Water Stewardship


Normal Runoff from British Columbia - Study 406

A study was completed in 1986 to estimate the runoff from British Columbia in a mean year, a high year and a low year. Since 1986 more data have become available and with computer facilities these data can be handled much more efficiently. As a result the present study was undertaken to determine annual runoff from all major basins of the Province from 1961 to 1993. The 30-year period 1961 to 1990 is the normal period. This period corresponds to the climatological standard for comparison of temperature and precipitation.

1. Introduction "The geographic location and the topographical variability of the Province have produced a hydro-climatic area of great diversity. Temperature, precipitation and runoff vary enormously from the exposed Pacific coast, up the mountain slopes, to the inter-mountain valleys and the interior plateaus." This is the introduction to the 1986 report and it is still as applicable now as it was then.

Although some hydrometric records stretch back to the early part of the century, is was not until the early 1960's that sufficient hydrometric gauges were installed on the major provincial rivers to allow an inventory of runoff from the Province. Even now large areas, particularly along the coast, remain ungauged. This study has made as much use as possible of available hydrometric data to determine runoff from the major basins of British Columbia. Data collected by the Water Survey of Canada in B.C. form the major part of the data used in this study but data collected in Alberta, the North West Territories and the Yukon Territory and the states of Washington, Idaho, Montana and Alaska were also used. Some unpublished hydrometric data were used where available.

2. Method

The Province was divided into 19 geographically separate basins. For each of these, the annual natural runoff from the portion of the basin within B.C. was determined for each year from 1961 to 1993. Where data for a year was missing or incomplete for a hydrometric station the missing record was estimated by graphical correlation and comparison with other similar gauged watersheds. Where a basin had a hydrometric gauge near the mouth or border, determination of annual runoff was relatively simple as it required estimation of runoff from the relatively small ungauged portion only. However, this was not always the case. Rivers crossing the border and those with tributaries crossing the border required special consideration so that only the runoff originating in B.C. was included in basin runoff. The basin areas used in the runoff computations were determined from the gauged watershed areas as published by the Water Survey of Canada plus measure-ment of the ungauged areas as determined from topographic maps. The map scale used was 1:250,000. The sum of the 19 basins came to 946,788 km2 which is slightly less than the accepted area of 948,600 km2. No adjustments were made to account for this difference. The actual procedures used in determining annual runoff for each basin are described in the following sections. Basin by basin annual runoff is shown in the attched table. It should be noted that the values in the table are shown in units of m3/s, km2 or mm. The number of significant figures shown should not be taken to reflect precision but only the results of the computations. Precision of all values is to three significant figures only.

2.01 Fraser

The gauge at Hope was the starting point for determining annual runoff for this basin. To the annual flow at Hope was added the major diversion out of the basin from the Nechako and the natural flow from the major downstream gauged tributaries: Harrison, Chilliwack, Chehalis, Stave, Alouette, Pitt and Coquitlam rivers. Annual runoff from the portion of the Chilliwack and Sumas rivers originating in the State of Washington was excluded. This left a relatively small ungauged area which was estimated by comparison with the above tributaries and the Sumas and Nicomekl rivers. This gave a normal annual natural runoff at the mouth of 3,832 m3/s or 521 mm over the watershed.

2.02 Skagit

Annual runoff from the portion of the Skagit River basin within the Province was estimated by correlations with inflow to the downstream Ross Reservoir and Chilliwack River at the outlet of Chilliwack Lake. The normal annual runoff was determined at 31.1 m3/s or a runoff of 971 mm over the basin.

2.03 Columbia

The Columbia River basin in the Province was broken down into four sub-basins for this study: the main Columbia including the Kootenay and the Flathead, the Kettle, the Okanagan and the Similkameen. The annual natural runoff for each, corrected for reservoir storage change, was determined.

The main Columbia is gauged at Birchbank, just north of Trail. To the gauged flow at this location was added the flow from the B.C. portion of Salmo River, Big Sheep Creek, local ungauged tributaries and the Flathead River. The flow originating in the Kootenay River basin from outside the Province was determined by using gauged data from the Kootenay, Moyie, Bull and Elk rivers. To the annual flow determined was added storage change on the major reservoirs: Arrow Lake, Revelstoke Reservoir, Kinbasket Lake, Duncan Lake and Kootenay Lake. (Koocanusa Lake storage change was also considered). This gave a normal annual natural runoff from the Columbia River in B.C. of 2,057 m3/s or 822 mm from the 79,000 km2 watershed.

