Spatial and temporal asssessment of groundwater quality for the Nif mountain karstic aquifer

This thesis presents a groundwater quality assessment study for the Nif Mountain karstic aquifer, which is located to the southeast of İzmir. The objectives were to present groundwater quality data, provide a spatial assessment of groundwater quality and to implement a statistical evaluation of seasonal alteration of groundwater quality. The study was basically conducted as a four-stage process involving field work and sampling, sample analyses, production of spatial distribution maps of groundwater quality data, and statistical analyses to test significance of temporal changes in groundwater quality and to understand the relationship between different groundwater quality parameters. Groundwater samples were collected from 59 different sampling points in April and September 2006, representing the wet and dry seasons, respectively. Laboratory analyses of major cations and anions were performed. Concentration distribution maps for nitrate, chloride, electrical conductivity (EC) and hardness were generated using a GIS. Moreover, statistical analyses were performed to test the significance of temporal groundwater quality change. The resulting distribution maps showed that groundwater quality in general deteriorates as water travels from the uplands to the plains. Nevertheless, all the investigated groundwater quality parameters were for the most part of the study area in compliance with drinking water standards, with the exception of some occurrences of high concentrations. The temporal assessment using the paired samples t-test and the Wilcoxon Signed Rank tests revealed that the apparent increase in nitrate, chloride and hardness concentrations from the wet to the dry season was statistically not significant. However, the observed increase in EC values was significant. It was concluded that less groundwater recharge in the dry period of the year does not always cause higher concentrations and that other factors such as water circulation times, lithology, quality and extent of recharge and land use also play an important role on the alteration of groundwater quality.