1. Groundwater KAUSHAL MODI (130260106014) JAYKUMAR PATEL (130260106024)

2. Groundwater Water resources Geologic Agent

3. Earth materials Rock Sediment (Soil) Fluids (Water) Geologic processes Form, Transform and Distribute (redistribute) Earth materials  Water is a primary agent of many (all?) geologic processes Hydrogeology Defined WaterEarth

4. Hydrogeology Defined Water Earth Interactions go both ways  Geology  Groundwater  Geology controls flow and availability of groundwater because  Groundwater flows through the pore spaces and/or fractures  Groundwater  geologic processes.  Interactions

5. Hydrogeology Defined Water  Earth Interactions Geology controls groundwater flow Permeable pathways are controlled by distributions of geological materials. E.g., Artesian (confined) aquifer Shale Sandstone

6. Hydrogeology Defined Water  Earth Interactions Geology controls groundwater flow Permeable pathways are controlled by distributions of geological materials. Groundwater availability is controlled by geology.

7. Hydrogeology Defined Water  Earth Interactions Geology controls groundwater flow Permeable pathways are controlled by distributions of geological materials. Groundwater availability is controlled by geology. Subsurface contaminant transport in is controlled by geology. Geology controls groundwater flow Permeable pathways are controlled by distributions of geological materials. Groundwater availability is controlled by geology. Subsurface contaminant transport in is controlled by geology.

8. Hydrogeology Defined Water  Earth Interactions Groundwater controls geologic processes Igneous Rocks: Groundwater controls water content of magmas. Metamorphic Rocks: Metasomatism (change in composition) is controlled by superheated pore fluids. Volcanism: Geysers are an example of volcanic activity interacting with groundwater.

9. Hydrogeology Defined Water  Earth Interactions Groundwater controls geologic processes Landforms: Valley development and karst topography are examples of groundwater geomorphology. Landslides: Groundwater controls slope failure. Earthquakes: Fluids control fracturing, fault movement, lubrication and pressures.

10. Hydrogeology Subdisciplines Water resource evaluation What controls how much groundwater is stored and can be safely extracted? What controls where groundwater comes from and where it flows? What controls natural water quality: natural interactions with geological materials control the chemistry of groundwater? How can we protect groundwater recharge areas and groundwater reservoirs from contamination and depletion? Water resource evaluation What controls how much groundwater is stored and can be safely extracted? What controls where groundwater comes from and where it flows? What controls natural water quality: natural interactions with geological materials control the chemistry of groundwater? How can we protect groundwater recharge areas and groundwater reservoirs from contamination and depletion?

11. Hydrogeology Subdisciplines Contaminant Hydrogeology Anthropogenic effects: degradation of water quality due to human influences (contamination) How fast are dissolved contaminants carried by groundwater? Transport pathways of contaminants: Where are sources of contamination impacting the groundwater, where are the going and what are the destinations? Remediation (clean-up) of contaminants dissolved in the groundwater.

12. Potentiometric Surface What controls: How much groundwater flows? How fast groundwater flows? Where groundwater flows? Darcy’s Law Answers the fundamental questions of hydrogeology.

13. Darcy’s Law Henry Darcy’s Experiment (Dijon, France 1856) xx Q Q : Volumetric flow rate [L 3 /T] Darcy investigated ground water flow under controlled conditions hh h1h1 h2h2 h x h1h1 Slope =  h/  x ~ dh/dx hh xx h2h2 x1x1 x2x2 K : The proportionality constant is added to form the following equation: K units [L/T] A : Hydraulic Gradient A : Cross Sectional Area (Perp. to flow)

14. Calculating Velocity with Darcy’s Law Q= V w /t Q: volumetric flow rate in m 3 /sec V w : Is the volume of water passing through area “a” during t: the period of measurement (or unit time). Q= V w /t = H∙W∙D/t = a ∙v a: the area available to flow D: the distance traveled during t v : Average linear velocity In a porous medium: a = A ∙n A: cross sectional area (perpendicular to flow) n : porous For media of porosity Q = A ∙n∙v v = Q/( n∙ A)=q/n VwVw v

15. Darcy’s Law (cont.) Other useful forms of Darcy’s Law Q A = Q A.nA.n = q n = Volumetric Flux (a.k.a. Darcy Flux or Specific discharge) Ave. Linear Velocity Used for calculating Q given A Used for calculating average velocity of groundwater transport (e.g., contaminant transport Assumptions: Laminar, saturated flow Volumetric Flow Rate Used for calculating Volumes of groundwater flowing during period of time

