Today’s Lecture Water levels and groundwater flow

Today’s LectureWater levels and groundwater flow

AnnouncementsLecture

today: groundwater flow Thursday: guest lecture

Joy Jenkins, EPA: Captain Jack Superfund site

Lab Lab 1: Phase I ESA

rewriting? Lab 2: Surface water sampling

grading in progress? Lab 3: Soil sampling

report due Wed Oct 21 Lab 4: Well drilling

report due Fri Oct 30

AnnouncementsLab

Wednesday, Oct 28 Lab 5 Groundwater

sampling / Slug test East campus

Water Levels and Groundwater FlowMeasuring water levels in wells

single measurements electronic water level sensors simple tape measures inaccurate

long-term monitoring pressure transducers data recorders

Water Levels and Groundwater FlowWater level meters

sensors on tapes weighted probe on marked tape (PVDF*) water completes circuit across electrodes buzzer, light notification

depth relative to known elevation;

e.g., top of well casing depths to 1,000 ft accuracy to 0.01 ft or 1 mm

* polyvinylidene difluoride


advantages reliable, rugged easy to operate accurate

disadvantages probe, tape catches on casing joints false readings from cascading water,

condensation a lot of reeling!


sounders (acoustic) travel time for sound wave low frequency (50-200 Hz)

depth relative to known elevation;

e.g., top of well casing accuracy to 0.01 ft or 1 mm

advantages quick; no decontamination

disadvantages reflections off untrue well casing

Water Levels and Groundwater FlowLong-term monitors

pressure transducers accuracy 0.05% temperature compensation barometric

compensation

data loggers 100,000s of readings

Water Levels and Groundwater Flow

Water Levels and Groundwater FlowGroundwater flow contours contours of

groundwater elevation potentiometric surface

of surficial aquifer less relevant for confined

aquifers direction and velocity of

groundwater flow important for

contaminant transport less useful for DNAPLs

Water Levels and Groundwater FlowGroundwater flow contours water flows from

high to low head often follows

topography, but not always

slope hydraulic gradient (L/L)

direction planar surface defined

byat least threewater level measurements

Water Levels and Groundwater FlowCalculation of groundwater flow direction water levels in three wells


28.1 ft

28.8 ft

28.4 ft


28.1 ft

28.8 ft

28.4 ft

170 ft


27.9 ft

28.8 ft

28.2 ft

170 ft

1 3

1 2 12

1 312

1 2

28.8 28.2170

28.8 27.9

113ft

x

x

x

h h Lh h L

h hL L

h h

L


27.9 ft

28.8 ft

28.2 ft

170 ft

113 ft


27.9 ft

28.8 ft

28.2 ft

170 ft

113 ft


27.9 ft

28.8 ft

28.2 ft

170 ft

113 ft


27.9 ft

28.8 ft

28.2 ft

170 ft


27.9 ft

28.8 ft

28.2 ft

170 ft28.7 ft

76 ft


27.9 ft

28.8 ft

28.2 ft

170 ft28.7 ft

76 ft

28.7 28.276

0.0066

dhdLdhdL


27.9 ft

28.8 ft

28.2 ft

170 ft28.7 ft

76 ft

0.0066

Kdhv

ndLK

vn

Water Levels and Groundwater FlowGroundwater Flow Calculator

doi: 10.1111/gwat.12211



Water Levels and Groundwater FlowErrors in groundwater level measurement recording and transcription

errors condensation in well casing poor flow through well

screen nearby infiltration sources

water line leaks presence of LNAPL (“free

product”)

leads to errors in groundwater velocity and direction

LNAPL

Next LectureGuest lectureMeasuring aquifer properties – slug tests

Documents

Today’s Lecture Water levels and groundwater flow