USING ¹³⁷Cs TRACER TECHNIQUE TO INVESTIGATE SOIL EROSION DISTRIBUTION AND TOTAL EROSION AMOUNT IN TAIHU LAKE CATCHMENT

The soil erosion distribution of different landforms and land use types in Taihu Lake catchment was investigated by using ¹³⁷Cs tracer technique, and the total annual erosion amount was primarily estimated by the distribution of soil erosion and area of each land use type. The results show that the erosion rate of middle mountain side is equal to the average of the total slope at the same land use type. In Taihu Lake basin, the upper and middle mountain side is main natural forest lands with a low erosion rate of 186.6 t/km²· a, while the lower mountain side is main tea plantations with a high erosion rate of 3 898.5 t/km²· a. The erosion rates of paddy fields in plain are positively related to their distance to the hill. The accumulation rate of paddy fields at the mountain food and the erosion rate of paddy fields near the lake are 2 585.9 t/km²· a and 6 325.7 t/km²· a respectively, and the average erosion rate of paddy fields in Taihu Lake basin is 1 869.9 t/km²· a. The total annual erosion amount is about 3 446.7 10⁴ t/a, which induced about 34.5 10⁴ t/a transport into the Taihu Lake. The result is consistent with monitoring data suggesting that soil erosion is the main source of the sediment in the Taihu Lake basin. Our study primarily proved the feasibility of quantifying the relationship between soil erosion and lake sediment flux by using ¹³⁷Cs tracer technique.