NASA CASE NO.

PRINT FIG. l(b)

NOTICE

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LAR 14835-1

The invention disclosed in this document resulted from research in aeronautical and

space activities performed under programs of the National Aeronautics and Space

Administration. The invention is owned by NASA and is, therefore, available for

licensing in accordance with the NASA Patent Licensing Regulation (14 Code of

Federal Regulations 1245.2).

To encourage commercial utilization of NASA-owned inventions, it is NASA policy to

grant licenses to commercial concerns. Although NASA encourages nonexclusive

licensing to promote competition and achieve the widest possible utilization, NASA

will provide the necessary incentive to the licensee to achieve early practical

application of the invention.

Address inquiries and all applications for license for this invention to NASA Patent

Counsel, Langley Research Center, Code 143, Hampton, Virginia 23681-0001.

Serial No." 07/988,077

12/07/92 LaRC

(NASA-Case-LAR-14835-1) FLOW

LOGGING SEEPAGE METER Patent

Application (NASA) 16 p

RATE N93-19328

Unclas

G3/35 0149906
AWARDS ABSTRACT FOR 

FLOW RATE LOGGING SEEPAGE METER 

NASA Case No. LAR 14835-1 

The movement of groundwater and its associated solutes from 

upland regions has been linked to the degradation of receiving 

surface water bodies. Current and conventional methods of 

measuring this influx of water include only manually operated 

seepage measuring devices which are disadvantageous for several 

reasons, one of which is the excessive amount of manual 

interaction. Thus, we have invented a remotely operating semicontinuous flow rate logging seepage meter for measuring the 

movement of groundwater seepage into surface water bodies on a 

semi-continuous basis and for logging the measured information. As 

groundwater seeps into a cavity created by a bottomless housing, it 

displaces water through an inlet and into a waterproof sealed upper 

compartment and bag chamber, at which point, the water is collected 

by a collection bag in the bag chamber. A magnet, which is mounted 

on the outside of the collection bag, approaches a proximity switch 

as the collection bag fills and expands, and eventually enables the 

proximity switch to activate a control circuit. The control 

circuit then causes a three-way valve to rotate from a collection 

port to a discharge port, and enables a pump to begin discharging 

the water from the collection bag through the three-way valve and 

pump, and into the sea. At the same time, the control circuit 

enables a data logger to record the time of the discharge cycle. 

After the collection bag has emptied a predetermined amount, the 

magnet is displaced away from the proximity switch so as to cause 

the control circuit to turn off the pump, and to rotate the valve 

back to the collection path. The water collection cycle is then 

restarted. 

Inventors: William G. Reay Harry G. Walthall 

Address : PO Box 124 PO Box 451 

Bellspring, VA 24058 Gloucester Point, VA 23062 

ss: - ss: 

Employer : Student NASA LaRC 

Initial Evaluator: Samuel S. Harris, Jr. 

Serial No.: 07/988,077 

Filed: 12-08-92 
LAR 14835-1 -1- PATENT APPLICATION

FLOW RATE LOGGING SEEPAGE METER

Origin of th_ Invention

5 The invention described herein was made by a Government employee

and a graduate student, and may be manufactured and used by or for the

Government for governmental purposes without the payment of any royalties

thereon or therefor.

10 Background of the Invention

The present invention relates to an apparatus and method of measuring

the movement of groundwater and, more particularly, to a remotely operating

semi-continuous flow rate logging seepage meter for measuring the

15 movement of groundwater seepage into surface water bodies on a semicontinuous basis and for logging the measured information.

The environmental concern for inland and coastal water bodies has led

to a considerable amount of research for defining material input into these

waters. Based on such research, the movement of groundwater and its

20 associated solutes from upland regions has been linked to the degradation of

receiving surface water bodies. Mechanisms responsible for advective

transport of solutes within nearshore sediments include elevated upland

hydraulic head (i.e., groundwater discharge), convective flows caused by

thermal and salinity density differences, sedimentation, spatial variations in

25 sea state (i.e., subtidal pumping), benthic boundary currents, and

bioadvection. In addition to influencing water quality management efforts,

such transport mechanisms are of biological and geological importance.

Macroscopic seepage rates of water across the sediment-water

interface typically range from 0.0 to 5.0 LeM-2ehr 1. Hydraulic head

30 differences between overlying surface waters and interstitial water is on the
LAR 14835-1 -2-

order of millimeters for most nearshore environments.

varied flow rates and hydraulic head differences,

PATENT APPLICATION

Given such low and

current flow meter

technology is inadequate and the measurement of such phenomena remains

a technical problem.

