Remote Sensing and GIS together are used in solving many problems of water resource engineering. In this current article, identification of ground water recharge potential zones using remote sensing and GIS is performed for Hyderabad area.
The main objective of the study is to identify suitable areas for construction of ground water recharge wells in Hyderabad region.
Landsat – 8 (B2, B3, B4), Cartosat – 2 DEM
ArcGIS, PCI Geomatica
Methodology for GWP Zones Identification:
In this study, GWP zones are identified using a Multi Criteria Decision Making (MCDM) approach, i.e., Analytical Hierarchy Process (AHP).
The following are the steps used for identification of ground water recharge potential zones in Hyderabad.
- The base map of study area is collected from “Survey of India” Toposheets.
- A digital base map is prepared in ArcGIS using Georeferencing and Digitization.
- Different factors which affect the ground water recharge potential are identified.
- Thematic maps are prepared in GIS for various factors identified in step 3.
- Different factors which affect the ground water recharge potential are as follows:
- Landuse landcover
- Slope is an important factor as it affects the direction in which the water flows and accumulates over the surface.
- Slope map can be prepared using Cartosat DEM data in GIS environment.
- Having good drainage is essential for the water to move over the surface. Areas having high drainage density normally tend to have good amount of ground water.
- Drainage map and drainage density map can be prepared from DEM data using GIS software.
- Lineaments are geologic features which are curvilinear structures on earth surface. They represent weaker zones of earth surface, which are potential for recharging ground water.
- Lineament map can be prepared from geological data obtained from geological survey of India maps. Lineaments can also be extracted from LISS -III sensor data using PCI Geomatica Software. The obtained lineament features can be exported into ArcGIS software for preparing lineaments density map.
- The areas where lineament density is high can be considered as a potential zone for ground water recharge.
- Landuse Landcover is another important factor as landuse categories such as builtup areas, rocky terrain etc., are not suitable for ground water recharge, whereas terrains such as vegetation cover, barren land etc., are suitable for recharge.
- Landuse Landcover map can be prepared from Landsat-8 Imagery using image classification methods such as supervised and unsupervised classification etc., with ArcGIS/QGIS software.
- After preparation of these thematic maps a Multi Criteria Decision Methodology (MCDM) such as AHP or Fuzzy Logic or Topsis is used for ranking the selected criteria and calculating the weights.
- The selected factors are main criteria in selecting the suitable sites for ground water recharge potential zones. However, there exist sub criteria also for solving this problem.
- For example, In case of LULC map builtup area, water body, barren land etc., are present. Depending on what is present in LULC map at a location, whether we can do the ground water recharge or not may vary. Hence, these builtup parcels, water body, barren land etc., act as sub-criteria in selecting the potential sites for GWP recharge zones.
- In the same fashion, in case of slope map, land parcels having 0-5% slope, 5% to 10% slope, 10% – 15% slope etc may act differently, hence can be considered as different potential in regard of ground water recharge.
- These sub-criteria can also be ranked, evaluated using the similar MCDM approach i.e., with AHP or TOPSIS etc., for calculating the weights.
- Once the weights are calculated, thematic maps can be reclassified with weight values obtained for the sub-criteria using GIS.
- Further, using map algebric operations (weighted overlay analysis) in GIS it is possible to combine all thematic maps.
- The overlay analysis produces ground water recharge suitability index for all locations in the study area. Based on the value of this index, it is possible to derive information of whether an area can be considered as potential for ground water recharge or not.
Following map represents the ground water recharge potential zones of Hyderabad area obtained through remote sensing and GIS approach.
Remote sensing and GIS can be used as an effective tool for identification of ground water recharge potential areas. However, since undelying ground conditions are highly dynamic, this method should be used as reconnaissance technique rather than a final decision making technique.