求翻译：污染物进入河流后，在一定范围内经过平流输移、纵向离散和横向混合后达到充分混合，或者根据水质管理的精度要求允许不考虑混合过程而假定在排污口断面瞬时完成均匀混合，可按一维问题概化计算条件，建立水质模型。是什么意思？

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pollutants into rivers, to a certain extent, after the transfer, vertical separation and Horizontal mixed up to full hybrid, or in accordance with Water Quality Management the accuracy requirements are not allowed into account mixing process, on the assumption that the sewage section transient compl

After the pollutant enters the rivers, loses in certain scope after the advection moves, longitudinal separate and the crosswise mix achieved the intensive mixing, or according to the water quality management precision request permission did not consider the mix process supposes in the pollution out

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正在翻译，请等待...