大渡河龚咀水库泥沙特性与淤积

CHARACTERISTICS AND SEDIMENT DEPOSITION IN GONGZHUI RESERVOIR OF THE DADUHE RIVER

龚咀水库库容3.1×10~8m^3,是大渡河上最大的水库,从1971年蓄水以来的15年间,淤积量达2.2096×10~8m^3,占库容的71.3％。淤积可分蓄水初期,三角洲发展和淤积接近平衡三个时期,其淤积率分别为83.5％,53％和2.9％。淤积物的平均粒径从1.82mm增加为3.38mm。卵砾推移质移动至坝前。淤积量变化过程即为输沙能力调整恢复过程。

The total storage capacity of Gongzhui Reservior, the largest one in the Daduhe River, was 3.1×10~8m^3. The average annual runoff of the Daduhe River is 4.74×10^(10)m^3/a, while the amount of sediments is 3.249×10~7t/a, of which pebble bed load is 9.24×10~5t/a, making up 2.85％ of the total. At Gongzhui Reservior there is about 88％ of pebble and gravel bed load with hardness being more than 6 (measured by Mo-hardness metre). Gongzhui Reservior began to impound water in October 1971. During fifteen years of oparation, up to the end of 1986, the total sediments reached to an amount of 2.2096 ×10~8m^3, making up about 71.3％ of storage capacity. About 2.14×10~8m^3 of sediments depositing in the dead capacity were silted up. Meanwhile the loss of effective capacity was 7.3％. According to the deposition processes, the depositional development in Gongzhui Reservoir can be considered as three stages, namely, reservior imounding water in initial stage, delta devolopment, and equilibrium transport and deposition. Fig. 2 shows the change of the accmulated deposits with time. It can be seen that in this figure the cumulative deposition increased rapidly in the first stage and the depositional rate reached up to 83.5％. In the second stage, the reservior delta devolops rapidly, moving toward the dam while the deposition amount reduced gradually with the deposition rate 53％. After sedimentation, the sediments became much coarser with an average grain size (d_(cp)) increasing from 1.82mm to 3.38mm. However, in the third stage, the depositional rate was only 2.9％, approaching to equilibrium. At the same time gravel and pebble bed loads moved toward the dam and then settled down to it. In conclusion, deposition process can be regarded as sediment transportation process.