California North Coast Waterboard, page 10, Klamath River TMDL's/Total Maximum Daily Loads Draft document:

1.6.1 Population and Land Ownership
The human population in the Klamath River basin was estimated in the 2000 US Census to be about 114,000 (United States Census Bureau [USCB] 2000). The largest population concentrations lie in the upper Klamath agricultural area, the Shasta River Valley, and Scott Valley. The largest population center is Klamath Falls in Oregon (19,462 people in 2000) followed by Yreka, California (7,290 people). The Klamath North Coast RWQCB June 2009 1-9 Klamath River TMDLs Addressing Temperature, Dissolved Oxygen, Nutrient, and Microcystin Impairments in California

River basin can generally be characterized as a rural watershed with limited population-related water quality issues.

More than two thirds of the Klamath River watershed is in federal ownership. Figure 1.2 shows, among other things, federal lands managed as National Forests, National Wildlife Refuges, and National Parks, in addition to Bureau of Land Management (BLM) land. The largest blocks of private ownership are agricultural areas in the upper Klamath watershed and agricultural and timber properties in the Shasta and Scott Valleys and adjacent areas of the mainstem. Also, much of the Klamath River Valley near the mouth of the river is privately owned.

The Hoopa Valley Tribe owns land, 12 miles by 12 miles, primarily in the Trinity River watershed but intersecting the Klamath River at Saints Rest Bar upstream of the confluence with the Trinity. The Yurok Reservation’s lands extend from 1 mile on each side from the mouth of the Klamath River and upriver for a distance of 44 miles. The Karuk Tribe owns 800 acres of tribal trust land along the Klamath River between Orleans and Happy Camp, and in Yreka, California. The Quartz Valley Indian Reservation is located near Fort Jones and encompasses 174 acres along the Scott River. The Resighini Rancheria spans 228 acres along the south shore of the mouth of the Klamath River.