The Pamphlet Collection of Sir Robert Stout: Volume 66

Rainfall

Rainfall.

Stations. Rainfall. Probability of Rain. Mean Max. in 24 Hours. Winter. Spring. Simmer. Autumn. Total for Year. Winter. Spring. Summer. Autumn. Year. N. Island. Percentage. Inches. Mongonui .. 36 24 23 17 58.132 0.66 0.50 0.33 0.39 0.47 3.500 Auckland .. 32 25 19 24 47.008 0.61 0.52 0.33 0.41 0.47 3.358 Taranaki .. 29 27 20 23 59.442 0.52 0.51 0.35 0.38 0.44 2.520 Napier .. 39 15 35 11 36.004 0.26 0.22 0.24 0.17 0.22 .. Wellington .. 29 24 24 22 51.542 0.51 0.43 0.37 0.40 0.43 2.610 S. Island. Nelson .. 27 26 29 17 61.599 0.27 0.25 0.22 0.18 0.23 7.189 Hokitika .. 24 28 28 20 111.653 0.52 0.61 0.57 0.48 0.54 3.532 Bealey .. 22 28 31 18 105.340 0.53 0.61 0.56 0.47 0.54 3.512 Christchurch 31 21 25 23 25.536 0.36 0.33 0.28 0.24 0.30 1.622 Dunedin .. 23 23 28 26 31.682 0.51 0.55 0.58 0.54 0.54 2.079 Southland .. 26 23 26 26 49.732 0.47 0.47 0.40 0.49 0.46 1.130

I. Review of the Proportions of Rain in New Zealand.

II. Totals of Monthly Rainfall in Inches.
Stations. Dec. Jan. Feb. Mar. April May June July Aug. Sept. Oct. Nov.
N. Island.
Mongonui 2.339 3.209 7.787 1.492 2.882 5.461 8.319 6.598 6.241 5.831 3.701 4.272
Auckland 3.409 2.071 3.272 3.150 3.402 4.771 5.721 5.279 4.331 4.331 3.520 3.752
Taranaki 4.921 3.221 3.908 2.579 3.520 7.720 5.914 6.299 5.177 5.252 5.969 4.858
Napier 5.630 3.571 3.650 1.130 1.358 1.532 3.402 3.681 6.870 2.414 1.539 1.201
Wellington 3.999 3.882 4.453 3.780 3.280 4.540 5.212 5.658 4.299 3.941 5.000 3.500
S. Island.
Nelson 4.319 5.358 8.331 2.063 3.221 6 177 4.441 6.319 6.233 6.319 5.000 4.815
Hokitika 12.169 8.902 9.871 6.752 8.611 6.370 8.240 9.638 9.130 5.878 13.402 12.690
Bealey 14.087 9.681 8.902 3.921 7.433 8.079 5.019 10.378 7.799 5.811 15.501 8.733
Christchurch 1.622 2.311 2.370 1.752 1.811 2.280 3.189 2.449 2.319 1.161 2.142 2.130
Dunedin 3.012 3.599 21.42 2.220 2.122 3.949 2.441 2.500 2.228 2.000 2.500 2.969
Southland 3.622 5.279 3.921 3.980 3.571 5.401 5.019 3.441 4.390 2.661 3.929 4.520

The fluctuation in the annual rainfall at the principal stations is shown in the following table :—

Rainfall.—1866 to 1884.
Stations. Means for each Year, and Difference from General Average.
North Island. 1866. 1867. 1868. 1869. 1870. 1871. 1872.
Auckland 42.000 53.180 49.087 52.797 44.831 47.505 42.096
−3.306 7.874 +3.781 +7.491 .475 +2.199 −3.210
Taranaki 55.700 60.690 50.420, 55.125 54.720 72.120 63.640
−2.384 +2.606 −7.664 −2.959 −3.364 +14.036 +5.656
Napier 30.000 32.850 35.890 23.940
−7.260 −4.410 −1.370 −13.320
Wellington 41.100 41.950 55.522 56.768 48.205 64.057 50.945
−9.681 −8.831 +4.741 +5.987 −2.576′ +13.276 +.164
South Island.
Hokitika 127.500 110.510 120.210 88.210 116.680 122.440 123.210
+15.344 −1.646 +8.054 −23.946 +4.524 +10.284 +11.054
Christchurch 19.400 30.070 30.041 27.292 28.364 27.935 19.741
−6.374 +4.296 +4.267 +1.518 +2.590, +2.161 −6.033
Dunedin 29.000 39.050 33.893 32.918 39.202 22.146 27.393
−3.019 +7.031 +1.874 +.899 +7.283 −9.873 −4.626
Southland 47.200 41.620 46.346, 42.680 53.950 39.030 40.110
+3.526 −2.054 +2.672 −.994 +10.2761 −4.644 −3.564
North Island. 1873. 1874. 1875. 1876. 1877. 1878.
Auckland 41.237 35.024 51.310 44.025 40.375 37.160
−4.069 −10.282 +6.004 −1.281 4.931 −8.146
Taranaki 53.120 57.220 66.960 48.180 52.000 56.730
−4.964 −.864 +8.876 −9.924 −6.084 −1.354
Napier 42.380 37.940 38.260 38.390 33.450 21.100
−5.120 +.680 +1.000 +1.130 −3.810 −16.160
Wellington 54.985 53.496 65.827 43.374 51.925 54.602
+4.204 +2.715 +16.046 −7.401 +1.144 +3.821
South Island.
Hokitika 96.170 104.480 130.790 116*325 136.660 154.446
−5.986 −7.676 +18.634 +4-169 +24.504 +42.290
Christchurch 26.330 22.790 32.310 23-990 23.720 13.540
+.556 −2.984 +6.536 −1-029 −2.054 −12.234
Dunedin 35.825 28.739 42.631 38-260 37.460 45.235
+3.806 −3.280 +10.612 +5-586 +5.441 +13.216
Southland 37.480 44.650 44.180 43.150 54.020
−6.194 +.976 +.506 −.524 +10.346
North Island. 1879. 1880. 1881. 1882. 1883. 1884.
Auckland 46.130 38.890 34.237 45.630 52.215 38.070
+.824 −6.416 −11.069 +.324 +6.909 −7.236
Taranaki 60.180 47.220
−2.096 −10.864
Napier 53.140 38.400
+15.880 +.140
Wellington 57.441 46.767 50.132 55.685 51.994 62.335
+6.660 −4.014 −.649 +4.904 +1.213 +11.554
South Island.
Hokitika 128.295 122.840
+16.139 +10.684
Christchurch 23.180 17.670 *28.071 25.391 30.336 28.451
−2.594 −8.104 +2.297 −.383 +4.562 +2.677
Dunedin 42.099 33.063 26.402 41.796 38.312 33.881
+10.080 +1.044 −5.617 +9.777 +6.293 +1.862
Southland 33.260 39.140
−10.4141 −4.534

