C10Use Constant-head Injection Test for In-Situ Estimation of Hydraulic Conductivity in Gravel Bed
Rivers〇ENBANG XIAO・Yasuhiro TAKEMON・Sohei KOBAYASHI・Tetsuya SUMIAbstract
In order to get more comprehensive understanding of the in-situ data of hydraulic conductivity in rivers that has
low accessibility, we use modified Constant Head Injection Test method and developed a set of portableequipment to conduct field survey of hydraulic conductivity in gravel bed rivers. Equipment includes a micro
water pump powered by portable electricity generator, a manually driven permeameter made by steel pipe,
measuring cylinder, and several accessories. Problems were detected during the trial in Tenryu River andimprovements were made afterwards.
Introduction
River bed hydraulic conductivity plays an important

Kh is horizontal hydraulic conductivity

role in the surface water and ground water exchange

Kv is vertical hydraulic conductivity

process which has been showed in many former

K is the general hydraulic conductivity

studies.（Butler et al. 2001; Kollet and Zlotnik 2003）

Q is the stabilized injection rate

Yet, it is difficult to directly measure the streambedL: screened length

hydraulic conductivity, due to it is usually beneath theP: shape factor (dimensionless coefficient)riverbed and submerged by stream water, especially

y: distance between stream stage and the desired

for the in-situ estimation or in relative larger spatial

water level in the permeameterscale and intensity survey. The traditional ways toinvestigate the river bed hydraulic conductivity suchas standard slug test, grain-size analysis andobservation

wells

are

bothtime-and

Where: A and B are dimensionless coefficients thatwere originally in graphic form. These coefficientsresource-consuming procedure.

were approximated by Van Rooy (1988) (details in

In order to quicker and use less resources to getButler, 1998)

intensive

hydraulic

The constant head injection test is standard tool usedconductivity in the field, we use modified Constantby many soil and civil engineers. While the original

Headandidea is for measuring the low K value media, e.g. silt

beforehand-made spread sheet to estimate the in-situ

and clay. We use the modified CHIT method

river bed hydraulic conductivity, and capable to getdeveloped by Cardenas and Zlotnik to measure thethe result almost immediately. This method fits better

higher K value rivers such as gravel bed rivers. Thefor large scale and intensively survey of the gravel bed

purposes of this report is to show the instrumentation,

river especially with low accessibility.

field process, and data analysis for using the CHIT

CHIT method

method to study the gravel bed rivers in Japan, for theinformation

Injection

Testofriverbed(CHIT)

methodFor sub-meter scale we assume Kh=Kv=K

development of the theory please refer the following𝐾=𝑄/2𝜋𝐿𝑃𝑦 (Cardenas, 2003) and (Cho, 2000)

papers. (Bouwer and Rice, 1976; Dagan, 1978;

Where:

Cardenas and Zlotnik, 2003).

Using the modified CHIT theory, we only need tohead y, K can be easily calculated.

measure the Q and y in the field, other values areField trial

given. By using a spreadsheet, the K value can becalculated in the field.
Instrumentation and field process

Figure 2 first trial in Tenryu river

The first trial was conducted in the upstream ofTenryu river on Oct 29th, 2018. The riverbed isFigure 1The instrumentation of CHIIT methodcharacterized by coarse materials and newly deposited

The permeameter was specially designed for thesediment. K value was expected to be very high. At

higher K value riverbed materials such as gravel andfirst we tried to measure the hydraulic conductivity ofsandy rivers. The total length of the pipe is 1220mm

the top 20-30cm layer of the riverbed. While when(1200+20mm inside the cap), the inner diameter of thestream water was pumped into the pipe it just wentpipe is 45 mm; the outer diameter is 50mm, thedown into the very loose sediment instantly, which

thickness of the pipe wall is 2.5mm. The tip of themeans the K was too high for this instrument toinstrument is a solid cone which the height is 75mm

measure. As we hammered the pipe into the 80cm

and the circumference is 50mm. The cone is made ofdepth, the water table inside the pipe was steadily kept

solid steel. The bottom part of the pipe is the hole area,

by adjusting the micro water pump, Q was measured

the length is 200mm. Diameter of all the holes is 5mm,

by a volume cylinder. As calculated, K= 0.01429

the distance between the center of the hole to the edge

cm/s= 12.35m/day.

of the hole area is 10mm, both the top edge and theReferences:bottom. （ assume the permeameter is stand ） theButler Jr, James J., Vitaly A. Zlotnik, and Ming‐Shu

vertical distance between two holes is 40mm, and theTsou. "Drawdown and stream depletion produced bylateral distance is 15mm. There are 110 holes in total,

pumping in the vicinity of a partially penetrating

10(vertical row) ×11(lateral row).

stream." Groundwater 39.5 (2001): 651-659.

Stream water was collected in a bucket (without much

Bouwer, Herman, and R. C. Rice. "A slug test forsuspended load, which could clog the hole area anddetermining hydraulic conductivity of unconfined

streambed

theaquifers with completely or partially penetrating

permeameter by the micro water pump which canwells." Water resources research 12.3 (1976):

adjust the discharge manually in order to keep a423-428.

constant water level in the top of the permeameter. As

Kollet, Stefan J., and Vitaly A. Zlotnik. "Streamthe water level attained the designed height y and was

depletion predictions using pumping test data from asteady (e.g. for 10s to several minutes), pull out theheterogeneous stream–aquifer system (a case study

pipe into a volume cylinder, as the same time start thefrom the Great Plains, USA)." Journal of Hydrology

timer, thus the injection rate Q can be measured.

281.1-2 (2003): 96-114.

sediment),

thenpumpedinto

Known test geometry, injection rate Q and operational