This presentation by ACWADAM deals with hydrogeology and sanitation guidelines. Safe water supply and sanitation choices are an important public health measure and source quality improvement is critical to this. The impact of different aspects of water and sanitation appears to be largely dependent on the conditions within a particular community and existing access to other components of water and sanitation.

The meaning of the presence or absence of indicators should be clearly understood and the analysis of indicator bacteria should be supported by risk assessment and source protection. Aquifer vulnerability to pollution and risks to groundwater supplies is described. The unsaturated zone is significant as it acts as the first natural line of defense based on rock type, weathering and fractures. The saturated zone is also significant in spreading of the contaminant. The key processes in the attenuation of microbiological contaminants are die-off, filtration, dilution/dispersion and adsorption.

Contamination of groundwater supplies may result either from contamination moving through the body of aquifer or via pathways resulting from the design and construction of the supply. General measures to avoid localized contamination of groundwater include boreholes, springs, dugwells and sanitary protection measures at headworks. The presentation deals with the guidelines for risk assessment and outlines the two principal routes by which sources of groundwater become contaminated by on-site sanitation systems -

• Natural vulnerability of the aquifer to pollution as subsurface is permeable
• Pathway created by poor design and construction of the groundwater supply

Based on the mentioned routes of contamination three cases are considered –

• Assessing the risk of microbiological contamination of groundwater supplies via aquifer pathway
• Assessing the risk of nitrate contamination of groundwater supplies as a result of widespread aquifer contamination
• Assessing the risk of microbiological contamination due to pathways created by construction of groundwater supply

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.