* Station moved from Christchurch to Lincoln, Canterbury.

Mean Annual Rainfall.
North Island.
Auckland 45.306
Taranaki 58.084
Napier 37.260
Wellington 50.781
South Island.
Hokitika 112.156
Christchurch 25.774
Dunedin 32.019
Southland 43.674

The observations that have been taken show that the northern part of New Zealand is within the influence of the subtropical winter rainfall, the probability of rainfall in winter in that part of the colony being twice as large as in summer.

In the south, however, the rainfall, though irregular, is distributed more equally over the year. The chief difference to be observed is that on the west coast spring rains prevail, and summer rains on the east coast; while in the middle of the colony the driest season is autumn, and in the south it is the winter and spring.

The contrast between the rainfall on the east and west coasts, as with the temperature, is most striking. Thus, in the North Island, Napier on the east has only half the amount of rain that falls in Taranaki on the west. But the South Island, with its longitudinal range of lofty mountains, exhibits this feature in a still more marked manner, for the rainfall on the west is nearly five times greater than that on the east. The excess of precipitation on the coast is clearly illustrated by the distribution of the glaciers on the opposite sides of the range. Those on the west slope have an excessive supply of snow, and descend to a line where the mean annual temperature is 50° Fahr., while on the east slope they descend only to the mean annual temperature of 37°. The winter snow-line on the Southern Alps on the east side is 3,000ft., and that on the west side is 3,700ft.

The distribution of the rainfall in different parts of the Islands is best expressed by an approximate statement of the hydraulic discharge from the various drainage-areas. The average rainfall, and the percentage allowed for evaporation and soil-absorption, have been estimated for each area from such information as is available, but must only be accepted as provisional.

Schedule of the Principal Rivers in New Zealand, showing approximately the Areas of Watersheds, the Average Annual Rainfall, and Discharge for each.

* Note.—Rivers marked have mountain sources not trapped by lakes, and are therefore subject to exceptional floods.

Rivers. Area. Average Rainfall. Estimated Discharge per Minute. Remarks.
North Island. Sq. Miles. Inches. Cubic Feet.
Waikato 4,768 40 839,168
Kaipara 2,622 47 545,376
Wanganui 2,525 47 525,200
Manawatu * 2,239 65 642,593
Thames 1,779 48 377,148 Including Piako.
Rangitaiki 1,033 30 215,556 Have a common embouchure in a coastal lagoon.
Whakatane 1,014 35 156,156 Have a common embouchure in a coastal lagoon.
Rangitikei 1,435 50 315,700
Wairoa 1,303 45 257,994
Mohaka 1,034 45 204,732
Ngaruroro 843 40 148,368 Might be concentrated on Napier Harbour.
Tutaekuri and Esk 487 35 73,998 Might be concentrated on Napier Harbour.
Tukituki 815 35 125,510
Mokau 815 60 215,445
Patea 622 55 151,146
Waipaoa, Poverty Bay 602 30 80,066 Partly combine in floods.
Gisborne 75 35 11,550 Partly combine in floods.
Hokianga 560 50 123,760
Waiapu 505 40 88,880
Waitara 501 56 123,747
South Island.
Clutha 8,248 30 1,088,736
Waitaki 4,730 26 539,220
Waiau (South) 3,079 41 557,299
Mataura 2,378 30 316,274
Buller 2,341 95 990,897
Taieri 2,317 37 379,988
Grey 1,572 90 624,084
Wairau 1,562 35 240,548
Oreti 1,422 40 250,272
Waimakariri 1,922 55 345,546
Rakaia 1,401 50 308,220
Rangitata 752 48 159,424
Selwyn (Lake Ellesmere) 718 30 94,776
Jacob's 633 40 111,408
Haast 412 125 227,424
Kaduka (Martin's Bay) 283 127 158,480
Hokitika 382 120 202,460
Oamaru Creek 23 22 2,231
Milford Lagoon and Opihi 888 28 109,224

Periods of lasting drought are almost unknown in New Zealand, and only in two instances do the records show a whole month at any station without rain. The greatest day's rain recorded is 6½in. at Auckland, and 9½in. in Nelson. Similar heavy showers occur at the north-west stations, where the general average shows 70in. in eighty-five days' in the year. The opposite extreme is on the south-east, where 34in. fell in 180 days.