Research on the Sedimentation and Erosion Problem of Ergene River Basin in Western Turkey and Precautions to Control

摘要

The objective of this study were to asses the rainfall-runoff-sedimentation relationship from directly measured data since 1972 and to find out the effect of present land use and soil cultivation techniques on the sediment yield, and finally to offerpractical solutions to the problems in Ergene River Basins located in the European Part of Turkey. Suspended sediment yield was calculated multiplying daily average discharged water by average sediment concentration while the eroded coarse sediment yieldwas computed using a regression equation developed by Japanese Ministry of Construction. The relationship between the runoff and suspended sediment rates was explained exponentially as S = 1.99 , QA'-62 P > 0.01 and R: = 0.846 S is suspended sedimentrate in t d'1 and QA is average daily runoff rates in in-1 s－1. The suspended sediment rates of Ergene Basin can then be predicted from the flow rate at any time of the year using this produced regression equation. According to the results. 70 % of thebasin's soil 9534 km2 and occupies 81.76 % of the total area of the region is under erosion hazard varying in intensity, namely 25.3 % light, 34.6 % moderate, 8.6 strong and 1.5 % very strong. 47.09 % of the average 604 mm precipitation falls in the critical period of October-January in terms of sedimentation. The coarse and suspended sediment yield was 74.040 t km2 per year, which was well below the average of Turkey. However, it was 2 and 2.5 times larger than the average of Europe and Africa, respectively. Being 76.93 % of the eroded land from the lm, 2nd and 3rd class cultivated land proves the severity of the sedimentation. The causes of high sediment yield were identified and a serious of precautions was suggested to minimize.