[8] After railroad baron Charles Crocker built the Hotel Del Monte, he commissioned construction of a Dam in 1883 on the upper river near present-day Cachagua.

[10] Although the length of the river is reported in various publications as 36 mi (58 km),[12] the river length from its origin on the southern side of Mission Mountain peak to its mouth at the Pacific Ocean is 41 miles (66 km) utilizing the United States Geological Survey (USGS) mouth and source coordinates and the USGS National Map.

Stream restoration and conservation projects are proceeding to return/enhance migrating fish in the family Salmonidae, such as the steelhead trout (Oncorhynchus mykiss), and other aquatic and terrestrial flora and fauna to the Carmel River ecosystem.

[16] The Carmel River supports the largest run of about 27 streams utilized by steelhead trout in the entire South-Central California Coast DPS region.

About 6.8 miles (10.9 km) upstream of Los Padres Dam there is a 75 foot waterfall in the river mainstem that is an impassable barrier to anadromous fish.

[17] A recent 2022 study has also shown that there is poor downstream passage at the Los Padres Dam which creates an ecological trap for migrating steelhead trout.

The steelhead can ascend the fish ladder and spawn above the Los Padres Reservoir but a truncated hydroperiod and low flows limit successfully outmigration back to the ocean.

The San Clemente Dam, built in 1921, was located 18.5 miles (29.8 km) upstream from the ocean, and once provided drinking water throughout the Monterey Peninsula.

State regulators declared in 1991 that it was in danger of collapsing in an earthquake and spilling the 40 million US gallons (150,000 m3) of water trapped behind its crumbling walls.

In January 2010 an agreement was reached with the California American Water Company to dig a new half-mile channel to bypass and strand the sediment behind the dam at a cost of $84 million, beginning in 2013.

[27] The Los Padres Reservoir is steadily filling with sediment, as the pervasively fractured granitic and metamorphic rock underlying the Carmel River watershed are easily eroded.

A cast-iron pipe 25 miles (40 km) long and 12 inches (30 cm) in diameter was used to deliver water from the dam to the first Del Monte Hotel on the Monterey Peninsula, crossing the Carmel River five times on its way.