Groundwater Quality Assessment and Monitoring Using Geographic Information Systems (GIS) in Port Harcourt, Nigeria

The study evaluated the spatial variation of groundwater parameters in Port Harcourt metropolis using GIS. Thirty two (32) water samples were collected from boreholes from different parts of the study area into a treated and well labeled 1.5 litres plastic bootle. The water samples were then subjected to laboratory analysis for temperature, pH, Calcium (Ca2+), Chloride (Cl-), Total Dissolved Solids (TDS), Nitrate (NO3-), Sulphate (SO42-), Sodium (Na+), Potassium (K+), Magnesium (Mg2+), Electrical Conductivity (EC), Salinity, and bicarbonate (HCO3-). Global Positioning System (GPS) was used to record the latitudes and longitudes of the sampled boreholes. The result from the laboratory was subjected to descriptive statistical analysis in order to determine the mean, range and standard error of each parameter with the use of SPSS. Thereafter the result was imported to ArcGIS to generate the spatial variability maps for some groundwater parameters through the use of kriging in geostatistic module. Surfer 8 was used to generate the 2D and 3D representation of the borehole depths while Idrisi for windows was used to generate the relationship between borehole depth and pH ; and borehole depth and Ca. The result showed that Cl had the highest concentration among the anions with a mean value of 161.49 mg/l and Ca had the highest concentration among the cations with a mean value of 6.53 mg/l. The mean values of the all the groundwater parameters were lower than the WHO standard. Moderately weak inverse relationship was observed between the borehole depth and groundwater pH concentration; and between borehole depth and groundwater calcium concentration. It is recommended that the use of GIS should be encouraged to periodically monitor and assess groundwater quality. Keywords: Borehole, Groundwater, GIS, Geostatistics, Port Harcour

Spatio-Temporal Analysis of Shoreline Changes in Bonny Island, Nigeria

The study examined the shoreline changes over time in Bonny Island of Rivers State, Nigeria. Satellite images comprising of Landsat TM of 30m by 30m of 1986, 2001, 2003 and 2006; and Nigersat image of 30m by 30m of 2004 were used as the sources of data. The satellite images underwent series of geo-processing. The bands (red, blue and green) of each image were combined using Erdas Imagine 9.0. The images were imported to ArcGIS 9.2 whereby the shoreline from each image was digitized as polylines. The shoreline of 1986 was overlaid on that of 2001, shoreline of 2001 was overlaid on 2003, 2003 on 2004 and that of 2004 on 2006. Thereafter, overlaid maps were converted to polygons using Features to  Polygon module of ArcGIS 9.2. The polygons were grouped to advanced (land gained) or retreat (land lost) with which spatial query was done. The result revealed that Bonny Island lost about 1793.24 km2 of land while 419.31 km2 was gained between 1986 and 2001 whereas between 2001 and 2003; 1246.46 km2 was lost while 1200.43 km2 of land was gained. During the period between 2003 and 2004, the analysis showed that 858.47 km2 was gained while 3408.68 km2 was lost whereas between 2004 and 2006, the 2460.30 km2 of land advanced seaward while 2450.03 km2 of land was lost. The percentage change was highest between 1986 and 2001 with 76.62% of land loss. The study recommended periodic monitoring of the coastal area on monthly and yearly bases.Keywords: Shoreline, GIS, Remote sensing, Bonny Island, Water transport, ArcGIS 9.2, Erdas Imagin