About the Mad River

Watershed Background

The Mad River Watershed is approximately 100 miles long and drains about 500 square miles of coastal hills within Humboldt County.  Mountain range elevations are from 6,000 feet at the headwaters to 3,000 feet along the western ridge.  The Mad River flows through, around and over a mélange of Franciscan bedrock geology, composed of an assemblage of radiolarian cherts, greywacke sandstone, limestone, serpentinite, shale, metamorphic and sedimentary rocks that are geologically unstable[1]. Surrounding vegetation is composed of coniferous forest (Douglas Fir, Spruce, and Redwood) toward the coast, while upland and interior are mixed hardwood forest, grassland, and in some areas riparian canopy.  The Mad River watershed is partitioned into three sub-watersheds: The Upper Mad River begins at the upper headwaters and concludes at Matthews Dam on Ruth Lake; the Middle Mad River extends from Matthews Dam downstream to the confluence of Cowen Creek; and the Lower Mad River runs from Cowen Creek through the estuary and to the mouth where the Mad River empties into the Pacific Ocean[2].  The Mad River estuary is recognized for protection by the California Bays and Estuaries Policy. “Estuaries, including coastal lagoons, are waters at the mouths of streams which serve as mixing zones for fresh and ocean waters. Mouths of streams which are temporarily separated from the ocean by sandbars shall be considered as estuaries. Estuarine waters will generally be considered to extend from a bay or the open ocean to a point upstream where there is no significant mixing of fresh water and seawater. Estuarine waters shall be considered to extend seaward if significant mixing of fresh and saltwater occurs in the open coastal waters. Estuarine waters include, but are not limited to Sacramento-San Joaquin Delta… …appropriate areas of the Smith, Klamath, Mad, Eel, and Russian Rivers”.[3]Humboldt Bay was not discovered until 1850 [4] and much of Humboldt County was untouched by Euro-American settlers until after the bay’s discovery.  Within 150 years much of the old growth forests have been cut down, resulting in old growth forests footprint representing less than 2% of what was once historically present.  A resource based economy led to rapid development around Humboldt Bay resulting in a concentration of the counties population.  Today nearly two thirds of the people living in Humboldt County live within 30 miles of the Mad River Watershed.Early logging practices within the Mad River watershed did not take into consideration the biology, or the geology of the area, and current land managers are still dealing with these legacy issues.  The Bureau of Land Management and the USDA Forest Service manage most of the upper one-third of the watershed. The industrial timber lands are owned and managed by a handful of companies including: Green Diamond Resource Company (the largest private land owner in the watershed), Sierra Pacific Industries, and Humboldt Redwood Company.  Most recent land uses within the watershed include Industrial and non Industrial timber harvest, cattle ranching, agriculture, gravel mining, urban and rural residential development, roads, and other infrastructural development.“In 1992, the Environmental Protection Agency added the Mad River to California’s Clean Water Act Section 303(d) impaired water list due to elevated sedimentation/siltation and turbidity. The North Coast Regional Water Quality Control Board (RWQCB) identified water temperature as an additional impairment to the watershed in 2006. The Total Maximum Daily Loads (TMDL) for sediment and turbidity were established in accordance with Section 303(d) of the Clean Water Act on 21 December 2007.”   MRWAThe Mad River is the source of drinking water for approximately 65% of Humboldt County’s Population.  The Humboldt Bay Municipal Water District (HBMWD) formed on March 19, 1956, and is currently supplying drinking water to 80,000 Humboldt County residents in the cities of Blue Lake, Arcata, Eureka, and the unincorporated areas of Mckinelyville, Fieldbrook, Glendale, Manila, and other rural residential areas within the county[5]. The California Department of Fish and Game has operated a fish hatchery on the Mad River since 1971. It was established as an enhancement hatchery to supplement ocean fish stocks to catchable levels and provide for sport fishing opportunities in the Mad River. The hatchery currently releases about150,000 juvenile steelhead annually in the spring[6].  It is also used as a rearing facility for salmonids that originate from and will be released back into other basins. The hatchery also raises rainbow trout for local put-and-take fisheries. Between 1990 and 2000, the hatchery released between 134,000 and 1,440,460 Age 1+ juvenile steelhead in the Mad River (Zuspan and Sparkman 2002).“Chilcote (2001 and 2003) reported that wild steelhead populations can decrease as more hatchery steelhead intermix with wild fish. McLean et al. (2003) reported that hatchery steelhead that spawn in the wild have a much lower reproductive success rate than wild fish. Chilcote (2001) estimated that if the proportion of hatchery fish in the wild exceeds 60% then the wild steelhead population may no longer be able to replace itself and would eventually become extinct. The Zuspan and Sparkman (2002) mark and recapture study found that hatchery fish comprised 91.7% of the population with wild fish making up the remaining 8.3%.[7]
The Mad River Watershed provides habitat to a wide array of flora and fauna surviving within the riparian corridor from the headwaters to the estuary.  A number of threatened Species Act (ESA) listed fishes live in the river, including: Chinook (Oncorhynchus tshawytscha) and Coho salmon (O. kisutch), summer and winter-run Steelhead (O. mykiss), Eulachon (Thaleichthys pacificus), and Longfin smelt (Spirinchus thaleichthy) are found within the Mad and it’s estuary.  

