4.1.2. Monthly observations of the precipitation (M. ZUPAN) The monthly precipitation sampling started in December 1992 at the four meteorological stations Vojsko, Trnovo, Podkraj and Bilje (changed in January 1995 by Slap). In April 1993 Lokve and Postojna were added. The samphng on Trnovo was stopped in July 1994 from technical reasons. The main purpose of the precipitation sampling was to provide the samples for isotope analyses. However we wanted to get some information about the physical and chemical composition of precipitation as well. The samphng was carried out by Bergerhoff (VDI 1972) samplers. In the precipitation samples we analyzed the same parameters than in the spring water samples. The same methods were used (chapter 2.5) and the same control criteria (chapter 4.1.2) than for spring water analysis. The data analysis showed some seasonal trends in some of the sampling points. However, we decided the meteorological data should be taken in to the consideration. Unfortunately it could not be done in the short period of time we had. 4.1.3. Weekly sampling in the springs Hubelj and Vipava (M. ZUPAN) In weekly samples we measured pH value, conductivity, calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), bicarbonate, nitrate, chloride and sulfate. The methods used are described in chapter 2.5 (Water Quality). All measured data were controlled by conductivity (measured and calculated) and ion difference. The permissible value of the coefficient between calculated and measured conductivity 0.9 - 1.1 was taken in to account (GREENBERG et al. 1992). In the Hubelj spring 90 % of analyzed samples were in this range while in the Vipava spring 87 %. The highest value of coefficient for the rest of samples was in the Vipava 1.24 and the lowest 0.85. In the Hubelj the highest coefficient was 1.19 and the lowest 0.85. The calculated ion difference (GREENBERG et al. 1992) was for the Hubelj between -3,5 % and -1-1.6 % and for the Vipava between -3.4 and -1-1.6 %. The summary of the measured concentrations of single parameters is presented in Tab. 4.1. In both springs the most changeable parameters have been conductivity and bicarbonate. The differences between minimum and maximum values have been higher in Vipava than in Hubelj. The changes of calcium concentration have been higher in the Vipava while the changes of magnesium concentration higher in the Hubelj (Fig. 4.6). For the establishment of seasonal changes in the investigation period of time we used AARDVARK (WRc 1995) seasonal model. In the Hubelj spring Tab. 4.1: The summary of the weekly samples in the springs Vipava and Hubelj in the entire investigation period TUE SPRING HUBELJ Parameter Number of samples Minimum value Maximum value Mean value Median value Standard deviation Conductivity - pS/cm - 25° C 145 155 273 217 219 14.4 pH 140 7.2 8.5 8.0 8.1 0.23 Calcium 145 26.1 45.8 38.2 38.3 3.4 Magnesium 144 3.7 11.1 6.9 6.7 1.5 Sodium 145 0.4 1.3 1.0 1.0 0.16 Potassium 145 0.1 0.5 0.2 0.2 0.04 Bicarbonate 114 106.8 158.6 141.7 143.4 6.1 Nitrate 143 3.8 10.4 5.9 5.6 1.1 Sulpliate 144 5.3 17.4 9.0 8.7 1.9 Chloride 144 1.2 7.7 2.0 1.8 0.75 THE SPRING VIPAVA 4/2 Parameter Number of samples Minimum value Maximum value Mean value Median value Standard deviation Conductivity - |jS/cm - 25° C 142 207 333 270 269 22.9 pH 140 7.3 8.4 8.0 8.1 0.19 Calcium 142 28.4 67.2 54.9 55.2 6.4 Magnesium 140 1.1 5.8 3.2 3.1 0.82 Sodium 141 0.5 3.3 1.5 1.5 0.46 Potassium 141 0.1 2.3 0.39 0.3 0.25 Bicarbojiate 103 128.1 213.5 17M 164.7 16.0 Nitrate 142 3.4 9.4 6.6 6.0 0.98 Sulphate 142 7.8 20.1 11.2 10.8 1.7 Chloride 142 1.5 3.9 2.3 2.2 0.44 we found seasonal changes for conductivity, Ca, Mg, Ca/Mg, bicarbonate and nitrate (Fig. 4.7). For other measured parameters