Water-Data Report 2009 11269500 Lake McClure at Exchequer, CA Basin

LOCATION.--Lat 37°3502, long 120°1609 referenced to North American Datum of 1927, in NW ¼ SE ¼ sec.13, T.4 S., R.15 E., Mariposa County, CA, Hydrologic Unit 18040008, on left end of on , 0.9 mi east of Exchequer, and 5.5 mi northeast of Merced Falls. DRAINAGE AREA.--1,037 mi². SURFACE-WATER RECORDS PERIOD OF RECORD.--April 1926 to September 1930 (daily gage heights; also summary of yearly contents in WSP 881), October 1930 to current year. REVISED RECORDS.--WSP 881: 1926-32 (yearly summaries only). WSP 1345: 1951 (instantaneous maximum discharge). WSP 1930: Drainage area. GAGE.--Water-stage recorder. Datum of gage is NGVD of 1929 (levels by Merced Irrigation District). Prior to Oct. 1, 1964, indicator in powerplant at same datum. Oct. 1, 1964, to July 31, 1966, nonrecording gage at center of upstream face of dam at same datum. COOPERATION.--Records, including diversion through Exchequer Powerplant (station 11269700), were provided by Merced Irrigation District, under general supervision of the U.S. Geological Survey, in connection with Federal Energy Regulatory Commission project no. 2179. REMARKS.-- is formed by a rock-fill dam with a reinforced concrete face completed in March 1967. Dam is downstream from and connected to the original concrete arch and gravity-type dam which was completed in April 1926. Usable capacity, 1,024,000 acre-ft, between elevations 440.0 ft, invert entrance to outlet tunnel, and 867.0 ft, top of spillway gates. Dead storage, 300 acre-ft. Water is released through Exchequer Powerplant down the Merced River to a diversion dam for Merced Irrigation District's main . Records, excluding extremes, represent total contents at 2400 hours. EXTREMES FOR PERIOD OF RECORD.--Maximum contents, 1,026,000 acre-ft, July 14, 15, 1969, elevation, 867.2 ft; practically no storage at times in 1926, 1930-31, 1964-65 when reservoir was drained for inspection or construction. Minimum since construction of New Exchequer Dam in 1966 and since lake first filled, 66,100 acre-ft, Feb. 28, 1991, elevation, 588.4 ft. EXTREMES FOR CURRENT YEAR.--Maximum contents, 681,300 acre-ft, June 11, 12, elevation, 810.94 ft; minimum, 248,800 acre-ft, Dec. 22, 24, elevation, 694.32 ft, Dec. 22.

Capacity table (elevation, in feet, and contents, in acre-feet) (Based on table provided by Merced Irrigation District, dated June 1966) Elevation Contents Elevation Contents Elevation Contents 590 67,900 660 173,500 780 534,500 600 79,900 680 215,200 820 729,600 610 92,800 700 263,000 840 845,800 620 106,700 720 317,800 860 975,700 640 137,800 750 415,900 870 1,046,000

U.S. Department of the Interior U.S. Geological Survey Water-Data Report 2009 11269500 Lake McClure at Exchequer, CA—Continued

RESERVOIR STORAGE, ACRE FEET WATER YEAR OCTOBER 2008 TO SEPTEMBER 2009 DAILY OBSERVATION AT 2400 HOURS Day Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep

