Uncertainty and Risk Assessment of Ground Water

Submitted to:- Submitted by: Dr. Parul Mathuria Pulkit Goyal

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IntroductionUncertainty:[1]

Uncertainty refers to a state of mind characterized by doubt, based on a lack of knowledge about what currently exists or what will or will not happen in the future.

1. Uncertainty in grondwater availability

2. Location of groundwater dependent vegetation, selected freshwater and wetlands within each groundwater source on the coastal plains.

3. Hydrological and geological structure, topography feature, vegetation, and human activities.

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Groundwater sources[3]

Groundwater sources are divided into four broad hydrogeological types: alluvial (weak rocks like clay, silt, sand, or gravel deposited during

recent geologic time by running water in the bed of a stream or on its floodplain.)

coastal sand porous rock (strong rocks such as sandstone) fractured rock (igneous and metamorphic rocks).

Each of these systems are hydrogeologically quite different from each other. For example, they have different rates of recharge, groundwater flow, yield and water quality.

For management purposes, geological sequences that are hydro geologically similar may be grouped together and defined as a groundwater source.

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Different types of water pollutants [4]

Heavy metals

Chemical waste.

Fertilizers from agricultural use. Nuclear waste Sewage Accumulation of toxic or flammable gas(eg landfill gas) Inappropriate management.

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Effects[4]

Aquatic ecosystems: including marine ecosystems and groundwater ecosystems.

Potable use: water is intended for human consumption (drinking and domestic use).

Primary contact covers activities : involves full body contact with the water such as swimming, surfing, diving etc.

Aesthetic (visual) use: does not involve physical contact but covers the visual appearance and enjoyment of the water. eg. waterfall

Industrial use: includes activities such as cooling, heating, washing and evaporation.

Buildings and structure: protection from chemical substances degrading building materials through contact (eg weakening of footings). hydrocarbons and solvents can degrade PVC pipes

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Steps in risk assessment processA risk assessment uses the ‘source−pathway−receptor’ model and involves following steps:

Problem formulation

Risk analysis

Risk characterization

Decision making and risk management

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Problem Formulation[1]

Problem formulation determines the focus and scope of the risk assessment.

Factors influencing the risk occurring and the impacts from these.

Assessing the source and properties of the chemical substance (solubility, toxicity of contamination groundwater etc)

From this information conceptual models and a risk analysis plan are developed. This involves all relevant risk managers, experts, resource managers and other stakeholders.

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Risk analysis[2]

Risk analysis is the actual determination of the probability and magnitude of an adverse effect with specific consequences occurring.

It includes:

• Groundwater dependent ecosystems (potential and actual impacts from groundwater extraction and climate change scenarios.)

• Mixing – hot & cold current waves, different salinity

• Eco-toxicity testing – Chronic(long time) toxicity testing

• Effluent water quality and toxicants – e.g. nutrients, ammonia, salinity, pH, biological oxygen demand, suspended solids, metals

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Risk characterization[1]

Risk characterization is the evaluation and reporting of the problem formulation and risk analysis results.

results provides the information needed for decision making and risk management.

The main outputs from the risk characterization phase.

Identification and evaluation of the level of change or impact to the water body and the risk occurring.

comparison and priority of the risks identified: health or the environment will be considered as a priority site and may require immediate action

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Decision making and risk management[4]

Risk assessment information is particularly useful to decision makers and managers.

evaluate the most cost effective management actions for achieving maximum environmental gains

Determine the extent of stress must be reduced to achieve a given outcome.

It combines the information and outcomes from the risk assessment with statutory, legal, social, economic, environmental and political factors in assessing options to manage risk.

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Decision Tree for Evaluating Ecological Risks Associated with the Discharge of Contaminated Ground-Water through the Transition Zone [4]

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References

1. GUIDELINES FOR RISK ASSESSMENT OF WASTEWATER DISCHARGES TO WATERWAYS- www.epa.vic.gov.au

2. Ground water management- http://www.water.nsw.gov.au/Water-management/Groundwater

3. ENVIRONMENT PROTECTION AUTHORITY – Guidelines for assessment and remediation of groundwater contamination.pdf

4. United States Environmental Protection Agency-Publication 9285.6-17 EPA-540-R-06-072 July 2008- Evaluating Ground-Water/Surface-Water Transition Zones in Ecological Risk Assessments