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Integration of Thematic Maps for Groundwater potential area zoning in Perlis, Malaysia using Geographical Information System and Remote Sensing Image
Ahmad Kamal Md. Issa *,
Zakaria Mat Arof**,
Kamaruzaman Wan Yusof ***
Ahmad Nadzari Yahaya****
* Department of Civil Engineering, Universiti Teknologi MARA (UiTM) Perlis Campus,02600 Arau, Perlis, Malaysia (E-mail : ail : a_kamal62@ perlis.uitm.)
**Associate Professor, Department of Geomatic Sciences, Universiti Teknologi MARA (UiTM) Perlis Campus,02600 Arau, Perlis, Malaysia (E-mail : Zakaria@ perlis.uitm.edu.my)
*** Associate Professor, Department of Civil Engineering, Universiti Teknologi MARA (UiTM) Perlis Campus,02600 Arau, Perlis, Malaysia (E-mail : kzaman@ rocketmail.com)
****Department of Geomatic Sciences, Universiti Teknologi MARA (UiTM) Perlis Campus,02600 Arau, Perlis, Malaysia (E-mail : nadzari @ perlis.uitm.edu.my)
Abstract
The area of study is Perlis, the most northern state of Malaysia. Groundwater forms part of the natural water cycle and occupies the pores within the underground strata. Water supply for irrigation and domestic use in Perlis is mainly supplied from surface waters, with groundwater supplementing this supply for localised uses. This study investigates the analysis of remote sensing image together with geological, contour, river and drainage data, boreholes and wells data using GIS to produce different thematic maps. These maps are tailored to the predefined criterias to predict the most potential groundwater zone in the study area. Darcy’s Law for groundwater flow and the modified DRASTIC equation have been employed in the prediction of groundwater potential.
1 INTRODUCTION
Groundwater forms part of the natural water cycle and constitutes a major portion of the cycle. Groundwater is present in various types of geological formation and occurs in permeable geologic formation called aquifers which can store and transmit water. In most parts of Malaysia, groundwater resources are underutilized. (Jasni Y. et al, 2006) The use of groundwater for domestic purpose is mainly confined to rural areas where there is no piped water supply except in Perlis and Kelantan, where groundwater is being significantly utilized for public water supply. (Table 1).
Groundwater Production (EPU (2000)
In the mineral water industry, groundwater is treated before bottling. For industrial purposes, groundwater is usually utilized in cleaning and cooling. Groundwater utilization for agricultural purposes is not very well developed and is normally confined to isolated agricultural areas or areas outside the many irrigation schemes. Thus a major portion of water demand in Malaysia is being supplied from surface water sources. These surface water resources are deemed inadequate to fulfill the water demand for the future (EPU, 2000). Productivity through ground water is quite high to fulfill this future water demand. But ground water resources have not yet been fully developed through exploration.
Water supply for irrigation and domestic use in Perlis state, Malaysia is mainly supplied from surface water from the Timah Tasuh dam in Perlis state, and the Muda and Pedu dams in neighbouring Kedah state. Groundwater supplements this supply mainly for localised uses (EPU, 2000). Malaysia is water-stressed, and recent severe droughts in the last few years have caused these dams’ water levels to drop drastically (Berita Harian-26 February 2005; The Star-18 August 2005). If groundwater can be a viable alternative source of water supply for multi-purpose usage, it can be better exploited if potential areas with abundant groundwater can be identified.
Groundwater cannot be seen directly from the earth surface, so a variety of techniques can provide information on its potential occurrence. Existing methods of identifying potential groundwater areas using geophysical and geo-electrical techniques are time consuming and costly. Geographical Information System (GIS) is used in this study to identify potential groundwater areas, by integrating satellite data on land use, with data on geology, topography and drainage. Water Resources Management using Geographical Information System (GIS) has been viewed as a critical solution to solve the water management problem. (Deepak et al, 2002)). The use of remote sensing and GIS techniques in prediction groundwater zones is not entirely new. The fullest utilization of the potential of the new technologies can be realized only when an integrated approach is adopted. Blending of these two technologies has proved to be an efficient tool in groundwater studies (Saraf and Chodhury, 1998).
