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U.S. Department of the InteriorU.S. Geological Survey
Introduction to Groundwater
George B. OzunaHydrologistUSGS Texas Water Science Center
Presentation
• Review Hydrologic Cycle• Focus on Groundwater• Discuss the Drought
Hydrologic Cycle
Evaporation
CondensationPrecipitation
Surface water
Infiltration
Transpiration
Groundwater
The Hydrologic Cycle
• Rainfall, snowfall, sleet, and hail are all forms of precipitation
Precipitation
Rainfall across Texas
Rainfall across Texas
Rainfall Distribution by Month
Source: National Weather Service
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
0.65 0.75
1.1
1.41
2.3
3.04
1.91 1.91
2.51
1.93
0.85 0.76
Monthly Lubbock Rainfall(1981-2010)
Inch
es
Rainfall across Texas
Rainfall Distribution by Month
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1.62 1.70 1.81
2.68
3.59
3.09
2.23 2.35
3.38
2.83
2.051.75
San Antonio Monthly Rainfall(1871 - 2013)
Inch
es
Source: National Weather Service
Rainfall across Texas
Rainfall Distribution by Month
Source: National Weather Service
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
3.38 3.2 3.41 3.31
5.09
5.93
3.79 3.76
2.51
5.7
4.34
3.74
Monthly Houston Rainfall(1981-2010)
Inch
es
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
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
Evaporation
CondensationPrecipitation
Surface water
Infiltration
Transpiration
Groundwater
The Hydrologic Cycle
Precipitation
Surface water
Surface Water Gaging Network
527 – Real-time Stream Gage Sites127 – Real-time Lake Sites
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.
Precipitation
The Hydrologic Cycle
Evaporation
Transpiration
Surface water
Infiltration
Groundwater
What is an aquifer?
This is an aqua fur
• 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.
Groundwater
Groundwater
Sandstone
Limestone
Groundwater
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
Trinity Aquifer
Geophysical Logs
An Aquifer
A
A’
Unconfined vs Confined
A A’
Water Levels
Water Levels400 ft
350 ft
200 ft
150 ft
300 ft
200’
300’
400’
100’
Water-Level Maps
December 1999
Cone of Depression
Brackish Water
A A’
Brackish Water
Brackish Water
A A’
• 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
Meteorological
Drought
• 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.
Hydrological
Drought
• 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.
Agricultural
Drought
• 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.
Socioeconomic
Drought
Surface Water Gaging Network
527 – Real-time Stream Gage Sites127 – Real-time Lake Sites
Map of real-time streamflow compared to historical streamflow for the day of the year
Map of below normal 7-day average streamflow compared to historical streamflow for the day
Monthly Comparisons
Monthly Comparisons
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.”
Selected Surface Water Sites
Selected Surface Water Sites
Selected Surface Water Sites
Texas Rainfall Records
Time Rainfall Location Date15 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
Presentation
• Hydrologic Cycle Precipitation Surface Water
• Groundwater Types of Aquifers Confined vs unconfined Water Levels Brackish Water
Presentation
• Drought Meteorological Hydrologic Agriculture Socioeconomic
• tx.usgs.gov
Questions?Questions? George B. OzunaUSGS210.287.0304gbozuna@usgs.govtx.usgs.gov
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