1. Introduction to Groundwater
George B. Ozuna
Hydrologist
USGS Texas Water Science Center
U.S. Department of the Interior
U.S. Geological Survey

2. Presentation
• Review Hydrologic Cycle
• Focus on Groundwater
• Discuss the Drought

3. Hydrologic Cycle

4. Evaporation
Precipitation Condensation
Surface water
Transpiration
Infiltration
Groundwater
The Hydrologic Cycle

5. Precipitation
• Rainfall, snowfall, sleet, and hail are all forms of
precipitation

6. Rainfall across Texas

7. Rainfall across Texas

8. Rainfall Distribution by Month
Source: National Weather Service
0.65
0.75
1.1
1.41
2.3
3.04
1.91 1.91
2.51
1.93
0.85
0.76
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Inches
Monthly Lubbock Rainfall
(1981-2010)

9. Rainfall across Texas

10. Rainfall Distribution by Month
San Antonio Monthly Rainfall
1.62 1.70 1.81
2.68
3.59
3.09
2.23
2.35
3.38
2.83
2.05
1.75
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Inches
(1871 - 2013)
Source: National Weather Service

11. Rainfall across Texas

12. Rainfall Distribution by Month
Source: National Weather Service
3.38
3.2
3.41 3.31
5.09
5.93
3.79 3.76
2.51
5.7
4.34
3.74
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Inches
Monthly Houston Rainfall
(1981-2010)

13. Monthly Lubbock Rainfall
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
San Antonio Monthly Rainfall
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Monthly Houston Rainfall
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

14. Evaporation
Precipitation Condensation
Surface water
Transpiration
Infiltration
Groundwater
The Hydrologic Cycle

15. Precipitation
Surface water

16. Surface Water Gaging Network
527 – Real-time Stream Gage Sites
127 – Real-time Lake Sites

17. Surface Water
• Base flow is sustained or fair weather runoff.
In most streams, base flow is composed
largely of groundwater effluent.
USGS: Langbein and others, 1947, p. 6.

18. Precipitation
The Hydrologic Cycle
Evaporation
Transpiration
Surface water
Infiltration
Groundwater

19. What is an aquifer?
This is an aqua fur

20. Groundwater
• An aquifer is a rock which contains and transmits
water in sufficient quantities
• Principal types of rocks through which water can
move underground are sandstones, limestones,
and igneous rocks.

21. Groundwater

22. Groundwater
Sandstone
Limestone

23. Trinity Aquifer
Aquifer Unit Geologic Formation
Upper
Upper Glen Rose Limestone
Lower Glen Rose Limestone
Middle
Hensel Sand
Cow Creek Limestone
Confining
Hammet Shale
Lower
Hosston/Sligo

24. Geophysical Logs

25. An Aquifer
A
A’

26. Unconfined vs Confined
A A’

27. Water Levels

28. Water Levels
400 ft
350 ft
200 ft
150 ft
300 ft
300’
200’
400’
100’

29. Water-Level Maps
December 1999

30. Cone of Depression

31. Brackish Water
A A’

32. Brackish Water

33. Brackish Water
A A’

35. • Meteorological drought is
the amount of dryness
and the duration of the
dry period. Atmospheric
conditions that result in
deficiencies of
precipitation change from
area to area
Drought
Meteorological

36. • Hydrological drought is associated with
the effects of periods of precipitation
shortages on water supply. Water in
hydrologic storage systems such as
reservoirs and rivers are often used for
multiple purposes such as flood control,
irrigation, recreation, navigation,
hydropower, and wildlife habitat.
Competition for water in these storage
systems escalates during drought and
conflicts between water users increase
significantly.
Drought
Hydrological

37. • Agricultural drought mainly
effects food production and
farming. Agricultural drought and
precipitation shortages bring soil
water deficits, reduced ground
water or reservoir levels, and so
on. Deficient topsoil moisture at
planting may stop germination,
leading to low plant populations.
Drought
Agricultural

38. • Socioeconomic drought occurs when
the demand for an economic good
exceeds supply as a result of a
weather-related shortfall in water
supply. The supply of many economic
goods, such as water, forage, food
grains, fish, and hydroelectric power,
depends on weather. Due to variability
of climate, water supply is sufficient in
some years but not satisfactory to meet
human and environmental needs in
other years.
Drought
Socioeconomic

39. Surface Water Gaging Network
527 – Real-time Stream Gage Sites
127 – Real-time Lake Sites

40. Map of real-time streamflow compared to
historical streamflow for the day of the year

41. Map of below normal 7-day average streamflow
compared to historical streamflow for the day

42. Monthly Comparisons

43. Monthly Comparisons

44. Current Drought
State Climatologist John-Nielsen Gammon stated
“…2011 was the driest year ever for Texas, with an
average of only 14.8 inches of rain…The drought
began in October 2010.”

45. Selected Surface Water Sites

47. Selected Surface Water Sites

49. Selected Surface Water Sites

52. Texas Rainfall Records
Time Rainfall Location Date
15 minutes 3.95” Galveston June 4, 1871
2 hours 15.00” D’Hanis May 31, 1835
2 hours,15 min 22.00” D’Hanis May 31, 1835*
18 hours 36.40” Thrall Sep. 9, 1921
24 hours 43.00” Alvin July 25, 1979

57. Presentation
• Hydrologic Cycle
 Precipitation
 Surface Water
• Groundwater
 Types of Aquifers
 Confined vs unconfined
 Water Levels
 Brackish Water

58. Presentation
• Drought
 Meteorological
 Hydrologic
 Agriculture
 Socioeconomic
• tx.usgs.gov

59. QQuueessttioionnss?? George B. Ozuna
USGS
210.287.0304
gbozuna@usgs.gov
tx.usgs.gov