1. The Hydrologic Cycle and Groundwater
Lecture 14
The Hydrologic
Cycle and Groundwater

2. About the Hydrologic Cycle
Hydrology is the study of movements and characteristics of groundwater.
The hydrologic cycle has a profound effect upon climate prediction.
Water is vital so we must understand where to find water and how water supplies cycle through Earth.

3. ● Flows into a reservoir include inflows and outflows
The Geologic Cycling of Water
● Flows into a reservoir include inflows and outflows
● Reservoirs include all the places that water is stored in and on Earth.

4. The Geologic Cycling of Water

5. ● infiltration and runoff ● evaporation, transpiration
The Geologic Cycling of Water
● The hydrologic cycle
● precipitation
● infiltration and runoff
● evaporation, transpiration
● groundwater flow

6. The Geologic Cycling of Water
The hydrologic cycle

7. ● Key climatic factors ● relative humidity ● rainfall ● landscape
2. Hydrology and Climate
● Key climatic factors
● relative humidity
● rainfall
● landscape

8. ● ocean-land relationships ● mountain rain shadows
2. Hydrology and Climate
● Key tectonic factors
● ocean-land relationships
● mountain rain shadows

9. 2. Hydrology and Climate:
The Rain Shadow Effect

10. Groundwater: the largest resource of accessible fresh water (glaciers are not accessible)

11. Groundwater:
Porosity and
the Amount
of Open Space
in Various
Materials

12. Permeability:
Just because pore space exists doesn't mean that water can flow through it. Pores may be isolated.
Permeability: the ability of a solid to allow fluids to pass through.

13. 3. The Hydrology of Groundwater

14. Groundwater: aquifers
What would be the properties (porosity/permeability) of conglomerate?
High porosity, high permeability

15. Groundwater: aquifers
What would be the properties (porosity/permeability) of un-fractured granite?
Low porosity, low permeability

16. Big concept I:
The Water Table is the basic description of how groundwater interacts with rocks.
If I pour water into a bucket of unconsolidated sand, the water won't spread evenly through the bucket. It will collect at the bottom. As a result, we will have two hydrologic zones in the bucket

17. ● Above and below the groundwater table ● unsaturated (vadose) zone
3. The Hydrology of Groundwater
● Above and below the groundwater
table
● unsaturated (vadose) zone
● saturated (phreatic) zone

19. Groundwater Basics
Beds of rock, sediment, and regolith with high porosity (% of pore space) are better suited to holding groundwater.
Aquifers: Beds that hold large amounts of groundwater.

20. Opposite of an aquifer? Aquitard / aquiclude
retards the flow of groundwater (it’s almost never really zero

21. Big concept II:
Equilibrium: Same amount of water enters and leaves saturated zone.
Recharge: process by which water enters. (e.g. stream flows over rock fractures, allowing water to percolate in.)
Influent stream: a stream that recharges groundwater.
Discharge: Process by which water leaves. (e.g through a spring)
Effluent stream: A stream which picks up water from saturated zone.

22. Aquifers are permeable layers of rock and sediment that have groundwater in enough quantity to supply wells.

23. 3. The Hydrology of Groundwater: Dynamics of the Groundwater Table

24. 3. The Hydrology of Groundwater

25. ● Balancing recharge and discharge ● balance = stable water table
3. The Hydrology of Groundwater
● Balancing recharge and discharge
● balance = stable water table
● excess recharge = rising water
table
● excess discharge = falling
water table

26. Groundwater:
Excess
Discharge
and the
Cone of
Depression

27. Wells
What happens when this well is heavily pumped?

28. When withdrawal >> recharge, the pores of the rock lose their water and compact leading to subsidence (lowering) of the ground surface

29. When withdrawal >> recharge, the pores of the rock lose their water and compact leading to subsidence (lowering) of the ground surface

30. Groundwater:
Excess
Discharge
and the
Movement
of Salt
Water

31. Groundwater:
Excess
Discharge
and the
Movement
of Salt Water

32. Groundwater: Darcy’s Law
Q = A [K ( ha – hb )] l
Darcy's Law is a generalized relationship for flow in porous media. It shows the volumetric flow rate is a function of the flow area, elevation, fluid pressure and a proportionality constant.