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
359
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996