IJERD – International Journal of Environmental and Rural Development (2018) 9-1

Research article
erd

Development of Water Harvesting Technique in Qargha
Reservoir Watershed of Paghman District, Afghanistan
SHAFIQULLAH RAHMANI
Graduate School of Agriculture, Tokyo University of Agriculture, Tokyo, Japan
Email: salarhaleem@gmail.com

TORU NAKAJIMA
Faculty of Regional Environment Science, Tokyo University of Agriculture, Tokyo, Japan

MACHITO MIHARA*
Faculty of Regional Environment Science, Tokyo University of Agriculture, Tokyo, Japan
Email: m-mihara@nodai.ac.jp
Received 31 December 2017

Accepted 12 May 2018(*Corresponding Author)

Abstract Harvesting surface runoff water from rainfall rather than allowing these waters to
run into the streams and rivers and eventually lost into sea is attaining popularity due to theincreasing demand for scarce water resources. In semi-arid countries such as Afghanistan
crops in need regular irrigation due to low and unequally divided annual rainfall throughout
the growing season. Therefore, this study aimed to develop water harvesting technique withclayey dressing application as a water harvesting strategy for surface runoff inducement to
reduce water shortage problems in Qargha Reservoir Watershed of Paghman District,Afghanistan. The results of laboratory and field experiments showed that, application of
clayey dressing on the soil surface was highly effective in surface runoff inducement. The
application of clayey dressing with silty clay loam and clay loam textures in the laboratory
and in the field and at various concentrations increased surface runoff considerably. The
plug radius of both silty clay loam dressing with 37.16% or lower concentration and clay
loam dressing with 46.96% or lower concentration can effectively clog pores and seal soil
surface. Therefore, development of proper water harvesting strategies such as clayey
dressing application is indispensable to achieve sustainable agriculture.
Keywords water harvesting, irrigation, clayey dressing, water resource management,
conservation strategies

INTRODUCTION
Water is the most essential input for successful farming. Afghanistan is often characterized as a dry
or arid to semi-arid country. Water utilization in Afghanistan is mostly for agricultural purposes.
Majority of the population lives in rural areas and are small subsistence farmers who live on smallplots of land (Qureshi, 2002). Recently, all the country is moaning from a serious drought due toclimate change. Recently National Disaster Management Authority (NDMA) (2018) stated in areport that, drought has reached to an emergency level in several parts of the country. According to
FAO (2018) report, drought impacted agricultural seasons of 2017 and 2018 in some part of thecountry of to a level in which the harvest was considered completely lost. As a semi arid region,
crops in the study area need regular irrigation due to low and unequally divided annual rainfall
throughout the growing season. Growing season starts in the march and ends in the month ofOctober. Hence, from June to October, Qargha Reservoir Watershed receives hardly any
precipitation. Therefore, irrigation water shortage during the latter half of the growing season is aserious problem causing crop failure and low productivity in the study area. Karezes (Karez is atunnel system used to extract shallow groundwater) and tube wells are the main irrigation sourcesin the study area. Mack et al., (2010) reported that, the water table has been continually dropping.
Rahmani and Mihara (2017) reported that 83% of the farmers in the Qargha Reservoir WatershedⒸ ISERD

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have an irrigation water shortage, and 66% of the farmers severely face it, especially in the latter
half of the growing season. Rain water management through water harvesting and inducement of
surface runoff by clayey dressing application onto soil surface can help in reducing water shortage
problems in the study area. Water harvesting techniques such as compaction by (Yazar et al., 2014),
gravel removel by (Parvizi et al., 2015), bitumen emulsion and tall oil, (Short and Lantzke, 2006),
less permeable soil (Amu-Mensah et al., 2013), wax and plastic cover by (Fink et al., 1980),
Sodium dispersants such as sodium carbonate and sodium chloride (Frasier et al., 1987 and Parvizi
et al., 2015) are widely used in the world for runoff inducement. In this study clayey dressing was
focused as a water harvesting techinque because it is an economical and environmental friendly
strategy.
OBJECTIVE
This study aimed to develop water harvesting technique with clayey dressing for runoff inducement
in order to reduce water shortage problems in Qargha Reservoir Watershed.
METHODOLOGY
Study Area
Qargha Reservoir Watershed is located within semi-arid region. Water utilization in Afghanistan ismostly for agricultural purposes. The study area lies between longitudes E 68° 49' 44'' and E 68°
40' 54'' and latitudes N 34° 25' 14'' and N 34° 40' 19.2''. The research was conducted in Qargha
Reservoir Watershed, Paghman District, Kabul Province, Afghanistan. The total area of Paghman
District is 361 km2, and Qargha Reservoir catchment area is 40.33 km2. Average annual
precipitation in the watershed is 280 mm and average annual temperature is 11.01 oC. The majorityof the rural population is small subsistence farmers with small plots of land.