In Malaysia groundwater potential is mainly in alluvial aquifers and hard rock aquifers. Alluvial aquifers mainly compose of gravel, silt, sand and clay are the most productive and are situated along rivers in the coastal plains. Hardrock aquifers can be limestone aquifers and fractured rock aquifers. Alluvial aquifers and limestone aquifers typically are most productive, while fractured rock aquifers (made up of various sedimentary, metamorphic and igneous rocks ) are comparatively poor yielding. (Jasni, Y. et al, 2006)
In Perlis, groundwater resources have been developed to meet the needs of small communities and isolated industries; generally those without access to piped supplies from surface resources. The geological stratigraphy of the study area is mainly alluvium soil, gravel and sand layers, and limestone hardrock formations peculiar to Perlis state and its surrounding regions. Almost all alluvial plains have a high potential of groundwater occurrence, while in hardrock areas, groundwater is greatest in the high density lineament zones. (Khairul Anam et. al , 2000). Current groundwater utilization for Perlis is at 10 Mld. (EPU, 2000). There are available groundwater resources in Perlis which can be utilized to supplement surface water sources to meet future demand of water. Potential areas are located mainly within the Setul and Chuping limestone formations, and the Batu Arang semi- consolidated formation, providing an estimated total yield of about 44 million litres per day (Mld). (Table 2)
Groundwater Quantity Potential in the three important formations in Perlis (EPU (2000)
1.1 Objective
In this study an attempt is made to produce thematic maps , using the technique of integration of various data using GIS. These thematic maps are tailored to identify zones of high and moderate potential groundwater in Perlis state.
1.2 Study Area
The study area is the whole Perlis state, situated in north- western tip of the Malaysian peninsular, bounded between latitudes 5o 05’ and 6o 35’ and between longitudes 99o 35’ and 100o 50’. The state of Perlis is bounded by Thailand in the north, Kedah in the south, while its western coastline borders the Straits of Malacca. Covering an area of 795 sq. km. Perlis state comprises of paddy areas in the south and the Mata Ayer Forest Reserve in the north up to the Malaysia- Thailand borders. At present, the land use of the state’s economic activities are mainly agricultural, where major crops are paddy, oil palm, rubber and sugar cane, which made up about 54.5%. Forest, bushes, shrubs and rivers cover about 32.7% of the total land area. In the last two decades, industrial areas have been created at various localities.
The population of Perlis was 190,000 as per census conducted in 1991 and is expected to reach 490,000 in 2050. (Dept. of Statistics Malaysia, 1995). Between 1980 and 1991 the population was growing at 2.15% per annum, a moderately low rate by Malaysian standards. Fertility can be considered as moderately high with a crude birth rate of 26.2 birth per thousand population for Perlis in 1991. This rate was slightly higher than those of Pulau Pinang, Perak, Negeri Sembilan and Kuala Lumpur but was lower than those of the other states. Mortality was low at 5.3 deaths per thousand population. As a result the rate of natural increase was moderately high at 20.7 to 22 per thousand populations (Dept. of Statistics Malaysia,1995)
The climate, which is usually hot and wet, is basically controlled by the annual fluctuations in position of the Inter Tropical Convergence Zone (ITCZ) as it follows the apparent movement of the sun north and south of the equator. This results in two distinct rainy periods, and a prolonged drought period. Perlis has a tropical monsoon with ‘winter winds’ (northernly wind from the Siamese Bay) with temperatures between 21 -33 degrees Celsius. Its climate experiences two distinct rainy periods (April- May, and September- October) and a prolonged drought period between December- March associated with the north-east monsoon. The drought period spans the months of December to March is associated with the north-east monsoon. The two periods of rainfall are associated with the advance and retreat of the south-west monsoon, in April –May and September –October. The latter period produces greater depths of rainfall. The annual range of the temperature is from 21oC to 32oC while the mean annual rainfall is between 2000mm to 3000 mm. The rainfall has peaks during both the post-equinoctial transition periods between the monsoons. Analysis of rainfall data indicates higher mean monthly rainfall occurs between May to November, while less rainfall in December to March. Less rainfall occurs to coastal areas compared to the interior areas (EPU, 2000).
1.3 Geology of Study Area
The geology of Perlis consist of mainly alluvium, gravel and sand layers, and limestone hardrock formation. The local stratagraphical nature of the study area indicates that several rock stratas in the area may be treated as groundwater aquifers.
The Chuping limestone forms a row of limestone hill outcrops, while the Setul limestone formations forms a major column in the west ,can be considered as important groundwater reservoirs. The Bukit Arang Coal Beds, which lie in the north-eastern region consists of a semi-consolidated sequence of gravel, sand and clay with thin lignite seams, also constitutes a principal source of groundwater.(Chong, F.S., 1976). These three formations offer a potential of good groundwater sources in Perlis. (Jones, 1978)
Two contrasting limestone formations occur in this region (Jones, 1978). The thick Lower Palaeozoic Setul limestone crops out in west Perlis. This rock is well bedded and contains considerable quantities of fine detrital and carbonaceous matter. This gives rise to fairly thick residual soil in places which supports thick vegetation. This to some extent inhibits the development of extreme karst conditions, which is very rugged and rocky country normally developed over limestone. Nevertheless, the terrain is extremely rugged with numerous protruding rock pinnacles, swallow holes, cliffs and dry valleys. Due to its thickness, the Setul formation tends to form long lines of continous country hill, as is the imposing Setul Boundary Range over west Perlis.
