Temporal Variation of Phosphate Contamination in Tropical Epikarst Springs, Gunungsewu Karst Area, Indonesia

Epikarst springs in less developed karst areas typically have predominant diffuse flows where groundwater chiefly moves through spaces between rock grains. This might lead to different flow characteristics between flow dominated by diffuse and dominated by large conduits resulting from dissolution processes. This research aimed to analyze the multitemporal characteristics of phosphate contamination of epikarst spring water in the Gunungsewu Karst Area, Java Island, Indonesia. Phosphate levels were determined from the spring water samples collected every two weeks for nine months to encompass two seasons characteristic of tropical environments: dry and rainy. Results show that the phosphate concentration of the Gedaren Spring exceeded the water quality standard at different times, was likely high in the rainy season and low in dry season and showed positive correlation with rainfall and flow discharge. Further, it was identified that the phosphate was probably generated by agricultural activities or different sources from sulfate and nitrate, as indicated by their weak positive correlations between phosphate-sulfate or phosphate-nitrate. © Published under licence by IOP Publishing Ltd.