PART 5Soil Moisture Monitoring5.1. Data collection methodsThe soil moisture data collection methods on both sides remained the same as in the previous years. Measurements on the Slovak side are performed by neutron probe down to a prescribed depth or to the depth of the ground water level. Measurements on the Hungarian side are performed by a capacity probe to the prescribed depth. The observation objects were put in the soil layer, down to the underlying gravel layer. The soil moisture on both sides is expressed by the total soil moisture content in volume percentage recorded in 10 cm depth interval for each measurement during the year. The observation points are situated on different monitoring areas. Measurements on the Slovak side are performed on 10 forest monitoring areas, on 5 biological monitoring areas and on 3 agricultural areas – Tab. 5-1. Measurements on the Hungarian side are performed on 9 forest monitoring areas and 5 agricultural areas - Tab. 5-2. The situation of observation objects is shown on Fig. 5-1. Table 5-1: List of monitoring stations on the Slovak side
Table 5-2: List of monitoring stations on the Hungarian side
5.2. Data presentation methodsBoth Parties use the same presentation principle of soil moisture content values: figures showing the average soil moisture content in volume percentage for the depth interval from 0 to 100 cm and from 110 to 200 cm. A small difference is at Hungarian data where the value for depth interval under the 110 cm represents the average value for the rest of total measured depth. The soil moisture time distribution for the whole measured depth is presented on colour figures. The graphical presentation of the whole set of measured data is given in the Slovak and Hungarian National Annual Reports. 5.3. Evaluation of results on the Hungarian sideThe thickness of the soil layer, its composition and the depth of the ground water level besides precipitation primarily influence the soil moisture conditions. The amount of precipitation before the vegetation period was higher by 13 to 46 % comparing to the previous year. During the vegetation period was the amount of precipitation satisfactory, only the last two months (September-October) were very dry. In general, the soil moisture content until July 1999 were good or satisfactory, after some decrease the precipitation in August restored the soil moisture content in the upper layer. At the end of the vegetation period due to the lack of precipitation the soil moisture content continuously decreased. High discharges, which occurred from February to July 1999 positively influenced the ground water level position. Moreover higher flood waves in February and May lifted the ground water level significantly and the ground water on many sites reached the surface. The decrease of discharges from July to the end of the hydrological year caused continuous and significant decrease of ground water levels. The soil moisture content in the forestry monitoring sites No. 9452, 9996 and 9998 was besides the water supply positively influenced by higher discharges in the Danube. The ground water level fluctuated in the soil layer for the whole vegetation period. The ground water level at observation points No. 9355, 9994 and 9995 moisturised the soil layer to a certain extent and the soil moisture in the upper part of soil layer was created also by precipitation (Fig 5-2). At the monitoring sites No. 9498, 9972 and 9997 the ground water arose, but remained in the gravel layer, therefore the water supply in these areas are not sufficient. Moreover the monitoring site No. 9972 is situated near the Danube and is strongly influenced by the drainage effect. The observation site 9997 is situated in the Ásványráró river branch system where the effect of the water supply is low or none and the water level fluctuation depends on the water level fluctuation in the Danube. In general, the soil moisture content, both in the depth down to 1 m and in the depth more than 1 m, comparing to the previous year was higher on all forest monitoring areas. The other observation sites are situated in the agricultural area. The observation object No. 2653 at Rajka is situated in the upper part of the Szigetköz region. The soil moisture conditions depend exclusively on the climatic conditions because the water level always fluctuates in the gravel layer. After construction of the submerged weir the ground water levels arose but still fluctuate in the gravel. The observation points No. 2605 and 9443 are situated in the middle part of the Szigetköz in the flood-protected area and are influenced by the water supply realised by the submerged weir (Fig. 5-4). The soil moisture conditions at the upper part of the soil layer are mainly influenced by the climatic conditions. The water level often reaches the soil layer and influences the soil moisture content. The monitoring site No. 2630 is situated near the Danube and the soil moisture conditions because of the drainage effect of the Danube are mainly influenced by the climatic conditions. The observation point No. 7920 is situated in the lower part of the Szigetköz region. The ground water level depends on the water level fluctuation in the Danube and during the whole year supplies the soil layer. In general, the soil moisture content in the upper part of the soil layer reached average values and during the vegetation period fluctuated in a satisfactory range. In the lower part of the soil layer the soil moisture content was supported by the ground water (except the monitoring site No.2653). 