نشریه پژوهش های آبخیزداری
پیاپی 91 (تابستان 1390)

Estimation of design flood is the first step in hydraulic structures and flood control projects designing. On the other hand، estimation of runoff and flood، need to precipitation and design rainfall informations. Therefore، with respect to the spatially variations of rainfall and providing Depth–Area–Duration relationship، we can obtain suitable patterns of rainfall for estimation of design rainfall values in various locations. In this study، after gathering all storms in Hamedan، Qazvin and Zanjan provinces، 9 maximun and overall storms from 50 storms were selected. The results showed that between all of storms،the November 5،1994 storm is maximum and overall than others. The number of stations varies from 116 – 125 of 169 total stations in different storms. After drawing rainfall accumulation curves for climatology raingage stations، the hytograph curves were drived for noun recorded stations. After that the rainfall maps provided for 9 storms. Finally Depth–Area–Duration curves provided using rainfall maps. Using this curves were derived rainfall amount in any region and duration.

Phosphorus (P) is an important nutrient for plants، in other hand P contaminates water resources. The present study aimed to access the applicability of rainfall and runoff variables of seven storm events occurred during 2008 in prediction of storm-wise peak and average P concentration and total P loss in Kojour watershed with the help of bivariate and multivariate regression models. Towards this attempt، seven storm events occurred during study period were analyzed، samples of river were collected for seven events with time intervals of 1 h. The results verified the capability of regression model with relatively high determination and efficiency coefficients of 0. 884، 0. 883 respectively. The results could facilitate the application of given methods obtained in the present study to other areas with similar conditions and leading to the suitable soil and water management.

Soil salinity and sodicity are escalating problems worldwide، especially in arid and semi-arid regions. This study investigates the effect of some mineral and organic amendments on reclaiming a saline- sodic soil based on distribution of soluble cations. The soil amendments consist of control، cattle manure، pistachio residue، gypsum، manure + gypsum and pistachio residue + gypsum; water treatments with and without sulfuric acid with three replicates were performed. At the end of experiments soluble cations were measured at different depths. The results indicated that monovalent cations and also the EC and SAR showed the lowest values near the soil surface، while bivalent cations had no significant variation with depth. This finding shows that monovalent cations would be more mobile than the bivalents. Also، it was found that in comparison with gypsum، sulfuric acid had more efficiency in the SAR decreasing. However، in calcareous soils، this aim would be achieved by only irrigation. Pistachio residue and cattle manure had the highest and the lost efficiencies in decreasing of the EC and SAR. The findings of this research reveal the relative importance and efficiency of pistachio residue in reclaiming of the sodium affected soil.