farzaneh sajedi

Ground water is one of the major resources of fresh water needed for humans, especially in arid areas. It will be seriously threatened in future due to climate change and global warming. The purpose of this study is to examine the effects of climate change on groundwater resources in the Kerman-Baghin plain. Accordingly, climate prediction at 2055 horizon (2065-2046) was used by the atmospheric general circulation model HadCM3 with A2 emissions scenario. Also groundwater table during the years (1986 -2009) and the quality situation (salinity) over the years (2003-2009) were studied. The results of LARS-WG model showed that the average annual rainfall at the 2055 horizon will be reduced about 3.6 mm. Also the annual maximum and minimum temperatures will increase during the 2055 horizon, 2.8°C and 2.8 °C, respectively. Assessing of unit hydrograph and chemograph in Kerman- Baghin plain highlighted a drop in the water table (0.89 meter depletion per year) and increase of aquifer salinity. According to the results of atmospheric general circulation model (HadCM3), this trend in the water table and increase in aquifer salinity expected to be continued.

To optimal and sustainable management of water resources in watershed scale, estimation of water balance and important to know of the different parameters of the water balance is inevitable. Goal of this study, is estimating the volume of actual evapotranspiration, infiltration, surface and subsurface flow based on hydrologic balance in Marghab and Abgelal watersheds. Hydrological balance in the hydrological stations these watersheds was calculated using the Salas approach. Results indicated that in Abgelal watershed, from 597 mm average of rainfall, about 438 mm is evaporated and about 95 mm as runoff out of the watershed. Thus, 64 mm of the total rainfall infiltrated. In the Marghab watershed, maximum of rainfall as runoff out of the watershed, so from amount of annually rainfall that is equal with 641 mm, amount of 192 mm as evapotranspiration and amount of 72 mm as infiltration and 377 mm as runoff out of the watershed. Model evaluation for the two stations was conducted using the error parameters such as Nash – Sutcliffe Error (NSE), Root-Mean-Square Error (RMSE) and Mean Absolute Error (MAE), results indicate that performance of model is better in Marghab station than Baghmalek station.

Recognizing of groundwater quality، which have the most important role in preparing of the drinking and agriculture water particularly in arid regions، is essential. In this study، the hydrochemical status of Semnan aquifer was drawn and analyzed using qualitative diagrams (Piper، radical، Collins، Schuler and Wilcox diagrams) during August 2008. Then، groundwater quality zonation (water type، drinking and agriculture purposes) were prepared using Arc GIS software. The results showed that the groundwater dominant type is chlorure sodium in Semnan plain. Also، groundwater quality for drinking in northern and northeast and a small area in west of plain is medium to acceptable، and in other regions especially in south and southwest of plain is low. According to Wilcox diagram، the most groundwater resources of the study area located in C4S1 to C4S3 classes. These resources are very saline and almost alkaline water and are not suitable for agriculture. Some groundwater resources in northern and northwestern of plain located in C3S1 and C3S2 classes. These resources are saline water، but can be used in agriculture.