农业非点源污染是水系或水体水质恶化的最主要原因，同时也是土地生产力退化的直接动因，农业非点源污染又往往与流域水文过程具有不可分割的关系。

As the main reason for the worse water quality, agricultural non-point pollution, which also causes soil productivity to degenerate directly, is tightly related with the hydrological process.

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