AG-ECO NEWS
Jose G. Peña
Vol. 22, Issue 29
Professor and Ext. Economist-Management
September 13, 2006
Driest Period On Record; Comparing The 50's To The 2000's
Recovery Will Be Slow And Require Special Planning
Jose G. Peña, Professor and Extension Economist-Management
Rains and the cool weather this past week were a welcome relief from the hot dry
summer, but the region remains very dry. It will take a major sequence of above average
rainfall to recover from the continuing drought. The last 17-month period, from April ‘05
through August ‘06, was the driest period on record. As measured in the weather station in
Uvalde, Texas, only about fourteen inches of total rainfall were received, compared to a long
term average of 39.9 inches for the same period,
How does this drought
compare to the drought of
Figure 1: Annual Rainfall,
Uvalde Weather Station
record of the ‘50s? A quick
comparison (see figure 1)
1904 to 2006
Rainfall in inches
50.0
would indicate that drought of
45.0
the 50's extended for several
35.0
years. Weathermen define a
25.0
true drought as a period when
15.0
average yearly rainfall has
been received. A review of
30.0
20.0
10.0
75% of
long
term
average
5.0
0.0
19
0
19 4
07
19
10
19
13
19
16
19
19
19
2
19 2
25
19
28
19
3
19 1
34
19
37
19
4
19 0
43
19
46
19
49
19
52
19
55
19
5
19 8
61
19
64
19
6
19 7
70
19
73
19
7
19 6
79
19
82
19
85
19
88
19
91
19
9
19 4
97
20
00
20
0
20 3
06
*
75% or less of the long term
40.0
*January-August 2006 only
figure 1 indicates that the drought of the 50's began in 1948, hovered at close to the 75%
classic definition of a drought for four years (1950-1954), skipped 1955 and resumed in 1956.
That year was the lowest rainfall year of the series with only 9.29 inches of annual rain. In
comparison, the current drought began in 2005.
The 50's vs. the 2000's
A comparison of the drought of the 50's and the current drought can be made by
comparing rainfall received, by month, as a percent deviation from the long term average
received (see figure 2). The drought of the 50's hovered at very close to the classic
definition of a drought for several years with an average deficit of 35 percent over 84
months, from January ‘50 through
Figure 2: Percent Deviation From Long Term
Average Rainfall By Month
Uvalde Weather Station
the average deficit for the current
drought is only six percent over an 80
% Deviation from long term average
350.0%
December ‘56 (see 2a). In comparison,
2a: January 1949 to December 1956
300.0%
month period, from January ‘00 through
250.0%
200.0%
August ‘06 (see 2b).
150.0%
100.0%
50.0%
0.0%
’50-’56 AVG
-35%
-50.0%
16 MO.* AVG
-60%
of each drought, rainfall received during
J49
A49
J49
O49
J50
A50
J50
O50
J51
A51
J51
O51
J52
A52
J52
O52
J53
A53
J53
O53
J54
A54
J54
O54
J55
A55
J55
O55
J56
A56
J56
O56
-100.0%
But, comparing the worst period
the sixteen month period, from
*September ‘55 to December ‘56
September ‘55 through December ‘56
%Deviation fromlong term average
350.0%
2b: January 1999 to August 2006
averaged 60 percent below the long
300.0%
250.0%
200.0%
term average compared to an average
150.0%
100.0%
deficit of 64 percent during the 17 month
50.0%
0.0%
-50.0%
17 MO.* AVG
-64%
J99
A99
J9
O- 9
99
J00
A00
J0
O- 0
00
J0
A- 1
01
J0
O- 1
01
J0
A- 2
0
J- 2
0
O- 2
02
J03
A03
J03
O03
J0
A- 4
04
J0
O- 4
04
J0
A- 5
05
J0
O- 5
05
J0
A- 6
06
J06
-100.0%
’00- Aug. ’06
-6%
*April ’05-August ‘06
period from April ‘05 through August ‘06.
Yes, that is about 64 percent less rainfall
than the average amount which has
created the ecological environment which is dependent on that rain. In addition, the drastic
reduction is over an extended monthly period, covering at least three growth cycles (spring,
fall, spring) and is entering a 4th growth cycle.
In the final analysis, the real effect of any drought is its influence on vegetation and
the vegetation’s capability to recover. To recover, the vegetation’s seed or rootstock must
survive a drought. Seed/rootstock must be protected during periods of reduced rainfall,
such as severely reducing grazing pressure. Recovery also requires abundant and timely
rainfall. Abundant, above average rainfall during the five years (1957-1961) after the
drought of the 50's (see figure 1) helped ranges to recover. In addition to continued
reduced stocking rates, we will need similar above average rainfall for several years to
recover from the current drought. Even then it may be difficult to recover. Rain forecasts
appear pessimistic in the short term.
In terms of the current drought, rainfall just prior to this past 17 month period
(Fall/Winter ‘04-‘05) was above average and may have encouraged over-grazing into the
summer ‘05, leaving very little vegetative cover into 2006. Field termites destroyed a lot of
the vegetative cover. Record high temperatures this past summer on bare soil probably
severely weakened the rootstock. It may be difficult to recover, even if we have above
average rainfall. Ranchers realize the severe absence of forage.
After several livestock liquidations during the last several months, especially in
southwest Texas, major livestock movement is underway again. Remaining cattle are being
moved out of Texas, to Colorado and to eastern parts of the U.S. where some forage is
available. The expansion of the U.S. cattle herd as indicated in USDA’s July 12, 2006 midyear U.S. cattle inventory report may be significantly delayed.