gorgan

Land-use changes by human activities are important issues in regional planning. The distributed hydrologic model is a suitable model to survey land-use changes and to estimate their quantities. This study aims to evaluate the effects of land-use changes (the expansion of residential areas) on the hydrological parameters using WetSpa model in the Ziarat Watershed, which has an area of 95.15 square kilometers. In order to execute the model, during the four-year period (2007-2010), the hourly hydrometeorology data including rainfall, temperature, evapotranspiration, and discharge rate are used as inputs. Additionally, three base maps of the digital elevation model (30meter cell size), soil map (soil texture), and land-use are also applied. As a result, there is a good agreement between the simulated and observed hydrographs. The scenarios of land-use changes (the expansion of residential area) have been used as input maps for the calibrated model in a GIS environment. The results show that some hydrological parameters such as the peak discharge, potential runoff coefficient and flow velocity increase in the all scenarios, but the Manning’s roughness coefficientis reduced.

One of the drinking water resources has been selected for research based on chemical analysis with nitrate concentration of 53/7 mg/l in northern part of Gorgan city. In this research, natural zeolite has been used for reducing nitrate under laboratory conditions. The results indicated that natural zeolite reduced nitrate at about 13 mg/lit and also reduced hardness by passing 1 lit water through zeolitic bed (at about 1 kg) during a 30-minute time lag. In the chemical analysis, the pH of the water was 7/5 which chaned to 7/3 after passing through zeolitic bed. In this research, the hardness of raw water was 670 mg/l and the hardness was reduced 85 mg/lit in 40 grms zeolite with a time lag of 10 minutes whereas if zeolite weight was 160 grams, during a 30-minute timelag, the hardness would reduce to 175 mg/lit. Therefore, it can be concluded that natural zeolite could be used for reduction of nitrate in contaminated water wells all over the country.

Physical and Chemical studies indicate that hydrochemical facies of Ziarat River, one of the drinking water resource, are (Ca-Mg -HCO+2; Cl3 - HCO3 -Ca-Mg). According to hardness classification, water class of Gorgan's drinking water isvery hard. While, the total dissolved solid of Gorgan's drinking water is rock-dominance, according to Gibbs classification. Regarding the present physical standards of drinking waters, turbidity is one of the most important parameters of the rivers which are used for drinking water. A several year evaluation of Ziarat River showed that the turbidity this river has been between 185-2572, prior to entrance to WTPG. High fluctuation of Ziarat River turbidity is due to flood nature of this river, so that turbidity of water manifest higher amount in 1378 compared to the following years. Regarding intensive erosion and sedimentation in the Ziarat watershed, in order to decrease the turbidity of water as well as consumption of chemical catalyzes in the WTPG, managements of watershed and construction of several pre-depositional ponds for collection of sediments in entrance of Ziarat River to the WTPG are recommended.

Gorgan region is located on the northern limb of the eastern Alborz. This region is bounded by Alborz heights and Gorgan plain to the south and north. Most of the existing faults in the region have NE- SW (N70- 90) trend with left lateral strike slip movement and reverse component (up to thrust). Furthermore, a number of faults also have NW- SE trend with right lateral strike slip movement and reverse component. Khazar and North Alborz faults are the most important faults in the region and make the structural boundary around the region. In this study, initially, major and main faults of the region were extracted by remote sensing techniques and then, controlled by field investigations. After that, the vector data layer of the springs of the study area was provided then both layers (the extracted faults and spring location) were entered into GIS environment to compare of the springs location and faults conditions. The results indicate that, most of the springs are situated on the breakage zones of the major faults. Further investigation of these results; confirm existing relationship between different type of faults and spring distribution pattern. The major faults of the region with southward slope (such as Khazar fault and North Alborz fault) prevent groundwater transition toward the Gorgan plain and thus, cause the appearing of various springs in the surrounding area of these fractures. Second- order fractures with N40- 50 and or N140- 160 strikes, truncated the major faults in 15- 55 and caused to making the transverse current towards the Gorgan plain.