THE USE OF INVERTEBRATE COMMUNITIES TO DESCRIBE GROUNDWATER-FLOW AND CONTAMINANT TRANSPORT IN A FRACTURED ROCK AQUIFER

Using an air-lift pump, groundwater invertebrates of a fractured limes tone site recharged with secondary sewage were collected by means of a dense network of deep observation wells. The spatio-temporal distribu tion of organisms throughout the dendritic system of interconnected jo ints and fissures was closely related to the heterogeneous groundwater and sewage flow pattern. During low water periods with high infiltrat ion rates of sewage, groundwater communities were dominated by epigean organisms, which colonized the most conductive fractures. Later on, d uring periods of intensive groundwater recharge, these epigean organis ms were displaced upstream or downstream of the study area and were al so disseminated throughout the adjacent fissure network. They were ass ociated with hypogean organisms, which were only collected when pristi ne groundwater circulated through the openings of the site.