Fig. 1 Location of Qargha Reservoir Paghman District, Kabul, Afghanistan
Rheological Analysis and Pore Size Distribution
Soil from Qala e Jan Big and Qala e Khwaja area of Qargha reservoir watershed was used forclayey dressing extraction in the laboratory. Sieves of 38 μm and 75 μm were used for the clayey
dressing extraction. Soil was diluted in the water and then passed it through sieves. Particles larger
than 38 μm and 75 μm were removed. Water content was reduced in room temperature. Clothsieving was used for clayey dressing extraction in the field. The extracted clayey dressing wasanalyzed for its soil particle size distribution. Rheological analysis of the clayey suspension was
carried out using MacMicheal rotational viscometer in the laboratory.

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Rotational rheometer tests have been used to determine the flow behaviors and shear strength
properties of very soft clays and muds with high moisture contents (Mahajan et al., 2008; Fakher etal., 1999). Standard wire number 26, and 10, 20, 30, 40, 50 rpm (revolutions per minute) were used.
Clayey suspension of silty clay loam (SiCL) and clay loam (CL) with 56.90%, 52.28%, 46.41%,
37.16% and 37.16% and 64.86%, 60.05%, 55.35%, 52.06 and 46.96% concentration were used,
respectiveley. Shear stress and shear rate values of the clayey suspension were measured and wereused to estimate Bingham yield values of the clayey suspension. Estimated Binghm yield values
were used to calculate plug flow radius of the suspension using equation below:
ro = 2L / ΔP

Eq. (1)

Where, ro is radius of plug flow (cm), L is pore length (cm) and ΔP is the difference in pressure(Pa).
The soil water retention curve was determined in the laboratory and was used to measure nongravitational pore size distribution, while gravitational pores were observed using morphologicalmethod. Soil sample was prepared from local soil in a cylinder with 10 cm depth and 10 cm
diameter, soil sample was adjusted at 5 cm depth and 10 cm of diameter and was compacted same
as field condition. The matric potential was determined using Em50 data logger and weightchanges were recorded using weight scale. Pore size distribution was calculated using Equation
below:
r = 0.15 / h

Eq. (2)

Where, r is the pore radius (cm) and h is the matric potential (cmH2O).
Surface Runoff Experiment
Runoff experiment was conducted in the laboratory of Land and Water Use Engineering, Tokyo
University of Agriculture using runoff plots with 0.90 m long, 0.052 m wide and 0.035 m deep.
Marriott bottle was used to provide constant water flow rate of 20 cm3 s-1 at constant pressure for aconcentrated surface scenario and 8% slope. Surface runoff experiments were also conducted in thefield (Fig. 2).

A

B

1

2

3

4

Fig. 2 Field (A) and laboratory (B) runoff experimental plots (1), cracks in the soil (2) andsoil surface after clay dressing (3, 4)
RESULTS AND DISCUSSION
Two types of clayey dressing 1st silty clay loam and 2nd clay loam were extracted with 38 μm and75 μm sieves, respectively in the laboratory and in the field using a cloth and were applied on theⒸ ISERD

