The little-known-so-far but ecologically significant San Diego National Wildlife Refuge Complex includes two units of coastal marshland along San Diego Bay, plus a much larger unit of inland territory near Jamul. Assuming that certain private lands are purchased and consolidated with federal lands, the inland section could end up with as many as 44,000 acres of relatively undisturbed sage-scrub, chaparral, and freshwater marsh landscapes. A recent acquisition of private land within the refuge along the Sweetwater River, just upstream from Sweetwater Reservoir, has opened much of that easily accessible area to legal visitation by hikers, bicyclists, runners, and birdwatchers.
The old Steele Canyon bridge over the Sweetwater River (east on Campo Road from the Jamacha Road junction) is a good place to start a cursory exploration of the new refuge property and its riverine habitat. The old bridge, which parallels a wider and newer concrete one, has been left in place for the benefit of bicyclists and hikers. There's room to park on both sides of it. Walk or ride over to Singer Lane on the bridge's west side, go a short distance, and then follow the access road on the left signed "11901 Singer Lane." After a few minutes' walking you'll be alongside a water-treatment plant. Just beyond that, miles of open space lie ahead, practically devoid of development save for a line of new houses creeping over the ridge to the right. The sluggishly flowing Sweetwater River lies to your left, its waters hidden by a screen of willows and other dense riparian vegetation -- home to endangered species of birds, such as the least Bell's vireo. Beyond that green strip, scrub-covered slopes, fluted with shallow ravines, rise toward antenna-bewhiskered summit of San Miguel Mountain.
After one mile of travel the canyon walls close in to form a shallow gorge, and at 1.5 miles, you'll notice a large pipe, armored with razor wire, crossing high above the river. Continue on the wide trail ahead for an additional 0.4 mile to where a narrow path descends obliquely left. For further exploration ahead, you can follow this path down through a gap in the green riparian strip and across the possibly wet or muddy river bottom to a trail on the far (left) bank of the river. By following that trail, which is signed in places, you can swing around the southern shore of Sweetwater Reservoir and eventually reach Sweetwater Summit County Park, about four miles away.