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Flooding events and elevated groundwater levels
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4.3.3. Flooding events and elevated groundwater levels
Flooding events and elevated groundwater levels in the transboundary areas of the Basin occur as a result of changes in the hydrological regime of rivers, the swamping of river floodplains and land drainage/irrigation activities (Table 4.1). A detailed causal chain reflecting the links between this issue and the immediate and underlying causes of the issue is shown in Figure 4.4.
Environmental impacts
The impacts of this issue are linked closely with those of a number of other issues including modification of the hydrological regime (Section 4.3.1) changes in the groundwater regime (Section 4.3.2) and modification and loss of ecosystems and ecotones (Section 4.5).
Changes in the nature of biotopes
Species community structure has changed in the flooded/waterlogged areas of the Ukrainian Polessie zone. The species pattern is now dominated by the common and pygmy shrew (Sorex araneus and Sorex minutus). There has also been an increased occurrence of the water shrew (Neomys fodiens), root vole (Microtus oeconomus Pall.), water vole (Arvicola terrestris) and bank vole (Clethrionomys glareolus), and a reduction in the dormice population (Muscardinus avellanarius L.).
More details on the degradation of riparian habitats and the modification and degradation of ecosystems in the Basin can be found in Sections 4.3.1 and 4.5.
Immediate causes
The major immediate causes of this issue in the Dnipro Basin are (also refer to Table 4.17):
- Modification of the hydrological regime;
- Runoff from land surfaces;
- Elevated groundwater and surface water levels;
- Discharges of water from energy and urbanisation.
1. Modification of the hydrological regime and runoff from land surfaces as a result of land reclamation activities
Over 2 million hectares were drained to provide land for arable agriculture in the Republic of Belarus and Russian Federation between the mid-1960s and 1980s, leading to a loss of over 50% of the natural wetland area. The area of drained land in the Republic of Belarus itself is 2 million hectares.
The highly intensive use of land in the region is illustrated by the fact that three fifths of the Basin area have lost their original natural landscape features. About 50% of the territory is occupied by agricultural fields of which over 60% is in Ukraine. Approximately 10% of the Basin area has been designated for land reclamation purposes, 4% is occupied by urban centres and about 1-4% has been lost due to construction of reservoirs and impoundments. Within Ukraine, large-scale land reclamation activities commenced in 1966 and the area of irrigated and drained farmland reached a peak of 2.6 and 2.5 million hectares respectively. More details on land reclamation activities can be found in Sections 3.1.2 (land resource), 3.2.5 (agriculture), 4.3.1 on modification of the hydrological regime and 4.4.4 on suspended solids.
2. Modification of the hydrological regime and elevated ground and surface water levels as a result of historical hydroengineering construction activities
The Dnipro flow has been significantly modified by a large number of reservoirs, channels, conduits, ponds, dams and shipping locks. The number of reservoirs constructed in the Basin is 564 (with a total area of 775.6 km2 and capacity of 46.2 km3). Waterlogging and salinisation of surface and groundwater have affected the surrounding area of many of these reservoirs.
In Belarus, 102 reservoirs have been constructed on the rivers draining the Dnipro Basin, with a total water surface area of 345 km2 and capacity of 1,044 million m3. In the Pripyat River Basin there are 55 reservoirs and 730 ponds. Of these, four major reservoirs (the Zaslavsk, Osipovichi, Svetlogorsk and Chigirin) have a combined water surface area of 74.29 km2. There are 25,000 artificial reservoirs covering 18,000 hectares within the Russian part of the Dnipro Basin. An example of these artificial reservoirs is the large cooling pond attached to the Kursk Nuclear Power Plant site which results in elevated groundwater levels in the adjacent housing area.
The main stem of the Dnipro River in Ukraine has been artificially formed into a series of 6 major reservoirs covering an area of 688 km2. In addition, 6 major channels and 5 conduits have been constructed to supply water from the Dnipro to dry regions of the country. The reservoir chain constructed on the Middle and Lower Dnipro stretch, from the Pripyat River mouth to Kakhovka, includes the Kyiv, Kremenchug, Dniprodzerzhinsk, Dniprovsky and Kakhovka reservoirs. Very little of the natural river channel remains downstream of Dniprodzerzhinsk.
Reservoir construction in this part of the Basin has resulted in the loss of 694,800 hectares of land (including 250,000 hectares of farmland). Continuous waterlogging and elevated groundwater levels have been reported to be a serious issue in areas adjacent to the reservoirs. Section 3.1.1 on water resources and major water bodies in the Basin gives more information on hydro-engineering construction activities.
3. Elevated ground and surface water levels water from mining activities
Sludge fields and tailing waste disposal sites are inherent to the ore enrichment and agglomeration industries concentrated in the Basin. They are mainly located in valleys and gullies and are often directly linked with other infrastructure elements such as water collection and drainage systems, access roads, treatment facilities, and settlement reservoirs. These sites pose a continuous threat of water logging and saline contamination to adjacent surface water and groundwater sources.
Underlying sectoral causes
The major sectors contributing to the issue of flooding events and elevated groundwater levels are agriculture and energy and mining. Urbanisation and transport contribute to a lesser degree. A list of the priority sectors for all issues is presented in Table 18 (Section 4.7)
A detailed causal chain reflecting the links between the immediate and underlying sectoral causes of this issue is shown in Figure 4.4 and a detailed description of terminology used in this causal chain is given in the definition of terms in Annex 2.
Priority inter-sectoral issues
Based on the causal chain in Figure 4.4, the priority sectoral resource uses and practices and the underlying political, economic and governance causes of this transboundary issue can be identified. These are shown in the Strategic Action Programme (SAP) decision making management tool (Figure 4.5).
The SAP decision making management tool shows the priority sectors for this issue (colour coded with the causal chain) together with three hierarchical levels of concern (shown in Section 4.3.1). Within each level the priority resource uses and practices and the underlying political, economic and governance causes for each transboundary issue are listed. These can either cut across all sectors (e.g. Lack of finance) or be sector specific (e.g. construction/poor design of reservoir chain).
Justification for sectoral prioritisation
Justification of the priority sectors that contribute to flooding events and elevated groundwater levels is shown in Table 4.4 below.
Table 4.4. Justification of priority sectors for flooding events and elevated groundwater levels
|
Priority |
Sector |
Justification of priority |
|
1 |
Agriculture: vast area of irrigated land in the southern regions of Ukraine (Kherson, Mykolaiv, Dnipropetrovsk and Zaporizhzhia Oblasts) |
- Excessive use of water for irrigation, exacerbated by elevated groundwater levels. - Inadequate irrigation practices. - Drainage/filtration of water from irrigation channels. - Development of rice fields without proper drainage systems. |
|
2 |
Energy and mining: elevated groundwater levels in the floodplain area of major reservoirs (Kyiv, Kaniv, Kremenchug and Kakhovka reservoirs) |
- Variation of water levels in the reservoirs directly affect groundwater levels and cause their elevation. - Construction and poor design of reservoirs, located in the river floodplains: vast area of agricultural land was inundated without proper containment and drainage arrangements. - Derelict mines and quarries are flooded, affecting the groundwater levels in the surrounding area. |
|
3 |
Urbanisation: within the boundaries of urban centres |
- Excessive watering of city parks and gardens located in the built-up areas and individual garden plots. - Lack of rainstorm water collection systems, combined with elevated groundwater levels. |
|
4 |
River transport |
- The need to meet the water-level requirement for navigation of river transport in the reservoirs. |