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soil surface. Soil properties of the two extracted clay dressing is shown in Table 1. Most water
harvesting techniques are quite expensive and usually interfere with the natural environment anddeprive the land for other possible uses. While, the use of less permeable soils as a top layer
dressing to reduce infiltration and enhance runoff presents an interesting and viable option that
could give appreciable results (Amu-Mensah et al., 2013).
Table 1 Particle size distribution of clayey dressing
Soil type
Loam
Sandy loam
Field

Sieve (μm)
38
75
Cloth

Sand (%)
14.3
27.2
19.6

Silt%
51.8
41. 7
52.7

Clay%
33.9
31.1
27.7

Total%
100
100
100

Sieved soil texture
Silty clay loam
Clay loam
Silty clay loam

Surface Runoff
The amounts of surface runoff generated under different treatments compared to control are shownin Table 2. Silty clay loam dressing with 57%, 53% and 47% concentration increased runoff by
30.07%, 28.29%, and 15.81%, respectively. While, clay loam dressing with 65%, 60% and 53%
concentration increased runoff by 42.57%, 40.59%, and 27.13%, respectively. The result showsthat, the clay dressing application is highly effective in increasing surface runoff, and the influenceof sieve size was not obvious. Sherazi et al. (2010) stated that permeability noticeably decreasing
by the increasing rate of clay in the clay-sand mixture. For instance, application of clayey dressing
on the soil surface is highly recommended as a runoff maximizer. Thus, it is very economical andeasy to use and extraction does not need expensive and difficult to use equipment. Availability andgeneration of extra rainfall runoff water can help to revive agriculture in the study area andcultivate large dry uncultivated lands.
Table 2 Surface runoff water under different treatments
Infil.
Percentage increase
Coef.
(dm3 m-2)
from control
Control
9.70 a**
12.96
3.20
0.75
SiCLD 57%
12.62 b**
12.96
0.00
0.97
30.07
Loam
1.3
SiCLD 53%
12.45 b**
12.96
0.99
0.96
28.29
SiCLD 47%
11.24 b**
12.96
1.68
0.87
15.81
Control
8.68 a**
12.96
3.82
0.67
CLD 65%12.38 b**
12.96
0.00
0.95
42.57
Loam
1.5
CLD 60%12.20 b**
12.96
0.00
0.94
40.59
CLD 45%11.04 c**
12.96
1.55
0.85
27.23
CLD = Clay loam dressing, SiCLD = Silty clay loam dressing, **denotes significance difference level at P<0.01

Soil Texture

Dry density
g cm-3Treatment

Disc. (dm3 m-2)

W. usedThe amounts of surface runoff generated under different treatments in the field compared tocontrol are shown in Table 3. Silty clay loam dressing onto Deh Ponba soil with 65% and 58%
concentration increased runoff by 42.55% and 41.47%, respectively. While, clay loam dressing
onto Doda Mast soil with 65%, 60% and 53% concentration increased runoff by 58.58% and55.28%, respectively. Parvizi and Sepaskhah (2016) examined the effect of gravel removal, rill
construction across to slope and applying of baking soda on surface runoff, rainfall infiltration. The
most effective in the runoff enhancement were gravel removal, rill construction across to slope andbaking soda 31.20, 29.30 and 22.00%. Application of less permeable soil onto soil surface to create
possibility for harvesting and storing rainwater (Amu-Mensah et al., 2013). Statistical analysis
showed that there was significant difference in surface runoff between control and clayey dressing
treated soils both in laboratory and in the field. Sandy soils have a relatively low water-holding
capacity but a high intake rate. Instead, a clay or loam soil on the other hand, hold more water thana sandy soil but will not absorb water as quickly. Hence, soils with 20% or more clay content were
found to be the most sensitive to crust formation and have the lowest infiltration rate. It was
concluded that the increase in surface runoff using clayey dressing was due to its low permeability.
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Table 3 Surface runoff experiment in the field
Site

Treatment

Discharge (dm3 m-2) W. applied

Coef.