1 278,900 257,200 256,400 249,700 285,200 329,000 398,200 493,400 675,500 661,000 575,200 492,300 2 278,400 258,800 256,100 249,800 286,400 331,200 401,200 508,500 677,100 658,800 572,300 489,800 3 277,900 260,300 256,400 249,800 287,600 334,400 404,300 517,500 678,000 656,200 569,300 487,100 4 277,200 260,800 255,700 250,300 288,900 346,400 405,400 525,400 678,000 654,000 566,400 484,600 5 276,600 260,800 255,100 250,800 290,100 351,300 407,000 531,100 679,900 651,700 563,200 482,000 6 275,800 260,700 254,900 251,400 290,900 354,600 408,800 537,000 679,200 649,400 560,400 479,600 7 275,300 260,500 254,300 251,900 289,700 356,800 411,100 543,700 679,300 646,900 557,300 477,400 8 274,600 260,500 253,800 252,400 288,400 358,600 413,500 549,300 680,400 644,600 554,400 475,000 9 273,700 260,400 253,500 252,500 290,300 360,400 415,600 555,100 680,100 642,100 551,600 472,800 10 273,000 260,500 253,100 251,100 291,800 361,900 417,400 561,100 680,300 639,500 548,900 470,500 11 271,900 260,400 252,800 250,500 293,200 362,900 419,000 567,800 680,600 636,800 546,000 468,400 12 271,100 260,300 252,200 251,000 294,800 364,100 420,900 575,700 679,800 634,300 543,300 466,100 13 270,500 260,200 252,100 251,600 296,100 365,200 422,600 583,200 679,200 631,700 540,800 463,900 14 269,500 260,200 251,600 252,300 296,200 366,400 424,900 589,800 678,200 628,900 538,100 461,700 15 269,100 260,300 251,200 252,900 297,200 367,600 426,800 596,400 677,100 626,300 535,300 459,800 16 268,400 260,400 250,800 253,000 299,100 368,700 428,200 604,700 676,100 623,400 532,700 457,900 17 267,400 260,700 250,400 252,200 302,900 370,300 429,300 613,700 675,900 620,600 530,100 456,200 18 266,600 260,600 249,800 251,800 305,900 372,100 431,400 622,400 675,800 617,700 527,100 454,700 19 265,900 260,400 249,600 252,100 308,000 373,900 435,100 628,900 674,600 614,900 524,300 452,900 20 265,100 260,100 249,200 252,600 309,000 376,000 440,600 635,200 674,500 611,800 521,400 451,400 21 264,700 259,900 249,100 253,200 309,300 378,100 447,300 640,200 674,000 608,700 518,700 449,700 22 263,900 259,600 248,900 253,900 310,500 380,900 454,600 644,800 673,000 605,400 515,800 447,900 23 262,900 259,300 249,100 259,200 315,000 382,500 462,500 649,400 671,900 602,200 513,000 447,000 24 262,200 258,900 248,900 270,900 319,300 383,700 470,100 653,300 670,600 599,200 510,200 445,200 25 261,800 258,400 249,600 276,700 322,300 385,100 474,000 656,600 669,500 596,200 507,600 443,300 26 261,100 258,100 250,100 279,200 324,800 386,000 476,700 659,900 668,200 593,200 505,200 441,200 27 260,400 257,900 250,200 279,000 326,900 387,300 479,300 663,200 666,700 590,100 503,100 439,100 28 259,700 257,600 250,100 279,400 328,100 388,700 482,400 665,700 665,100 587,200 500,900 436,900 29 259,000 257,200 249,900 281,000 --- 390,900 485,100 667,700 663,700 584,200 499,100 434,700 30 258,300 256,800 249,800 282,500 --- 394,100 487,800 669,900 662,300 581,300 496,800 431,900 31 257,800 --- 249,800 283,900 --- 396,500 --- 672,500 --- 578,200 494,600 --- Max 278,900 260,800 256,400 283,900 328,100 396,500 487,800 672,500 680,600 661,000 575,200 492,300 Min 257,800 256,800 248,900 249,700 285,200 329,000 398,200 493,400 662,300 578,200 494,600 431,900 Elevation, in feet, at end of month 697.92 697.53 697.74 707.96 723.45 744.52 768.85 809.25 807.26 789.80 770.51 754.39 Change in contents, in acre-feet -21,700 -1,000 -7,000 +34,100 +44,200 +68,400 +91,300 +184,700 -10,200 -84,100 -83,600 -62,700 Diversion, in acre-feet, through Exchequer Powerplant 25,450 23,550 21,370 15,800 16,030 39,810 63,010 110,800 110,700 119,400 95,130 70,690

Calendar Year 2008 Water Year 2009 Change in contents, in acre-feet +5,200 +152,400

— 2 — Water-Data Report 2009 11269500 Lake McClure at Exchequer, CA—Continued

700,000

600,000

500,000

400,000 OBSERVATION AT 2400 HOURS RESERVOIR STORAGE, ACRE FEET, RESERVOIR STORAGE, ACRE 300,000

200,000 O N D J F M A M J J A S 2008 2009

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