Groundwater occurrence and flow patterns in the Ishiagu mining area of southeastern Nigeria

摘要

The Ishiagu area is a water scarce region and has played host to mining activities for more than four decades. Mining-related activities have become a threat to potable water supply in the area. This paper is an attempt to show the extent of this threat and in particular, investigate the regional groundwater occurrence and flow pattern based on GPS, water well and geological data. This basinwide model can be used for further groundwater assessment, pollution control and contaminant management. Groundwater occurs between 2.4 and 9 m in the Lekwesi-Lokpaukwu area; 1.5–3.7 m in the Ndi-Ugbugbor-Ayaragu axis and 1.2–4.6 m in the Ishiagu area. Recharge areas include the Leru-Amaubiri-Lekwesi sandstone hills and the Ihetutu-Ugwuajirija mine field. While the ultimate sink of contamiants is the Ivo River system, other discharge axis is the Ishiagu-Ayaragu axis and the Ogwor Ndi-Ugbugbor zone. An unconfined and a confined (10) circulation groundwater system was inferred, and flow model reveals that a large part of Ishiag-Ayaragu and Ndi-Ugbugbor part of the study area suffer polluted recharge from the Pb/Zn mining area. Groundwater was also subjected to hierarchical cluster analysis and the existence of 3–4 hydrological regimes, which revealed: Unpolluted recharge areas, areas affected by polluted recharge, a deep water and shallow water circulation and mine effluents.