Abstract
Groundwater constitutes an important source of water supply for various purposes, such as domestic industries and agriculture needs. In the hydrological cycle, groundwater occurs when surface water (rainfall) seeps to a greater depth filling the spaces between particles of soil or sediment or the fractures within rock. Groundwater flows very slowly in the subsurface toward points of discharge, including wells, springs, rivers, lakes, and the ocean. In this study, the integration of remote sensing and geographic information system (GIS) method were used to produce map that classified the groundwater potential zone to either very high, high, moderate, low or very low in terms of groundwater yield. Almost all alluvial plains have a high potential of groundwater occurrence. Meanwhile, in the hard rock areas, groundwater potential is in the high density lineament zones.
1.0 Introduction
Groundwater forms the part of the natural water cycle, which is present within underground strata. The principle sources of groundwater recharge are precipitation and stream flow (influent seepage) and those of discharge include effluent seepage into the streams and lakes, springs, evaporation and pumping (Gupta, 1991). Ground water cannot be seen directly from the earth's surface, so a variety of techniques can provide information concerning its potential occurrence. Geological methods, involving interpretation of geologic data and field reconnaissance, represent an important first step in any ground water investigation. Remote sensing data from aircraft or satellite has become an increasing valuable tool for understanding subsurface water condition (Todd, 1980). They are particularly useful, very detailed and also show up features which cannot be seen easily on the ground. The various surfacial parameters prepared from remotely sensed data and ancillary data can be integrated and analyzed through GIS to predict the potential of ground water zone.
2.0 Objectives
The objectives of this study are as follows:
- To collect the ancillary data and to analyze the remote sensing data for getting information that is related to groundwater occurrence.
- To prepare difference thematic maps from the above information.
- To predict the groundwater potential zone through the various thematic maps using GIS technique.
- To develop a GIS model to identify groundwater potential zones.
- To show the integration of remote sensing and GIS techniques for prediction of the groundwater potential zone in the study area.
3.0 Study Area
Langat Basin is located in south of Selangor and north of Negeri Sembilan within latitude
2
°40'U to 3
°20'U and longitude
101
°10'E to
102
°00'E with the geographical area extent of around 2,394.38 km2 (Figure 1).
Figure 1: Map showung the location of the study area.
4.0 Methodology
In order to prepare the map showing potential zone for groundwater, five stages were applied; Source Data Collection, Image Processing, Building Database, Data Processing and Data Integration as outlined in Figure 2.
4.1 Source Data Collection
The Landsat TM data acquired on 6 March 1996 was collected together with the geological maps sheets 93, 94, 95, 101, 102 and 103 on 1:63,360 scale, prepared by the Minerals and Geoscience Department (JMG); topography maps sheets 3858, 3657, 3757, 3857, 3656, 3756, 3856, 3755 and 3855 on 1:50,000 scale, prepared by Survey and Mapping Department (JUPEM); rainfall data from 1982 to 1996 collected by the Meteorology Department of Malaysia, Drain and Drainage Department (JPS) and Universiti Kebangsaan Malaysia (UKM), soil series map of the study area on 1:150,000 scale, prepared by the Agriculture Department of Malaysia. In addition, hydrogeological map of Peninsular Malaysia on a scale of 1:500,000 and borehole data collected by the JMG were also utilized.
4.2 Satellite Data Analysis
The main task in this stage is to do an analysis and interpretation of satellite data, in order to produce basic maps such as structural and land use map in digital form. Basically, satellite data registration, correction and other image processing (such as enhancement, filtering, classification and other GIS process), together with field checking of the relevant area will be applied in this stage.
4.3 Spatial Database Building
The main task is to bring all the appropriate data (from stage 2 and existing relevant data) together into a GIS database. Basically, all the available spatial data will be assemble in the digital form, and properly registered to make sure the spatial component will overlap correctly. Digitizing of existing data and the relevant processing such as transformation and conversion between raster to vector, griding, buffer analysis, box calculating, interpolation and other format will also be conducted. This stage produces derived layers such as annual rainfall, lithology, lineament density, topography elevation, slope steepness, drainage density, land use and soil type.
4.4 Spatial Data Analysis.
This stage will process all the input layer from stage 2 and 3 in order to extract a spatial features which are relevant to the groundwater zone. This phase includes various analysis such as table analysis and classification, polygon classification and weight calculation. Polygons in each of the thematic layers were categorised depending on the recharge characteristics and suitable weightages were assigned (Table 1-8). The values of the weightage are based on Krishnamurthy et al. (1996 & 1997).