The annual runoff for the Kettle was determined from the gauge at Laurier. The normal annual runoff is 68.5 m3/s or 263 mm from the 8,222 km2 watershed.

The observed flow on the Okanogan River at Oroville was corrected for storage change on Okanagan Lake and for the portion of the watershed outside the Province. The normal annual runoff for the Okanagan basin is 17.4 m3/s or 68 mm over the watershed of 8,013 km2.

The gauge on the Similkameen River at Nighthawk corrected for the portion of the watershed outside B.C. gave a normal annual runoff of 52.7 m3/s or 224 mm from the 7,436 km2 watershed.

The total Columbia River runoff, the sum of these four sub-basins is 2,196 m3/s or 675 mm on the watershed.

2.04 Peace

This basin includes the Peace, Pouce Coupe, Redwillow, Wapiti and Kakwa River basins in British Columbia. The annual runoff from each was determined from gauge data in B.C. and Alberta.

The Peace River gauge at Taylor formed the base for the main Peace River. To the annual flow at this point was added the flow from the downstream tributaries in B.C.: the Beatton, Kiskatinaw and Alces rivers and local inflow to the border. The resulting annual flows were corrected for storage change on Williston Lake and for runoff originating in Alberta to give a normal annual runoff of 1,548 m3/s or 417 mm from the 117,100 km2 watershed.

The annual runoff from the Pouce Coupe, Redwillow, Wapiti and Kakwa was determined from available gauge data adjusted to give runoff from B.C. only. The individual results are:


		normal annual runoff	drainage area

m3/s mm km2

Pouce Coupe River 4.7 90 1,657

Redwillow River 5.4 120 1,413

Wapiti River 54.5 492 3,492

Kakwa River 6.3 587 340

The sum of the five sub-basins gave a normal annual runoff of 1,619 m3/s or 412 mm.


2.05 Hay

Both the Hay and Chinchaga River basins in B.C. are included in this section. Annual runoff from both basins was estimated from gauge data on the Beatton, Fort Nelson, Sikanni Chief, Hay and Fontas rivers. The normal annual runoff and drainage areas are:


		normal annual runoff	drainage area

m3/s mm km2

Teslin River 136.1 323 13,304

Atlin River 99.2 581 5,387

Tagish River 123.5 673 5,796

Takhini River 25.6 779 1,039

2.06 Liard

Although the Liard River is gauged fairly close to the border where it enters and leaves the Province, many of the major tributaries between these gauges have a portion of their drainage area in Alberta, the Northwest Territories or the Yukon. This made estimation of annual runoff from B.C. somewhat difficult but sufficient data was available to give reliable estimates for the Fort Nelson, Petitot, Beaver, Smith, Coal, Irons, Hyland and Little Rancheria rivers. The resulting normal annual runoff from the Liard basin in B.C. is 1,281 m3/s or 279 mm over the drainage area.


2.07 Yukon

The Yukon River originates in British Columbia in Tagish and Atlin lakes with the major tributaries, Teslin and Takhini rivers also draining north from the Province. Annual runoff from the four sub-basins in B.C. was determined and added to give the total runoff for the basin. The normal annual runoff results are:


		normal annual runoff	drainage area

m3/s mm km2

Teslin River 136.1 323 13,304

Atlin River 99.2 581 5,387

Tagish River 123.5 673 5,796

Takhini River 25.6 779 1,039


2.08 Alsek

The Alsek River and its major tributary the Tatshenshini River originate in the Yukon and flow through British Columbia before passing into Alaska. In addition to the Alsek, this basin includes other coastal drainage in the northwest corner of the Province including the Kelsall and Skagway Rivers. Determination of annual runoff for the basin is difficult due to sparse gauging and the large areas of permanent ice. Hydrometric data used to estimate annual runoff included gauge data from the Takhanne, Tatshenshini, Alsek, Dezadeash, Takhini, Skagway and Lindeman rivers. The total normal annual runoff is 613 m3/s or 1750 mm over the watershed in B.C. Sub-basin runoff is as follows:


		normal annual runoff	drainage area

m3/s mm km2

Alsek River (8AB & 8AD) 170 1801 2,980

Tatshenshini River 280 1750 5,046

Kelsal River 85 1500 1,782

Skagway River 2.4 1500 51

(the sectors 8AB and 8AD and others mentioned in this report refer to the Water Survey of Canada basin numbering system).