5 Current efforts to measure the direct influx of water have

conventionally been through a manually operated seepage measuring devices,

such as that disclosed by D.R. Lee, in "A Device for Measuring Seepage Flux

in Lakes and Estuaries," Limnoloqy and Oceanography, 22: 140-147, 1977.

A typical seepage meter generally includes an open-bottom cylinder covered

10 by a vented lid that allows a water collection bladder to be attached. The

seepage meter is placed into the sediment, and water entering the meter is

collected into the collection bladder. After a certain amount of time and if the

collection bladder is full, the full collection bladder is retrieved and replaced

with a new bladder. This is typically performed by a diver. The amount of

15 groundwater discharge is determined by the volume of water displaced per

cross-sectional area of seepage meter per unit time.

However, such manually operated seepage meters are disadvantageous

in that they require extensive manual intervention and work effort.

In addition, conventional apparatus and methods require divers to

20 monitor and replace collection bags, and record the number of discharges

over a given time period. This leads to only being able to obtain a small

number of data samples, which in turn renders incomplete and sometimes

inaccurate results.

25 Summary of the Invention

It is accordingly an object of the present invention to overcome the

above disadvantages and problems of the prior art by providing a remotely

operated semi-continuous flow rate logging seepage meter by automating the
LAR 14835-1 -3- PATENT APPLICATION

collecting-discharging-data logging cycle to allow remote collection and more

sample data with less effort.

Another feature and advantage of the present invention is the ability

to gather numerous data samples without manual interaction for time periods

5 on the order of weeks.

Another feature and advantage of the present invention is the ability

to attain data at increased depths. Divers are no longer needed to periodically

retrieve and replace the collection bladders and log the data points, therefore

the present invention can be deployed deeper than manual seepage meters.

10 Other features and advantages of the present invention include

additional applications that address extremely low flow rates in conjunction

with low pressures. When used along with proper hardware material,

potential industrial uses of this flow meter concept may include flow rate

measurements of caustic and corrosive fluids.

15 The above and other objects, advantages, and features of the present

invention are accomplished by providing an apparatus for determining the

flow rate of groundwater seepage including a collection inlet and a discharge

outlet, a collection bag, coupled to the collection inlet and the discharge

outlet, for collecting groundwater through the collection inlet during a

20 collection cycle and discharging groundwater through the discharge outlet

during a discharge cycle, a controller, responsive to first and second signals,

for controlling the collection and discharge cycles, a switching circuit

producing the first signal after a predetermined amount of groundwater is

collected in the collection bag during the collection cycle and producing the

25 second signal after a predetermined amount of groundwater is discharged

during the discharge cycle, and a data logger, responsive to a first output of

the controller, for measuring at least one of the amount of groundwater

collected and discharged so as to determine the flow rate of groundwater

seepage.
LAR 14835-1 -4- PATENT APPLICATION

Further in accordance with the above objects, advantages, and

features, the present invention provides an apparatus for determining the flow

rate of groundwater seepage including inlet means, outlet means, collecting

means, coupled to the inlet and outlet means, for collecting groundwater

5 through the inlet means during a collection cycle and discharging groundwater

through the outlet means during a discharge cycle, control means, responsive

to first and second signals, for controlling the collection and discharge cycles,

switch means for producing the first signal after a predetermined amount of

groundwater is collected in the collecting means during the collection cycle

10 and producing the second signal after a predetermined amount of

groundwater is discharged during the discharge cycle, recording means,

responsive to a first output of the controller, for measuring at least one of the

amount of groundwater collected and discharged so as to determine the flow

rate of groundwater seepage.

15 In further accordance with the above objects, advantages, and

features, the present invention provides a method for determining the flow

rate of groundwater seepage including the steps of a) collecting water into a

collection bag, b) determining when a predetermined amount of water has

been collected in the collection bag, c) discharging the water from the

20 collection bag, d) recording the time of one of collecting and discharging

steps, and e) repeating the steps a) through d).

Brief Description of the Drawings

25 Figs. la and 1 b respectively illustrate a top and side view of a seepage

measuring apparatus in accordance with a preferred embodiment of the

present invention.

Figs. 2(a) - (c) are an electrical schematic of a control circuit of Figs 1.

