GIS in Geoscience: The recent trends
P K Champati Ray
Indian Institute of Remote Sensing,
4-Kalidas Road, Dehradun-248001 (India)
Geological features or factors vary in space and time. This fundamental characteristic is responsible for making it a most genuine application field of Geographical Information Systems, where the strength lies in defining the two dimension (X,Y extent), third dimension (Z component) and the fourth dimension (time) of spatial information. In the beginning, due to the geological variability in space and time, various attempts were made to solve complicated geological problems using multivariate and geostatistical methods. In fact these two fields were developed in a way for addressing various geological applications starting from simple data interpolation/ extrapolation to mineral exploration. These two methods almost laid the foundation of the geological application of spatial information system. In the initial years, such spatial techniques were developed and were used for data analysis of late techniques have been developed for 3-D visualisation of geological data, which eventually resulted in the development of specialised mining packages in the late 70s and 80s, having many features similar to present day advanced GIS packages. However, as it was meant to be used for commercial purposes such as mineral and oil exploration and exploitation, the cost of the packages were prohibitive and general geological community had to be content with cheaper multivariate/geostatistical packages or such package available in public domain. Some statistical packages like Statgraf, Statistica and SPSS contain useful modules on multivariate statistics, which were exploited for many geological applications.
In the initial years of GIS, the systems was visualised as a little more than a graphic tool with very limited spatial analysis capabilities. It was essentially addressing the needs of the geographical community. Therefore, the traditional geological community was skeptical about its usage in solving serious geological problems and it still preferred specialised mining software or geostatistical packages for their applications. However, the GIS developers soon realised the need for incorporating multivariate, geostatistical modules and powerful 3-D analysis and these components work often considered as advanced components and became the selling point of GIS packages. Another advantage was the low cost of the GIS packages as compared to the expence on specialised mining packages. Now it is understood that many of the geological applications can be conducted without such specialised packages. This resulted in the popularity of GIS in geological community.
One of the most fundamental applications in the field of geology is the geological mapping. In geological mapping it is often required to bring on to one scale various existing geological maps often in different scales. Traditionally, it was done through graph sheet or reflecting projector, which is extremely time consuming as it needs re-tracing of the map itself in the required scale often compromising a lot on quality. With the help of GIS, maps of any scale can be scanned, georeferenced and reproduced in any desired scale thereby bringing all old maps to one scale, at which more information can be collected either by field investigation or by remote sensing techniques to prepare a final updated geological map. In one such attempt at IIRS, the published geological maps on 1:250,000 and 1:50,000 from different sources were brought on to one scale of 1:25,000. Then all maps could be compared and the final map was prepared on 1:25,000 scale, which was later updated using merged IRS-LISS-III and PAN imagery on 1:25,000 scale and supported by ground investigation.
GIS can be used for a multiplicity of applications related to occurrence and movement of groundwater. One of the main benefits of using GIS with groundwater modelling programs is that simulation results can be displayed geo-referenced, allowing further analysis and display of topological relationship between the model and other spatial features.
In recent years various hydrological modeling options have become available in commercial GIS packages. Additionally, some hydrological packages have a live link with GIS packages and to perform specific hydrological operations. The most notable amongst them are:
GIS can be used for almost all application related to groundwater management such as hydrogeological database management, groundwater targeting, resource estimation, groundwater recharge estimation, evaluation of ground water exploitation impact on environment (runoff, soil moisture, vegetation growth conditions etc.), evaluation and re-evaluation of groundwater resources for urban and rural fresh water supplies. Groundwater risk assessment can also be carried out using GIS such as studies related to removal, localisation and remediation of contaminant plumes (including oil and radioactive pollution), ground water vulnerability assessment, environmental impact evaluation for civil engineering and human activity affecting ground water etc. Attempts have been made to develop Groundwater GIS using ArcView and ARC/INFO software in South Australia. This GIS contributes significantly to the assessment, development and management of the groundwater resources.
- ModelGIS – pre-processor for the MODFLOW (USGS software for GW modelling) groundwater code that allows model input and output to be created, stored and displayed within ARC/INFO GIS on UNIX workstations.
- SiteGIS – Windows based software package for analysing and presenting environmental data for soil and groundwater remedial investigations. SiteGIS is an application for a desktop mapping package MapInfo.
- Visual MODFLOW- is a commercial program developed by Waterloo Hydrogeologic. Its main advantage over MODFLOW is that it allows the user to design the finite difference grid and input the boundary conditions of the model in a graphical environment. Coupling Visual MODFLOW with ArcView, the most popular GIS software, promises increased accuracy in data input and opportunity to further process modelling output in GIS environment, as well as visually appealing presentation of results.
In one novel attempt at IIRS, groundwater prospect maps were produced for entire National Capital Region of India covering around 67 topo-sheets on 1:50,000 scale. Geological, geomorphological and groundwater quality data were integrated and results were produced on 1:50,000 scale using ARC/INFO GIS software. Similar efforts are going on at the national level under Rajeev Gandhi National Drinking Water Mission to prepare ground water prospect maps on 1:50,000 scale in most drought prone districts of India.
Fig. 1: Liquefaction susceptibility in parts of Doon valley
(Source: G. Dole and B. K. Srivastava, IIRS)