Study of Permability Changes in Water Spreading Projects. (Case Study: Jajarm Projects)

Study of Changes in surface soil permeability of flood spreading system، which in the past years has been built in the country، is one of the most important issues in this field. Changes in soil permeability have been studied in different fields. Flood spreading station is located in Jajarm city of North Khorasan province and 15 years of data have been recorded. In this study، the permeability of the soil in a field of 223 hectares of the first phase flood spreading has been studied. In this regard in 9 strips of spreading 27 samples and Adjacent to strip at outside the spreading area، Infiltration test have been done by double rings. Results show that the average permeability in control samples 5. 22 cm per hour which Classified based on surface permeability in the range of moderate permeability. In Flood spreading system، permeability has varied from 0. 88 at the first strip to 4. 19 cm per hour at the ninth strip And the average for all strips are 3. 23 cm per hours. These changes are due to differences in the frequency in flooding of strips. Permeability reduction in various strips in compared with observed area، have seen from maximum of 83% in fist strip to 11. 7 % in the eighth strip. The results show that the firs strip has slow permeability and strips 2 to 4 is in near slow classification and strips 5 and 9 still remain at a moderate level. Permeability reduction dependence of Flood number is significant at 99% confidence level.