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HYDROGRAPHY.
■i 9
a number of SimUsh Streams
Summer low-water Autumn high-water Winter hieh-water Average Absoln
variation vari uti
Date Height Date Height Date Height ___ cm cm
30 Sept. + 12 22 Oct. + 17 427 570
9 , -15 22 » +- 36 ___ 385 536
3 — 23 10 > + 58 — — 371 430
6 v 44 24 + 65 — — 298 439
24 Aug. -32 6 , 11 WH 150 202
21 » —15 30 Sept. + 15 — - 119 175
8 Sept. 10 23 Oct. + 8 — 78 113
3 « -23 26 - + 26 — - 118 183
27 Aup. — 34 18 Nov. + 29 — - 156 290
18 > — 51 30 Oct. + 25 8 Jan. + 55 149 250
22 » — 34 28 » -i- 15 15 * + 34 82 121
14 - — 57 17 + 59 12 » + 62 140 195
9 Sept. — 39 8 . + 12 21 + 43 116 184
the draining-areas abounding in forest- and bog areas. The low-watg® discharges,
on the other hand, fall in exceptional cases to 1 second-litre per square kilometer.
In the lowland rivers of Central Sweden the variations of the
discharges are of a more southern type, with the summer and winter low-water levels
about equal. The spring level of the water is decidedly the highest of the
year, and occurs, on an average, about the middle of April. As a rule, there
is an autumn flood, too. The amount of the variation is very different, violent
floods occurring in rivers possessing but few lakes, on a surface stratum which
often largely consists of clay.
The run-off is further diminished, as compared with that of the preceding
groups, and remains as a rule (the Fyrisån = 230 millimeters; the
Nyköpingsån = 200 millimeters) at between 5 and 10 second-liters per square kilometer,
the amount of water carried off by the western rivers being considerably greater
than that discharged by the eastern. The run-off percentage falls to o0—40 <v
The highwater discharges are often very great (150 — 200 second-liters per square
kilometer) in the plains where there are few lakes; the low-water discharges, on
the other hand, are very low (< 1 second-liter per square kilometer).
The rivers of the Highlands of Småland have the character of forest
rivers, but their southerly situation gives the variations of water-level a southern
type, with a distinctive summer low-water and a winter low-water of less
importance. As a rule, the former reaches its minimum about the middle of
August, and the latter as early as in the middle of February. The spring
high-water, which, in general, reaches its maximum by the close of March or the
early days of April, is, it is true, the highest of the year as a rule, but the
autumn- and winter floods are, on an average, not much lower.
In general, the average run-off is higher than that of the former group. A
great difference prevails between the eastern and the western rivers. In the
former, the run-off often falls below 10 si per sq. km, especially on the northern
and eastern slopes, or else remains at about that figure (the Helgeån 11
second-liters per square kilometer = 350 millimeters). In the western rivers, again, the
run-off is very great and even exceeds that of the larger number of the
mountain rivers (the River Nissan = 17’3 second-liters per square kilometer = 550
millimeters). This is connected with the strongly marked precipitation maximum
on the western slope of the Småland Highlands. The run-off percentage probably
varies between 30 and 60 %. The high-water discharges are not especially great,
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