2.09 Taku

This section includes both the Taku and the Whiting rivers in B.C. Gauge data is available for the Taku but the Whiting had to be estimated. By sub-basin the normal annual runoff is as follows:


		normal annual runoff	drainage area

m3/s mm km2

Taku River 368 684 16,992

Whiting River 181 2400 2,375


2.10 Stikine

The Stikine River and its major tributary the Iskut River are well gauged making determination of runoff from within the Province relatively easy although local runoff to the border on the Stikine and runoff from Alaska entering the Iskut River had to be estimated. The sub-basin normal annual runoff is:


		normal annual runoff	drainage area

m3/s mm km2

Stikine (excluding Iskut) 1004 781 40,580

Iskut in B.C. 436 1496 9,200


2.11 Unuk

The Unuk River is gauged near the border but annual runoff from local drainages in B.C. on the Unuk, Leduc and Chichamin rivers was estimated. Normal annual runoff is 140 m3/s or 2,254 mm.


2.12 Nass

This section includes the Nass River and Bear River as well as coastal drainage in the 8DC and 8DB sectors. Both the Nass and Bear rivers are gauged but estimates of annual runoff from the coastal watersheds were required. These estimates are based in gauged data from the Bear, Kitsault and Exchamsiks rivers. The normal annual runoff from the sub-basins is:


		normal annual runoff	drainage area

m3/s mm km2

Bear River 50.5 2243 711

Nass River 770 1313 18,500

coastal 839 3368 7,867


2.13 Skeena

The Skeena River watershed and coastal drainage within the 8EG sector are included in this section. The Skeena is gauged at Usk, just above Terrace. The annual flow at this point plus the major gauged tributaries (Zymoetz, Kitsumkalum, Zymagotitz, Exchamsiks rivers) form the basis of the determination of flow for this section. To this is added estimates of the local inflow down to the mouth and estimates of annual flow from other drainage in the 8EG sector including adjacent islands. The normal annual runoff is 2,157 m3/s or 1190 mm.


2.14 North Coast

This section includes the Kitimat, Kemano and Dean rivers which are gauged as well as all other drainage within sectors 8FC, 8FD, 8FE, 8FF, 8FG, including adjacent islands which is not gauged . The total area gauged in this section is 6,660 km2 or 18% of the total section area. Annual runoff for the ungauged area was estimated by separating it into three zones, the coastal lowlands, the Coast Mountains and the rainshadow zone. Estimates were made separately for the zones based on gauge data from the above three rivers and the Salloomt, Bella Coola, Nusatsum, Zymagotitz, Hirsch, Little Wedeene, Morice and Wannock rivers. The normal annual runoff for this section is 2,735 m3/s or 2326 mm.


2.15 Mid-Coast North

This section includes all of sectors 8FA and 8FB and adjacent islands. The gauged rivers in this section are the Bella Coola, the Salloomt, the Nusatsum and the Wannock rivers which together compromise 48% of the total drainage area. Annual flow for the ungauged area was estimated as described for the North Coast section. The normal annual runoff is 1,195 m3/s or 2254 mm.


2.16 Mid-Coast South

This section includes all of sectors 8GD, 8GE and 8GF and adjacent islands. The gauged rivers, the Klinaklini and the Homathko account for 41% of the total drainage area. The remaining ungauged area was divided into the coastal lowland and Coast Mountain zones and estimates of annual flow were made for each based on gauged data from the Bella Coola, Wannock, Mosley, Homathko, Chilko, Powell and Zeballos rivers. Normal annual runoff is 1,813 m3/s or 2062 mm.


2.17 South Coast

This section includes all of sectors 8GA, 8GB and 8GC plus the portion of 8MH which is not in the Fraser River drainage basin. Gauged data from 9 watersheds accounted for 37% of the drainage area of this section: Powell Lake, Clowhom Lake, Lang Creek, Roberts Creek, Mamquam River, Squamish River, Cheakamus River, Capilano River and Nicomekl River. Estimates of annual flow for the ungauged areas were based on data from these 9 gauges and from Daisy Lake and the Elaho River. Normal annual runoff is 1,192 m3/s or 2444 mm.


2.18 Queen Charlotte Islands

The Queen Charlotte and adjacent islands have a total drainage area of 10,075 km2. Within this area three watersheds are gauged, Yakoun River, Premier Creek and Pallant Creek and together account for 553 km2. Annual runoff from the ungauged area was based on these three gauges. Normal annual runoff is 874 m3/s or 2737 mm.


