Summary: Lec 3 & 4 - Hydrogeological Systems

Read the summary and the most important questions on Lec 3 & 4 - Hydrogeological systems

• 1 Accumulation and coastal areas

• Name the 4 characteristics of GW abstraction at the coast

  
   low abstraction rate
   many wells 
   parallel to the coastline
   Ghyben Herzberg

• Give the formula for Ghyben Herzberg and indicate what it is used for in the context of GW abstraction?

  See

• When do steady and when do transient states occur during regression, transgression and steady sea levels and what is the result for freshwater occurence?

  Current sea lvl - steady
  Regression - steady
  Transgression - transient state of system
  
  Anomalous freshwater and saltwater intrusion could occur in the transient system.

• What could be causes of salinisation during a transient states when transgression (rising sea lvl) occurs?

  Salinisation by free convection and sideways sag of dense GW (think about the salt wedge pictures of estuaries from CODG). A freshwater wedge occurs in this case.

• Where does freshwater sequestration occur and what do these places have in common?

  Nantucket, Florida, Suriname, New Jersey - east coast of the Americas

• 2 River plains in lowland areas

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• What kind of river system is this? 

  Braiding

• What is the result of the properties: climate, vegetation, hydraulic gradient, flow rate, flow velocity, sediment load on the characteristics of the river system, that influence porosity? How does this influence porosity?

  See. Meandering
  rivers : large total porosity , low effective porosity, low saturated conductivity
  
  Braiding: Relatively large total porosity , high effective porosity , high saturated conductivity

• How do erosion terraces form on river plains in lowland areas?

  See

• This is a picture of the river Berounka in Czech Republic. What do the two layers on the bedrock represent and how do they affect GW occurence?

  
  EROSION TERRACES: groundwater occurrence
  o thickness of the saturated layer
  o fragmentation of the terrace
  o interaction of the terrace with the river

•  Which well would be most suitable for long term GW abstraction and why? Look at the properties like porosity, rock types, distance to drainage, etc. 

  See fig