Control
27.73 a**
45.00
0.62
SiCLD 65%
39.53 b**
45.00
0.88
Deh Ponba
SiCLD 58%
39.23 b**
45.00
0.87
Control
25.27 a**
45.00
0.56
b**
Doda Mast
SiCLD 65%
40.07
45.00
0.89
SiCLD 58%
39.23 b**
45.00
0.87
SiCLD = Silty Clay Loam Dressing, **denotes significance difference level at P<0.01

Percentage increase fromcontrol
42.55
41.47
58.58
55.28

With an increasing percentage of clay, the soil structure become more stable (Ben-Hur et al.,1985). The result showed remarkable improvements in runoff generation and the percolation
reduction over the layered (dressed) soil surface as opposed to the control runoff experiments.
Amu-Mensah et al., (2013), reported that, application of a clay soil layer (dressing) on the soil
surface remarkably improving runoff generation. Clay is applied at the bottom of ponds alone onto
porous soils or mixed with a porous soil form an impermeable layer (Keese, 2006).
Rheological Properties of Clayey Suspension
The results of rheometer tests showed that suspension Bingham yield and plastic viscosity values
increased with increase in the mass concentration of clayey, and with decrease in massconcentration, Bingham yield and plastic viscosity values decreased. The results of rheometer tests
as shown in Fig. 3 had a direct impact on the plug flow radius of the clayey suspension.
B

A

Fig. 3 Changes in Bingham yield value and plastic viscosity with mass concentration ofsilty clay loam (B) and clay loam (A) suspension
Relationship between Pore Size Distribution and Plug flow
The result of plug flow radius calculation showed that the radius of plug flow minimizes with adecrease in concentration of clayey suspension as shown in Table 4. Clayey suspension of silty clay
loam at 56.95%, 52.28%, 46.41%, 45.88% and 37.16% concentration produce plug flow radiuswith 0.61 m, 0.195 m, 0.079 m, 0.048 m and 0.023 m, respectively, and clayey suspension of clay
loam at 64.86%, 60.05%, 55.35%, 52.06% and 46.96% concentration produce plug flow radiuswith 0.725 m, 0.292 m, 0.086 m, 0.071 m and 0.017 m, respectively. Clay soils are insensitivecohesive soils that have a water content higher than the liquid limit. The behavior of clay soils andsandy soils or even clay-silt soils differ from each other and even become more complex with watercontent. The transformation of soil from a plastic state to a viscous liquid state is primarily causedⒸ ISERD

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by a change in the water content of the soil mass. As the water content increases, the soil mass
gradually starts to behave like a viscous liquid (Fakher et al., 1999).
Table 4 Plug radius of clayey dressing suspension(Conc.)
cg g-1
56.90
52.28
46.41
45.88
37.16
(Conc.)
cg g-1
64.86
60.05
55.35
52.06
46.96

(θ)
Pa
5888.01815.0
694.4
426.5
189.9
(θ)
Pa
7370.02851.0
814.1
650.2
150.9

(ρ)
kg m-3
1939
1863
1766
1757
1613
(ρ)
kg m-3
2070
1991
1913
1859
1775

(h)
m
0.005
0.005
0.005
0.005
0.005
(h)
m
0.005
0.005
0.005
0.005
0.005

(m sec-2)
G
9.81
9.81
9.81
9.81
9.81
(m sec-2)
G
9.81
9.81
9.81
9.81
9.81

(ΔP)
Pa
95.1
91.36
86.61
86.18
79.13
(ΔP)
Pa
101.5
97.65
93.85
91.18
87.05

(ro =2Lθ/ΔP)
(m)
0.610
0.195
0.079
0.048
0.023
(ro =2Lθ/ΔP)
(m)
0.725
0.291
0.086
0.071
0.017

Θ=Bingham yield, h= clayey dressing depth, ρ=Bulk density

Bingham flow

Newtonian flow
V= 0
0
dr

Vmax

dv

Plug
flow

R ro
ro

Fig. 4 Newtonian and Bingham flow
Plug flow radius of the clayey suspension also increased with an increase in Bingham yieldvalues as it is shown in Table 4. Two type of structural clogging take place 1st immediate clogging
course particles fixed in the pores and 2nd gradual clogging by adhesion and sedimentation of fineparticles to the inner wall. Bingham fluids such as clayey suspension produces plug flow. Clayeysuspension causes both immediate and gradual clogging (Mihara and Ysutomi, 1992).
The mechanism of pore clogging and surface sealing with dressing
Dressing