The younger Chuping limestone crops out in central Perlis. This rock is a pure carbonate, and is thinner and more massive than Setul limestone. It is characterized by extremely rugged terrain with abundant cliffs and stunted vegetation, most distinctive being the isolated limestone hills in central Perlis. Here, the superimposition of the hill sculptures form some drainage patterns within a narrow synclinally folded outcrop has deeply dissected the limestone to form lines of abrupt disconnected hills, which rise vertically to dramatic heights above the coastal plains and low undulating country.
The Kubang Pasu- Singa formation is a Devonian-Carboniferous sedimentary rock consisting of quartzite, subgreywackle, shale, mudstone and siltstone, is a major make- up of the northern part of Perlis. Alluvium forms most of the southern part of Perlis.
A haphazard pattern of meandering streams is found over much of central and eastern Perlis. A well developed system of underground streams occur throughout the limestone of the Setul Boundary range. Occasionally rivers run at the surface for short distances as in Wang Kelian and Wang Tangga, before disappearing below ground to pursue subterranean courses. All rivers drain ultimately into the estuaries of the Sungai Perlis (Figure 1).
1.4 Hydrogeology
Groundwater is recharged by the infiltration of rainwater through permeable soil and rock cover, irrigated lowlands, and fault surface. Groundwater supply is also supplemented by stream percolation and by seepage from the paddy fields. Stream and deep percolation of rainfall combine to provide a greater amount of recharge than from irrigation water. Recharge by subsurface inflow can be considered negligible compared to other sources.
Discharge from aquifers occur naturally by transpiration through vegetation, direct evaporation from saturated zones, return to surface drainage through seepage and springs, outflow to sea, and extraction. Results from hydrogeological survey carried out in 1957 to 1959 sponsored by the United Nations concluded that the alluvium in southern Perlis contained aquifers with abundant supply of groundwater. (Jones, 1978). Further investigations involving ground surveys, seismic investigations and exploratory drilling were carried out by the Malayan Geological Survey with the cooperation of the UNDP between 1957 and 1958. However, the Kedah- Perlis Water Resources Management Study (1981) reported that there was no regionally extensive aquifer system in Perlis and that groundwater is localized depending upon geological conditions.
Geological Map of Perlis
.2 METHODOLOGY
In this study, GIS software (ERDAS Imagine 8.6, Arc View 3.1 and MapInfo 7.0) is used as a data processing tool, on all spatial data and attribute data. GIS is used fully to do spatial analysis on input data to produce thematic layer maps. These thematic layer maps are integrated to produce a map of potential groundwater zones in Perlis state. In this study groundwater potential is based on the universally accepted Darcy’s Law for groundwater flow and the modified DRASTIC equation (Khairul et al (2000). Table 3 below shows the schematic outline to this approach.
First Stage ------------------------------------------------------------------------------------------------------------
Second Stage ------------------------------------------------------------------------------------------------------------
Third Stage ------------------------------------------------------------------------------------------------------------
Fourth Stage ------------------------------------------------------------------------------------------------------------
Fifth Stage ------------------------------------------------------------------------------------------------------------
TABLE 3: Methodology of Study
2.1 Darcy’s Law for groundwater flow
In saturated conditions, one-dimensional flow is governed by Darcy’s Law (Todd, 1980) which states that the flow velocity is proportional to the hydraulic gradient
v= k.i
where v = flow velocity
k = coefficient of permeability
(measure of soil resistance to flow)
i = hydraulic gradient = H/L
Whitlow (2001) then stated that in an aquifer, the quantity of flow through an aquifer is given by Q= A.v. = A.k.i
where Q =quantity flowing in unit time
A =cross-sectional area through which flow is taking place
i = slope of water table
2.2 DRASTIC Empirical Model
DRASTIC is an empirical model developed by U.S. Environmental Protection Agency (EPA) which is widely used for evaluating relative groundwater pollution susceptibility by the use of hydro-geological factors (Aller et al, 1985). It is an acronym for the seven (7) most important hydro-geological features affecting groundwater pollution, which are:
Groundwater Pollution Potential= D+ R+ A+ S+ T+ I+ C
Where D= depth to water table
R= net recharge
A= aquifer media
S= soil media
T= topography
I= impact of vadose zone media
C= hydraulic conductivity of aquifer
Kiran, P.S.R et al (2008) has demonstrated the successful use of this model in developing a groundwater contamination risk map using GIS techniques in Younggwang, Korea.