2.19 Vancouver Island

In addition to Vancouver Island, this section includes the Gulf Islands, Texada, Quadra, Malcolm, Nootka, Flores and Meares and other islands. Total drainage area is 35,158 km2 of which 10,102 km2 is gauged on 25 watersheds. The annual runoff for the ungauged area was estimated from the data for these 25. The normal annual runoff for the sub-groups is as follows:


		normal annual runoff	drainage area

m3/s mm km2

Vancouver Island 2,717 2669 32,137

Gulf Islands 7.3 508 451

Straits islands 57.2 1261 1,432

West coast islands 108 3000 1,138


3. Annual Runoff

The annual runoff from the 19 sections was added to give the total runoff from British Columbia for each year from 1961 to 1993. These figures are shown in the attached table. The year 1967 was identified as having the greatest runoff in the period while 1970 had the least. The years 1969, 1971, 1980, 1981, 1987 and 1992 were close to the normal runoff of 26,600 m3/s.

The total annual normal runoff for the Province amounts to 840 km3 which if spread evenly over the 947,000 km2 area of the Province would give a depth of 887 mm.


B.C. Runoff for Period 1961 to 1993

Annual Runoff from British Columbia

corrected for major storage, diversion and runoff originating from outside the province

Fraser Skagit Columbia Peace Hay Liard

River River River River River River

m3/s m3/s m3/s m3/s m3/s m3/s

DA km2 231 961 1 010 102 627 124 011 8 275 144 756

1961 3873 35 2389 1456 16 1222

1962 4102 29 2097 1722 33 1749

1963 3892 30 2095 1673 33 1305

1964 4559 37 2375 2155 23 1250

1965 3801 29 2197 1702 14 1114

1966 4032 30 2248 1705 14 1070

1967 4330 39 2530 1729 12 1184

1968 4520 38 2380 1571 18 1080

1969 3754 29 2319 1401 18 975

1970 2895 21 1671 1310 16 1098

1971 3912 39 2367 1658 40 1258

1972 4572 49 2798 1988 10 1150

1973 3449 19 1814 1672 26 1200

1974 4432 43 2647 1771 36 1458

1975 3775 38 2128 1263 17 1076

1976 4753 38 2678 2021 41 1504

1977 3508 21 1587 1681 36 1445

1978 3310 25 2226 1182 20 923

1979 3241 22 1708 1428 26 1298

1980 3492 31 2082 1308 17 1426

1981 3907 26 2457 1556 8 1159

1982 4256 33 2438 1633 21 1108

1983 3672 29 2263 1529 24 1095

1984 3770 27 2098 1696 33 1342

1985 3384 24 1889 1456 19 1318

1986 3591 29 2127 1545 20 1410

1987 3320 23 1868 1866 28 1653

1988 3396 28 1951 1616 36 1723

1989 3353 30 2011 1492 25 1491

1990 4112 39 2442 1784 34 1337

1991 4112 40 2517 1656 30 1302

1992 3501 22 1899 1619 24 1222

1993 2988 19 1690 1345 36 1419

Normal 3832 31 2196 1619 24 1281

mm 521 971 675 412 91 279


B.C. Runoff for Period 1961 to 1993

Annual Runoff from British Columbia

corrected for major storage, diversion and runoff originating from outside the province

