Vízhiány és adaptív vízgazdálkodási stratégiák a magyar-szerb határmenti régióban

A projektet az Európai Unió
társ-finanszírozta

Water shortage hazard and
adaptive water management strategies in the Hungarian-Serbian cross-border region

 
  nincs bejelentkezve

Kutatási háttér

European Commission has been increasingly focusing on water-related problems, since increasing frequency of droughts and increased stress on water resources have been experienced in the last decades. Many places showed spectacular landscape changes caused by increasingly rapid alterations of natural phenomena. Due to that, research, monitoring and forecasting become of great importance in Europe and beyond. The importance of the problem is confirmed by the aims of the European Environment Agency that focuses on such proper environmental policies, methods and projects that mitigate the damages due to the effects of climate change. Due to the threatening environmental hazards, adaptation to climate change must be one of the most important goals in water-related investments of Lower Tisza valley. In severe water shortage periods, the lack of water is harmful for all living organism (including humans). Thus the preservation of surface and subsurface water bodies and the supplying in concordance with the natural conditions are also crucial to meet the goals of the WFD until 2015.

In the last century a 0.8°C rise in surface temperature and a 60–80 mm decrease in precipitation were detected in the Carpathian Basin, where water shortage is one of the greatest natural hazards causing serious damages to national economy, especially to agriculture and water resources in the affected years (Rakonczai 2011). The annual temperature trend over Serbia is also following the global changes, but there is a difference between the northern part, where the increasing trend is registered, and the southern part, where the linear trend is negative. Drought is a quite often natural hazard in Serbia; dry years were particularly frequent in the last two decades of the 20th century (Spasov et al. 2002).


Fig. 1.: The triggering deficiency of precipitation is responsible for a typical sequence of meteorological, agricultural and hydrological drought
(from www.drought.unl.edu)
The main types of drought are meteorological, agricultural, hydrological and socioeconomic droughts (Table 1). Droughts are induced by natural climate variability and its propagation through the hydrological cycle. Meteorological drought is the first stage of drought and it starts with deficit in precipitation. Agricultural droughts are initiated by precipitation deficit, stimulated by prolonged period with high temperatures, and (as a consequence) indicated by soil moisture deficits. Hydrological droughts are indicated by surface and/or ground water deficits prolonged in time and space. Socio-economic droughts consequences are highly connected with water, land use practice as well as water competition indices for specific region. As components of hydrological cycle, different drought types are highly connected, but with different speed (dynamic) for separate process and their interactions. Thus, the order of drought types listed in Table 1. describes a gradation in time of appearance and spatial spread. Meteorological, agricultural and hydrological droughts are based on natural processes, whereas socioeconomic drought is a consequence of the previous three drought types - it associates economic good with the elements of meteorological, agricultural and hydrological drought.

Table 1. Basic types of drought (according to American Meteorological Society, 2003)
Type of droughtDefinition
METEOROLOGICAL measure of the departure of precipitation from the normal and the duration of the dry period
AGRICULTURAL precipitation shortages cause differencies between actual and potential evapotranspiration, and soil moisture deficits; moisture in the soil is no longer sufficient to meet the needs of the crops growing in the area
HYDROLOGICAL extended periods of lacking precipitation cause surface and subsurface water supplies (stream flow, reservoir/lake levels, ground water) to drop below normal
SOCIOECONOMIC occurs when water shortages begin to effect people and their lives; it is different than the other definitions in the fact that this drought is based on the process of supply and demand – a socioeconomic drought takes place when the supply of n economic good cannot meet the demand for that product (in this case water)
Drought is such a natural hazard that is the most difficult to define: to give its actual beginning, duration, ending and to quantify its intensity and impacts. Drought is caused by climate variability, which cannot be prevented, but its effects can be reduced through management systems that include self-monitoring and drought early warning of its possible occurrence. Impact of a drought can be identified through the determination and monitoring of various parameters such as the amount of available water, crop condition, the degree of degradation of land, farm productivity, adverse economic impacts through reduced production, loss of profits, staff redundancies, the requirements related to the size of irrigation systems and fields etc.

