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Suspended solids
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4.4.4. Suspended solids
Suspended solids refers to the adverse effects of
modified rates of release of suspended particulate matter to water bodies
resulting from human activities. Suspended solids are transported from the
territories of the riparian countries and accumulated in the Dnipro Delta. The
pollution potential is thereby significantly increased in the coastal areas of
the Black Sea. The transboundary status of the issue is shown in Table 4.1.
However, based on the prioritisation exercise detailed in Chapter 4, this
issue was not considered a priority transboundary issue. Consequently, detailed causal chain analysis beyond the immediate causes of the issue was not carried out.
Environmental impacts
The impacts of this issue are linked closely with those of a number of other issues including modification of hydrological regime (Section 4.3.1), flooding events and elevated groundwater levels (Section 4.3.3) and modification and loss of ecosystems and ecotones (Section 4.5). The impacts of other water resource pollution issues in this section such as eutrophication and chemical and microbiological pollution are also closely linked.
Modification of habitats and changes in the composition of biological communities
The retrospective analysis of the taxonomic composition of zooplankton inhabiting the Pripyat River Basin indicates that significant changes in zooplankton species composition have occurred since the commencement of intensive land drainage activities in 1961, indicating that elevated levels of suspended solids may have had an environmental impact. Further details on habitat modification can be found in Section 4.5.
Increased rate of sedimentation and siltation
Bank degradation processes in the Kremenchug reservoir have lead to massive inputs of soil material, resulting in progressive sedimentation and siltation. The total annual amount of soil material received by the reservoir as a result of bank degradation is 87.5 million m3/year, with an annual degradation rate of about 100 hectares per year. Erosion processes account for 150-180 kg/ha of humus, 8-10 kg/ha of nitrogen, and 5-6 kg/ha of phosphorus received by the water bodies with surface runoff. Further information on sedimentation and siltation can be found in Section 3.1.2 on land resources and Section 3.2.5 on agriculture in the Dnipro Basin.
Immediate causes
The following immediate causes contribute to suspended solid pollution in the Dnipro Basin (also refer to Section 4.2):
- Significant inputs of suspended solids from point sources.
- Significant inputs of suspended solids from diffuse sources.
- Significant inputs of suspended solids as a result of land drainage/irrigation activities.
1. Significant inputs of suspended solids from point sources
Annually, 18,000 tonnes of suspended solids enter the water bodies of the Dnipro Basin with effluent discharges generated in the Russian Federation. In Belarus, averaged data for the period between 1995 and 2000 indicates that suspended solids accounted for 5% of the total volume of effluents discharged, with the City of Minsk being the major contributor (Figure 4.8). In 2000, the Basin received 28,720 tonnes of suspended solids with effluent discharged from Ukrainian sources. More details on the inputs of suspended solids from point source pollution can be found in Section 4.4.1. The transboundary transport of suspended solids is described in Section 3.3.2.
2. Significant inputs of suspended solids from diffuse sources
The following diffuse pollution sources are considered to contribute to the pollution of water bodies by suspended solids:
- Surface runoff from urbanised areas and major highways;
- Microbiological pollution entering water bodies with surface runoff;
- Direct discharges from livestock-rearing sites and rural settlement areas not connected to centralised wastewater treatment services;
- Transboundary transport of contamination with atmospheric precipitation;
- Pollution transport with rainstorm and snowmelt water runoff from agricultural land;
- Lack of rainstorm runoff collection and treatment capacity.
Information provided by the UkrKommunNIIProgress Institute indicates that 78% of suspended solids enter the water bodies of the Basin with surface rainstorm runoff from urbanised areas. More details on diffuse source pollution can be found in Section 4.4.1.
3. Consequences of land drainage/irrigation activities
In the Republic of Belarus, 1.3 million hectares have been affected by erosion or classified as susceptible to erosion, with about 7.5% of arable farmland being subject to water and wind erosion. A significant proportion of agricultural land in the Russian Federation has also been affected by water erosion.
In Ukraine, large areas of land in the Western Volyn-Podol Province have been affected by erosion, waterlogging and swamping. According to data provided by the State Committee of land Resource Management of Ukraine, 35.2% of the Dnipro catchment area has been eroded. A breakdown by Oblast is shown in Figure 4.15. The largest eroded areas lie in the Donetsk Oblast followed by the Kirovograd, Mykolaiv and Kharkiv Oblasts where about 50% of arable farmland has been affected. In the Dnipropetrovsk, Zaporizhzhia and Kirovograd Oblasts, the total area of eroded land has increased by between 4.6 and 11.2 % over the past 30 years.
The annual loss of fertile soil due to washout from agricultural land is 14.3 tonnes/ha. Of 12.8 million hectares of eroded land in the Dnipro Basin, 1.2 million hectares consists of excessively washed-out soil that requires urgent restoration and grassing. The most fertile Ukrainian black-earth soils have been especially hard hit by erosion (up to 70%). The proportion of slightly washed-out soil has increased by 26% over the last 15 years, with medium to excessive soil washout increasing by 23%.
Figure 4.15. Breakdown by Oblast of eroded arable farmland (%)
The elevated right-bank catchment of the Dnipro between Kyiv and Dnipropetrovsk is dissected by a dense eroded valley network, within which the erosion base is relatively deep (100-160 m) in. The length of the valleys in this network range between 2 km to 6 km, with slopes ranging between 8o and 30o, and depths of several tens of metres. In the Kyiv, Cherkassy, Poltava and Kirovograd Oblasts about 1.5 million hectares of land surrounding the Dnipro reservoirs has been affected by erosion. Within the catchment of the Kremenchug reservoir, over 1.0 million hectares has been eroded.
Further details on the consequences of land drainage/irrigation activities can be found in Section 3.2.5 describing the agricultural situation in the Basin.
Underlying sectoral causes
The underlying causes of suspended solid pollution are mainly associated with resource uses and practices from the following key sectors: agriculture, urbanisation, industry and transport (see Section 4.2).
