drains . Most of its major tributaries are dammed, including the Kent, Alpine, Bon Tempe, Lagunitas, and Nicasio reservoirs. The San Geronimo Valley is the last un-dammed headwater tributary of Lagunitas Creek. Each of the reservoirs in the watershed has a dam and the biggest problem in the watershed is their blocking of the streams, which prevents fish migration. The dams dewater the streambed, especially as the first winter rains fill the reservoirs instead of flowing downstream. Also, water from the late winter rains are partially lost from streamflows because of evaporation from the reservoir surfaces. Erosion is also a significant problem in the watershed. Sedimentation from Lagunitas Creek into Tomales Bay resulted from nineteenth century logging and cattle grazing of riparian plants which otherwise slow erosion. However, sediment loads have been decreasing since the mid-twentieth century and the tidal marsh at the mouth of the creek is no longer aggrading likely due to sediment capture in the many upstream reservoirs. Sir Francis Drake Boulevard follows the course of San Geronimo Creek west and then north along mainstem Lagunitas Creek through Samuel P. Taylor State Park. Ecology The Lagunitas Creek Watershed is home to the largest remaining wild run of coho salmon (Oncorhynchus kisutch) in Central California. These coho are part of the "Central California Coast Evolutionarily Significant Unit," or CCC ESU, and are listed as "endangered" at both the state and federal level. The CCCESU has declined from an estimated 50,000–125,000 adult returns to only 500 spawning adults, and is at high risk for extinction, with only 67 adults returning in 2013. Significant efforts to protect and restore these fish have been underway in the Watershed since the 1980s. Before Seeger Dam was constructed in 1960 by the Marin Municipal Water District (MMWD), Nicasio Creek supported half of the steelhead trout (Oncorhynchus mykiss) and coho salmon spawning populations in the Lagunitas Creek watershed. The 50% of remaining historical salmon habitat in the Lagunitas Creek watershed is now also behind dams. Because dams also block sediment transport, there is a lack of suitable spawning gravel in many lower stream reaches for spawning. Most spawning in the Lagunitas Creek watershed now takes place in San Geronimo Creek, an unregulated tributary, and the region immediately downstream of its confluence with Lagunitas Creek. Strong efforts are also being made to protect and restore undammed, headwater reaches of this Watershed in the San Geronimo