As shown drought is not a well-defined phenomenon, the professional and the everyday language use this term in very different sense as well. Absence of a precise and universally accepted definition of drought can lead to some confusion as to whether a drought exists and its severity. This causes considerable debate among meteorologists, farmers and public officials. The professional language uses this term to describe the periods with water shortage, when the precipitation is less than the average and it cannot meet the demands (Vermes 2000). Moreover drought is a creeping phenomenon. It is often difficult to ascertain when a drought begins, and when it ends (Warrick et al. 1975). In addition to precipitation, a number of other factors play a significant role in the occurrence of drought such as evaporation, (affected by temperature and wind), soil types and their ability to store water, the depth and presence of ground water supplies, vegetation. Taking this into account, three types of drought are commonly noted: meteorological, agricultural, and hydrological (Fig. 1.).

Past droughts

Each type of drought can be described and characterized through a large number of parameters (temperature, precipitation, intensity of wind, amount of solar radiation, evapotranspiration etc.), or via an indicator, representing the physical processes or the relationship of two or more processes taking place in nature. Drought indicators integrate these climate and hydrological parameters determining the intensity and occurrence of drought. However, drought is a phenomenon characteristic and specific for a particular region, and its temporal and spatial distributions depend on the characteristics of the region being influenced by the particularities of the area exposed.

For the numerical characterization of water shortage, several other drought indices are in use. All of these indices have advantages and also deficiencies, therefore comprehensive studies generally applying more indices to obtain a better result by eliminating the deficiencies of the single indices. The PaDI (Palfai Drought Index) characterises the strength of drought for an agricultural year with one numerical value (Table 1.), thus having strong correspondence with crop failure. It expresses the evaporation (temperature) and precipitation relations (the last one with time-varying water demand of plants), and is in consideration of groundwater level state.

Table 1. Drought categories (Kozák et al. 2011)
PaDI (ºC/100 mm)ClassificationPaDI (ºC/100 mm)Classification
< 4droughtless year10 – 15serious drought
4 – 6mild drought15 – 30very serious drought
6 – 8moderate drought> 30extreme drought
8 – 10medium strength drought  
The strength of drought in Southeastern Europe shows different spatial distribution year by year (Fig. 2). The map constructed from the 10% probability of occurrence of PaDI expresses the spatial difference of droughtness inside the SEE region (Fig. 3.) and clearly confirms the fact that the Hungarian-Serbian cross-border area is seriously affected by drought (Kozák et al. 2011).


Fig. 2. Spatial distribution of PaDI in SEE region in 1988, 2003 and 2007 (Kozák et al. 2011)


Fig. 3. The 10% probability of occurrence of PaDI for SEE region (Kozák et al. 2011)
The precipitation variability in a region can be characterised by the Standardised Precipitation Index (SPI). This index emphasizes the role of the precipitation in drought, thus it shows the degree of water shortage. Also on the basis of the SPI, the cross-border area suffers frequently from water shortage. Figure 4 shows serious water shortage in 2003 and also in 2011 in both countries.
Fig. 4. Spatial distribution of SPI in Europe in 2003 (EurAqua 2004) and in 2011 (ATIKÖVIZIG 2011)
The study of SPI series indicates an increasing frequency of droughts over the last 20 years (1981-2000) in Serbia and also in Hungary. In Serbia in 1990, drought assumed extreme characteristics in wide area of Southwest Serbia and in Norh-East part (Kikinda). In 2000, only western areas were under the strike of a moderate drought, while the drought in all other parts was catastrophic, especially in Vojvodina, Timočka Krajina and South-Eastern areas (Spasov et al). In Hungary there were several years with severe water shortage in the last decades. A typical spatial distribution of the SPI was occurred in 2003, the Fig 5(a) shows that the southwest part of the country is effected mainly by water shortage.
Fig. 5. Spatial distribution of drought in Hungary in 2003(a) (Szalai – Lakatos 2010) and in Sebia in1990(b) and 2000(c) and its severity expressed in SPI values (Spasov et al)

Consequences of water shortage

Water shortage affects the environment and human activities, having social and economic consequences, such as drinking water shortages, agricultural yield reduction, and limitations on touristic activities.

