Geography Reference
In-Depth Information
several areas including environmental field. This chapter aims at
highlighting the role of GIS in synthesising, compiling, presenting and
interpreting chemical data of both surface and ground waters. Firstly, few
relevant fundamental terms and process of water quality evaluation are
defined and/or described. Thereafter, the chapter contains theoretical
procedure for applying GIS to assess spatial change or variability in water
quality by characterizing extent and patterns of contamination. In general,
a water quality monitoring network consists of a group of point locations
with known chemical attributes of water. GIS helps converting the point
values into areal information through spatial interpolation.
Hence, an overview of spatial interpolation techniques is provided,
together with the methodologies for employing geostatistical modelling
(kriging) and inverse distance weighting techniques and for computing
spatial statistics (mean, median, standard deviation and coefficient of
variation). The major application of GIS in past groundwater studies has
been for assessing groundwater vulnerability.
Therefore, the concept of groundwater vulnerability along with its
historical perspective is described and different GIS-based overlay and
index methods used for groundwater vulnerability assessment are
summarized. Methodologies for applying different GIS methods in
evaluating
the
groundwater
vulnerability
are
illustrated
through
flowcharts.
The major tools for describing groundwater vulnerability in GIS
framework include DRASTIC, modified DRASTIC, DRAMIC, GOD,
AVI, SINTACS, EPIK, GLA, PI and COP.
Furthermore, the development of GIS-based water quality index for
evaluating water quality is discussed. Finally, combined use of GIS and
multivariate statistical analysis techniques in delineating water quality
zones is discussed. It is concluded that GIS is a promising geospatial tool
which offers efficient framework for sustainable management of
freshwater resources.
1.
I
NTRODUCTION
Water quality is governed by a set of complex factors and there is large
choice of variables use to describe water quality status in quantitative terms.
Hence, it is difficult to provide a simple definition for water quality. Water
quality of the aquatic environment is defined by (a) set of concentrations,
speciation, and physical partitions of inorganic or organic substances, (b)
composition and state of aquatic biota in the waterbody, and (c) description of
temporal and spatial variations due to factors internal and external to the
waterbody (Meybeck and Helmer, 1992).
