A SUMMER OPERA tour in Western America points up two inexorable facts: the watering holes are few and far between, and the springs do not run especially deep, nor flow too bounteously.

Indeed, opera all but dries up during the summer in the West, since San Francisco abandoned its summer season, Seattle gave up its Ring cycle, and the Colorado Festival drew in its horns. Even light opera is in short supply on any significant basis.Undaunted, we set out in early August to see the Mountain West's two major summer opera festivals - at Central City, Colo., and Santa Fe, N.M. - covering 2,000 miles in 10 days.

My impression remains basically the same as 10 years ago when I first made the Santa Fe junket, and eight years ago at Central City: if you want entertainment, go to Colorado; if you want esoterica, try Santa Fe.

The opera at Central City, in the historic opera house at the top of a tourist-oriented town that thrives on mining memorabilia, dates back more than 50 years. Since then, the old gaslight theater has yielded its boxes and much of its charm to some doubtless necessary enlargement. But the straight wooden chairs remain, and a crier with a loud bell announces curtain time before the show, even invading the Teller House next door to alert lingering diners.

Since the early '30s, Central City has been an outpost for Broadway and other professional stars, both dramatic and musical. Dark for a few seasons in the early '80s, the theater has been revived under John Moriarty's artistic direction and was in good estate for the past summer's lively fare.

Casting is regional opera style, with the sort of up-and-coming names one would find on Utah Opera bills. Competent apprentices comprised one of the finest opera choruses anywhere, and filled small roles with panache.

"The Ballad of Baby Doe" by Douglas Moore led off the season, in its sixth Central City mounting since it premiered there in 1956. The fascinating story of beautiful Elizabeth Doe who split up Horace and Augusta Tabor is a natural for the little theater, since its true counterpart unfolded in nearby Leadville and Denver, and Donald Onslager's original designs could hardly be improved upon.

Authoritative baritone Brian Steele of New York City Opera took charge as the rambunctious Silver King, Amy Burton was a spirited yet tender Baby Doe, who made the most of her fine solos, and Dana Krueger, a veteran Augusta, maintained a poignant portrayal of a Victorian woman gnarled within and without, and eventually hardened into immobility.

Central City does not shrink from grand opera, usually doing two a season along with a light opera. This year's heavyweight was Verdi's "Macbeth," which one little imagined could be done on so small a stage. Yet it proved surprisingly adaptable to intimacy, with its soliloquies and eerie encounters.

International baritone David Holloway has the right voice for Macbeth, but his acting was stolid, never really conveying the man's paranoia and hysteria. Though dramatically inexperienced, Christine Seitz brought exciting vocal timbre and heft and natural feeling to Lady Macbeth. Andrew Wentzel made a humanly engaging Banquo, and the chorus was topnotch, but the witches' sedate costumes placed them more logically in Salem, rather than crawling from under a rock on a Scottish moor.

Central City's commitment to the operetta resulted in "The New Moon" by Sigmund Romberg, which brought out the over-50 crowd in droves for an afternoon of nostalgia.

The plot is vapid frou-frou set in New Orleans of 1792, a dated pastiche of foolishness and high-minded sentiments involving bond servants, transported brides and provincial French royalty. Yet Romberg lavished some of his finest tunes on this show - "Wanting You," "Stouthearted Men," "Softly as in a Morning Sunrise," "One Kiss," and "Lover Come Back to Me."

Utah Opera favorite Eric Allen Hanson cut a dashing figure as Robert Mission, a nobleman in bond servant's clothing. Hanson will return in U.O.'s season-opening "Lucia." Also coming to Utah in "The Marriage of Figaro" is Maryanne Telese, who sang the pampered, rich heroine, Marianne. Telese is like the young Roberta Peters in vivacity and voice, though she has a disquieting tendency to spin the tone too far over into the head.

Next year, should you turn up between July 8 and Aug. 13 at Central City, you may chose from "Lucia di Lammermoor," "The Magic Flute" and Romberg's "Desert Song."

[For comments on the Santa Fe Opera season, see next Sunday's arts section.]