Course Code

Cej

Description

• cours - matière potentielle : general studies
• exposé - matière potentielle : analysis
• exposé
• expression écrite - matière potentielle : essay
• cours - matière potentielle : faculty
• exposé - matière potentielle : skills
• cours - matière potentielle : code course title units
• fiche de synthèse - matière potentielle : business transactions
• leçon - matière potentielle : skills
• exposé - matière potentielle : ideas
• cours - matière potentielle : thought
• cours - matière potentielle : details

DEPARTMENT OF ECONOMICS UNIVERSITY OF IBADAN COORDINATOR: PROF. FESTUS EGWAIKHIDE DEPUTY COORDINATOR: DR. ADEWUYI Duration The duration of the programme is 4 years for direct entry candidate (Starting from 200 level) and 5 years for candidate with O/L (100 level). 100 Level Course Code Course Title Units/Status Departmental Courses ECO 101 Introductory Economics I 3 R ECO 104 Introductory Mathematics for Economists I 3 C Subsidiary Courses 2 Subsidiary 100 Level courses from any Department in the Faculty 6 Total 12 [First Semester] Departmental Courses ECO 102 Introductory Economics II 3 R ECO 103 Nigerian Economy in Perspective 3 R Subsidiary Course 2 Subsidiary 100 Level

• methods of resources allocation
• introduction to social accounting
• departmental courses
• monetary theory
• trade policies with particular reference
• economic development theory
• human resources courses details
• technology with reference to thei independence
• principles
• economics

Sujets

• General Studies
• Analysis
• Exposé
• Faculty
• Skill

Informations

• Publié par: mevang
• Nombre de lectures: 26
• Langue: English

Extrait

1.72, Groundwater Hydrology Prof. Charles Harvey Lecture Packet #5: Groundwater Flow Patterns

Local Flow System

Intermediate Flow System

Regional Flow System

20,000 feet

Hydrologic section showing local, intermediate and regional groundwater flow systems determined from an analytical solution to the groundwater flow equation

1.72, Groundwater Hydrology Prof. Charles Harvey

Lecture Packet 5 Page 1 of 8

Conceptual picture based on Hubbert’s potentials

Recharge Zone between two streams. Discharge Zone (generally 5% to 30% of a watershed)

Beneath ridge and valley one getsGroundwater Divide, an imaginary impermeable boundary.

• •

Recharge area – saturated flow is directed away from the water table. Discharge area – a component of flow upward and saturated flow is toward the water table.

Streamlines exist for steady-state systems. Is this realistic?

Pathlines can be constructed for transient systems. Apathlineis the trajectory a particle would travel over time.

Discharge Area

1.72, Groundwater Hydrology Prof. Charles Harvey

Midline

Recharge Area

Water table

Lecture Packet 5 Page 2 of 8

Groundwater Flow Patterns in Homogeneous Aquifers From flow nets we know that:

• •

Equipotential lines corresponding to the water table reflect the elevation head. Equipotential lines beneath the water table are curvilinear and reflect both pressure and elevation.

Note: artesian conditions can begeologically controlledortopographically controlled. Water Table

Flow Line

Equipotential

Water Table

Effects of Geology or Regional Flow (contrasts in K) Three most influential factors affected head distribution: 1.Ratio of basin depth to extent. 2.Configuration of the water table. 3.Variations in hydraulic conductivity.

Layered systems: lower layer 10 times the hydraulic conductivity.

If the lower layer increased to 100 times the hydraulic conductivity: •Lower gradient in lower aquifer. •More flow through the system (less bottom impedance). •Lower aquifer acts like a pirating agent for flow creating near vertical flow through upper aquifer. •Large discharge area in upper aquifer for water to get out.

