Chemistry of groundwater – A presentation by ACWADAM

This presentation by ACWADAM deals with the chemistry of groundwater. It is now recognized that the quality of groundwater is as important as its quantity. All groundwater contains salts in solution which are derived from the location and the movement of water through rocks. The quality of groundwater supply depends where and for what it is planned to be used. Thus water quality standards for drinking water, industrial water and irrigation water differ significantly.

Most groundwater abstracted for domestic, industrial or agricultural use is the groundwater derived from rainfall and infiltration within a normal hydrologic cycle. The rainwater is pure water containing between 10mg/l and 20mg/l of dissolved material. After the interaction with the rock or soil, the chemical composition of water changes. The groundwater quality can vary from one rock type to another and also within aquifers along groundwater flow paths. Because of slow water movement there is scope for chemical interaction between rock and groundwater

The quality criteria for groundwater use is set out in the presentation –

• Groundwater is free from suspended impurities and pollution and is of constant temperature.
• Groundwater is superior to surface water supplies.
• Groundwater supply points closer to saline zones may affect the salinity of water.
• Certain standards are set for evaluating the suitability of water for drinking, domestic, irrigation and industrial use.

The water quality problems and issues outlined in the presentation are –

• Excessive fluoride concentrations above the upper limit may cause mottled enamel of teeth.
• Excessive concentrations may cause skeletal deformities.
• Generally deeper groundwater has higher fluoride than shallow groundwater; however, local conditions override.
• Shallow groundwater are marked with fluoride due to number of reasons including high evaporation rates.

Finally the presentation deals with a groundwater protection strategy comprising of –

• Defining and mapping of aquifers
• Understanding of geology
• Studying underlying rock strata
• Chemical and biological analysis of water samples
• Improved awareness among the citizens about general health and hygiene
• Groundwater management              

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.