1. Groundwater Flow: Blackboard Example

2. U.S. Water Supply / Water Budget
Depends on rates of precip., evap., stream flow, and subsurface flow

3. Developing a Regional Water Budget
Depends on local precip. and evaporation scenario – Pacific Northwest vs. Desert Southwest vs. Florida Peninsula
Problem: Timing is critical – can’t store all of the mean annual runoff. Example: Snowpack in British Columbia – Spring of 1998.

4. Groundwater Supply 20% of U.S. consumptive water withdrawls
Needs protection, because residence times in aquifers can be hundreds to thousands of years
Groundwater seepage provides baseflow to streams
Groundwater mining – if withdrawl exceeds natural inflow, groundwater can be considered a non-renewable resource

5. Groundwater Depletion – Ogallala Aquifer
Gravel and sandstone aquifer extending from So. Dakota to Texas
In places, groundwater withdrawal is 20x the natural recharge rate
Well-water levels have dropped meters in places due to long-term irrigation
Sustainability?
As water table level drops, yields decrease and it becomes more costly to pump.

6. Water Supply - De$alination
Thermal Distillation - Process of taking in seawater, evaporating, moving, condensing, and collecting.
Reverse Osmosis- Use semi-permeable membranes and pressure to separate salts from water – less energy intensive than thermal distillation.
Largest desal plant in US = Tampa Bay.