the seasonal changes had not appeared. In the Hubelj spring the parameters characterizing the geological origin showed the seasonal changes. The conclusion from the seasonal model could be the hinterland of the Hubelj is not changing a lot in different hydrological conditions. In the Vipava spring only conductivity, the sum Ca + Mg and bicarbonate disclosed the seasonal changes. We could presume the hinterland of the Vipava 12 10 8 ♦ ♦ ♦ i ♦♦ ^ 1 a 6 - f u % \ 4 P 30 40 50 Ca (mg/1) 60 70 ♦ Hubelj o Vipava Fig. 4.6: Calcium and magnesium concentrations in the springs Hubelj and Vipava (412) from the analyses of all weekly samples taken during the observation period. is changing at different hydrological conditions. Namely the concentrations of Ca and Mg are changing very unregularly (Fig. 4.8). Very similar behavior we establish by the comparison of the ratio Ca/Mg with the flow (Fig. 4.9). In the Hubelj the ratio is very constant while in the Vipava much more variable. However, we observed the diminution of the magnesium concentration in the Hubelj up to the discharge about 5 mVs (Fig. 4.10) while in the Vipava spring this interdependence did not occur. Other analysed parameters (pH, sodium, potassium, sulphate, and chloride) have not shown any seasonal variation. Probably they are influenced besides geological structure from pollution sources (wastewater, fertilizers) as well. Finally we tried to find out which time period and frequency of sampling would be enough to get satisfied statistical confidence level. The calculation of the statistical characteristics showed that the results for one year weekly sampling gave us almost the same result than three years long weekly sampling (Tab. 4.2 and Fig. 4.11). For the comparison we choose the year 1994 which was after hydrological characteristics a dry year and the year 1995 which was after hydrological characteristics an average year. T-V I r-T-i—S h k k k i TTS- Fig. 4.9: Measured Ca/Mg-mtios versus discharge of the Hubelj and Vipava (412) springs for all weekly samples. 10 20 30 Flow 40 50 ♦ Hubelj o Vipava Tab. 4.2: The summary of the weekly samples in the spring Vipava and Hubelj in year 1994 and 1995. IHE SPRING HUBELJ Parameter Number of samples Minimum value Maximum value Mean value Standard deviation Year 1994 1995 1994 1995 1994 1995 1994 1995 1994 1995 Conductivity - |jS/cm - 25 "C 51 49 155 170 273 237 218 216 19.2 13.4 pH 46 49 7.2 7.2 8.3 8.5 8.0 8.0 0.27 0.21 Calcium 51 49 34.3 30.9 44.2 42.5 39.5 37.8 2.2 2.7 Magnesium 51 48 3.9 3.7 11.1 10.5 7.2 7.1 1.6 1.6 Sodium 51 49 0.9 0.8 1.2 1.2 1.0 1.0 0.08 0.14 Potassium 51 49 0.2 0.1 0.5 0.3 0.2 0.2 0.04 0.04 Bicarbonate 51 39 106.8 122.0 158.6 158.6 142.7 140.6 11.4 10.1 Nitrate 51 47 4.6 4.8 8.7 10.1 5-9 5.8 0.97 0.88 Sulphate 51 49 5.3 5.8 15.5 17.4 9.1 9.1 2.1 2.1 Chloride 51 49 1.3 1.5 3.3 2.5 2.0 1.8 0.38 0.31 THE SPRING VIPAVA 4/2 Parameter Number of samples Minimum value Maximum value Mean value Standard deviation Year 1994 1995 1994 1995 1994 1995 1994 1995 1994 1995 Conductivity - pS/cm - 25° C 49 48 228 207 333 325 270 269 24.6 25.7 pH 47 48 7.5 7.4 8.3 8.4 8.0 8.0 0.18 0.17 Calcium 49 48 46.8 28.4 65.3 67.2 56.3 53.8 4.2 6.8 Magnesium 49 46 1.1 1.4 5.S 5.0 3.3 3.3 0.93 0.73 Sodium 49 47 1.1 0.8 2.3 3.3 1.6 1.5 0.25 0.40 Potassium 49 47 0.2 0.2 0.7 2.3 0.4 0.4 0.11 2.3 Bicarbonate 45 35 137.3 128.1 201.9 213.5 169.3 166.3 16.1 13.7 Nitrate 49 48 5.2 3.4 8.0 8.4 6.3 6.7 0.62 0.92 Sulphate 49 48 7.8 8.2 17.5 14.5 10.9 11.3 1.7 1.4 Chloride 49 48 1.5 1.6 3.9 2.9 2.3 2.2 0.46 0.34 12 ^ 10 - 8 - i B 6 ' M S 4 - 2 - 0 ^ 30 1994 ♦Vn ♦ ♦ 40 o o o CO o o 50 Ca (mg/l) I ♦ Hubey o Vipava 60 70 12 : 10 8 1 B 6 i M S i 4 - 2 J ♦ \ * ♦ ♦ ♦ O 30 40 1995 C 50 Ca (mg/l) ♦ Hubelj o Vipava o o o 60 70