Fig. 3 is a graphic representation of the data recorded during a field

30 test of a tidal creek site in the Chesapeake Bay.
LAR 14835-1 -5- PATENT APPLICATION

Fig. 4 is a graphic representation of the data recorded during a field

test of a nearshore site in the Florida Bay.

5

Detailed Description of the Preferred Embodiments

Figs. 1 (a) and 1 (b) respectively illustrate a top and side view of a flow

rate seepage measuring apparatus. The apparatus is housed in a waterproof

upper compartment 2 of a bottomless cylinder 1, which is made of, for

example, 16 gauge stainless steel and has a cross-sectional area of 0.25 m 2.

10 The bottomless cylinder 1 is placed in the sediment at a predetermined water

depth of up to approximately 40 meters. The total weight of the seepage

meter and components is approximately 50 kilograms.

The apparatus includes a collection bag 5 contained within a chamber

6, which has openings through tubes 18, 19 to the surrounding atmosphere,

15 which may be sea water, such that the chamber and the collection bag 5 are

maintained at sea pressure. During water collection cycles, the collection bag

5 receives and collects ground water through a pipe 17, a three-way valve 4,

which is controlled by a valve motor 10, and an inlet pipe 3, which

communicates to the area below the waterproof upper compartment 2 within

20 the bottomless cylinder 1. The collection bag 5 expands as water is collected

therein. During water discharge cycles, water is discharged from the

collection bag 5 through the pipe 17, three-way valve 4, a pipe 1 6, metering

pump 11, and pipe 15 to the nearby body of water or open sea.

A magnet 7, which may be a ceramic magnet, is affixed to the

25 collection bag 5 so that after the bag expands a predetermined amount during

the water collection cycle, a magnetically responsive proximity switch 8 (e.g.,

a single pole, single throw magnetically triggered reed switch) is switched to

trigger a control circuit 9 to begin a discharge cycle. The control circuit 9,

which is shown in more detail in Fig. 2, controls the water collection and

30 water discharge cycles as well as controlling a data logger 12. The data
LAR 14835-1 -6- PATENT APPLICATION

logger 12 records data, such as the time of day or the time between

consecutive water collection or discharge cycles in order to measure the

amount of groundwater seeping into the surface water bodies, and data

corresponding to the tidal/sea conditions, which is detected by a pressure

5 transducer 13 on a periodic basis.

The apparatus is powered by a power supply, for example,

rechargeable batteries 14.

Referring to Figs. 2(a), 2(b), and 2(c), there is shown a schematic

diagram of the control circuit 9. The circuit 9 is powered by DC power,

10 which is provided by two 12-volt rechargeable batteries 908, 909, connected

in series to provide both 12 and 24-volt terminals. Alternatively, the DC

power could be provided by, for example, four 6-volt rechargeable batteries

connected in series. An input of a manually operable switch 901, such as a

single-throw switch, is connected to the 12-volt terminal of the first battery

15 908, and an output of the switch 901 is connected to a first input of the

proximity switch 8. An output of the proximity switch 8 is connected to a

first input 903b of a relay 903, whose second input 903a is coupled to the

24-volt terminal. The relay 903 is illustrated by way of example as a singlepole, double-throw relay. Two outputs 903d, 903e of the relay 903 are

20 respectively coupled to a discharge input 910 and collection input 911 of a

cam-operated switch. The cams CS1 applies power to the valve motor 10

for a predetermined period of time, which is long enough to allow the valve

4 to rotate from the discharge port to the collection port or vice versa. The

discharge terminal 910 of the motor 10 is also connected to a triggering input

25 905c of a relay 905, which is shown in Fig. 2 as a double-pole, double-throw

relay 905, through a second cam CS2. The relay 905 has inputs 905a, 905b

connected respectively to the 24-volt terminal and the data logger 12, and

outputs 905d, 905e connected to an input of the pump 1 O, its solenoid timer

1 la, and an output of the data logger 12, respectively. The closing of the

30 poles 905(b), 905(e) enables the data logger to begin the recording process.
LAR 14835-1 -7- PATENT APPLICATION

In a typical application, the circuit 9 is turned on and initiated by

manually closing the switch 901. The apparatus is placed into the

underwater, coastal sediment of a surface water body so that the sediment

and water fills the bottomless cylinder 1. At this time, the apparatus is in the

5 water collection cycle wherein groundwater, which seeps from the ground

into the bottomless cylinder, is collected by the collection bag 5 through the

inlet 3, three-way valve 4, and pipe 17. During the water collection cycle,

the system is electrically shut down to conserve power. As the collection

bag 5 fills with water and expands, the magnet 7 on the collection bag 5

10 approaches the magnetically responsive proximity switch 8. After the magnet

7 is within a predetermined distance from the proximity switch 8, the switch

8 closes so as to provide 12-volts to the relay 903. The single pole of the

relay 903 is switched to make contact with the discharge cycle pole 903e so

as to provide power to the valve motor 904 through the pole 910 for a period

15 of time, which determined by the cam switch CSl. The cam switch CSl

applies power to the valve motor 904 long enough to rotate the valve 4 to

the discharge port.