2.3 Modified DRASTIC Equation from Khairul et al (2000)
Based upon the original DRASTIC model for evaluating groundwater pollution above, Khairul Anam et al (2000) has proposed that the modified formula for groundwater potential (GP) has eight (8) important factors, and is as follows:
Groundwater Potential = Rf + Lt + Ld + Lu + Te + Ss + Dd + St
Where Rf= annual rainfall
Lt= lithology
Ld= lineament density
Lu= land use
Te= topography elevation
Ss= slope steepness
Dd= drainage density
St= soil type
This modified DRASTIC model has been successfully used in a similar study (Khairul Anam et al, 2000) to predict groundwater potential in the Langat basin area, Malaysia using the integration of remote sensing and GIS.
3. DATA PROCESSING
Based upon these models, the initial choice of main input is spatial data consisting of a multi spectrum SPOT (Systeme Pour l’Observation de la Terre) satellite image of Perlis state (dated 2005) with a resolution of 20 meters. In a similar study employing GIS to map the landuse cover of northern Perlis, Kamaruzaman et al (2005) successfully utilised a Landsat TM image of Perlis.
Other spatial data were obtained from various Malaysian government agencies as in Table 4, consisting of topography map, geology map, soil series map, state road map, and borehole and well site map. Attribute data used here mainly consists of data on rainfall and existing boreholes and wells abstraction in the study area.
4. ANALYSIS AND DISCUSSION
4.1 Generation of Thematic Layers
Satellite data processing and analysis by method of unsupervised classification of the image, was carried out using ERDAS Imagine software at Universiti Teknologi MARA (UiTM) Perlis Campus’ Remote Sensing Laboratory. Next, GIS processing for building the database involved digitizing the topography map, geology map, soil series map and state road map. Using Arc View software, attribute data on volume of daily rainfall was entered to produce a rainfall coverage map. Coordinates (x and y) of existing boreholes and wells were recorded. A landuse map of Perlis state was produced where six classes of landuse were identified; consisting of water bodies (Timah Tasuh dam), human settlement areas, forests, paddy planted areas, sugar cane plantations in Chuping area, and rubber plantations. A total of eight thematic layer maps were produced: landuse, geology, rivers and drainage, land administration areas or ‘mukim’, borehole, well, soil types, and rainfall. This follows a similar technique used by previous researchers (Rao Toleti et al, 2000; Khairul et al, 2000; Singh and Prakash, 2004).
4.2 Discussion of Results
Figure 2 shows the result of this study. This map of Perlis indicates the most potential zone (pink) and moderately potential zone (grey). The high terrains in the north of Perlis serves as collecting points of groundwater sources. Due to the high gradient of slope groundwater seeps and collects in the Chuping and Setul Limestone formation and the Kubang Pasu- Singa formations. The map indicates that the central Perlis area around the towns of Arau and Kangar are highly potential areas of groundwater. These two towns are situated around the Chuping and Setul Limestone formation and the Kubang Pasu- Singa formations.
Map of Potential Groundwater zones in Perlis
4.3 Comparison with Past Studies
There have been many high yielding tubewells drilled by various parties in Perlis over the last 50 years. The National Water Resources Study 2000 records that around 130 tubewells were drilled in Perlis with approximately 60 yielding wells. Most of the high yielding wells are located within the Chuping Limestone and Setul Limestone formations and the semi-consolidated Bukit Arang Coal Beds formation. The geology of the study area indicates that the Chuping Limestone and the Setul Limestone formations can be considered as important groundwater reservoirs. The gravel and sand layers of the Bukit Arang Coal Beds also constitute principal sources of groundwater. These three formations make up the best groundwater sources in Perlis. Finally alluvium is probably an important source of groundwater because of their natural distribution, thickness of aquifer, permeability and proximity to recharge area. (Jones, 1978)
The results obtained from this study, based on the integration of Remote sensing and GIS of the study area, is comparable to The National Water Resources Study 2000-2050 (EPU, 2000) which estimated the groundwater quantity potential expected from these three important formations.
5. Conclusion
Based on the present investigations, the following hydrogeological evaluations can be made in relation to the geological setting of Perlis:
The three geological environments listed below are the most favourable for occurrence of groundwater:
a) limestone bedrock
b) gravels and sands in sub-alluvial valleys
c) the upper 10 to 20 feet of coastal alluvium
There is adequate scope for future development of groundwater in Perlis, especially from the Chuping Limestone, Setul Limestone and Bukit Arang Coal Beds formations.
These results suggests that the spectral and spatial characteristics of SPOT satellite data can serve groundwater investigations. The results also suggest that a raster-based GIS can facilitate the necessary digital analysis and manipulations, including data integration, geocorrections, and handling classification. It is foreseen that some of the recommended refinements for future advancement of this study may include addition of other data (e.g. recharge, soil suction, pore pressures, temperature changes) as thematic GIS layers, determining the criterias/ constraint factors, processing of thematic maps using supervised classification, and assigning weightage to data layers based on accepted engineering principles to reflect their characteristics and relative importance.
In conclusion, satellite remote sensing and GIS has been successfully used to generate the necessary dynamic information for groundwater prediction in Perlis, Malaysia.