Ground water table

Among the Hungarian landscapes the Danube-Tisza Interfluve faces the most significant environmental problem nowadays. The land-use changes intensifying from the 20th century have contributed to the alteration of landscape (Bíró 2003); the natural areas became degraded and fragmented. The problem is worsened by the melioration in the middle of the 20th century, the growing water consumption of inhabitants (drinking water, communal water use and irrigation), the increasing number of arid years (Pálfai 2000) and the water-uptake of forests extending in the region. Due to these factors, a significant groundwater-table sinking process has been recording since the 1980s in the area (Fig. 6). The water-shortage around the millennium has almost reached 5 billion m3 which amount is equivalent with the total annual Hungarian water-use (Rakonczai 2007).


Fig. 6. The declining groundwater table at a test site (Ladánybene) with higher elevation, where precipitation is the only source of groundwater (Data source: VITUKI, Hungary)

Soil

The continuous sinking of the groundwater-table due to precipitation-shortage causes the alteration of certain soil types (Ladányi et al. 2009, Puskás et al. 2012). The most spectacular changes can be observed in the case of saline soils (Barna et al. 2010). Since the waters of the Carpathian Basin are characterised by high salt content, the decrease of groundwater modifies vertical salt transfer processes (and its direction) in the soil profile, resulting usually the descending of the salt-accumulation zone(Rakonczai et al. 2009).

Vegetation

Landscape alterations related to climate change are much more complex than the decreasing extent of wetlands – however it is doubtless that most of the changes are due to the alteration in the natural water-cycle of landscapes. The effect of climate change in the case of non-woody vegetation of the plains can be very various because of the differences in water supply, soils and micro-relief. Certain vegetation-assemblages have disappeared, the species composition of the different plant associations and their surface-coverage ratios transformed significantly (Ladányi et al. 2010).

The drying of wetlands (Rakonczai-Kovács 2006) and shifts in vegetation zones (Ladányi et al. 2009) can be observed in many cases. The changing circumstances, via aridification, result in the alteration of vegetation dynamics (Kovács 2007). Due to these processes, one third of the vegetation on the Danube–Tisza Interfluve is endangered by the aridification (Kovács 2006). The strong relationship between precipitation and biomass (based on NDVI and EVI vegetation indices) detected in the highest part of the Danube-Tisza Interfluve (Ladányi et al. 2011) also refers to the sensitivity of vegetation.

Damages

In 2007 21 326 hectares of forests were affected by drought damage in Hungary (Hirka, Csóka 2008). The average yield of maize showed a 50 percent decrease in 2007 (3.7 t/ha) related to the previous years (2005: 7.6 tons/hectare; 2006: 7.1 tons/hectare) (Széll, Dévényi 2008). The drought in May 2003 caused serious damages (15-80 %) in the case of 90 percent of the area under cereal production (1.7 million hectares) (Hazafi 2003).

In Serbia, the most extensive damages since 1988 were registered in 1990, 1993, 2000 and 2003. In 1990 the amount of damage was 873 million US dollars (3.5% of total national income). In 1993 the damage was estimated at half a billion US dollars, in 2000 reached 750 million US dollars and in 2003 at one billion US dollars (Dragovic et al 2004). Depending on drought intensity, crop yields may be reduced to 50%. In extremely dry years, yield reduction reach 90% in comparison with years with favourable rainfall. When compared with 1991, which was a favourable year, the yield reductions in year 2000 were 5.9-2.6 t/ha for corn, 2.2-1.6 t/ha for sunflower, 44.9-25.0 t/ha for sugarbeet and 2.6-1.2 t/ha for soybean (Dragovic, Maksimovic).

Future

In Hungary the highest increase in the drought hazard until the end of the 21st century is expected on the Hungarian Great Plain, since the increase of annual mean temperature and the summer days and also the decrease of precipitation will be the highest in this region. Moreover the increase of the extremely heavy precipitation days and the simple daily intensity index indicates that the precipitation will fall more concentrated, which suggests that the frequency and the duration of drought periods will increase. Additionally this region has already the highest drought hazard (Blanka et al., Csorba et al.).

The drought hazard projection can provide valuable data for several sectors of the society and the economy and promoting the development of more optimal planning strategies to mitigate the consequences.

Preparing for prospective drought by developing a more optimal land use and water management should be a key objective of the spatial planning to mitigate the damages of droughts.

Although both countries have climate and drought monitoring programs, until now there has been only limited cooperation and coordination between the countries' drought experts. Past drought assessments typically have stopped at each country's borders as differences in resources and policy objectives as well as differing methods for monitoring drought in each country effectively prevented an integrated view of drought conditions across the continent.