COMPARISON OF INFILTRATION MEASURING
IRRIGATION IN CRACKING CLAY SOIL
By
TECHNIQUES
FOR
FURROW
Haitham. Ragab Elramlawi 1 , Hassan Ibrahim Mohammed 2 , Abdel Moniem ElAmin
Mohammed 3
1- Center of Dry land Farming Research and Studies, Faculty of Agricultural and Environmental Sciences, University of
Gadaref, Sudan. hairamlawi@yahoo.com 2- Department of Agricultural Engineering, College of Agricultural Studies, Sudan
University of Science and Technology, 3-Agricultural Engineering Department, Faculty of Agricultural and Environmental
Sciences, University of Gadarif.
KEY WORDS:
infiltration measurement, furrow irrigation, cracking clay soil.
ABSTRACT
Four different techniques of determining infiltration rate: namely ring
infiltrometer, level basin-furrow, inflow-outflow and volume-balance, were compared
in cracking clay soils in Rahad Irrigation Project to determine their effect on
Kostiakov-Lewis equation on the basis of field measurements. The functional
relationships among the coefficient of infiltration equation were studied for each
method of infiltration measurement. Volume-balance technique showed the highest
value of the intercept of Kostiakov equation while the inflow-outflow technique
showed the lowest values. The exponent obtained by inflow-outflow technique was
highest while the one found by volume-balance was lowest. Infiltration rate measured
by the double ring infiltrometer method was found to be significantly (p < 0.05)
different from the result of other methods. Statistical analysis showed that volumebalance technique was the most suitable and accurate method among the tested
techniques for estimating infiltration rate in cracking clay soils.
:‫الملخص‬
‫تم مقارنة أربع طرق لتقدير معدل التسرب في األراضي الطينية المشققة في‬
‫ وشملت الطرق حلقات التسرب المزدوجة واألحواض المستوية‬.‫مشروع الرهد الزراعي‬
‫ استخدمت هذه الطرق لتحديد تأثيرها على دوال‬.‫التي بها سراب وطريقة الموازنة الحجمية‬
‫ نتج عن الطريقة الموازنة‬.‫لويس بناء على القياسات الحقلية‬-‫وثوابت معادلة كوستياكوف‬
‫الحجمية أكبر قيمة للقاطع في معادلة كوستياكوف بينما أظهرت طريقة الدخل والخرج اقل‬
‫ كما أن األس الناتج بطريقة الدخل والخرج كان أعلى قيمه بينما ذلك المحدد بطريقة‬.‫قيم‬
‫ وجد أن معدل التسرب باستخدام طريقة حلقات التسرب‬.‫الموازنة الحجمية كان اقل قيمه‬
‫ اظهر التحليل اإلحصائي أن‬.‫المزدوجة يختلف معنويا عن القيم المحددة بالطرق األخرى‬
‫طريقة الموازنة الحجمية أكثر الطرق دقه ومالئمة مقارنة بالطرق األخرى التي تمت‬
.‫دراستها لتقدير معدل التسرب في األراضي الطينية المتشققة‬
INTRODUCTION
The design, operation, management and hydraulic evaluation of on-farm
irrigation application methods depend on the water infiltration properties of the soil
(Bali and Wallinder, 1987, Abdelwahab, 2000). This is because infiltration behavior
of the soil directly determines the essential variables such as inflow rate, furrow
length, application time, depth of percolation and tail-water run-off in furrow
irrigation. Estimation of infiltration rate is a difficult task especially in clay soils due
to: (a) temporal and spatial variations caused by soil heterogeneity, difference in soil
moisture content, compaction, surface crust and cracking depth, (b) difficulty in
choosing most suitable technique to best duplicate field conditions while making
accurate measurement, and (c) use of empirical infiltration models rather than
physical based mathematical ones and the difficulty in the characterization of
coefficients of the empirical relations. Different methods were used to quantify
infiltration rate of soil and each was yielding different results. However, ring
infiltrometers were frequently used to determine the infiltration rate in clay soils
(Adel Nour, 1988; Mohammed, 1982; Elkhidir, 1985). (Walker and Skogerboe, 1987)
classified infiltration measure-ment techniques for irrigation purposes into techniques
that use stagnant or ponded water conditions (cylinder infiltrometer and blocked furrow
infiltro-meter), those which use flowing water (furrow and border infiltrometer) and