Yukon Alsek Taku Stikine Unuk Nass

River River River River River River

m3/s m3/s m3/s m3/s m3/s m3/s

DA km2 25 526 11 056 19 367 49 775 1 955 27 077

1961 451 875 718 1652 177 1970

1962 439 620 600 1688 147 1774

1963 449 649 606 1531 147 1634

1964 397 548 524 1430 133 1896

1965 343 453 474 1221 113 1451

1966 365 466 434 1337 128 1646

1967 401 605 544 1568 183 2028

1968 372 571 478 1331 135 1674

1969 388 416 428 1446 154 1700

1970 328 486 467 1363 137 1478

1971 372 498 477 1370 137 1502

1972 380 544 527 1502 139 1786

1973 314 445 426 1315 116 1527

1974 363 468 465 1519 146 1769

1975 388 730 603 1255 120 1467

1976 398 504 534 1495 141 1797

1977 419 729 611 1372 129 1522

1978 306 598 459 1178 126 1536

1979 431 813 684 1468 137 1645

1980 399 686 600 1554 143 1796

1981 452 895 750 1724 164 1758

1982 358 457 468 1339 133 1407

1983 341 616 532 1312 129 1444

1984 295 409 411 1178 109 1424

1985 346 572 540 1340 127 1531

1986 386 647 571 1524 138 1648

1987 387 663 554 1579 142 1829

1988 414 807 614 1427 140 1752

1989 416 800 689 1604 154 1705

1990 434 818 683 1571 166 1690

1991 421 688 615 1752 166 2081

1992 448 767 668 1584 167 1929

1993 442 753 668 1642 172 1692

Normal 384 613 549 1440 140 1660

mm 475 1750 895 913 2254 1934


B.C. Runoff for Period 1961 to 1993

Annual Runoff from British Columbia

corrected for major storage, diversion and runoff originating from outside the province

Skeena North Mid-Coast Mid-Coast South Queen

River Coast north south Coast Charlotte

m3/s m3/s m3/s m3/s m3/s m3/s

DA km2 57 186 37 100 16 736 27 743 15 394 10 075

1961 2484 2791 1222 1912 1344 838

1962 2294 3313 1456 2121 1233 1066

1963 2031 3001 1298 1976 1268 966

1964 2578 3125 1345 1913 1243 994

1965 1925 2885 1283 1922 1167 874

1966 2210 3062 1310 1985 1239 1016

1967 2536 3523 1591 2501 1443 849

1968 2259 3113 1402 2311 1425 910

1969 2176 2855 1227 1813 1261 1074

1970 1847 2219 949 1414 927 748

1971 1998 2969 1326 1969 1267 866

1972 2442 2889 1265 1858 1243 794

1973 2021 2397 1037 1566 1058 842

1974 2343 2792 1220 1815 1302 946

1975 1914 2673 1147 1713 1220 886

1976 2558 3400 1480 2071 1258 973

1977 2012 2461 1065 1628 1022 796

1978 1968 2516 1092 1654 1071 727

1979 2091 2360 1033 1622 1084 765

1980 2156 2724 1194 1794 1213 883

1981 2183 2463 1081 1697 1279 874

1982 1870 2468 1094 1699 1154 613

1983 1851 2157 945 1507 1255 803

1984 1928 2490 1090 1670 1170 1008

1985 2004 2311 1006 1453 923 730

1986 2111 2525 1108 1732 1150 844

1987 2363 2818 1226 1906 1191 962

1988 2266 2612 1139 1728 1116 992

1989 2135 2596 1116 1674 1050 721

1990 2150 2534 1114 1764 1189 848

1991 2618 2859 1234 1901 1245 974

1992 2552 2795 1211 1834 1196 815

1993 2085 2237 971 1526 964 742

Normal 2157 2735 1195 1813 1192 874

mm 1190 2326 2254 2062 2444 2737


B.C. Runoff for Period 1961 to 1993

Annual Runoff from British Columbia

corrected for major storage, diversion and runoff originating from outside the province

Vancouver Sum Volume Annual

Island Runoff Runoff

Depth

m3/s m3/s km3 mm

DA km2 35 158 946 788

1961 3284 28 708 905 956

1962 3218 29 699 937 989

1963 3210 27 792 876 926

1964 2617 29 140 921 973

1965 2758 25 726 811 857

1966 3588 27 886 879 929

1967 3648 31 245 max 985 1041

1968 4296 29 882 945 998

1969 3055 26 487 835 882

1970 1920 21 295 min 672 709

1971 3208 27 234 859 907

1972 2975 28 913 914 966

1973 2578 23 823 751 794

1974 3380 28 916 912 963

1975 3314 25 726 811 857

1976 2689 30 333 959 1013

1977 2524 24 568 775 818

1978 2066 22 982 725 766

1979 2551 24 405 770 813

1980 2891 26 388 834 881

1981 2816 27 249 859 908

1982 2703 25 254 796 841

1983 3197 24 701 779 823

1984 2916 25 064 793 837

1985 1566 22 538 711 751

1986 2897 26 002 820 866

1987 2915 27 295 861 909

1988A 2641 26 399 835 882

1989 2248 25 310 798 843

1990 3040 27 750 875 924

1991 2635 28 845 910 961

1992 2562 26 817 848 896

1993 2221 23 612 747 789

Normal 2890 26 624 840 887

mm 2594 887