References
Ahmad Kamal Md. Issa *,
Zakaria Mat Arof**,
Kamaruzaman Wan Yusof ***
Ahmad Nadzari Yahaya****
* Department of Civil Engineering, Universiti Teknologi MARA (UiTM) Perlis Campus,02600 Arau, Perlis, Malaysia (E-mail : ail : a_kamal62@ perlis.uitm.)
**Associate Professor, Department of Geomatic Sciences, Universiti Teknologi MARA (UiTM) Perlis Campus,02600 Arau, Perlis, Malaysia (E-mail : Zakaria@ perlis.uitm.edu.my)
*** Associate Professor, Department of Civil Engineering, Universiti Teknologi MARA (UiTM) Perlis Campus,02600 Arau, Perlis, Malaysia (E-mail : kzaman@ rocketmail.com)
****Department of Geomatic Sciences, Universiti Teknologi MARA (UiTM) Perlis Campus,02600 Arau, Perlis, Malaysia (E-mail : nadzari @ perlis.uitm.edu.my)
Abstract
The area of study is Perlis, the most northern state of Malaysia. Groundwater forms part of the natural water cycle and occupies the pores within the underground strata. Water supply for irrigation and domestic use in Perlis is mainly supplied from surface waters, with groundwater supplementing this supply for localised uses. This study investigates the analysis of remote sensing image together with geological, contour, river and drainage data, boreholes and wells data using GIS to produce different thematic maps. These maps are tailored to the predefined criterias to predict the most potential groundwater zone in the study area. Darcy’s Law for groundwater flow and the modified DRASTIC equation have been employed in the prediction of groundwater potential.
1 INTRODUCTION
Groundwater forms part of the natural water cycle and constitutes a major portion of the cycle. Groundwater is present in various types of geological formation and occurs in permeable geologic formation called aquifers which can store and transmit water. In most parts of Malaysia, groundwater resources are underutilized. (Jasni Y. et al, 2006) The use of groundwater for domestic purpose is mainly confined to rural areas where there is no piped water supply except in Perlis and Kelantan, where groundwater is being significantly utilized for public water supply. (Table 1).
Groundwater Production (EPU (2000)
In the mineral water industry, groundwater is treated before bottling. For industrial purposes, groundwater is usually utilized in cleaning and cooling. Groundwater utilization for agricultural purposes is not very well developed and is normally confined to isolated agricultural areas or areas outside the many irrigation schemes. Thus a major portion of water demand in Malaysia is being supplied from surface water sources. These surface water resources are deemed inadequate to fulfill the water demand for the future (EPU, 2000). Productivity through ground water is quite high to fulfill this future water demand. But ground water resources have not yet been fully developed through exploration.
Water supply for irrigation and domestic use in Perlis state, Malaysia is mainly supplied from surface water from the Timah Tasuh dam in Perlis state, and the Muda and Pedu dams in neighbouring Kedah state. Groundwater supplements this supply mainly for localised uses (EPU, 2000). Malaysia is water-stressed, and recent severe droughts in the last few years have caused these dams’ water levels to drop drastically (Berita Harian-26 February 2005; The Star-18 August 2005). If groundwater can be a viable alternative source of water supply for multi-purpose usage, it can be better exploited if potential areas with abundant groundwater can be identified.
Groundwater cannot be seen directly from the earth surface, so a variety of techniques can provide information on its potential occurrence. Existing methods of identifying potential groundwater areas using geophysical and geo-electrical techniques are time consuming and costly. Geographical Information System (GIS) is used in this study to identify potential groundwater areas, by integrating satellite data on land use, with data on geology, topography and drainage. Water Resources Management using Geographical Information System (GIS) has been viewed as a critical solution to solve the water management problem. (Deepak et al, 2002)). The use of remote sensing and GIS techniques in prediction groundwater zones is not entirely new. The fullest utilization of the potential of the new technologies can be realized only when an integrated approach is adopted. Blending of these two technologies has proved to be an efficient tool in groundwater studies (Saraf and Chodhury, 1998).