prediction from measurement of water advance (Abdelwahab, 2000). Measure-ment
methods under stagnant water conditions were reported to yield lower initial
infiltration rate (Mohammed, 2002). They are widely used because of their simplicity
and ease of operation. These methods are recommended in study of basin, drip and
sprinkler irrigation. The methods involving stagnant water are described to be one
dimensional are characterized by the sealing effect of fine soil particles when water is
added to the ring, and in accuracy of simulating the field conditions when cracks are
avoided (El Khidir, 1985). The methods employing flowing water express two
dimensional water movements but can not be used for designing new irrigation
system. These methods are reported to be difficult to employ in the fields and their
accuracy is affected by back water curve (Yoo, 1987; Mohammed, 2002). There are
different functional forms to characterize the infiltration behavior of a soil. These
include theoretical and empirical equations. The theoretical infiltration equations are of
little practic-al use because they inadequately describe the variable conditions that
tend to dominate in furrow irrigation. While, the empirical equations are often used
due to their simplicity and adequate representation of actual field conditions
(Clemmens, 1981). The latter includes Kostiakov-Lewis, modified Kostiakov, Philip
and Soil Conservation Equations of USDA-SCS (Walker and Skogerboe, 1987).
However, Kostiakov-Lewis equation is the most popular equation for overland flow
and takes the form:
D  kT0n
Where: D: accumulated infiltration depth, mm, To: infiltration opportunity time, min,
k and n: empirical constants.
The objectives of this study were to compare different infiltration determine-ation
methods on Vertisols on basis of field measurements and to establish the adequacy of
Kostiakov-Lewis equation from field data of four infiltration estimation techniques.
Consequently, the study was made to avail input data to aid in designing and
evaluating the performance of furrow irrigation in clay soils.
MATERIALS AND METHODES
The infiltration measurements were made on montimorillonite clay soil
(Vertisols) in Rahad Irrigation Project (latitude 14o 35/N and longitude 35o 55/E) to
compare four infiltration techniques (double-ring infiltrometer (D. R.) basin-furrow
infiltrometer (L. F. B), inflow-outflow (In-out), and volume-balance (V.B.) over a
tested area of 16.3 ha prepared normally for cultivation of cotton crop using Rahad
Irrigation Project standard practices. Each technique was conducted and replicated
three times, whereas the double-ring infiltrometer was replicated nine times. The
materials used and measurement procedure employed with each method were as
follows:
For the double-ring infiltrometer, the procedure outlined by (Elramlawi 1992
and Mohammed 1982) was adopted. Double-rings (28cm high, 0.25cm thick and
25cm diameter for inner ring and 55cm diameters for outer ring) were installed in
crack free locations, for level basin-furrow infiltrometer, the method described by
(Walker and Skogerboe, 1987) with basin area of (262.5m2) was used. In each basin
six-50cm length rulers were randomly distributed to measure changes in depth of the
ponded irrigation water with time, for the inflow-outflow the procedure proposed by
(Merriam and Killer, 1978) and partially modified by (Elkhidir, 1985) was used. The
inflow into each furrow (0.8m spacing) was delivered from the field by using a
calibrated 5cm diameter siphon tubes while the rate was measured by Parshall flume
(Elkhidir, 1985). The flume was installed at distance of 50m from inlet point of the
siphon tube and the water levels were recorded every 5minutes, for the volumebalance method, the procedure given by (Shepard et. al., 1993) was followed. A flow
rate of 1.3 l/s was turned into each furrow (275 m length). The furrow was divided
into eleven stations spaced at 25m and advance and water surface profiles (depth and
width) were recorded at each station.
