Groundwater Jeopardy What is primary porosity? Porosity between grains Porosity caused by fractures What is secondary porosity? What is a Confining layer? layer having low or no peremeability - layer of low permeability that can store and transmit groundwater slowly between aquifers (now more commonly referred to as “leaky confining layer”) - absolutely impermeable and contains no water - general term for layers of low permeability What is an aquiclude? What is an aquifuge? What is an aquitard?

What’s the difference between this and this

What’s under the boxes? 1 2 3 4 5 6

What’s this??

What’s under the boxes?

Review What is freshwater head? What is point water head? What is Reynold’s number? What is specific discharge What is average linear velocity? (seepage velocity) What is effective porosity? - height of a column of freshwater in a well is just sufficient to balance the pressure in the aquifer at that point - the actual water level in a well or piezometer - defines whether flow is laminar or turbulent...if turbulent we can’t use Darcy’s Law or just about any of the models/assumptions discussed in this course - groundwater velocity calculated using Darcy’s law - the actual velocity the water moves through the aquifer - porosity used to calculate above

defines flow potential in a porous medium in a linear direction between 2 points of known head and is the basis for all laminar groundwater flow modeling and equations. in it’s simplest form does not take into account boundary conditions of the flow field, anisotopy, heteorogeneity, leaky confining layers or other complexities that complicate reality. - these complexities need to be build into groundwater models that approximate reality... Darcy’s Law Darcy’s Law What’s this?

Groundwater flow equations (which are all based on Darcy’s Law and ) can be used to solve complex flow problems in computer models, or we can use analogs such as flow nets, and electrical flow analogs to define the subsurface flow field (discharge/recharge areas, flow paths, potential distribution, etc.) - flow nets break the aquifer down into manageable chunks (flow tubes) where we can apply Darcy’s Law directly (in the modified form of the flow tube equations) Conservation of mass

parallel in a homogeneous, isotropic media, flow lines will be . . and to grad h in a media (i.e. 2 layers with different K values) lines and lines will get refracted at boundaries of units with different K values. Flow follows grad h because grad h is being refracted as well - can predict the amount of refraction knowing K and the angle of flow on one side or another of the boundary opposite What’s this?? heterogeneous flow equipotential

What’s this??

- in anisotropic media, flow is deflected at some angle away from grad h dependant on the degree of anisotropy - amount of deflection can be calculated using a ellipse - Simple mathematical models of groundwater flow such as the Dupuit Equation have been developed, but they are approximations only that ignore complexities of natural aquifers tensor