Although Mopang Stream in Washington County is a significant tributary of the Machias River, it’s rarely paddled. Limited road access, obtaining a reliable description and determining an adequate water level make planning a trip complex. Another complication: Since it enters the Machias River some distance from dependable road access, an overnight trip is necessary.

This spring, I decided to incorporate Mopang Stream into a multiday trip that included two days on the Machias River. Two of my regular river-tripping companions, Ken Gordon and Eggman DeCoster, also wanted to explore the elusive stream.

Ascertaining the necessary water level was my first consideration. There is no online gauge for Mopang Stream (or the Machias River), but I concluded the gauge for Old Stream, another Machias River tributary with a similar-sized watershed, would be a good indicator. I’ve been using the Old Stream gauge for years as a guide for Machias River levels and deduced that a flow of at least 70 cubic feet per second (CFS) was necessary for Mopang to be passable.

A quality weather forecast was also needed. We identified an excellent, late-April, three-day forecast, and the Old Stream gauge was 110 but dropping.

The Appalachian Mountain Club’s Maine river guide states the distance from Route 9 to the Machias River near Wigwam Rapids is 23.75 miles. Based on our calculations, using the Delorme Atlas, we concluded the actual mileage for the winding stream was only about 15 miles.

We made a reservation to stay at a Downeast Salmon Federation cabin at the Wigwams on the first night of our trip. Given the estimated distance, that goal appeared easily attainable.

Three of us met at the Mopang Stream landing on Route 9 a few miles east of Beddington on a warm, sunny morning. The Old Stream gauge read 73. Seemingly, all of the required elements were in place.

The water level seemed adequate when we launched two expedition kayaks and a canoe in quick water on the narrow stream. Numerous blowdowns were an early impediment that required careful negotiation and slowed our progress.

Initially, rapids were short and steep but too shallow for fluid descents in our heavily loaded boats. Instead, we maneuvered down narrow, congested channels. Although passable, more water would have been an improvement.

Signs of beaver activity were abundant throughout the trip. At one location, we plunged over a vertical, four-foot beaver dam. Following our maps as we traveled downstream, progress was slower than anticipated.

The rapids lengthened and blowdowns continued to the first of several pipelines that mysteriously cross the stream. Some were submerged while others interfered with navigation. At one point, we passed under a bridge with an attached pipeline on what we surmised was Shadagee Road.

Below, we entered an extended circuitous stretch of flat water. We weaved for several miles through a swampy valley with blueberry barrens visible high above. Near the end, we passed through a large culvert under a road we couldn’t identify. It was getting late.

Soon after, the gradient steepened and more rapids ensued. We began watching for Penman Rips, purportedly the most challenging falls on the stream. When rounding a sharp bend in whitewater, Eggman caught an emergency eddy and signaled to stop. He was perched at the top of a precipitous pitch and a downed tree blocked the primary channel.

We scouted the long, difficult falls, which I rate Class IV, from river left. Due to the fallen tree, the only option was a series of three steep, shallow slides through narrow, boulder-enclosed slots followed by a rocky runout for as far as we could see. I lined my kayak along the slides while my companions successfully bounced down.

The remainder of Penman Rips required maneuvering through a continuum of boulders in narrow, twisting passages that tested our skills. Subsequently, we navigated through a few short rapids and several miles of calm water to the Machias River.

After descending through big waves in First Wigwam Rapid, we finally reached the much-anticipated cabin shortly before dark. Our voyage on Mopang was a learning experience. We needed more water, and the distance reported in the AMC’s “River Guide: Maine” is likely correct.

We had two more days of exciting paddling remaining on the Machias River.

My book, “Maine Al Fresco: The Fifty Finest Outdoor Adventures in Maine,” narrates the six best river trips in Maine.

Ron Chase resides in Topsham. His latest book, “Maine Al Fresco: The Fifty Finest Outdoor Adventures in Maine” is available at northcountrypress.com/maine-al-fresco or in bookstores and through online retailers. His previous books are “The Great Mars Hill Bank Robbery” and “Mountains for Mortals — New England.” Visit his website at ronchaseoutdoors.com or he can be reached at ronchaseoutdoors@comcast.net.