RESULTS AND DISCUSSION
(Fig. 1) shows the best fitted curves for the mean values of various infiltration
measuring techniques. Each infiltration technique gave different value of infiltration
rate at a given time. The rate during the first one to 1.5hours was in order of 29 to
35mm/hr. This is inconsistent with the result obtained by (Marriam and Killer, 1978)
(Table1). Different results were given by (Elkhidir, 1985) and attributed to seepage
from or into the furrow.
(Fig.1) Infiltration rate (mm/hr) by using double-ring infiltrometer (D.R.), level
furrow-basin infiltrometer (L.F.B.), inflow-out flow method (In-out.) and volumebalance method (V.B.).
The initial infiltration rates (after 5minutes) of both level basin- furrow and
double ring infiltrometers were 156.3 and 109.6mm/hr respectively. The relatively
high initial infiltration rate of level basin-furrow infiltrometer might be attributed to
the two-dimensional infiltration process that increases the infiltration rate (Holzapfel
et al., 1988), while the process of cracks isolation before conducting the test of double
ring infiltrometer decreases the infiltration rate Hanson, 1998). This is in contrast with
(Yoo, 1987) who found that water infiltrates into border irrigation (one dimensional
flow) to be faster than in the furrows (two dimensional flow). (Ali, 1964) found that
the presence of extensive cracking in both fallowed and cotton fields resulted in high
initial infiltration rate (after 5minutes using single ring infiltrometer) of 335.6mm/hr
and 254mm/hr in fallowed and cotton fields respectively. However, these results
neither justify nor compare to the results of (fig.1). As shown (Fig.1) after the initial
period of infiltration, the rates of infiltration falls quiet abruptly and drastically falls
to much lower values that ranged from 8.5 to 19.34mm/hr after six hours.
180
160
Infiltration rate (I) mm/hr
140
120
100
D.R.
80
L.F.B
In-out
V.B.
60
40
20
0
0
50
100
150
Infiltration
opportunity
time (To) (min)
200
250
Infiltration Opportunity time (To) min
The situation
of accumulated infiltration depth (D) is depicted in (Table 1). The
Fig. 1: Infiltration rate (I) in mm/hr by using double-ring infiltrometer (D.R.), level furrow-basin
inflow-outflow method
gave(L.F.B),
the inflow-outflow
highest infiltration
rate,
while the volume
- balance
infiltrometer
method (IN-out)
and volume-balance
method (V.B)
gave the lowest (Abdelwahab, 2000). This may be due to of the flume back water
effect or negligence of the estimation of surface storage in the inflow – outflow
method (Singh and Chauhan, 1973). In contrast (Smedema, 1984) found that the
infiltration rate decreases to a value of 2 to 3mm/hr. after a very long watering time
(12hours). Similar trend of decreasing values of infiltration rate with time was
observed by (Ali, 1964) who found decreasing values from 88mm/hr to 55mm/hr after
30minutes in cotton cultivated and fallow fields respectively. This high value may be
due to effects of cracks. (Abd El Nour, 1988) found a final and constant infiltration
rate of 22.0mm/hr in clay soils. This is close to the value of 23.1mm/hr obtained in
this study.
Table (1): Parameters of Kostiakov Equation Determined from the four Methods of Infiltration
Measurement.
Method of measuring
Parameters of
Accumulated Infiltration
Infiltration
infiltration
Kostiakov Equation
Depth (D) in cm
Rate mm/hr
K cm/minn
n
At 5 min
At 240 min
I* =k/ To n/
Double-ring infiltrometer
0.943
0.462
1.980
11.820
260.5 To-0..538
Level furrow-basin method
1.635
0.411
3.170
15.550
403.27 To-0.589
Inflow- outflow method
0.593
0.571
1.490
13.560
203.0 To-0.429
Volume – balance method
4.295
0.227
6.190
14.900
585.02 To-0.773
I*= infiltration rate mm/hr at To (min) , n/ = n- 1 , K/
= 600(n*k).
