1920] Allen: Plankton of the San Joaquin River 9 



King's River basin has fifty miles of Sierra divide as its eastern 

 border, with some altitudes above 14,000 feet. Its length is about sixty 

 miles in the mountains, with an area approximating 1,840 square miles. 

 The river source consists of many little glacial lakes at the edge of 

 glaciers and perpetual snow. The length of the river to the mouth 

 of its canon is nearly 85 miles. 



The basin as a whole is very rough and irregular, the head espec- 

 ially including the most rugged region in the Sierra. Nearly all the 

 tributaries run through glacial canons cut through solid granite. Sev- 

 eral of the latter are 2,000 or 3,000 feet deep. The whole formation 

 is granitic. 



The larger part of the basin is well forested up to 10,000 feet, 

 Most of it is in the National Forest Reserve. Precipitation ranges 

 from eight to ten inches in the San Joaquin Valley to fifty or sixty 

 inches in the high altitudes. Most of the precipitation of this basin is 

 in the form of snow. 



The Merced River 

 The Merced River drains an area sixty-five miles in length from 

 Mount Lyell on the Sierra divide (13,090 feet) down to the San 

 Joaquin River. This includes a total of 1,200 square miles. The river 

 itself is about 135 miles in length, with four or five tributaries of some 

 importance, including the famous Yosemite Creek. Though the Yosem- 

 ite Valley is the most remarkable, there are other parts of the 

 basin very rough and broken, with many waterfalls and glaciated 

 regions. About 850 square miles of the upper part of the basin is 

 included in national forests, though there is little growth above 

 12,000 feet. The annual precipitation in the San Joaquin Valley near 

 the mouth of the Merced sixty or seventy miles from Stockton, is ten 

 to fifteen inches and it ranges through twenty-five inches in the foot- 

 hills to about sixty inches near the divide. Even in the mountains this 

 precipitation occurs mainly in the rainy season, mostly as snow, the 

 melting of which is most rapid in May and June. 



The Tuolumne River 



The Tuolumne River traverses a basin 105 miles long, two-thirds 

 of which is in the mountains. The mountainous portion is about 

 1,680 square miles in area. This river is 150 miles long, about 

 80 miles of which is through a deep canon cut down into solid granite. 

 This canon drains numerous glacial lakes at the Sierra divide, and 

 the upland meadows slightly lower down. The basin as a whole is 