  • The Mad River contains fall-run Chinook salmon that are part of the California Coastal (CC) Chinook Evolutionarily Significant Unit (ESU). CC Chinook salmon were listed under the ESA as threatened on 16 September 1999 (64 FR 50394).”[8]
  • The Mad River contains Coho salmon that are part of the Southern Oregon/Northern California Coast (SONCC) ESU. Coho salmon were listed under the ESA as threatened on 6 May 1997(62 FR 24588).”[9]
  • “The Mad River contains winter-run and summer-run steelhead, which belong to the Northern California (NC) Distinct Population Segment (DPS). NC steelhead were listed as threatened under the ESA on 7 June 2000 (65 FR 36094)”.[10]
  • “On March 18, 2010, we listed the southern Distinct Population Segment of Eulachon (Thaleichthys pacificus; hereafter, “southern DPS”) as threatened under the Endangered Species Act (ESA) (75 FR 13012). National Marine Fisheries Service (NMFS) identified the geographical area occupied”.[11]
  • The Mad River Estuary contains Longfin smelt which On March 5, 2009 the California Fish and Game Commission determined that longfin smelt should be listed as threatened throughout their range in California which includes Humboldt bay and nearby river/ estuary systems.”[12]
  • Other native fishes include resident rainbow trout, coastal cutthroat trout, California roach, three-spine stickleback, riffle and prickly sculpins, pacific lamprey, brook lamprey, green sturgeon. and the Humboldt sucker. Non-native fish species include brown bullhead, channel catfish, Sacramento sucker, largemouth bass, crappie, and bluegills.[13]” Endangered avian species found within the riparian corridor include: the Willow Fly Catcher, Yellow Billed Cuco, Marbled Murrelet, and the Western Spotted Owl. Sensitive amphibians include the northern red legged and yellow legged frog, torrent salamander, and tailed frog. A species of concern, the Western pond turtle is also found within the Mad River.  The listed species above are only just a brief summary of some of the key species.


[2] Mad River Watershed Analysis (MRWA)

[3] Water Quality Control Policy For The Enclosed Bays and Estuaries of California as Adopted by Resolution. 95-84  State of California 11/16/95

[4] Wikipedia,

[5] Humboldt Bay Municipal Water District, Habitat Conservation Plan

[6] Mad River Watershed Assessment June 2010 Stillwater Sciences

[7] Mad River Watershed Assessment June 2010 Stillwater Sciences

[8] Mad River Watershed Assessment June 2010 Stillwater Sciences

[9] Mad River Watershed Assessment June 2010 Stillwater Sciences

[10] Mad River Watershed Assessment June 2010 Stillwater Sciences

[11] Critical Habitat for the Southern Distinct Population Segment of Eulachon, Final Biological Report, September, 2011 National Marine Fisheries Service, Northwest Region, Protected Resources Division


[13] Mad River Watershed Assessment June 2010 Stillwater Sciences

Interactive Watershed Map Coming Soon!