(Table 1) shows the parameters of Kostiakov equation (k and n) obtained from
each of the studied techniques. The predicted values of infiltration functions (Table 2)
match very well the actual field data for the various infiltration techniques used (R2 =
0.77-0.93). However, though the poorest fit was given for inflow–outflow method but
was still acceptable for estimating infiltration rate. The values of (n) which represent
the incremental rate of cumulative infiltration ranged from 0.227 to 0.571, in which
the largest (n) values were obtained from inflow–outflow method. This is in
agreement with Yoo, 1987). The lowest (n) value was given by the volume balance
method. However (n) is usually considered as soil character rather than to be
dependent on the measurement technique used (Smerdon, 1988). (Table 1) also shows
the value of (k) which described the initial infiltration rate for each method. The (k)
value was reported to be the parameter that is most influenced by the type of
measuring technique (Yoo, 1987). The lowest intercept was obtained by the inflowoutflow method (k = 0.593cm/min). This result is in agreement with the value given
by (Yoo, 1987). He attributed his result to tendency of water to seal the soil surface
causing a relative decrease in infiltration rate. However, the low (k) value obtained in
inflow-outflow method of this study may be related to lack of measurement of storage
volume inherent in the method itself. (Smederam, 1984) reported that infiltration rate
in Vertisols during the first 1.5hr was in order of 20 to 35mm/hr. This is in agreement
with the range of 29 to 35mm/hr reported in the first 1.5hr in this study (Fig.1). The
large (k) value was given the volume balance method (k = 4.295cm/min), and it was
mainly due to the nature of heavy clay soil which cracks when dry. (Smedema, 1984)
found that dry cracking clay soils would absorb almost instantaneously an equivalent
water depth of 15mm simply by filling the cracks. Using double ring infiltrometer
method (Mohammed, 1982) found values of (k) and (n) for the dry soil to be
0.859cm/min and 0.44 respectively. This is in line with the results of this study when
using double ring infiltrometer technique. However, using the same technique in the
same soils, (Elkhidir, 1985) obtained values of (k) and (n) to be 0.99cm/min and
0.405 respectively. He also reported values of 8.05cm/min and 0.175 for (k) and (n)
coefficient when using volume balance technique in furrow of 50 m length and 1.6 m
apart. (Table 2) shows the regression analysis of the relation of the accumulated
infiltrated depth (D) to infiltration opportunity time (T0) for all studied infiltration
techniques. Significant correlation (p< 0.05) was obtained for the different techniques.
Coefficient of determination in the range of 0.771 to 0.929 indicating acceptable fit to
field conditions. However, the allowed value of coefficient of variance (CV%) of 2.62
was given by the volume balance technique which means that this method is stable
and capable to give consistent results.
Table (2): Regression Analysis of Accumulated Infiltration Depth (D) for the Different Methods of
Measuring Infiltration
Methods of Measuring
Level of Significance
Coefficient of
Coefficient of
Infiltration
(P<0.05)
Determination (R2)
Variation (C.V %)
Double-ring infiltrometer
S*
0.873
12.8
Level furrow-basin method
S
0.929
12.7
Inflow- outflow method
S
0.771
13.2
Volume-balance method
S
0.851
2.62
S* = coefficient at 0.05 probability level
CONCOLUSIONS
The comparison of infiltration measuring methods for furrow irrigation under
clay soils reveals that: The predicted Kostiakov infiltration coefficients matched very
well with actual field data measured by the studied techniques, the relationships
among infiltration functions obtained from different techniques were developed. These
functional relations are related to the type of the technique used and the purpose of
intended study. They are also useful for estimating infiltration rate that may be used
as a tool for the evaluation of the performance of surface irrigation, double ring
infiltrometer method was found to be not suitable for measuring infiltration rate in
heavy clay soils and it does not give a reliable measure for infiltration rate in real field
conditions of furrow irrigation, inflow–outflow method, which ignores surface storage
water, tends to overestimate the basic infiltration rate and underestimate the initial
rate, Level basin–furrow method is recommended to measure infiltration rate in level
basin–furrow irrigation fields, the volume balance method is the most suitable and
most statistically acceptable technique to estimate infiltration rate in cracking clay
soils and furrow irrigation due to its capability to maintain flowing water conditions
and consider effects of cracks and surface storage.
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