一级河流

根据一级河流阶地沉积物的~（14）C测年资料估算，平均年上升速率约为3毫米。

According to the data of 14C dating of terrace sediment in the first class river , it estimates that the ascendant rate is about 3 mm per year .

三峡库区蓄水135米后，发现部分一级河流的回水段出现了不同程度的富营养化现象，引起了广泛关注。

After the water level of the Three Gorges Reservoir rising to 135 meters , it has been discovered that there appears the phenomenon of eutrophication to varying degrees in the backwater section of part of first-level rivers , which has aroused the general concern .

主要考虑了该地区一级河流支流的影响，根据模型的率定结果分析，该模型具有较高的模型精度，模型所取的参数能较好地反映该段的河道特点。

In accordance with the results of the model calibration analysis , the model which considers the major tributary of the Yangtze River has a high accuracy . The model by choosing the parameters can better reflect the topographic features , so the model is available .

利用1：50000的地形图对香溪河的河级划分，研究发现香溪河为一条6级河流。

The stream of Xiangxi River system was divided into six orders based on 1:50,000 relief maps .

到目前为止，海南省的环境一直处于良好的状态，大气环境各项指标基本上符合国家一级标准，全省河流和水库中的水有80%符合国家地面水环境质量类及以上标准。

Up to now , Hainan environment has been in good situation , indexes of atmosphere basically come up to the state 's first grade standard , and 80 % of water in the rivers and reservoirs of the whole province agrees with the second grade standard for surface water .