5.4. Evaluation of Slovak resultsThe monitored area on the Slovak side according to the location of the observation objects can be divided into two basic parts: the inundation area and the agricultural area behind the power canal (Fig. 5-1). According to the soil moisture observation at objects situated in the agricultural area it can be stated that the soil moisture content during the whole observed period remained unchanged (Fig. 5-5). The position and fluctuation of ground water level remained unchanged as well. The fluctuation of soil moisture content in the depth interval from 0 to 1 m mostly depends on climatic conditions. In the depth from 1 to 2 m the soil moisture fluctuation is partly influenced by the ground water level fluctuation during higher discharge in the Danube. In 1999 due to good climatic conditions the soil moisture during the vegetation period was slightly higher comparing to the previous year. The situation in the inundation area is more complex. The changes of the soil moisture content depend mainly on the location of the monitoring site in respect to the Danube, in respect to the river branch water supply and to the soil profile thickness. The soil moisture is besides the ground water level and precipitation highly dependent on artificial floods. In 1999 there were no floods simulated due to favourable climatic conditions. However, the soil moisture content due to the lack of artificial floods in general reached lower values comparing to the previous years and from June to October 1999 showed continuous decrease (monitoring sites No. 2703, 2704, 2759-2764). In the upper part of the inundation area, in the region around Dobrohoą» and Bodíky, the thickness of the soil profile, similarly to the Hungarian side, is low (monitoring sites No. 2703, 2764, 2763, 2761). The ground water level fluctuated only in the gravel layer already before damming the Danube. The average values of the soil moisture content, in the layer down to 1 m below the surface, significantly fluctuated, which proves their high dependence on the climatic conditions. The ground water supplied this layer only at higher discharges in the Danube (Fig. 5-6a, Fig. 5-6b, Fig. 5-7). The soil moisture values in the depth interval from 1 to 2 m are less dependent on the short periods of extreme precipitation or temperature. Generally it can be stated that the soil moisture conditions in the upper part of the inundation area in the depth interval from 0 to 1 m depends mainly on the climatic conditions and in the depth interval from 1 to 2 m depends mainly on the water supply from the ground water level. In the middle part of the inundation area the thickness of the soil profile is higher. The ground water regime in this region is influenced by the water supply of the river arms, introduced in May 1993. After a temporary ground water level decrease, just after damming the Danube, the ground water levels returned to the previous level (monitoring sites No. 2758, 2759, 2761) - Fig. 5-8. The ground water level fluctuates mostly above the boundary between the soil profile and gravel layers. The lack of artificial floods in 1999 resulted in continuous decrease of the soil moisture content in the second half of vegetation period. The ground water significantly supplies the soil profile both in the depth to 1 m as well as in the depth interval from 1 to 2 m. In the lower part of the inundation area, downstream of the confluence of river branch system and the Danube, the ground water level fluctuates around the boundary between the soil profile and the gravel layer. The average values of the soil moisture significantly fluctuate. The minimum and maximum values are related to the minimum and maximum ground water levels respectively. The soil moisture in this area highly depends on the ground water level position. After damming the Danube the soil moisture values slightly decreased (Fig. 5-9a, Fig. 5-9b). In 1999 the soil moisture was positively influenced by the long term high discharges in the Danube. Part of the area was often flooded and the soil moisture reached maximal values. But in the second half of vegetation period, when discharges in the Danube dropped down, the soil moisture content rapidly decreased.
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