تقييم حركة الرسوبيات في القنوات الاروائية الصغيرة (تفرعات شط الحلة كحالة دراسية )

Abstract

In this research, a field and laboratory study have been conducted to evaluate the movement of sediment load in irrigation canals of small discharge. Ten irrigation canals ( divided into two groups A & B) branching from the main canal (Shatt Al-Hillah) were selected, which characterized by different hydraulic parameters . The research started from the date of 1 / 8 / 2014 , and continued for a period of time about 14 months . The results showed that the soil texture at the upstream of canals section was more rough and homogeneous compared to the section of downstream, and the silt ratio increased by twice at the downstream section. The relative density of soil was about 2.68 . Sediment concentration at the downstream section of canals increased with the amount of (64, 41 ppm) for the two canal groups (A & B) respectively , besides the increasing of concentration ratio of 50% in summer and 21% in winter of the downstream section compared to the upstream section of canals.The results proved that the decreasing rate in the flow section and hydraulic depth was about 34% at the downstream of canals, which means that the canals of groups (A & B) are classified as unstable and unbalanced canals . Also the search stated that the application of Van_Rijn , Engelund and Hansen equations is the closest to the result of a field discharge of sediments compared to the other studied equations , with correlation coefficient not less than 97% for their positive logarithmic relationships . Results indicated that the water discharge and the shoulder slope of canal cross – section have a clear role in determining the amount of sediment load .The results showed that the water discharge effects on the calculations of suspended & bed sediment loads,and the relationship between them is a positive logarithmic. Also it stated the positive logarithmic relation between the field sediment discharge and these loads. The ratio of suspended to bed loads is about 30 times at the upstream section , while it was about 110 times in the downstream section of canals .