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Soil - land use - surface water relationshipPre-remarks: This page is designed to underline the importance of river basin soil characteristics and land use for an understanding of the eco-chemical characteristics of surface waters. Most surface waters can be considered as a very small part of a bigger water body (the ground water within the catchment). The headwater reaches of rivers are usually cleaner and more influenced by soil characteristics than the lowland sections (called potamon). This is the case in streams originating in the Carpathians (example figure 1). Further downstream, physical and chemical reactions in the water body and biological influences gain increasingly more importance for the type and composition of organic and inorganic matter. In the potamon (lowland part of the river), anthropogenic pollution (sewage, polluted ground water) gain more and more importance for the water quality. Additionally macrophytes, phytoplankton and organic sediments change the water quality significantly.
Fig. 1: The River Siret and its basin (red line) down to the Ukrainian state border. The columns show results of electr. conductivity measurements. Anthropogenic loads lead to increases in the downstream direction. In Kiev, the smaller city streams show the opposite: Source waters can be more polluted by agriculture, garden, cattle, etc. than the water downstream. Sedimentation in reservoirs (fish ponds), self-purification and, maybe dilution with cleaner drainage water improve the water quality
Fig. 2: Regular changes of electr. conductivity (medians 1997- 2000, n=96) between source (0 km) and mouth of river Nivka and Siretz
Other than water, sediments are also transported down the river. They originate from erosion caused by agriculture, from storm water run-off in the cities and from river bank erosion. They also have a strong influence on the ecological state of a river. Kiev city rivers (catchments and connected storm water drains): (1.) The first example shows the catchments of four city rivers delineated with the ArcView SWAT program. These are the rivers (from left to the right): Nivka, Siretz, Libid, Darnitza. The source area of the r. Darnitza is divided into 2 subbasins. The big river in the middle of Kiev, flowing from the North to South, is the Dnepr with the reservoir in the North.
Fig. 3 Kiev City River basin delineation The second picture shows the storm water run-off canalisation system connected to the river Siretz (scan from the "Ecological Atlas of Kiev"). During rainy weather and snow melt the Siretz becomes heavily polluted. In times of dry weather, water looks quite clean and clear and its electrical conductivity decreases.
Fig. 4: Rain water canalisation (thick black lines) connected to the r. Siretz in Kiev (flowing from South-West to North-East) Information on the resulting hydrochemical and hydrobiological state of the city rivers are provided here. (2.) Groundwater and soil types The second
example concerns the water quality of
village wells
north and south of Kiev. In spite of local anthropogenic influences, the
concentration of organic compounds (here
controlled by SAC254
measurements) in the
north (sandy soils) was always higher than in the south where one
finds dense soils with bigger buffer capacity
and higher carbonate content.
Here, water only slowly infiltrates into deeper layers
and is filtered more effectively. Fig. 5
shows results of repeated samplings; not all results
are visible because of the map scale!
Fig. 5: Electr. conductivity (EC) and organic matter (SAC254) in village wells west of the Kiev reservoir (A) and south of Kiev (B) (3) The Dnepr and the Pripjat subbasin - large scale differences The main Dnepr tributary from the Northwest is the Pripjat river. In the area west and north-west of the Kiev reservoir (distances up to several hundred km), soils are usually sandy and with low buffer capacity. In lowlands are bogs and marshes or have been there in former times. Ground water in those areas has a smaller el. conductivity (EC), but is rich in humic matter (compare SAC254 in figure 5! of ground water north and south of Kiev. The river water contains humic acids reducing photosynthetic activity. During springtime, many river valleys are flooded and huge landscapes are under water. The water results from snow melt on-site and thereafter in the upstream hills. In early summer, these waters are still connected to rivers but then they evaporate, infiltrate into the soil, shrink and get more and more isolated. In these waters, micro-organisms develop forming the main food source for primary consumers. Among them, Culex (mosquito) larvae appear to be most significant. The Dnepr itself flows from the Northeast (Russia) into the reservoir. It is charged with nutrients enhancing seasonal phytoplankton development. Differences between the west and east side of the reservoir decrease when water flows to the south and becomes more and more mixed. (4) Groundwater lakes in Kiev Another type of water that is strongly influenced by soil characteristics are artificial sand and gravel pits in and around Kiev; they must be considered as "groundwater windows". They are strongly influenced by the inflowing groundwater that was in contact with the upstream aquifer (1). As the organic load has different origins it must be analysed more in detail using various methods of geographical and simple physico-chemical analyses (s. above and and more in detail in the Dnepr report). Organic matter, like humic acids, which are released from the underground, must be taken into account, when assessing anthropogenic influences.
Fig. 6: Sand pit in Kiev and its catchment. A small area near the northern lakeshore (garages and workshops) has the strongest influence on water quality. West and south of the lake, forest is dominating. The aim of the study is to identify the origin of pollution that obviously comes from the northern basin part, to make recommendations for improvements and to assess the possible reduction of nutrients inflow. Conclusion The page underlines the importance of land use and soil types in the river basin on the surface water quality (beside point sources as polluted storm water). This can have an effect on the inorganic and organic water chemistry in general and on eutrophication that must be considered as one of the main problems of water quality (in northern Ukraine) today. This underlines the necessity to include many more aspects into water resources management and to analyse the role of soil types, land use, vegetation cover etc. with corresponding simulation models as the above mentioned SWAT model. (see also another basin study example, the River Ob in Siberia).
Literature: 1. Arbeitsgruppe Baggerseen der Dt. Ges. f. Limnologie (1996): Untersuchung, Ueberwachung und Bewertung von Baggerseen - Empfehlungen und Entscheidungshilfen der DGL. - Mitt., ISBN 3-9802188-7-2, 125 p.
2. HOFFMANN, M. (1986): Untersuchungen zur oekochemischen Bewertung organischer Stoffe im Grundwasser. - Vom Wasser, Bd. 65, 6 p.
3.. HOFFMANN, M., and GALAGAN, A. (1999): Hydrochemical Investigations on the Occurrence of Toxicological Relevant Matter in Rivers and Drinking Water (in Russian). - Chemistry and Technology of Water, 2, p.154 - 166);
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