In Malaysia groundwater potential is mainly in alluvial aquifers and hard rock aquifers. Alluvial aquifers mainly compose of gravel, silt, sand and clay are the most productive and are situated along rivers in the coastal plains. Hardrock aquifers can be limestone aquifers and fractured rock aquifers. Alluvial aquifers and limestone aquifers typically are most productive, while fractured rock aquifers (made up of various sedimentary, metamorphic and igneous rocks ) are comparatively poor yielding. (Jasni, Y. et al, 2006)
In Perlis, groundwater resources have been developed to meet the needs of small communities and isolated industries; generally those without access to piped supplies from surface resources. The geological stratigraphy of the study area is mainly alluvium soil, gravel and sand layers, and limestone hardrock formations peculiar to Perlis state and its surrounding regions. Almost all alluvial plains have a high potential of groundwater occurrence, while in hardrock areas, groundwater is greatest in the high density lineament zones. (Khairul Anam et. al , 2000). Current groundwater utilization for Perlis is at 10 Mld. (EPU, 2000). There are available groundwater resources in Perlis which can be utilized to supplement surface water sources to meet future demand of water. Potential areas are located mainly within the Setul and Chuping limestone formations, and the Batu Arang semi- consolidated formation, providing an estimated total yield of about 44 million litres per day (Mld). (Table 2)
Groundwater Quantity Potential in the three important formations in Perlis (EPU (2000)
1.1 Objective
In this study an attempt is made to produce thematic maps , using the technique of integration of various data using GIS. These thematic maps are tailored to identify zones of high and moderate potential groundwater in Perlis state.
1.2 Study Area
The study area is the whole Perlis state, situated in north- western tip of the Malaysian peninsular, bounded between latitudes 5o 05’ and 6o 35’ and between longitudes 99o 35’ and 100o 50’. The state of Perlis is bounded by Thailand in the north, Kedah in the south, while its western coastline borders the Straits of Malacca. Covering an area of 795 sq. km. Perlis state comprises of paddy areas in the south and the Mata Ayer Forest Reserve in the north up to the Malaysia- Thailand borders. At present, the land use of the state’s economic activities are mainly agricultural, where major crops are paddy, oil palm, rubber and sugar cane, which made up about 54.5%. Forest, bushes, shrubs and rivers cover about 32.7% of the total land area. In the last two decades, industrial areas have been created at various localities.
The population of Perlis was 190,000 as per census conducted in 1991 and is expected to reach 490,000 in 2050. (Dept. of Statistics Malaysia, 1995). Between 1980 and 1991 the population was growing at 2.15% per annum, a moderately low rate by Malaysian standards. Fertility can be considered as moderately high with a crude birth rate of 26.2 birth per thousand population for Perlis in 1991. This rate was slightly higher than those of Pulau Pinang, Perak, Negeri Sembilan and Kuala Lumpur but was lower than those of the other states. Mortality was low at 5.3 deaths per thousand population. As a result the rate of natural increase was moderately high at 20.7 to 22 per thousand populations (Dept. of Statistics Malaysia,1995)
The climate, which is usually hot and wet, is basically controlled by the annual fluctuations in position of the Inter Tropical Convergence Zone (ITCZ) as it follows the apparent movement of the sun north and south of the equator. This results in two distinct rainy periods, and a prolonged drought period. Perlis has a tropical monsoon with ‘winter winds’ (northernly wind from the Siamese Bay) with temperatures between 21 -33 degrees Celsius. Its climate experiences two distinct rainy periods (April- May, and September- October) and a prolonged drought period between December- March associated with the north-east monsoon. The drought period spans the months of December to March is associated with the north-east monsoon. The two periods of rainfall are associated with the advance and retreat of the south-west monsoon, in April –May and September –October. The latter period produces greater depths of rainfall. The annual range of the temperature is from 21oC to 32oC while the mean annual rainfall is between 2000mm to 3000 mm. The rainfall has peaks during both the post-equinoctial transition periods between the monsoons. Analysis of rainfall data indicates higher mean monthly rainfall occurs between May to November, while less rainfall in December to March. Less rainfall occurs to coastal areas compared to the interior areas (EPU, 2000).
1.3 Geology of Study Area
The geology of Perlis consist of mainly alluvium, gravel and sand layers, and limestone hardrock formation. The local stratagraphical nature of the study area indicates that several rock stratas in the area may be treated as groundwater aquifers.
The Chuping limestone forms a row of limestone hill outcrops, while the Setul limestone formations forms a major column in the west ,can be considered as important groundwater reservoirs. The Bukit Arang Coal Beds, which lie in the north-eastern region consists of a semi-consolidated sequence of gravel, sand and clay with thin lignite seams, also constitutes a principal source of groundwater.(Chong, F.S., 1976). These three formations offer a potential of good groundwater sources in Perlis. (Jones, 1978)
Two contrasting limestone formations occur in this region (Jones, 1978). The thick Lower Palaeozoic Setul limestone crops out in west Perlis. This rock is well bedded and contains considerable quantities of fine detrital and carbonaceous matter. This gives rise to fairly thick residual soil in places which supports thick vegetation. This to some extent inhibits the development of extreme karst conditions, which is very rugged and rocky country normally developed over limestone. Nevertheless, the terrain is extremely rugged with numerous protruding rock pinnacles, swallow holes, cliffs and dry valleys. Due to its thickness, the Setul formation tends to form long lines of continous country hill, as is the imposing Setul Boundary Range over west Perlis.