When the valve 4 reaches the discharge port position, the cam switch

CS1 is opened to remove power from valve motor 904 and cam switch CS2

20 is switched to pole 913 thereby applying 12-volts to the relay 905. This

applies 24-volts to the pump timer 1 la and metering pump 11 through the

inputs 905a and 905d and causes the input 905b to make contact with the

pole 905e so as to signal the data logger 12 to being recording the date and

time of the cycle. The data logger 12 records data, such as the time-of-day

25 of the beginning of the discharge cycle or the time between consecutive

discharge cycles, depending on data preference. At the same time, the

metering pump 11 discharges the seepage water, which was collected in the

collection bag 5, to the open sea through pipe 17, three-way valve 4, pipe

16, pump 11, and pipe 15.
LAR 14835-1 -8- PATENT APPLICATION

When the collection bag 5 deflates enough to displace the magnet 7 •

a predetermined distance from the proximity switch 8, the proximity switch

8 opens and 12-volts is removed from relay 903 coil causing the relay input

903a to switch to the 903d pole. This action causes 24-volts to be applied

5 to the collection input 911 of the valve motor 904 for the predetermined time

period which is determined by the cam switch CSl. As power is applied to

the valve motor 904, it causes the valve 4 to rotate to the collection port.

The start of this rotation also switches cam switch CS2 to the open pole F

thereby de-energizing the relay 905 and stopping the timer 11a and the

10 metering pump 11. At this time, another collection cycle begins.

During the discharge and data logging cycles, the collection of water

is interrupted for approximately fifteen seconds. Depending upon hydrologic

conditions and data requirements, discharge volumes can be modified over a

wide range by varying the size of the collection bag 5, or adjusting the

15 proximity switch 8, or discharge rate of the pump 11.

Since the volume of water discharged in one cycle can be

predetermined and will subsequently remain relatively constant, the recorded

discharge times can be used to determine the groundwater discharge rate for

the ground surface area covered by the meter during any measured time

20 period. At the same time, the use of the pressure transducer 13 enables a

correlation to be made between the groundwater discharge and the tidal/sea

state conditions in the coastal areas.

Using other commercially available sensors, the present invention can

also simultaneously record other hydrological conditions, including tidal

25 pressure as discussed above, to afford scientists a correlation capability.

For example, tests in the Florida and Chesapeake Bays were performed

with the addition of a commercially available pressure transducer that

measured and recorded tidal pressure, while the seepage meter was

measuring groundwater seepage. These tests substantiated the theory that

30 there is a correlation between high tide and the reduction of groundwater
5

10

LAR 14835-1 -9- PATENT APPLICATION

seepage. The results of these tests are illustrated in the charts of Figs. 3 and

4.

Due to the flow resistance caused by the components inherent to the

seepage meter design and alterations of the water's flow path induced by the

meter itself, experiments were conducted to compare actual versus measured

discharge rates. Efficiency experiments were conducted in a constant head

flow tank (having 1.0 m 2 cross-sectional area) filled with a well-sorted fine

sand. The constant head flow tank was allowed to equilibrate to a specific

discharge for one hour and calibration experiments were conducted for a two

hour period. The seepage meter was reinstalled for each individual test.

Measured discharges (Q') were determined by equation (1):

Q' = (Co*V)/(A*T) (1)

15

2O

25

wherein:

l

C_

V

A

T

= Measured discharge L,m-2,hr _

= Cumulative counts

= Pump out sequence volume (L 3)

= Area enclosed by seepage meter (m 2)

= Time period (hr)

The ratio of Q' to Q, where Q is the actual discharge rate, was

compared to determine seepage meter efficiency and accuracy. Experimental

results, which compare the seepage meter efficiency under varying discharge

rates are given below in TABLE 1.

