Topic 5 Subsurface Flow and

1

• Topic 5 Subsurface Flow and
• Groundwater
• Basic Concepts
• Storage and Movement of Groundwater
• Groundwater Development

Reading for this topic pp 107-121 Reading for
Wed pp 77-88 Infiltration, Runoff, Streamflow
2

• Basic Concepts
• Water occurring in saturated zones
• gt97 liquid freshwater
• 30 streamflow in US
• 50 drinking water in US
• Can be affected by forests their mgt

WT
Groundwater
WT
Groundwater
3

• F. Zone of saturation pores filled w water
• G. Aquifer porous water-bearing
• underground formation
• H. Water table surface of zone of saturation
• ?0
• measured in wells that penetrate zone
• Zone of aeration soil profile between
• soil surface and water table (can be temporarily
• saturated) also called vadose zone.

4
J. Capillary fringe above water table negative
? dep on texture K. Effluent stream fed by
groundwater L. Influent stream losing water to
groundwater M. Unconfined aquifer direct
contact w atm through porous medium
5
N. Confined aquifer below impermeable geologic
formation under positive pressure artesian O.
Perched aquifer unconfined above impermeable zone
6
Summary of terms
7
Another view
http//www.ec.gc.ca/water/images/nature/grdwtr/a5f
1e.htm
8
(No Transcript)
9
Where groundwater occurs
10
Water table level in a tupelo-cypress swamp
11

• II. Storage and Movement of Groundwater
• Aquiclude impermeable stratum excludes
• water movement
• B. Aquitard slowly permeable stratum
• C. Storage amt and movement
• Amt of porosity
• Pore connectivity
• Hydraulic head
• D. Pumping rate vs. recharge rate..

12
F. Determining groundwater movement 1.
Unconfined aquifers water table elevation
contours mapped using wells 2. Confined
aquifers positive pressure piezometric surface
contours mapped based on level to which water
would rise in wells drilled into the confined
aquifer Artesian well land surface below
piezometric surface
13
G. Aquifer characteristics 1. Transmissivity
(m2/sec) amt of water flowing horizontally
through thickness of aquifer w hydraulic
gradient 1m/1m Tr bkv where b
saturated thickness (m) kv hydraulic
conductivity (m/sec)
14
2. Discharge from aquifer, Q, (cm3/sec) (Darcys
Law) Q kv A dht/dx where kv hydraulic
conductivity (cm/sec) A x-section of flow
(m2) dht/dx hydraulic gradient (m/m)
15
III. Groundwater Development A. gt50 world
population depend on groundwater for
drinking B. Beware of surface features C.
Major river valleys alluvial plains
16

• D. Management
• 1. Continued use of large quantities
• Negative change in storage
• Subsidence
• Saltwater intrusion
• Decline in baseflow of streams

17

• E. Forests and groundwater
• 1. Affects groundwater recharge
• changing ET, changes water table
• 2. Logging can
• decrease infiltration
• increases runoff
• decreases recharge
• lowers water table
• OR
• decrease ET
• raises water table
• 3. Net effect of forest mgt???

18
2. High water table adverse for tree growth 3.
Drainage lowers water table -can improve
establishment growth -can improve wet-season
access