Delineating groundwater prospect zones using Multi Criteria Analysis ( MCA)
Spatial choice issues commonly include a huge arrangement of practical choices and different assessment models more often than not, these are clashing. Options and measures are regularly assessed by various people (chiefs, directors, partners, intrigue gatherings). More often than not, they likewise have clashing thoughts, inclinations, targets, and so on. GIS strategies and techniques have a significant task to carry out in breaking down choice issues and perceived as a choice emotionally supportive network including the combination of spatially referenced information in a critical thinking condition. Multi-Criteria Analysis (MCA) or Evaluation (MCE) is a procedure utilized in dynamic to break down and think about how well various choices accomplish various targets and through this procedure distinguishing a favored other option. GIS based Multi-Criteria Decision Analysis is a procedure that changes and consolidates geological information and worth decisions (chiefs inclinations) to get significant data for dynamic.
Multi-criteria analysis (MCA) is a technique used to consider many different criteria when making a decision. MCA gives a logical, well-structured process to follow so different factors can be clearly identified and prioritised. It allows the alternative solutions being considered to be ranked in order of suitability. Spatial MCA is used for decisions with a geographical element, most often in site selection processes where multiple factors need to be considered. Eg:
Site location
Land use
Distance to areas of population
Local area demographics
Proximity to transport and road infrastructure
Environmentally sensitive areas
Assessment of ground water resource using GIS & Multi-Criteria Analysis (MCA)
Assessment, planning and management of groundwater resource are becoming crucial and extremely urgent in recent time. In order to do assessment of groundwater availability, it is required to delineate groundwater potential zone using remote sensing, GIS and Multi-Criteria Analysis (MCA). Different thematic layers such as hydrogeomorphology slope and lineament density maps have been transformed to raster data. To assign weights and ranks to different input factor maps, multi-influencing factor (MIF) technique has been used. The weights assigned to each factor have been computed statistically. Weighted index overlay modeling technique is used to develop a groundwater potential zone map with three weighted and scored parameters. A groundwater development program requires a large volume of data from various sources. Remote sensing and GIS study with its advantages of spatial, spectral and temporal availability of data covering large and inaccessible areas within a short time has come out as an efficient tool to provide the appropriate platform for convergent analysis of large volumes of multi-disciplinary data and decision making for groundwater studies. Various thematic maps such as geomorphology, slope and lineament density maps have been generated to determine the groundwater potential zones.
Fig 1 Methodology Flowchart of Delineating Ground-Water Potential Zone Map
Hydrogeomorphology
Hydrogeomorphological studies include identification and mapping of different landforms that have a direct control on the occurrence of groundwater. Based on the interpretation of the satellite image and SOI Toposheet, different hydrogeomorphological units have been delineated. Remote sensing studies provide an opportunity for better observation and more systematic analysis of various hydrogeomorphic units/ landforms/lineaments, features following the multispectral repetitive coverage of the terrain.
Fig 2 Map of Hydrogeomorphological Units
Lineament and lineament density
Lineaments are topography of the underlying linear structural features. Lineaments play an important role in groundwater recharge in hard rock terrains; groundwater potential is high near lineament zones. Lineament density is the total length of all the lineaments present in the basin/watershed divided by the area of basin/ watershed. Lineament density map was prepared by dividing the study area into 1 km/1 km grids, and the lineament density values of each grid was then obtained from the values of the ratio of total length of the lineaments in a single grid (L) and the area of that single grid (A). By calculating the value of L/A for each grid, the value is plotted at the centre of each grid.
Fig 3 Lineament Length Density Map
Groundwater Potential Zones
Different thematic maps describing favourable sites for groundwater potentiality have been prepared. These maps were then integrated with the help of GIS software. All the thematic maps were converted into grid (raster format) and analyzed by weighted overlay method (rank and weightage wise thematic maps). As a result, four different zones have been identified i.e.
Excellent
Good
Moderate
Poor
Fig 4 Map showing groundwater potential zones
Summary
Geospatial technology is a rapid and cost-effective tool in producing valuable data on geology, geomorphology, lineaments and slope, etc., that plays a significant role in deciphering groundwater potential zone. The spatially complete and temporal nature of the remote sensing data provides excellent opportunities to hydrogeologists for improving the understanding of the hydrogeological system. Several factors such as geomorphology, land use/land cover, geological structures, fractures, groundwater table distribution, slope and drainage—all contribute in the movement and occurrence of groundwater in an area.