3O

Actual Discharge Rate Measured Discharge Rate Percent Mean Efficiency

L,m-2,hr -1 Lem-2,hr -1

6.00 1.26 21

10.32 2.52 26

TABLE 1
LAR 14835-1 -10- PATENT APPLICATION

The mean efficiency of standard manual meter design has been shown

to be approximately 60 percent. Following initial installation, a specific time

period is required to equilibrate hydraulic pressures between ambient surface

water and water enclosed within the meter system, however, this is generally

5 on the order of minutes.

Even though the seepage meter displays a slight negative buoyancy,

settling of the meter into the sediment may occur, resulting in an increase of

pressure inside the meter and displacement of water into the collection bag

(i.e., 1 mm of settling would equal approximately 250 ml displacement of

10 water). The effect of settling was determined by installing the meter into the

sediment under no-flow conditions. Results using well-sorted sand indicated

no significant settling effect. However, caution should be exercised in high

porosity, low dry bulk density unconsolidated sediments (i.e., silt-clay mixes).

The apparatus as described above was field tested at two locations,

15 which varied in sediment type and seepage discharge. The first site was

located in a tidal creek on Virginia's Eastern Shore and characterized by a tidal

range of approximately 1.0 meter. Nearshore surficial (upper 20 cm) quartz

sandy sediments were conducive for water transport, exhibiting a mean

porosity and vertical hydraulic conductivity of 0.45 and 10 .2.4 cmesec 1,

20 respectively. The second site was located in the nearshore zone of Florida

Bay which exhibits a tidal range on the order of 0.10 m. Vertical hydraulic

conductivity and porosity of surficial carbonate sediments were on the order

of 10 .2.0 cmesec -1 and 0.40, respectively. Field test results for the Virginia

Eastern Shore and Florida Bay sites are presented in Figs. 3 and 4,

25 respectively.

As illustrated in Figs. 3 and 4, the discharge (i.e., counts) rates show

an inverse relation to the tidal elevation at the Chesapeake Bay site. During

high tides, water levels within the tidal creek caused hydraulic gradients

between 0.7 meters below the sediment-water interface and surface waters

30 to approach and equal 0.00, thereby effectively shutting down submarine
LAR 14835-1 -11- PATENT APPLICATION

groundwater discharge. (Hydraulic gradient (dh/dl) is the change in hydraulic

head per unit distance (I), where hydraulic head (h) describes the total energy

in a moving mass of water at a particular point.)

Conversely, as the tide recedes, vertical hydraulic gradients (up to 0.19

5 mere 1 at ebb tide) and discharge rates increase in concert. The remotely

controlled seepage meter allowed for the collection of 246 discharge data

points as compared to the four to ten time integrated data points that would

have normally been collected using manual methods.

As with the Chesapeake Bay site, the Florida Bay study site displayed

10 a correlation with tidal stage (Fig. 4). It should be noted that the data set for

the Florida Bay was summarized and consists of 1166 data points collected

over a 22 hour time period.

There has thus been shown and described a novel remotely operating

semi-continuous flow rate logging seepage meter for measuring the

15 movement of groundwater seepage into surface water bodies on a semicontinuous basis and for logging the measured information, which fulfills all

the objects and advantages sought therefor. Many changes, modifications,

variations and other uses and applications of the subject invention will,

however, become apparent to those skilled in the art after considering the

20 specification and the accompanying drawings which disclose preferred

embodiments thereof. All such changes, modifications, variations and other

uses and applications which do not depart from the spirit and scope of the

invention are deemed to be covered by the invention which is limited only by

the claims which follow.

25
LAR 14835-1 PATENT APPLICATION

FLOW RATE LOGGING SEEPAGE METER

Abstract of the Disclosure

5 An apparatus for remotely measuring and logging the flow rate of

groundwater seepage into surface water bodies. As groundwater seeps into

a cavity created by a bottomless housing, it displaces water through an inlet

and into a waterproof sealed upper compartment, at which point, the water

is collected by a collection bag, which is contained in a bag chamber. A

10 magnet on the collection bag approaches a proximity switch as the collection

bag fills, and eventually enables the proximity switch to activate a control

circuit. The control circuit then rotates a three-way valve from the collection

path to a discharge path, enables a data logger to record the time, and

enables a pump, which discharges the water from the collection bag, through

15 the three-way valve and pump, and into the sea. As the collection bag

empties, the magnet leaves the proximity of the proximity switch, and the

control circuit turns off the pump, resets the valve to provide a collection

path, and restarts the collection cycle.
FIG.1(o)

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BATTERIES

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FIG.1(b)

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TIME(hr)

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