Assessment and modeling of groundwater quality in Tripoli using ArcGIS and PMWIN

Abstract

The extensive groundwater beneath the Tripoli city is an important source of domestic water. In some areas the potability of groundwater is at risk from high bacteria and nitrate, chloride,sulfate, salinity, & TDS concentrations. A combination of human activities on the land and an unconfined aquifer has led to groundwater pollution. This pollution is a perceived potential hazard and threat to the health and safety of Tripoli community. This study is divided into two sections; the assessment of groundwater in Tripoli city and groundwater modeling flow. The purpose of the first section is to (1) provide an overview of present groundwater quality, (2) determine spatial distribution of the studied groundwater quality parameters using GIS software and (3) generate groundwater quality zone map for the city of Tripoli. Groundwater physicochemical and microbiological characteristics of the Tripoli City aquifer in Lebanon were evaluated over a one-year period. 24 samples were collected from 24 private wells. The ground water quality information maps for the studied parameters and locations of the whole study area have been prepared using GIS spatial interpolation technique. The evaluation result indicates that the levels of the studied parameters were above the Lebanese standards desirable for human consumption and a great attention of the concerned parties is highly needed. Moreover, it is concluded that a combination of groundwater quality parameters and GIS methods is very useful as GIS provides efficient capacity to visualize the spatial data. . It is the first study of its kind in Lebanon where the GIS was applied as an important tool for spatial analysis and data visualization for groundwater quality in Tripoli city. In the second section, groundwater flow modeling, two groundwater models were used, a geographic information system (GIS) and Processing Modflow (PMWIN). ArcMap was linked to the PMWIN to simulate the hydrological dynamic of the aquifer of Tripoli. Groundwater data base imported into the GIS where the aquifer boundary and the hydraulic head of the aquifer were analyzed by raster overlay techniques and imported into PMWIN. The simulation is made in a one layer unconfined aquifer with spatially variable hydraulic conductivities under well-defined boundary conditions. The calibrated model is used to estimate groundwater flow pattern and the interaction of groundwater and surface water. The simulation result shows that the groundwater flows from south eastern escarpment to north-west directions finally join the Mediterranean Sea. This thesis explores the groundwater resource, and assesses the pollution potential. Management options and decision-making as they relate to this pollution problem should be taken into consideration. This thesis has recognized that the groundwater is currently and will continue to be highly used; therefore holistic management of the groundwater and land resources is necessary.