition during the rainy season ranges for ?O18 between -6/05 ‰ and -6/92 ‰ and for ?H2 between-45/92 ‰ and -52/27 ‰. The changes in ?O18 are correlated with those of ?H2 with R2 =0.9 that was similar to GMWL line. proving their meteoric origin. Cluster analysis supported by the Hierarchical Cluster Analyze, Chebychev and Mann-Whitney tests classified the analyzed rivers water samples into two main groups: the first cluster was included Kordan, Aqasht, Sorheh and Khor rivers. Because of the low runoff and high infiltration these rivers are recharged through groundwater. The second cluster was consisted Valian, Fashand and Hiv-shalamzar rivers. Because of the low infiltration these rivers are recharged through runoff. Cluster Analysis shows that the samples of groundwater of Hashtgerd plain were divided into three clusters. The first cluster was included west and north-east of Hashtgerd plain (Nazarabad, Hashtgerd town, Baraghan and Kordan) were recharged through surface water and rainfall. The second cluster was included north and center of Hashtgerd plain were recharged through surface and groundwater. The third cluster was included south-west and south-east of Hashtgerd plain which were recharged through groundwater. The results show that concentrated recharge (CR) supply groundwater more than diffused recharge (CR). Concentrated recharge was performed by watersheds and flood spreading. Using isotopic method, mean values of ? O18 and ? H2 in a mass-balance equation, the relative contributions of diffused recharge (DR) and concentrated recharge (CR), to groundwater were estimated to be 78 درصد and 22 درصد, respectively. According to results of this study, groundwater resource level decrease and there is a drought period in Hashtgerd plain.
