Groundwater can be termed as the water found below the ground in the spaces in soil and between rocks. Geological formations known as aquifers are underground layers which store and pass on groundwater. The groundwater is located at a certain depth underground, which is termed as the water table. Deeper the water table, the more resources and manpower required to extract groundwater. The groundwater gets recharged through rainwater, water from lakes, ponds, rivers and other bodies, which seeps into the ground and fill up the spaces between soil and rocks.
The major uses of groundwater are:
Groundwater is one of the most extracted resources in the world, maybe even the most. As the world exploits the perishable reserve for a variety of uses, its stock is often taken for granted due to its invisibility. India is one of the top consumers of groundwater along with USA and China as millions of people depend on groundwater for drinking and household purposes. The annual water availability in India is roughly 1,869 billion cubic meters, out of which only 1,123 billion cubic meters falls under the usable bracket. The surface water constituted over 61 per cent of the usable water, while groundwater is the source of the remaining 39 per cent (PRS, 2016).
India’s booming population has catalysed the extraction rate in the country. In major parts of the country, the rate of extraction has outpaced the rate of replenishment of groundwater. The ratio of the two is called groundwater development. The groundwater development for some major states in India is given below:
Delhi has a groundwater development more than 100 per cent, which means it is extracting groundwater at a higher rate than it is being replenished. On the other hand, Assam, Goa and Jharkhand have a low groundwater development, which keeps the resource in check. Interestingly, Meghalaya and Arunachal Pradesh have a 0 groundwater development, which signifies their low dependence on groundwater (PRS, 2016).
If groundwater is extracted at inflated rates, major problems can occur. Some of them are:
- Lowering of the Water Table: As more and more groundwater is extracted, the water table reaches further below into the ground, requiring additional effort and resources to pump out the water.
- Increase in Extraction Cost: As the water is available at increased depths, the cost of extraction is increased through direct capital investments or manpower required.
- Surface Supply: Surface water sources such as lakes, ponds and rivers help in the replenishment of groundwater. When groundwater extraction is high, the bodies connected to the groundwater can have their volume cut down as well.
- Water Quality: Excessive water pumping in coastal areas may lead saltwater into the groundwater stock, causing a saltwater contamination.
Space Technology for Groundwater Mapping and Analysis
As India witnesses a shortage of groundwater with excessive extraction rates, multiple government bodies are using space technology to better understand and alleviate the issues seeping in. Natural Resources Data Management System (NRDMS), under the Department of Science and Technology (DST), Government of India has utilised space technology through a Geographical Information System (GIS), which can be used to create synoptic maps through non-related parameters. These maps can be used for in-depth analysis and assist in policy formation and decision-making. The Karnataka NRDMS programme used the system in Chitradurga District of Karnataka.
The district is spread across an area of 8,440 sq km. The data used in the study included
- Location of observation wells
- Monthly observation of bore well statistics
- The water level in the meter for a period of ten years
- Location of the nearest rain gauge stations
- Recorded rainfall for the identified observation wells
- Water quality parameter analysis for the identified observation wells
Making use of the data and GIS, NRDMS analysed the groundwater level both spatially and visually and data maps were generated using multiple parameters. Using multiple maps of different time instances, change in groundwater-level can be visualised and calculated. The spatial analyst tool was used to generate contours of observational wells and showcase the level-change. Some of the maps generated are given below.
Figure 3 shows the groundwater levels with contours of the observational wells. As it can be seen, many areas have a higher groundwater level which signifies the overexploitation of groundwater. Figure 4 depicts the fluoride content in the groundwater present in the district. Fluoride is a toxic element which seeps in groundwater, causing fluorosis, which can mottle teeth and calcify ligaments.
Using such maps, policy-makers can understand the groundwater levels, fluoride content, locations of wells and much more. Mapping of such data can help in decision-making and eradicate groundwater associated problems.
Groundwater mapping is only one of the many possibilities that spatial technologies can be deployed in. GIS has shown that it is more than just a tool and has emerged as a decision support system for governments. NRDMS is constantly working towards employing ‘Geo-Spatial applications for good Governance’. Groundwater Mapping is one of the countless projects NRDMS has initiated to act as a decision support system for good governance all around the country