The younger Chuping limestone crops out in central Perlis. This rock is a pure carbonate, and is thinner and more massive than Setul limestone. It is characterized by extremely rugged terrain with abundant cliffs and stunted vegetation, most distinctive being the isolated limestone hills in central Perlis. Here, the superimposition of the hill sculptures form some drainage patterns within a narrow synclinally folded outcrop has deeply dissected the limestone to form lines of abrupt disconnected hills, which rise vertically to dramatic heights above the coastal plains and low undulating country.
The Kubang Pasu- Singa formation is a Devonian-Carboniferous sedimentary rock consisting of quartzite, subgreywackle, shale, mudstone and siltstone, is a major make- up of the northern part of Perlis. Alluvium forms most of the southern part of Perlis.
A haphazard pattern of meandering streams is found over much of central and eastern Perlis. A well developed system of underground streams occur throughout the limestone of the Setul Boundary range. Occasionally rivers run at the surface for short distances as in Wang Kelian and Wang Tangga, before disappearing below ground to pursue subterranean courses. All rivers drain ultimately into the estuaries of the Sungai Perlis (Figure 1).
1.4 Hydrogeology
Groundwater is recharged by the infiltration of rainwater through permeable soil and rock cover, irrigated lowlands, and fault surface. Groundwater supply is also supplemented by stream percolation and by seepage from the paddy fields. Stream and deep percolation of rainfall combine to provide a greater amount of recharge than from irrigation water. Recharge by subsurface inflow can be considered negligible compared to other sources.
Discharge from aquifers occur naturally by transpiration through vegetation, direct evaporation from saturated zones, return to surface drainage through seepage and springs, outflow to sea, and extraction. Results from hydrogeological survey carried out in 1957 to 1959 sponsored by the United Nations concluded that the alluvium in southern Perlis contained aquifers with abundant supply of groundwater. (Jones, 1978). Further investigations involving ground surveys, seismic investigations and exploratory drilling were carried out by the Malayan Geological Survey with the cooperation of the UNDP between 1957 and 1958. However, the Kedah- Perlis Water Resources Management Study (1981) reported that there was no regionally extensive aquifer system in Perlis and that groundwater is localized depending upon geological conditions.
Geological Map of Perlis
.2 METHODOLOGY
In this study, GIS software (ERDAS Imagine 8.6, Arc View 3.1 and MapInfo 7.0) is used as a data processing tool, on all spatial data and attribute data. GIS is used fully to do spatial analysis on input data to produce thematic layer maps. These thematic layer maps are integrated to produce a map of potential groundwater zones in Perlis state. In this study groundwater potential is based on the universally accepted Darcy’s Law for groundwater flow and the modified DRASTIC equation (Khairul et al (2000). Table 3 below shows the schematic outline to this approach.
First Stage ------------------------------------------------------------------------------------------------------------
Second Stage ------------------------------------------------------------------------------------------------------------
Third Stage ------------------------------------------------------------------------------------------------------------
Fourth Stage ------------------------------------------------------------------------------------------------------------
Fifth Stage ------------------------------------------------------------------------------------------------------------
TABLE 3: Methodology of Study
2.1 Darcy’s Law for groundwater flow
In saturated conditions, one-dimensional flow is governed by Darcy’s Law (Todd, 1980) which states that the flow velocity is proportional to the hydraulic gradient
v= k.i
where v = flow velocity
k = coefficient of permeability
(measure of soil resistance to flow)
i = hydraulic gradient = H/L
Whitlow (2001) then stated that in an aquifer, the quantity of flow through an aquifer is given by Q= A.v. = A.k.i
where Q =quantity flowing in unit time
A =cross-sectional area through which flow is taking place
i = slope of water table
2.2 DRASTIC Empirical Model
DRASTIC is an empirical model developed by U.S. Environmental Protection Agency (EPA) which is widely used for evaluating relative groundwater pollution susceptibility by the use of hydro-geological factors (Aller et al, 1985). It is an acronym for the seven (7) most important hydro-geological features affecting groundwater pollution, which are:
Groundwater Pollution Potential= D+ R+ A+ S+ T+ I+ C
Where D= depth to water table
R= net recharge
A= aquifer media
S= soil media
T= topography
I= impact of vadose zone media
C= hydraulic conductivity of aquifer
Kiran, P.S.R et al (2008) has demonstrated the successful use of this model in developing a groundwater contamination risk map using GIS techniques in Younggwang, Korea.
2.3 Modified DRASTIC Equation from Khairul et al (2000)
Based upon the original DRASTIC model for evaluating groundwater pollution above, Khairul Anam et al (2000) has proposed that the modified formula for groundwater potential (GP) has eight (8) important factors, and is as follows:
Groundwater Potential = Rf + Lt + Ld + Lu + Te + Ss + Dd + St
Where Rf= annual rainfall
Lt= lithology
Ld= lineament density
Lu= land use
Te= topography elevation
Ss= slope steepness
Dd= drainage density
St= soil type
This modified DRASTIC model has been successfully used in a similar study (Khairul Anam et al, 2000) to predict groundwater potential in the Langat basin area, Malaysia using the integration of remote sensing and GIS.
