EXTRACTION AND MODELLING SPATIAL PARAMETERS IN GROUNDWATER 
POTENTIAL STUDIES IN A HARD ROCK TERRAIN, SRI LANKA 
K.A.W. Kodituwakku, Deputy General Manager, Water Resources Board, Sri Lanka 
KEY WORDS: Hydrology, GIS, Remote Sensing, Geostatistics 
Commission VII 
ABSTRACT: 
Study of flow through fractured hard rocks needs geometrical properties of the fracture network as well as 
fracture properties such as fracture width, permeability, porosity etc. Since hard rocks (Precambrian 
metamorphic rocks) of Sri Lanka has undergone through polydeformations and polymetamo- rphism, in 
geologic history, it has very complex fracture net work system. Hence it is a difficult task to understand 
fracture properties, mentioned above, to use mathematical equations to study flow characteristics. To 
overcome this problem, Remote Sensing and GIS techniques can be used in order to model productive 
fractured aquifers. Some surficial features related to geology, geostructure, geomorphology and surface 
water bodies which may influence the yield capacities of tube wells can be detected by Remote sensing 
techniques. Relevant spatial parameters identified by statistical analyses of surficial features, mentioned 
above, together with yield capacities of deep tube wells are used as inputs to the GIS in order to model 
potential groundwater zones. Also it is possible to develop groundwater exploration strategies with 
emphasis on well location studies based on the statistical analytical results of surficial features which 
influence well yields. 
INTRODUCTION 
Sri Lanka is an Island with an area about 65,000 x»? and is situated southern part of Indian ocean. Three 
major climatic zones were identified as Dry, Intermediate and Wet zone(Figure.1). A hard rock terrain 
located in the intermediate zone has been selected for the detailed study. However preliminary data analysis 
have been based on data on more than one thousand deep tube wells drilled in the entire Kurunegala 
district(Figure. 1) for rural water supply schemes. CERT 3 
Since surface water remains as a major constraint N 
to the accelerated agricultural, industrial and some 
settlement projects, groundwater is under consider- 
ation as an additional water source. It was found 
that some surficial features such as lineament 
(originated possibly by faults, joints, foliations etc.), 
valley (generally occupied by paddy cultivation in 
he study area), geology, geomorphology, drainage 
network and ancient irrigation system spread over 
the study area have been closely related to the yield 
capacities of deep tube wells drilled in the area. 
Hence the above mentioned surficial features can 
be used as surface indicators to the sub surface 
weathering and fracturing which are essential for 
currency of high yielding productive aquifers in 
hard rocks. Remote sensing techniques can be used 
to detect the above surficial features and image pro- 
cessing may be used for extraction of required spatial parameters which in turn have to be applied as input 
tothe GIS. Relevant surficial features have been detected by interpretation of 1:40,000 scale aerial 
photographs as cloud free landsat imageries were unable to find during data analysis. The same aerial 
  
  
DETAILED 
STUDY AREA 
STUDY AREA 
* KURUNEGALA 
OISTRICT 
  
FIG-!- LOCATION 
  
  
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996