Introduction Groundwater Hydraulics Daene C. McKinney

Course Objectives Introduction to groundwater, including: – Groundwater in the hydrologic cycle – Characteristics of porous media – Darcy's law of flow in porous media – Continuity principles – Well hydraulics and aquifer testing – Applications of groundwater hydraulics – Characteristics of unsaturated flow

Housekeeping Prerequisites: CE 356 Hydraulics Text: – Groundwater Hydrology, Todd, David Keith, Larry W. Mays, John Wiley & Sons, 2004 Homework: – Due dates on web site – Excessively late (> 2 days) penalized 50% per day late – Expectations: Clear presentation, No computational errors, Answers clearly marked, Units marked and used correctly Software: – GroundwaterVistas (graphical interface for USGS MODFLOW) – Available on CAEE Virtual Workspace

Housekeeping (Cont.) Grading: Exams (2): 34% No makeups No Final Homework: 32% Project: 34% Letter grades will be assigned as follows: A 92 – 100% A- 89 – 91% B+ 86 – 88% B 82 – 85% B- 79 – 81% C+ 76 – 78% C70 – 75% C- 67 – 69% D+ 64 – 66% D 58 – 63% D- 55 – 58% F< 55%

Projects Work in a team on a design project dealing with limiting hydraulic containment of a contaminated aquifer Real, complex groundwater issue Each team – Make a video presentation of their results – Deliver the final video (the presentation, model and results) – Critique other teams’ videos Purposes of the project: – Enable you to explore in-depth an aspect of groundwater – Provide experience formulating, executing and presenting a groundwater investigation

Groundwater and Aquifers Groundwater Hydraulics Daene C. McKinney

Some Terminology Hydrology (  ) –  - “water”;  - “study of” – Study of Water: properties, distribution, and effects on the Earth’s surface, soil, and atmosphere Water Management – Sustainable use of water resources – Manipulating the hydrologic cycle Hydraulic structures, water supply, water treatment, wastewater treatment & disposal, irrigation, hydropower generation, flood control, etc.

Some History Qanats –Subterranean tunnels used to tap and transport groundwater –Originally in Persia –Kilometers in length –Up to 3000 years old –Many still operating Chinese Salt Wells –1000 years ago: Drilled wells –Over 300 meters deep –Bamboo to retrieve cuttings –By year 1858: 1000 meters deep –Called “cable tool” drilling today Ancient Persian Qanat Ancient Chinese Salt Well

Old Theories Homer (~1000 BC) “from whom all rivers are and the entire sea and all springs and all deep wells have their waters” Seneca (3 BC -65 AD) “You may be quite sure that it not mere rainwater that is carried down into our greatest rivers.” Da Vinci ( ) accurate representation of the hydrologic cycle Descartes ( ) Vapors are drawn up from the earth and condensed… Kircher ( ) Water from the ocean is vaporized by the hot earth, rises, and condenses inside mountains.

Old Theories (Cont.) Vitruvius (~80-20 BC) –8 th Book on Water and Aqueducts. Rain and snow on land reappears as springs and rivers Palissy ( ). –French scientist and potter - accurate representation of the hydrologic cycle Perrault (1670): –Water balance on the Seine. River flow explained by rainfall. Mariotte ( ). –French physicist. First recharge estimates. Leaky roof analogy. Vallisnieri (1723) –At lower altitudes in the Alps, artesian wells are common. Higher altitudes in Alps, streams are losing water Groundwater originates from rain.

Modern Theories Henri Darcy (1856) –Relationship for the flow through sand filters. Resistance of flow through aquifers. Solution for unsteady flow. King (1899) –Water table maps, groundwater flow, cross-section Hazen, Slichter, O. E. Meinzer (1900s) –Practical applications, basing on theoretical principles of French hydrogeology C.V. Theis (1930s) –Well Hydraulics C.V. Theis Henri Darcy

Global Water Resources 68.9% Glaciers & Permanent Snow Cover 29.9% Fresh Ground water 0.9% Other including soil moisture, swamp water and permafrost 97.5% Salt Water 0.3% Freshwater Lakes & River Storage. Only this portion is renewable 2.5% OF TOTAL GLOBAL (Freshwater) TOTAL GLOBAL (Water) Groundwater Management in IWRM: Training Manual, GW-MATE, 2010

Global Water Cycle Principal sources of fresh water for human activities (44,800 km3/yr) Residence time: Average travel time for water through a subsystem of the hydrologic cycle T r = S/Q Storage/flowrate

Atmospheric Moisture Interception Snowpack Surface Soil Moisture Groundwater Streams and Lakes Runoff Rain Snow Evaporation Evapotranspiration Evaporation Throughfall and Stem Flow Snowmelt Infiltration Overland Flow Percolation Groundwater Flow Channel Flow PerviousImpervious Watershed Boundary Energy Hydrologic Cycle (Local view) Our focus

Water Budgets 1.Surface water budget P + Q in – Q out + Q g – E s – T s – I = D S s 2.Groundwater budget I + G in – G out - Q g – E g – T g = D S g System budget (1 + 2) P - Q – E – T = D S If T s = 0 G = D S - P + E - Q in + Q out

Major Aquifers of Texas Edwards Ogallala

Edwards Aquifer Primary geologic unit is Edwards Limestone One of the most permeable and productive aquifers in the U.S. The aquifer occurs in 3 distinct segments: Contributing zone Recharge zone Artesian zone

Formation of Edwards Aquifer

Contributing Zone of Edwards Aquifer Located north and west of the aquifer in the region referred to as the Edwards Plateau or Texas Hill Country Largest part of the aquifer spanning 4400 sq. miles Water in this region travels to recharge zone

Recharge Zone of Edwards Aquifer Geologically known as the Balcones fault zone It consists of an abundance of Edwards Limestone that is exposed at the surface -provides path for water to reach the artesian zone

Artesian Zone of Edwards Aquifer The artesian zone is a complex system of interconnected voids varying from microscopic pores to open caverns Located between two relatively less permeable layers that confine and pressurize the system Underlies 2100 square miles of land

The Edwards Group

Flowpaths of the Edwards Aquifer

The Ogallala Aquifer Approximately 170,000 wells draw water from the aquifer. Water level declines of 2-3 feet per year in some regions. Only 10% is restored by rainfall.

Example Ogallala Well Hydrograph

The Ogallala Aquifer Water Level Change Water Level Change up to 1980

Summary Course Introduction and Housekeeping Groundwater and Aqufiers – Terminology – History Global Water Resources – Global Water Cycle Texas Aquifers – Edwards – Ogallala