|关键词: 泥沙淤积 龚咀水库
|Characteristics and sediment deposition in Gongzhui Reservoir of the Dadu River
Department of Geo and Ocean Sciences Nanjing University Nanjing 210008
|The total storage capacity of Gongzhui Reservior, the largest one in the Daduhe River, was 3.1×108m3.The average annual runoff of the Daduhe River is 4.74×1010m3/a, while the amount of sediments is 3.249×107t/a.of which pebble bed load is 9.24×105t/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 ×108m3, making up about 71.3% of storage capacity.About 2.14 ×108m3 of sediments depositing in the dead capacity were silted up.Meanwhile the loss of effective capacity was l.2%.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 development, 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 (dcp) increasing from 1.82mm to 3.38mm.However, in the third staget 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.
|Key words: sediment deposition Gongzhui Reservoir Dahu River