From Steve Schweitzer's A Fly Fishing Guide To Rocky Mountain National Park, flyfishingrmnp.com:
This river page and description is for a few hundred yards upstream of Sprague Lake.
Boulder Brook feeds Sprague Lake from the southwest. It is a quaint little stream above the marshy area and beaver dam just to the southwest of the lake. While past ...
From the center of Estes Park, take Moraine Avenue, also known as Highway 36 West, for 3.5 miles to the Beaver Meadows Entrance Station, Proceed past the visitor center and turn left onto Bear Lake Road. From Bear Lake Road, turn south onto Sprague Lake Road a little over 5 miles from the Beaver Meadows Entrance Station. This road leads to a large parking lot and picnic area immediately west of Sprague Lake.