The Ana River originates in a series of springs located east of Winter Ridge, a high basin and range escarpment.
 The source springs are located near and under Ana Reservoir.
 The 60 acres (0.24 km²) reservoir is owned by the Summer Lake Irrigation District; however, the district's reservoir frontage property is surrounded by the Summer Lake Wildlife Area, a wildlife refuge operated by the Oregon Department of Fish and Wildlife.
 For most of its course, the Ana River flows through the Summer Lake Wildlife Area.

After leaving the reservoir, the Ana River flows southeast for approximately 2 miles (3.2 km) with private ranch land on its north bank and the Summer Lake Wildlife Area on the south bank.
 Then for a short distance, the river passes through Bureau of Land Management range land.
 As the river enters the Bureau of Land Management area, it turns south, reaching the River Ranch Campground in the Summer Lake Wildlife Area in about two miles.

Between Ana Reservoir and the River Ranch Campground, the Ana River retains its natural features and topography.
 It has a clearly defined channel, an unconsolidated bottom, and a narrow border of water dependent vegetation.
 The native aquatic vegetation is well established in that part of the river.
 In this area, the river flows through a small canyon with open range on both sides of the river.
 The vegetation along the river is dominated by big sagebrush, rabbitbrush, greasewood, needlegrass, ricegrass, and squirreltail.
 Trees are rare along the Ana River.
 However, there are a few native western juniper and small cottonwood and willow groves that were planted by early homesteaders.

Just after the River Ranch Campground, the Ana River turns toward the southwest and flows through a large impounded wetland.
 In this area, the Oregon Department of Fish and Wildlife uses a series of man-made dikes and channels to maintain critical wildlife habitat.
 The wetlands and marsh pools cover approximately 4,500 acres (18 km²).
Throughout the area, water from the river's main channel is diverted to maintain the wetland areas.
 In the marsh, vegetation varies from sedges, rushes, and bluegrass in the wetland meadows to cattails and bulrushes around the marsh pools.

In the lower part of the river, the water becomes increasingly alkaline.
 Approximately 7 miles (11 km) from its source, the Ana River empties into the north end of Summer Lake.
 At its mouth, the Ana River is very shallow, spreading out as it flows into the large endorheic lake.
The Ana River originates in a series of springs located east of Winter Ridge, a high basin and range escarpment.  The source springs are located near and under Ana Reservoir.  The 60 acres (0.24 km²) reservoir is owned by the Summer Lake Irrigation District; however, the district's reservoir frontage property is surrounded by the Summer Lake Wildlife Area, a wildlife refuge operated by the Oregon Department of Fish and Wildlife.  For most of its course, the Ana River flows through the Summer Lake Wildlife Area.
After leaving the reservoir, the Ana River flows southeast for approximately 2 miles (3.2 km) with private ranch land on its north bank and the Summer Lake Wildlife Area on the south bank.  Then for a short distance, the river passes through Bureau of Land Management range land.  As the river enters the Bureau of Land Management area, it turns south, reaching the River Ranch Campground in the Summer Lake Wildlife Area in about two miles.
Between Ana Reservoir and the River Ranch Campground, the Ana River retains its natural features and topography.  It has a clearly defined channel, an unconsolidated bottom, and a narrow border of water dependent vegetation.  The native aquatic vegetation is well established in that part of the river.  In this area, the river flows through a small canyon with open range on both sides of the river.  The vegetation along the river is dominated by big sagebrush, rabbitbrush, greasewood, needlegrass, ricegrass, and squirreltail.  Trees are rare along the Ana River.  However, there are a few native western juniper and small cottonwood and willow groves that were planted by early homesteaders.
Just after the River Ranch Campground, the Ana River turns toward the southwest and flows through a large impounded wetland.  In this area, the Oregon Department of Fish and Wildlife uses a series of man-made dikes and channels to maintain critical wildlife habitat.  The wetlands and marsh pools cover approximately 4,500 acres (18 km²). Throughout the area, water from the river's main channel is diverted to maintain the wetland areas.  In the marsh, vegetation varies from sedges, rushes, and bluegrass in the wetland meadows to cattails and bulrushes around the marsh pools.
In the lower part of the river, the water becomes increasingly alkaline.  Approximately 7 miles (11 km) from its source, the Ana River empties into the north end of Summer Lake.  At its mouth, the Ana River is very shallow, spreading out as it flows into the large endorheic lake.
Ana River