To apply the point‐dilution method of measuring the rate of ground water flow by tracers, the distortion of the flow field by the well must be known. The distortion can be calculated with sufficient accuracy if the permeabilities of the aquifer, k3, of the gravel pack, k2, and of the well screen, k1, fulfill the condition k3 ≤ k2 ≤ k1. The tracer must be adequately mixed during the dilution procedure. Experiences obtained from model tests are applied in investigations in the field. By using peak‐to‐peak and total count methods in wells where vertical flow occurred, we could determine the depths and the rates of inflow and outflow, which relate to seepage under dams and water exploration. To determine the direction of ground water flow, a radio tracer was injected into a well‐screen section and, after having left the well‐screen, was detected by a collimated detector. The use of tracers that are fixed on the soil is advisable; 198Au, having been homogeneously distributed within the dilution volume initially, has proved most suitable. Strong vertical currents in the well represent a serious obstacle in field measurements of the rate and of the direction of ground water flow.
Studies that had been started in 1971 were continued in the summer of 1972 in order to gather information on the intraglacial run-off system in the ablation region of Hintereisferner, In a long-term test of 30 h, the daily fluctuations of the inflow into a moulin and the discharge at the glacier mouth were measured. A number of injections of dye tracers were made to measure the curve of concentration versus time. Finally, a test was made to compare with last year's results, in which the inflow was marked with dye at three different points on the glacier. From the long-term measurements, the daily fluctuations of the average velocity of flow in the intraglacial run-off system and the dispersion coefficient were determined. The results confirm the experiments of last year, showing that the melt water reaches the glacier bed taking the shortest possible route without passing through cavities within the glacier, flowing mostly in an open channel.
Relationships between the stable isotope contents (c:5 2 H, c:5 13 C) in dendrochronologically dated tree rings of firs (Abies alba, Black Forest) and air temperature, relative humidity, as well as precipitation rate were investigated for the period 1959 to 1980. Only the late wood of each ring was used, since isotope data from early wood, grown during spring, does not unambiguously reflect the climate of the respective growth season. The c:5 13 C-values, but not the c:5 2 H-values show significant correlations with temperature, humidity, and precipitation. Based on this observation, c:5 13 C-values were used to construct a paleoclimatic record for the past millenium. This required correction for anthropogenic 13 C-inputs since about 1850. The reconstructed temperatures are largely in agreement with presently-accepted variations in the recent past, whereby a "climatic optimum" appears during the Early Middle Ages with August temperatures about 0.5°C higher than today.
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