16. Darcy’s Law Application Settling Pond Example* Questions to be addressed: How much flow can Pond 1 receive without overflowing?  Q? How long will water (contamination) take to reach Pond 2 on average?  v? How much contaminant mass will enter Pond 2 (per unit time)?  M? A company has installed two settling ponds to: Settle suspended solids from effluent Filter water before it discharges to stream Damp flow surges *This is a hypothetical example based on a composite of a few real cases 5000 ft 652 658 0 N Pond 1 Pond 2

17. Application (cont.) W 1510 ft  x =186 Pond 1Pond 2 Outfall Elev.= 658.74 ft Elev.= 652.23 ft Q? v? M? K  x =186 ft b=8.56 ft Water flows between ponds through the saturated fine sand barrier driven by the head difference Sand Clay  h =6.51 ft Contaminated Pond b xx Not to scale Overflow

18. Application (cont.) Develop your mathematical representation (i.e., convert your conceptual model into a mathematical model) Formulate reasonable assumptions Saturated flow (constant hydraulic conductivity) Laminar flow (a fundamental Darcy’s Law assumption) Parallel flow (so you can use 1-D Darcy’s law) Formulate a mathematical representation of your conceptual model that: Meets the assumptions and Addresses the objectives M = Q C Q?Q?v?v?M?M?

19. Application (cont.) Collect data to complete your Conceptual Model and to Set up your Mathematical Model The model determines the data to be collected Cross sectional area (A = w b) w: length perpendicular to flow b: thickness of the permeable unit Hydraulic gradient (  h/  x)  h: difference in water level in ponds  x: flow path length, width of barrier Hydraulic Parameters K: hydraulic tests and/or laboratory tests n: estimated from grainsize and/or laboratory tests Sensitivity analysis Which parameters influence the results most strongly? Which parameter uncertainty lead to the most uncertainty in the results? M = Q C Q?Q? v?v? M?M?

20. Ground Water Zones Degree of saturation defines different soil water zones

21. Unsaturated Zone: Saturated Zone: Where all pores are completely filled with water. Phreatic Zone: Saturated zone below the water table Water in pendular saturation Water Table: where fluid pressure is equal to atmospheric pressure Soil and Groundwater Zones Caplillary Fringe: Water is pulled above the water table by capilary suction

22. Ground water and the Water cycle Infiltration Infiltration capacity Overland flow Ground water recharge GW flow GW discharge

23. Bedrock Hydrogeology Hydraulic Conductivity of bedrock is controlled by Size of fracture openings Spacing of fractures Interconnectedness of fractures

24. Porosity and Permeability Porosity: Percent of volume that is void space. Sediment: Determined by how tightly packed and how clean (silt and clay), (usually between 20 and 40%) Rock: Determined by size and number of fractures (most often very low, <5%) 1% 5% 30%

25. Porosity and Permeability Permeability: Ease with which water will flow through a porous material Sediment: Proportional to sediment size Gravel  Excellent Sand  Good Silt  Moderate Clay  Poor Rock: Proportional to fracture size and number. Can be good to excellent Excellent Poor

26. Porosity and Permeability Permeability is not proportional to porosity. Table 11.1 1% 5% 30%

27. Water table: the surface separating the vadose zone from the saturated zone. Measured using water level in well The Water Table Fig. 11.1

28. Precipitation Infiltration Ground-water recharge Ground-water flow Ground-water discharge to Springs Streams and Wells Ground-Water Flow

29. Velocity is proportional to Permeability Slope of the water table Inversely Proportional to porosity Ground-Water Flow Fast (e.g., cm per day) Slow (e.g., mm per day)

30. Infiltration Recharges ground water Raises water table Provides water to springs, streams and wells Reduction of infiltration causes water table to drop Natural Water Table Fluctuations

31. Reduction of infiltration causes water table to drop Wells go dry Springs go dry Discharge of rivers drops Artificial causes Pavement Drainage Natural Water Table Fluctuations

32. Pumping wells Accelerates flow near well May reverse ground-water flow Causes water table drawdown Forms a cone of depression Effects of Pumping Wells

33. Pumping wells Accelerate flow Reverse flow Cause water table drawdown Form cones of depression Low river Gaining Stream Gaining Stream Pumping well Low well Cone of Depression Water Table Drawdown Dry Spring Effects of Pumping Wells

34. Dry river Dry well Effects of Pumping Wells Dry well Losing Stream Continued water- table drawdown May dry up springs and wells May reverse flow of rivers (and may contaminate aquifer) May dry up rivers and wetlands

35. Ground-Water/ Surface-Water Interactions Gaining streams Humid regions Wet season Loosing streams Humid regions, smaller streams, dry season Arid regions Dry stream bed

36. Confined Aquifers