Assessment of the Runoff Production within Marly Units in Geological Formations in Zandjan Province by Using an Rain Simulator

Marly units cover about 4438 square kilometers, i. e. 20 per cent of Zanjan province territory. In this paper, the volume of runoff within marly units in Zanjan province was studied using a rain simulator. In this regard, by overlying slope, climate, and marly units of geological formation maps, a number of 18 homogeneous units were distinguished using ArcGis 9.3 software and during field operations, runoff within 1*1 meter plots were recorded within each homogeneous unit, by incorporating a rain simulatorand an overall of 220 plots were tested. Data collected from field operations, were analyzed on the basis of Randomized Complete Block Design with Factorial Treatment Structure, General Linear Method (GLM Model) procedure, F Test and Duncan Multiple Range Test. Investigation into the links between lag time, volume, and the coefficient of runoff within marly unitssuggested that the association will be described by a second power equation, by which trends of differences ill be interpreted. The results of analyses showed that the effect of homogeneous units on the variations oflag time of runoff is significant; while the effect of climate is not significant. The effects of homogeneous units and slopes on volume and coefficient of runoff of marly units were significant; but, slope and climate factors had no effect on these two characteristics. A closer scrutinizing of averages showed, according to volume and coefficient of runoff, homogeneous units can be classified into four groups; on the bases of volume and coefficient of runoff of these groups, they were significantly different. The more silt content of soil, as a result of low or scant water holding capacity, the shorter lag time and larger volume of runoff is expected. The lag time of runoff, homogeneous units were classified into three groups. As well the effects of slope and climate on volume and coefficient of runoff of homogeneous units were also significant.