[en] We have already reported the migration of ⁹⁰Sr and ¹³⁷Cs in lake sediment (Ogi Dam) and its forestry catchment. The ⁹⁰Sr infiltrates more to 10 cm soil profile in contrast to ¹³⁷Cs, showing a faster vertical migration of ⁹⁰Sr than that of ¹³⁷Cs. Sediment to soil ratio for ⁹⁰Sr showed a higher value than that of ¹³⁷Cs, which depicted more horizontal flowing of ⁹⁰Sr from forest soil to lake sediment than ¹³⁷Cs. The surface sediments became relatively uniform by the disturbance near surface (0∼4 cm) for ¹³⁷Cs. Cesium-137 adsorbed strongly to sediment became uniform, while ⁹⁰Sr weakly adsorbed to sediment re-dissolved to the lake water. The re-dissolved ⁹⁰Sr was adsorbed to the sediment again (0∼1 cm). Therefore, the sediment (0∼1 cm) has significantly higher ⁹⁰Sr concentration compared to the rest. The ⁹⁰Sr concentration of 4∼5 cm lake sediment is higher than that of 1∼4 cm, which might suggest the migration by pore water. In the present study, we discussed the distribution and migration of ⁹⁰Sr and ¹³⁷Cs using solid-liquid distribution coefficient (K_d), The larger K_d for ¹³⁷Cs revealed the slow migration in the soil, while the smaller K_d for ⁹⁰Sr revealed the fast migration in the soil. The first horizontal migration of ⁹⁰Sr from catchment to lake was explained by the elution of ⁹⁰Sr from the soil surface. The distribution in the lake sediment was also explained using K_d. The present discussion is based on the simple model. The more detailed discussion is needed by considering a biological diffusion and more detailed environmental factors. (author)