A drop here, a drop there, the United States government is beginning to join the effort against the blight of acid rain. Acid rain is, forgive us, the umbrella term for various kinds of chemically polluted precipitation blamed for severely damaging lakes, forests, soil, living creatures, and man-made structures. Here are a few signs of activity in Washington amid all the temporizing on the subject:
* Congress is considering legislation to require substantial reduction of poisonous industrial emissions blamed for contributing to acid rain.
* Secretary of State Shultz has stepped up discussions with Canada, which - like the US's own Northeast - wants action to control air polluters. He has called for ''disaggre-gating'' the problem; that is, breaking off pieces of it to be solved on the way to more general solution.
* President Reagan has told his new environmental chieftain, William Ruckelshaus, to meet the issue ''head on.'' Mr. Ruckelshaus reportedly plans to require increasing antipollution standards without waiting for more of the endless official study process that has often been used to excuse inaction.
* A significant stage in the official study process was reached this week when an interagency task force's report nudged the administration away from a position it has shared with some of the polluting utilities: a position stressing lack of knowledge about acid rain and the possible role of natural causes. The report echoes much independent opinion in stating that the major sources are power plants, factories, and vehicles. Thus Mr. Ruckelshaus has no reason for delay in establishing the best ways to control those sources.
* Another far-reaching study is coming close to completion. It was started under a memorandum of understanding between the US and Canada. The results of joint working groups are being examined by independent peer review panels on both sides of the border. The panels will compare notes in July and probably report in August.
It may be too early for actually singing in the rain, but perhaps a small whistle now would not be entirely whistling in the dark.