MERRIMACK RIVER BASIN
01076500 PEMIGEWASSET RIVER AT PLYMOUTH, NH
LOCATION.--Lat 43°45'33", long 71°41'10", Grafton County, Hydrologic Unit 01070001, on right bank, 150 ft downstream
from bridge at Plymouth and 0.3 mi downstream from Baker River.
DRAINAGE AREA.--622 mi².
PERIOD OF RECORD.--Discharge records: October 1903 to current year. Records for April 1886 to September 1903,
published in WSP 124, are unreliable and should not be used.
Water-quality records: Water years 1953, 1967-74, 1976-79.
REVISED RECORDS.--WSP 471: 1912-14. WSP 726: Drainage area. WSP 1231: 1904-11, 1913-14, 1917-18, 1919(M),
1920-25, 1926-27(M), 1929-31(M). WSP 1721: 1959(M). See also PERIOD OF RECORD.
GAGE.--Water-stage recorder. Datum of gage is 457.07 ft above sea level. Prior to January 1, 1910, nonrecording gage
at sites 150 ft and 200 ft upstream at present datum or datum 1.ll ft lower. January 1, 1910, to September 30, 1926,
nonrecording gage at site 200 ft upstream at present datum.
REMARKS.--Records good except those for estimated daily discharges, which are fair. Stage-discharge relationship at
times is affected by variable slope. Some diurnal fluctuation during period 1940-52 caused by powerplants upstream.
EXTREMES FOR CURRENT YEAR.--Peak discharges greater than base discharge of 12600 ft³/s and maximum (*):
Discharge Gage height Discharge Gage height
Date Time (ft³/s) (ft) Date Time (ft³/s) (ft)
Oct. 21 Unknown 22,400 a 13.78 Dec. 2 1415 * 24,800 * 14.50
Nov. 9 2100 22,400 13.45 Apr. 19 1315 19,400 12.64
Minimum discharge, 197 ft³/s, October 7, 8.
DISCHARGE, CUBIC FEET PER SECOND, WATER YEAR OCTOBER 1996 TO SEPTEMBER 1997
DAILY MEAN VALUES
DAY OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP
1 350 1190 1010 e910 e700 e1900 2130 4730 2160 377 342 571
2 271 998 17200 e1350 e640 e1600 1690 7300 2140 355 325 471
3 237 884 9070 e1580 e645 e2100 1580 4770 1810 562 315 453
4 218 806 4440 e1560 e660 e1800 1760 4490 1610 3080 324 453
5 215 742 3050 e1450 e670 e1500 2140 3620 1430 1240 303 388
6 204 705 2370 e1720 e640 e1400 3750 3360 1310 811 291 349
7 199 692 1970 e1560 e650 e1300 5940 6620 1210 636 269 316
8 197 1330 1820 e1150 e590 e1100 7000 4320 1120 598 248 435
9 303 12800 1640 e1050 e585 e1100 3880 3410 1050 546 239 436
10 628 10100 1410 e1180 e610 e1150 2620 3100 1040 1890 232 371
11 989 4400 1270 e1070 e630 e1100 2220 3040 1090 1270 224 331
12 714 2860 1190 e1030 e645 e900 2050 2640 1000 812 221 510
13 498 2150 1190 e990 e585 e850 2040 2750 1020 628 275 702
14 414 1690 1150 e940 e600 e800 2190 2910 1180 554 708 501
15 357 1370 1150 e830 e565 e850 2170 2850 925 5310 470 402
16 313 1140 1140 e880 e595 e950 2370 3450 761 4080 373 346
17 291 1150 1260 e860 e570 e850 3260 3240 664 1910 357 308
18 271 1070 3320 e680 e550 e850 5960 2680 634 1560 300 287
19 258 1020 3180 e760 e580 e750 16600 2590 1850 2680 263 283
20 292 992 2770 e760 e770 e850 9910 2970 1570 1720 231 291
21 8780 914 1910 e750 e1070 e800 7110 3130 1070 1190 244 379
22 13600 849 1680 e800 e1010 e800 6080 2600 966 962 664 384
23 4980 795 1450 e760 e1690 e750 5440 2420 976 794 770 332
24 3270 735 1520 e760 e1650 e650 5430 2220 788 678 593 317
25 2460 687 6190 e790 e1210 e750 4350 2150 669 612 438 327
26 1860 810 3220 e770 e1060 e750 3970 2270 613 551 363 299
27 1520 1190 2330 e880 e1250 e1200 4260 2000 548 499 345 275
28 1300 1130 1840 e780 e1900 e1150 5530 1800 477 465 701 263
29 1190 1130 1630 e770 --- 1640 5250 1940 439 439 1490 279
30 1050 820 2110 e690 --- 2230 4210 2030 401 404 1170 521
31 1330 --- e1300 e650 --- 2880 --- 1990 --- 365 762 ---
TOTAL 48559 57149 86780 30710 23320 37300 132890 99390 32521 37578 13850 11580
MEAN 1566 1905 2799 991 833 1203 4430 3206 1084 1212 447 386
MAX 13600 12800 17200 1720 1900 2880 16600 7300 2160 5310 1490 702
MIN 197 687 1010 650 550 650 1580 1800 401 355 221 263
CFSM 2.52 3.06 4.50 1.59 1.34 1.93 7.12 5.15 1.74 1.95 .72 .62
IN. 2.90 3.42 5.19 1.84 1.39 2.23 7.95 5.94 1.94 2.25 .83 .69
STATISTICS OF MONTHLY MEAN DATA FOR WATER YEARS 1904 - 1997, BY WATER YEAR (WY)
MEAN 972 1337 1140 869 732 1711 3944 2806 1137 642 512 583
MAX 3423 4578 4588 3191 4379 9266 7206 5304 3878 3103 3345 3813
(WY) 1978 1928 1974 1996 1981 1936 1969 1940 1917 1973 1990 1938
MIN 129 308 216 148 138 205 1222 806 283 160 111 107
(WY) 1948 1979 1948 1931 1931 1940 1995 1921 1921 1923 1923 1923
SUMMARY STATISTICS FOR 1996 CALENDAR YEAR FOR 1997 WATER YEAR WATER YEARS 1904 - 1997
ANNUAL TOTAL 782265 611627
ANNUAL MEAN 2137 1676 1366
HIGHEST ANNUAL MEAN 2156 1996
LOWEST ANNUAL MEAN 735 1965
HIGHEST DAILY MEAN 23800 Jan 20 17200 Dec 2 57300 Mar 19 1936
LOWEST DAILY MEAN 167 Sep 24 197 Oct 8 45 Sep 20 1923
ANNUAL SEVEN-DAY MINIMUM 181 Sep 19 220 Oct 2 66 Oct 11 1923
INSTANTANEOUS PEAK FLOW 24800 Dec 2 65400 Mar 19 1936
INSTANTANEOUS PEAK STAGE 14.50 Dec 2 a 29.00 Mar 19 1936
INSTANTANEOUS LOW FLOW b 197 Oct 7 c 39 Oct 1 1948
ANNUAL RUNOFF (CFSM) 3.44 2.69 2.20
ANNUAL RUNOFF (INCHES) 46.78 36.58 29.84
10 PERCENT EXCEEDS 5090 3520 3180
50 PERCENT EXCEEDS 1170 1010 676
90 PERCENT EXCEEDS 247 317 235
a From flood marks.
b Also on October 8.
c Also on October 3, 1948.
e Estimated.
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