Articles containing the keyword 'pohjaveden pinta'

The aim of this investigation was to examine the dependence of stand volume and increment on different growth factors on drained peatlands drained 20 years ago. Measurements were made in 1977-79 on 35 sample plots in Central Finland on relatively poor pine bogs with a thick peat layer.

It became evident that the stand volume, increment and radial growth and growth development are primarily functions of groundwater depth. Groundwater depth is dependent, in the first place, on ditch depth and ditch condition. With regard to the variation in ditch spacing (ca. 35-70 m) under examination, the effect of ditch spacing on the stand was insignificant. As a practical recommendation it was concluded that ditches should be kept deep enough (> 70 cm) in order to maintain undisturbed stand development.

The PDF includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown

The present study deals with the ground water table in the soil of drained peatlands and with the technique used for its determination. The terms depth and height of the ground water table are defined in the paper. Because of the fact that the surface of peatlands moves under the influence of a great number of different factors, the depth of the ground water table and the height of the ground water table are not parallel concepts. The present paper concentrates on the depth of the ground water table.

Observations on the depth of the ground water table in the sample plots in 1966-67 and 1968-69 show that the maximum of the late summer usually exceeds that of the early spring, and that the minimum occurring in the period of snow melting is more clearly discernible than that of the fall. Great differences occur in the depths of the ground water table in different sample plots. These differences are due to the specific properties of the peat of different peat layers, which are expressed in terms of the ground water coefficient. The duration of the depth of the ground water table proved to be a useful way to express the long-term changes.

Four kinds of short-term fluctuations in the ground water table were observed: a) the ground water table falls during the night hours, although the rate of falling is slower than in daytime, b) the ground water table rests at the same depth during the night, whereas during the day it clearly falls, c) the descent of the ground water table is similar throughout the whole 24-hour period, d) the ground water table rises during the night hours and falls in daytime. Occurrence of these types are discussed. Typical short-term fluctuation is the fall due to evaporation in the daytime.

The third part of the paper discusses the techniques used to measure the changes in ground water table.

The PDF includes a summary in English.

• Heikurainen, E-mail: lh@mm.unknown