India’s groundwater typologies – A presentation by ACWADAM

This presentation by ACWADAM deals with groundwater typologies in India. The typology of groundwater can be defined in many ways based on a) Uses of Groundwater, b) Geography, c) Geology, d) Hydrogeology (Aquifers), e) Groundwater Quality, f) Stage of Groundwater Development, and g) Socio-ecology of Groundwater.

The presentation provides details of the six regional groundwater settings of the country at (a) aquifer scale (spatial), (b) time scale for effects of overuse to appear and (c) significance, with regard to recharge and drinking water security -

• Mountain Systems: These are highly localized aquifers but often with non-coherent village/watershed and aquifer boundaries but with more than one aquifer within the scope of a village. The time scale with effects of overuse to appear is shortest (texp = 5 yrs). These are local recharge systems often outside village/watershed boundaries. There has been depletion in natural discharge points, i.e. springs due to overexploitation through borewells. The major groundwater quality impact is bacteriological contamination from ‘open sanitation’.
• Alluvial (Unconsolidated) Systems: These are marked by regional systems of multiple aquifers wherein an aquifer is overlain by many villages and also each village can vertically tap parts of multiple aquifers. The time scale with effects of overuse to appear is longest (texp = 25-50 years). These areas are marked by regional recharge systems with large-scale recharge. Overexploitation trends involve successive depths of ‘aquifer tapping’ with exponentially rising costs of drilling and pumping. The vulnerability of groundwater quality (geogenic and human-induced) increases at a quicker pace as compared to depletion in quantities.
• Sedimentary (Soft) Systems: In these systems the scales are variable, from local to regional aquifers but not of the scale of alluvial systems. These aquifers have somewhat regional connections and more than one village is likely to tap a common aquifer beneath. The time scale with effects of overuse to appear is relatively long (texp = 15-20 years). The recharge is local although its magnitude can be large. The drinking water impacts on the groundwater quality tend to be more pronounced than on the quantitative side.
• Sedimentary (Hard) Systems: The area is marked with localized occurrence of aquifers often with coherence between watershed and aquifer boundaries. The scenario is usually of a one village-one aquifer. The time scale with effects of overuse to appear is very short (texp = 5-10 years). The area has local recharge systems, at places, outside village and watershed boundaries. The depletion tends more on the quantitative side, with associated impacts on groundwater quality.
• Volcanic Systems: These systems have largely localized occurrence, often as multiple aquifers (vertical). Watershed and aquifer boundaries often coherent but village may be underlain by many aquifers. The time scale for effects of overuse to appear is short (texp = 5-15 years). The area is marked by local recharge systems, at places, outside village and watershed boundaries. Depletion tends more on the quantitative side, sometimes associated impacts are felt on groundwater quality.
• Crystalline (Basement): These are marked by two types of situations – regional and local. There are complex relationships between shallow and deep aquifers. Some aquifers have boundaries coherent with watersheds, others extending below more than one watershed. There may be a variable scale of one village – one aquifer to many villages – one aquifer. The time scale for effects of overuse to appear is highly variable (texp = 5-15 years). There are variable systems of recharge – regional at places, local at others. Depletion concurrently affects quantities and quality, making drinking water sources highly vulnerable.

This presentation is part of the training modules on planning, development and management of groundwater with special reference to watershed management programmes by ACWADAM. Please write to ACWADAM at acwadam@vsnl.net for sourcing these presentations.