Abstract
The alluvial aquifer system of the Florina basin (320 km2) in North Greece is a representative area where irrigated agriculture is applied. Groundwater is the main source of water. The highest and mean nitrate concentrations in groundwater are 67.9 mg/L and 25 mg/L, respectively. High values could be associated with the use of nitrogen fertilizers from agricultural activities. This study deals with the evaluation of the groundwater quality. For this reason, hydrochemical analyses from 29 groundwater samples and water level measurements were performed for the wet and dry periods of 2016. The suitability of groundwater quality for irrigation purposes is examined by using different indices (Chlorinity Index, SAR, Sodium Percentage, Potential Salinity and Kelly’s index). In addition, the DRASTIC method was modified by using statistical methods, land use map and nitrate concentrations and applied in order to assess the groundwater vulnerability to external pollution. Notably, there was no correlation between the standard DRASTIC method and nitrate concentrations. However, the modified version and the obtained risk map showed high correlation with nitrate concentrations (ρ = 0.55) and the Groundwater Quality; hence, it is suggested as the base for a protection plan of the alluvial aquifer.
Highlights
Groundwater constitutes a valuable source of fresh water for sustainable water supply for humanity
The aquifer is recharged by the direct infiltration of rainfall with a mean annual value of 50 mm/year, the infiltration of surface water through torrent beds during the wet period, the lateral supply from the neighboring aquifers and the return flow of irrigated water
May and September 2016 verified the direction of the groundwater flow, which is from south to north
Summary
Groundwater constitutes a valuable source of fresh water for sustainable water supply for humanity. Greece and other Mediterranean countries are groundwater dependent, while this invaluable source is under constant stress. In these regions, groundwater constitutes the main source to meet the irrigation and domestic use demands. Degradation of groundwater quality is a limiting factor for the socio-economic development of a region. Direct and indirect human activities such as application of fertilizers, disposal of untreated household wastewater and leachate from landfills in rivers constitute the main causes of groundwater quality degradation [1]. Elevated concentrations of nitrate in groundwater are observed due to extensive agricultural activities and intensive application of nitrogen fertilizers, which is one of the most widespread non-point pollution sources [2]. After 1930, agricultural development led to the use of mineral nitrogen fertilizers [3]
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