Dressing

0.5
cm

0.5
cm
Pore clogging

Soil poreFig. 5 Mechanism of pore clogging and surface sealingⒸ ISERD

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The pore volume for each pore class was calculated from the pore size distribution curve. The
pore diameter was classified into 5 categories as shown in Table 5. Pore classes of macropores,
mesopores, micropores, ultramicropores and cryptopores constitute at 26.47%, 30.88%, 19.85%,
6.62% and 16.18% of the total pore volume, respectively. A pore is not simply a void in the solid
structure of soil. However, various pore size categories have different characteristics and contributedifferent attributes to soils depending on the number and frequency of each type. A widely usedclassification of pore size is that of (Brewer, 1964).
Table 5 Pore size distribution of Qargha Reservoir Watershed soils
Class*
Cryptopores
Ultrmicropores
Micropores
Mesopores
Macropores

Subclass

Pore size (mm)Volume (cm3)

CoarseMediumFine
Very fine

0.1>
0.1 to 5
5 to 30
30 to 100
100 to 1000
1000 to 2000
2000 to 5000
5000>

47.16
55.02
35.37
11.79
0.10
0.91
1.99
4.34

Volume
(%)
26.47
30.88
19.85
6.62
0.22
2.00
4.39
9.57

*Source: Brewer (1964)
Changes in the pore size distribution evidently modify soil water retention. The direct relation
between pore size distribution and the soil water content can be defined as macropores andmesopores control the water content at soil saturation, micropores and ultramicropores control
water content at field capacity and cryptopores are very tinny pores filed by water for long time andvery little amount of water of these pores are available of plant consumption. It is to be concluded
that the increase observed in surface runoff by clayey dressing application compared to control was
due to clogging the soil pores and sealing the surface. Pore clogging and surface sealing happens
when the plug flow radius of suspension is bigger than the radius of soil pores. Mihara et al. (1993)
also confirm that pore radius smaller than radius of plug flow causes structural clogging.
CONCLUSION
As a semi arid country, crops in Afghanistan need regular irrigation due to low and unequallydivided annual rainfall throughout the growing season. During the growing season hardly any
rainfall event takes place in the study area. Therefore, this study aimed to develop water harvesting
technique with clayey dressing for runoff inducement in order to reduce water shortage problems inthe study area. The results from both laboratory and in the field experiments indicated that clayey
dressing application onto soil surface considerably increase surface runoff. Two types of clayey
dressing 1st silty clay loam and 2nd clay loam were extracted with 38 μm and 75 μm sieves,respectively in the laboratory and in the field using a cloth and were applied on the soil surface.
Silty clay loam dressing at 57%, 53% and 47% concentration increased runoff by 30.07%, 28.29%
and 15.81%, respectively compared to control. While, clay loam dressing at 65%, 60% and 53%
concentration increased runoff by 42.57%, 40.59%, and 27.13%, respectively. The results of field
expeiments showed that, clayey dressing applied onto Deh Ponba soil at 65% and 58%
concentration increased runoff by 42.55% and 41.47%, respectively. While, clayey dressing onto
Doda Mast soil with 65% and 60% concentration increased runoff by 58.58% and 55.28%,
respectively compared to control. Clayey suspension of silty clay loam at 56.95, 52.28%, 46.41%,
45.88% and 37.16% concentration produced plug flow radius at 0.61 m, 0.195 m, 0.079 m, 0.048
m and 0.023 m, respectively, and clayey suspension of clay loam at 64.86%, 60.05%, 55.35%,
52.06% and 46.96% concentration produce plug flow radius with 0.725 m, 0.292 m, 0.086 m, 0.071
m and 0.017 m, respectively. It is concluded that, silty clay loam dressing at 37.16% or lower
concentration and clay loam dressing with 46.96% or lower concentration can effectively clog
pores and seal soil surface. Therefore, development of proper strategies on water resourceⒸ ISERD

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development/management is needed to achieve sustainable agriculture.
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