Freshwater - State and impacts (Greece)

The state of freshwater may be described by adequate structural (e.g. river morphology), physical (e.g., temperature), chemical (e.g., phosphorus and nitrogen concentrations) and biological (e.g. phytoplankton or fish abundance) indicators. Following any possible changes in the state, society may suffer positive or negative consequences.

The catchments in Greece are marked by high spatial differences in morphologic, climatic, hydrographic, petrographic and vegetative features and variability in pollution impact. As a result, river and stream habitat, hydrochemical regime and biocommunity structure, vary considerably along their courses. In addition, research on ecological quality assessment is limited and geographically restricted and classification systems are absent. Hence, the assessment of the ecological quality of Greek rivers is a complex task and needs a special approach, since an optimal ‘ecological quality assessment’ can only be achieved through regional adaptations.

The nitrate concentrations in groundwater bodies generally reflect the relative importance and intensity of agricultural activities above them. Mean nitrate concentrations in groundwaters are above the background levels (10 mg/l NO₃), but well below the parametric value of 50 mg/l NO₃ (Drinking Water Directive). Data for 2005 is more representative than those for 1996, due to a greater number of samples (Figure 1; GR – EEA CSI 020). Between 2000 and 2007, the annual average nitrate concentrations in Greek rivers decreased by approximately -43.5 % (from 2.67 to 1.51 mg N/l), reflecting the effect of measures to reduce agricultural inputs of nitrate. Nitrate levels in lakes are generally much lower than in rivers and vary between 0.27 mg N/l and 0.44 mg N/l over the period 2000-2007. The number of monitoring stations in lakes increased from 13 stations in 2000 to 26 stations in 2007 (Figure 2; GR – EEA CSI 020). Phosphorus concentrations in Greek rivers and lakes have generally low levels over the period 2000-2007 (Figure 3; GR – EEA CSI 020).

Greece accounts for about 9.8 % of the reported bathing waters of the European Union (2094 bathing waters). Since the start of reporting in 1990, under the Directive 76/160/EEC, the number of coastal bathing waters has remarkably increased from 683 in 1990 to 2088 in 2008. There were 39 more coastal bathing waters in 2008 than in the previous year. In 2008, 99.5 % of the coastal bathing waters (2078) met the mandatory values, the same as in the previous year. The rate of compliance with the guide values increased by 2.1 %, reaching 97.7 % (2039 bathing waters) (Figure 4; GR – EEA CSI 022).

The number of freshwater bathing waters increased from four since 1992 to six in 2006, and remained the same afterwards. In 2008, all six reported freshwater bathing waters were in compliance with the mandatory and more stringent guide values, compared to the previous year, when four bathing waters met the mandatory values and three bathing waters met the guide values. The compliance rate fluctuates widely from year to year due to the low number of reported freshwater bathing waters (Figure 5; GR – EEA CSI 022).

The complicated geological structure of Greece, in addition to the fact that tectonic movements have occurred many times, had as a consequence the formation of an enormous number of river basins compared to the total surface area of the country. The hydro-geological conditions differ significantly with the geographical latitude and longitude. The main aquifers have been formed either from depositions in layers of sand, gravel and shingle or from chalky rocks that become karst due to the flow of water through cracks that were shaped by tectonic movements. It should be emphasised that groundwater that flows in aquifers of the first category can be utilised more easily and therefore has already been exploited intensively. On the other hand, karst groundwater was not abstracted until 1968 and hence, there is still the possibility of further utilisation. The over-abstraction/exploitation of groundwater resources has in many instances led to the decline of the water table as well as to the deterioration of water quality, primarily through saltwater intrusion in coastal areas.

Figure 1. Nitrate (NO₃) concentrations in groundwater bodies in Greece, 2004-2005

(GR – EEA CSI 020)

Figure 2. Nitrate (NO₃) concentrations in Greek freshwater bodies, 2000-2007

(GR – EEA CSI 020)

Figure 3. Phosphorous concentrations (OP or TP) in Greek freshwater bodies,

2000-2007(GR – EEA CSI 020)

Figure 4. Percentage of Greek coastal bathing waters complying with mandatory standards

and meeting guide levels of the Bathing Waters Directive (GR – EEA CSI 022)

Figure 5. Percentage of Greek freshwater bathing waters complying with mandatory standards

and meeting guide levels of the Bathing Waters Directive (GR – EEA CSI 022)