Introduction Groundwater Hydraulics Daene C Mc Kinney 1

Introduction Groundwater Hydraulics Daene C. Mc. Kinney 1

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 2

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: – Groundwater. Vistas (graphical interface for USGS MODFLOW) – Available on CAEE Virtual Workspace 3

Housekeeping (Cont. ) �Grading: – Exam 1: 17% – Exam 2: 17% – Homework: 32% – Project: 3 parts • • • Part 1 – 5% Part 2 – 10% Part 3 – 19% 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% C 70 – 75% C 67 – 69% D+ 64 – 66% D 58 – 63% D 55 – 58% F < 55% 4

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 5

Groundwater and Aquifers Groundwater Hydraulics Daene C. Mc. Kinney 6

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. 7

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 Ancient Persian Qanat • 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 Chinese Salt Well 8

Old Theories �Homer (~1000 BC) � “from whom all rivers are and the entire sea and all springs and all deep wells have their waters” • Vitruvius (~80 -20 BC) – 8 th Book on Water and Aqueducts. Rain and snow on land reappears as springs and rivers �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 (1452 -1519) � accurate representation of the hydrologic cycle • Palissy (1509 -1590). – French scientist and potter - accurate representation of the hydrologic cycle 9

Old Theories (Cont. ) �Descartes (1596 -1650) � Vapors are drawn up from the earth and condensed… �Kircher (1615 -1680) � Water from the ocean is vaporized by the hot earth, rises, and condenses inside mountains. • Perrault (1670): – Water balance on the Seine. River flow explained by rainfall. • Mariotte (1620 -1684). – French physicist. First recharge estimates. Leaky roof analogy. 10

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 Henri Darcy • Hazen, Slichter, O. E. Meinzer (1900 s) – Practical applications, basing on theoretical principles of French hydrogeology • C. V. Theis (1930 s) – Well Hydraulics C. V. Theis 11

Global Water Resources TOTAL GLOBAL (Water) 2. 5% OF TOTAL GLOBAL (Freshwater) 68. 9% Glaciers & Permanent Snow Cover 97. 5% Salt Water 29. 9% Fresh Ground water 0. 3% Freshwater Lakes & River Storage. Only this portion is renewable Groundwater Management in IWRM: Training Manual, GW-MATE, 2010 0. 9% Other including soil moisture, swamp water and permafrost 12

Global Water Cycle Residence time: Average travel time for water through a subsystem of the hydrologic cycle Tr = S/Q Storage/flowrate Principal sources of fresh water for human activities (44, 800 km 3/yr) 13

Hydrologic Cycle (Local view) Atmospheric Moisture Rain Snow Evaporation Interception En er gy Throughfall and Stem Flow Snowpack Snowmelt Pervious Our focus Watershed Boundary Surface Impervious Infiltration Soil Moisture Percolation Evapotranspiration Overland Flow Groundwater Flow Streams and Lakes Channel Flow Runoff Evaporation 14

Water Budgets 1. Surface water budget P + Qin – Qout + Qg – ETs – I = DSs 2. Groundwater budget I + Gin – Gout - Qg – ETg = DSg 3. System budget (1 + 2) P + DQ + DG – ET = DS 4. Net to groundwater DG = DS - P + DQ + ET DQ = (Qin–Qout) = Net to Surface Water DG = (Gin–Gout) = Net to Groundwater 15

Major Aquifers of Texas Ogallala Edwards 16

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 17

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 18

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 19

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 20

Flowpaths of the Edwards Aquifer 21

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. 22

Example Ogallala Well Hydrograph 23

The Ogallala Aquifer Water Level Change up to 1980 Water Level Change 1980 - 1994 24

Summary • Course Introduction and Housekeeping • Groundwater and Aqufiers – Terminology – History • Global Water Resources – Global Water Cycle • Texas Aquifers – Edwards – Ogallala 25