149 
usually in September, the occurrence of minimum levels being 
distributed among the months as follows: In the records at 
Copperas Creek, eight occur in September, six in August, five 
in October, three in July, and one each in November, December, 
and June. The lowest level was recorded at Copperas Creek in 
1879, when the low-water mark was established. It has not 
again been reached, owing since 1889 to the dam at LaGrange. 
The low-water period is often one of marked stability as 
contrasted with other parts of the year, the total movement of 
river levels falling to 0.10 foot per month in November, 1893,. 
and frequently amounting to less than one foot in September, 
October, and November, while even this movement is probably 
caused to a considerable extent by the operation of the locks 
and by changes in the direction or force of the wind. The stage 
of extreme low water is followed by a gradual but very slight rise 
during the fall months, which cannot be attributed entirely to 
rainfall since, as shown in the table on page 126, these are 
months of lessened precipitation. This increase is well shown in 
the hydrographs of 1893 and 1897. It seems more probable that 
with the falling temperatures the loss by evaporation, both from 
the river and its tributaries, is sufficiently lessened to account 
for this slight rise in levels, amounting in most cases to about 
one foot. 
This low-water period is frequently interrupted by minor 
fluctuations, some of which appear at or subsequent to the 
autumnal equinox. These fluctuations are due to heavy sum- 
mer rains, and usually appear suddenly and decline with almost 
equal abruptness. They rarely rise to eight feet and are usually 
below five; they thus do not. cause overflows, and affect only 
those bayous and lakes which maintain connections with the 
river at low-water levels. Their duration is short also, being 
but a week or ten days, rarely a fortnight. In 1896 there was 
a repetition of such rises of more than usual prominence and 
duration, giving a unique character to the hydrograph of that 
year. The equinoctial period, marked by the slightly increased 
rainfall of September, is not marked in the average hydrograph 