1.72, Groundwater Hydrology Prof. Charles Harvey

Lecture Packet 5 Page 3 of 8

Groundwater-Lake Interactions •Lake type Surface water dominated o Most of the lake water was originally surface water Lake has an inlet and an outlet (rivers) Groundwater dominated o Most of the lake is groundwater •Seepage Distribution Recharge Lake. o Discharge Lake. o Flow-through Lake. o Combinations of the above. o •Seepage depends on groundwater-lake communication, which depends on the “Darcy parameters” Thickness and permeability of lake sediments. o Hydraulic gradient across lake sediments. o But lake is in the context of a regional flow system. o

Discharge Lake

1.72, Groundwater Hydrology Prof. Charles Harvey

Flow-through Lake

Recharge Lake

Lecture Packet 5 Page 4 of 8

Numerical Modeling of Groundwater-Lake Interactions

• •

Winter (1976) presents numerical model of lake flow systems The focus of the study is the effect on the position and head value of stagnation point of Height of water table relative to lake level o K h /K v o Position and size of aquifers o Lake depth o

The Model •Boundary Conditions Aquifer base is impermeable o Vertical no-flow boundaries on sides o •Major topographic high on upslope side •Major drain (stream) on downslope side Upper boundary is the water table o •Parameters chosen to be consistent with lakes and glacial terrain. Silty till o Sand o Ratios of K h /K v = 100 and 1000 based on field observations o

Stagnation Point •A location where flow is zero (stagnant) •Complex flow systems show one or more stagnation points •The point of lowest head on dividing streamline is a stagnation point There is a head value at the location of the stagnation point o For lake systems occurs under the shoreline on the downslope side of o the lake If the head at the stagnation point is higher than the head in a lake, o flow is toward the lake (no water flows out the bottom of the lake)

Groundwater-Lake Flow Systems •Flow systems exist on different scales Local o Intermediate o Regional o •Flow systems are separated by dividing streamlines Separation of flow systems explains chemical differences between o nearby lakes More minerals dissolve the longer water is in flow system o Water in intermediate and regional flow systems has a higher mineral o content

1.72, Groundwater Hydrology Prof. Charles Harvey

Lecture Packet 5 Page 5 of 8

Geologic Processes Controlling Regional Flow

Flow controlled by single or coupled processes:

Uplifted Foreland

Maximum flow rate: 1-10 m/yr

200 km

2 km

1) Topographically driven flow (gravity driven) •Dominant mechanism for shallow and deep groundwater flow systems •Water table subdued replica of landscape •Deep groundwater migrates 1 to 10 m/y in aquifers and much less in aquitards •Key factors: topography, conductivity, heterogeneity, anisotropy, and basin geometry Intracratonic Sag or Rift

Maximum flow rate: 0.1-1 m/yr

Aquitard

200 km

2 km

2) Free convection •Circulation cells develop with or without regional horizontal flow (can coexist with gravity-driven flow) •Driven by buoyancy forces associated with thermal and salinity fields •Flow rates are on the order of 1 m/y •Key factors: fluid-density gradient, aquifer thickness, and conductivity

1.72, Groundwater Hydrology Prof. Charles Harvey

Lecture Packet 5 Page 6 of 8

50 km

2 km

Thrust Terrane

Maximum flow rate: 0.1-1 m/yr

Compression

3) Tectonically-driven flow •Compression and thrusting during mountain building produces large overpressures in orogenic belts •Regime characteristic of accretionary wedges (subduction zones) with flow rate of cm/y •Theoretical flow (high) rates of 0.5 m/y

Rapidly Subsiding Margin

Maximum flow rate: 0.1-1 cm/yr

Strongly Overpressured

200 km

4 km

4) Overpressure buried continental margin •Fluid pressures can approach weight of overburden (lithostatic load) •Overpressuring typically occurs in young, low K basins •Also contributing to overpressure are: dehydration reactions and hydrocarbon generation •Flow rates generally < 1 cm/y (due to low K shales)

1.72, Groundwater Hydrology Prof. Charles Harvey

Lecture Packet 5 Page 7 of 8

Normal fault

Seismic Pumping in Rift

Earthquake Focus

5) Seismic pumping •Catastrophic faulting vents overpressure

No flow boundary

P 1

Pressure Compartments

P 3

P 2

P 4

P 5

200 km

5 km

5 km

No flow between compartments

2 km

6) Pressure compartments •Permanent impermeable barrier maintains pressures forever; seals into isolated compartments •Not believed by most hydrogeologists who feel there is always some permeability and flow over geologic time

1.72, Groundwater Hydrology Prof. Charles Harvey

Lecture Packet 5 Page 8 of 8