HISTORICAL RECORDS: Average Rainfall is increasing though cyclical and a
severe drought occurs on average every 15 years
Rainfall records have been kept at the Millthorpe Post office 13 km away since the year 1900. Sadly
this station was closed in June 2002 and replaced with a station at Orange Airport (OAP), about 10
km north-west of Millthorpe. The Millthorpe records in particular allow us to see how the average
rainfall in the area has fluctuated over that 103 year period. The data in the graph below shows the
Millthorpe data up to 2002, supplemented with the OAP data for the later years until the end of
2011. A moving average with a 10 year cycle is shown together with an average line which appears
to be increasing over time.
Annual average rainfall for Millthorpe (19002002) & Orange Airport (2002-2011) in mm
1800
y = 1.3852x - 1899
1600
1400
1200
1000
800
600
400
200
0
1880
1900
1920
1940
1960
1980
2000
2020
Rainfall records for the property Godolphin are extant for the years 1942-1946, 1965-66, and 1982
to currently. No doubt other years were also recorded but they have been since lost. From May
2006 the data has been recorded automatically using a Davis Vantage Pro weather station which
additionally records every 30 minutes , a range of other variables including temperature,
barometric pressure, evapo-transpiration, solar radiation, wind data and a range of other derived
variables. Automated records are likely to give higher results, particularly for rainfall for the simple
reason the device, unlike humans rarely forgets to take a reading.
Pasture measurement data from 2007 on Godolphin using satellite estimates suggest that annual
average annual pasture growth is zero below an annual rainfall of around 500mm. Using this
definition of a “ severe drought” year, at least for this area, we find that there have been 7 years
when rainfall has been below 500mm, or a “severe drought”, on average every 15 years in the 112
years of records. The 10 driest and 10 wettest years from 1900 to 2011 as recorded at Millthorpe to
2002 and OAP from 2002 to 20011 are shown in the table below. Data from Godolphin is shown in
brackets.
Extremes of rainfall at Millthorpe &OAP
(Godolphin figures in brackets)
10 driest years
10 wettest years
Year mm
Year mm
293 (326)
1944
2010 1580 (1282)
328 (231)
1464
1982
1950
403
1370
1957
1956
455
1347
1940
1973
461
1316
1919
1916
487 (427)
1171
1965
1992
494 (438)
1160
2006
1978
504 (485)
1155
2002
1998
520
1146
1902
1990
543
1138
1908
1974
COMPARATIVE RECORDS: Agreement is good between Orange Airport and
Godolphin but Godolphin is a little colder in winter and warmer in summer.
In fact for the years 1997 to 2011 the correlation coefficient between the average annual rainfall at
the two sites is 0.95 (a figure of 1.0 is an exact match and zero is no relationship at all).
Average annual rainfall from1997 to 2011 is available for both sites although Godolphin records
have only been automated since May 2006. The average annual rainfall for OAP in the period is
867mm compared to 768 mm for Godolphin although there are year by year exceptions.
Historical temperature readings are harder to find than for rainfall. Comparison of the Automated
temperature and rainfall records for 2011 are shown in the table below compared with similar
readings obtained at the Orange Airport. The Godolphin weather station is at an altitude of 850
metres compared to the OAP at 967. Godolphin had slightly lower (colder) minimum temperatures
for each month but mostly warmer (except for January) maximum temperatures.
Year 2011
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
2011
Godolphin
Rain 826.0
mm
24.6
69.8
132.8
35.1
71.1
24.1
29.7
76.7
68.3
54.5
144.8
94.5
Total
826.0
2011
Orange
Airport
Rain 816.0
mm
18.6
66.2
73.4
36.4
66.4
26.6
38.6
80.8
87
55.8
169.6
2011
Godolphin
Temp Mean
min
13.5
12.5
9.5
3.6
-0.4
0.3
-0.2
-0.2
1
4.4
8.8
8.3
97
Total Mean
816.4
5.1
2011
Orange
Airport
Temp Mean
min
14.2
13.7
10.6
5.1
0.9
1.2
0.5
1.3
2.6
5.5
9.9
8.7
Mean
2011
Godolphin
Temp Mean
max
26.7
26.6
22.6
18
13.9
10.7
10.1
14.7
16.7
18.4
23.4
21.7
Mean
6.2
18.6
2011
Orange
Airport
Temp Mean
max
26.8
25.4
21.1
17
12.7
9.9
9
13.2
15.2
17
21.9
20.5
Mean
17.5
Extremes of Temperature at Godolphin ... drought years are colder
The property is hilly and the altitude undulates between 825 and 935 metres so the winters are
naturally cold. Systematic temperature data for the property has been recorded only since its
automation in May 2006. The coldest months are between July and September when it often snows.
At temperatures below zero (it frosts) and above 32 degrees pasture growth stops so the number of
days outside these extremes is critical to plant growth despite adequate rainfall. Plant growth in
2006 (the seventh driest year in the 112 year record) was hit with a double whammy of an above
average number of cold days (117 days from May onwards from table below) and a below average
rainfall (438 mm ... see table above).
Frosts are common. Interestingly it was the drought year of 2006 (the seventh worst since records
began at Millthorpe) where the frosts were most common with nearly one day in three falling below
zero.
Not surprisingly while the winters can be cold, there are not many days that temperature rises above
32 degrees Centigrade in the summer....the range for the 5 ½ years shown below is from 4 to 32
days. Frosts occur as early as March and as late as November.
Jan
Feb
Mar
April
May
June
July
August
September
October
November
December
Number of days below Zero degrees C
2006 2007 2008 2009 2010 2011
0
0
0
0
0
0
0
0
0
0
0
1
1
0
0
0
4
2
3
4
25
6
8
10
9
19
26
12
6
7
13
11
20
17
19
9
16
15
23
5
20
21
12
16
13
16
10
10
5
11
7
5
6
6
2
4
3
0
0
0
0
1
0
0
0
0
0
0
Total >>
117
Month
61
74
66
60
81
Number of days above 32 degrees C
2006 2007 2008 2009 2010 2011
6
3
9
11
4
4
0
9
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
4
0
0
8
0
0
3
0
0
6
0
0
7
11
3
32
11
4
WIND DATA FROM GODOLPHIN
Wind measurements are made by an anemometer which rotates in the wind and as with the
odometer of a car records the total wind run (km), speed (km/h) and additionally the direction.
The monthly wind run data for each month from May 2006 to Dec 2011 are shown as Km below.
2.5
1
2
2
3
1.5
4
5
1
6
7
0.5
8
0
2006
2007
2008
2009
2010
2011
2012