Although he has no opponent yet, Sen. Frank Church (D-Idaho), chairman of the Foreign Relations Committee, is collecting 1980 campaign money at a rapid pace in fund-raisers around the country,

Reports filed this week at the Federal Election Commission by the Idaho for Church Committee, based in Boise, show that more than $100,000 was raised between April and June for the campaign.

Among the individual contributors to the Church campaign were two of the largest owners of federally irrigated farmland in the West, who were keenly interested in legislation Church was then shepherding through a Senate committee.

Less than a month after the J.G. Boswell Co. political action committee in Los Angeles and Everett and Fred Salyer, of Corcoran, Calif., gave the Church campaign $4,500, the senator's committee approved a reclamation bill that protected their holdings.

Cleve Corlett, press secretary to Church, rejected any suggestion of a connection between the contributions and the bill reported out of the Senate Energy and Natural Resources Committee last month.

"Frank Church's record on reclamation reform is and has been widely known," Corlett said. "There is absolutely no connection between that bill and the campaign money - Frank has never done business that way."

During the same week that the Senate committee finished action on the reclamation bill, the Church campaign staged a fund-raiser at the Washington home of W. Averell Harriman, the former ambassador and New York governor.

Although the affair was held during the reporting period for which Church's committee filed statements, there is no indication of receipts from the Georgetown reception. Corlett estimated contributions at $50,000.

Reports circulating here before the event indicated that representatives of some of the larger western irrigated-land-owners were purchasing some of the $250 tickets.

Corlett said he could not explain why the Harriman party's receipts had not been included in the April-June report from Boise. Neither the committee's chairman not its treasurer could be reached yesterday for comment.

The legislation in which the Boswells and Salyers were interested was the Senate committee's rewrite of the Reclamation Act of 1902, the basis for the irrigation development of the West.

Church, although not chairman of the committee acted in that capacity during the panel's final work in streamlining and revising the 1902 law.

The committee bill is expected to be debated on the Senate floor within the next few days and will face stern opposition, including that of the Carter administration, which feels the bill is too lenient on large landholders.

The bill as written by the committee would exempt holdings in the Kings River and Kern River districts of California from acreage and other limitations.

Boswell, the country's largest cotton producer, has 90,000 acres in Kings River and about 25,000 acres in Kern. Boswell employes contributed $2,500 to the Church reelection campaign.

The Salyer brothers, who ponied up $1,000 each, have an estimated 35,000 acres in the Kings River project. The committee exempted Kings and Kern River on the ground that their water comes from Army Corps of Engineers projects, rather than Bureau of Reclamation projects.

Another group with a keen interest in the outcome of the Senate committee's work is the Desert Caucus, a political-campaign money group of land developers, bankers and lawyers, among others, in Tucson, Ariz.

The caucus' reports at the FEC show that it has given Church $2,000 for his 1980 campaign.

The reclamation law rewrite also will have an impact on the Central Arizona Project, which has an aqueduct running through Tucson. The Boswell firm holds between 15,000 and 20,000 acres in the Central Arizona Project.

Church and his political aides expect him to be the target of a concerted effort by conservative forces in the 1980 campaign, although he has no formal opposition yet. Rep. Steve Symms (R-Idaho) is considered a leading possibility to run against Church. CAPTION: Picture, Church has no opponent yet, but more than $100,000 has been raised for 1980. By James K. W. Atherton - The Washington Post