3. DATA PROCESSING
Based upon these models, the initial choice of main input is spatial data consisting of a multi spectrum SPOT (Systeme Pour l’Observation de la Terre) satellite image of Perlis state (dated 2005) with a resolution of 20 meters. In a similar study employing GIS to map the landuse cover of northern Perlis, Kamaruzaman et al (2005) successfully utilised a Landsat TM image of Perlis.
Other spatial data were obtained from various Malaysian government agencies as in Table 4, consisting of topography map, geology map, soil series map, state road map, and borehole and well site map. Attribute data used here mainly consists of data on rainfall and existing boreholes and wells abstraction in the study area.
4. ANALYSIS AND DISCUSSION
4.1 Generation of Thematic Layers
Satellite data processing and analysis by method of unsupervised classification of the image, was carried out using ERDAS Imagine software at Universiti Teknologi MARA (UiTM) Perlis Campus’ Remote Sensing Laboratory. Next, GIS processing for building the database involved digitizing the topography map, geology map, soil series map and state road map. Using Arc View software, attribute data on volume of daily rainfall was entered to produce a rainfall coverage map. Coordinates (x and y) of existing boreholes and wells were recorded. A landuse map of Perlis state was produced where six classes of landuse were identified; consisting of water bodies (Timah Tasuh dam), human settlement areas, forests, paddy planted areas, sugar cane plantations in Chuping area, and rubber plantations. A total of eight thematic layer maps were produced: landuse, geology, rivers and drainage, land administration areas or ‘mukim’, borehole, well, soil types, and rainfall. This follows a similar technique used by previous researchers (Rao Toleti et al, 2000; Khairul et al, 2000; Singh and Prakash, 2004).
4.2 Discussion of Results
Figure 2 shows the result of this study. This map of Perlis indicates the most potential zone (pink) and moderately potential zone (grey). The high terrains in the north of Perlis serves as collecting points of groundwater sources. Due to the high gradient of slope groundwater seeps and collects in the Chuping and Setul Limestone formation and the Kubang Pasu- Singa formations. The map indicates that the central Perlis area around the towns of Arau and Kangar are highly potential areas of groundwater. These two towns are situated around the Chuping and Setul Limestone formation and the Kubang Pasu- Singa formations.
Map of Potential Groundwater zones in Perlis
4.3 Comparison with Past Studies
There have been many high yielding tubewells drilled by various parties in Perlis over the last 50 years. The National Water Resources Study 2000 records that around 130 tubewells were drilled in Perlis with approximately 60 yielding wells. Most of the high yielding wells are located within the Chuping Limestone and Setul Limestone formations and the semi-consolidated Bukit Arang Coal Beds formation. The geology of the study area indicates that the Chuping Limestone and the Setul Limestone formations can be considered as important groundwater reservoirs. The gravel and sand layers of the Bukit Arang Coal Beds also constitute principal sources of groundwater. These three formations make up the best groundwater sources in Perlis. Finally alluvium is probably an important source of groundwater because of their natural distribution, thickness of aquifer, permeability and proximity to recharge area. (Jones, 1978)
The results obtained from this study, based on the integration of Remote sensing and GIS of the study area, is comparable to The National Water Resources Study 2000-2050 (EPU, 2000) which estimated the groundwater quantity potential expected from these three important formations.
5. Conclusion
Based on the present investigations, the following hydrogeological evaluations can be made in relation to the geological setting of Perlis:
The three geological environments listed below are the most favourable for occurrence of groundwater:
a) limestone bedrock
b) gravels and sands in sub-alluvial valleys
c) the upper 10 to 20 feet of coastal alluvium
There is adequate scope for future development of groundwater in Perlis, especially from the Chuping Limestone, Setul Limestone and Bukit Arang Coal Beds formations.
These results suggests that the spectral and spatial characteristics of SPOT satellite data can serve groundwater investigations. The results also suggest that a raster-based GIS can facilitate the necessary digital analysis and manipulations, including data integration, geocorrections, and handling classification. It is foreseen that some of the recommended refinements for future advancement of this study may include addition of other data (e.g. recharge, soil suction, pore pressures, temperature changes) as thematic GIS layers, determining the criterias/ constraint factors, processing of thematic maps using supervised classification, and assigning weightage to data layers based on accepted engineering principles to reflect their characteristics and relative importance.
In conclusion, satellite remote sensing and GIS has been successfully used to generate the necessary dynamic information for groundwater prediction in Perlis, Malaysia.
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