Stream water quality in the western regions of Iran

Stream water quality of a part of the four western mountainous regions of Iran: Lorastan, Kordestan, Hamadan and Kearmanshah, with a total area of 101.102´103 km2 was investigated. The chemistry ofmajor elements such as Ca, K, Na, Mg, Cl, HCO3, SO4 and alkalinity from hydrological basins of the regions was examined based upon samples from the relatively important basins. The difference inthese chemical elements of streams was verified on a region-by-region basis. Temporal changes of water quality in the stream water were examined using a seasonal classification of data. The resultsshowed that the dissolved load of about 70% of all water samples (at all basins during all seasons) was less than 500 mg/l. The same result can be concluded for seasonal variability of EC for the entire area. Itwas less than 0.550 ds/m for 68% of samples. The pH variation was from 5.5 to 9 with an average of 8.2. The highest and lowest values are from autumn and summer samples, respectively. In summer, thesodium adsorption ratio (SAR) value was maximal, and the agricultural activities cause an increasing on its normal (average annual) rate in the rivers. The results also indicated a very good relationship between the total anions and total cations, during all of seasons. There were no significant relationships between the area of the basin and the chemical element concentrations. These results have been used for the water resources management of the mountainous regions of Iran and themodelling of water quality predication

GEOGRAPHICAL FACTORS AFFECTING THE PRECIPITATION REGIME IN IRAN

This study compares the precipitation regime by using harmonic analysis during the last four decades (1965-2004).We used interpolated precipitation data from different weather stations distributed across Iran by applying 15x15 km spatial grids for the interpolated data. Data validations were employed by statistical tests. In this study three harmonies of precipitation variances were evaluated. Variability of precipitation regime was explored by using three-harmonic analysis method. In addition, the effect of geographical factors (altitude, latitude, longitude) affecting to the precipitation regime was verified. Analysis of the first harmonic method proved that the main precipitation regime in Iran occurs in winter season as result of large scale Mediterranean systems passing over Iran in the mentioned season. Moreover, the fluctuations of the seasonal precipitation regime were found to be different, so that in one region led to the appearance of the new regimes and in other region caused change or disappearance of the regimes. In all three harmonics, variances of precipitation were mainly a function of the geographical factors. This effect was more evident in the third harmonic, in such a way that the increases in latitudes (moving to northern region) caused higher precipitation variance. This means that precipitation regime in northern sites are more exposed to local factors and seasonal precipitation than those of southern sites. The results of this research can be used in land–use projects, environmental plans and water resources management