IJERD – International Journal of Environmental and Rural Development (2010) 1–1

Research article
erdInfluences of Land and Water Use on the Water Quality ofCanals through Agricultural Areas
MOHAMMED KAMRUL HASAN
Graduate School of Agriculture, Hokkaido University, Hokkaido, Japan
Email: hasan@env.agr.hokudai.ac.jp

YAMAMOTO TADAO
Research Faculty of Agriculture, Hokkaido University, Hokkaido, JapanNAGASAWA TETUAKI
Research Faculty of Agriculture, Hokkaido University, Hokkaido, Japan
Received 29 December 2009

Accepted 5 March 2010

Abstract Shinotsu Canal passes through an agricultural area that contains a high pollutant
load from catchments. This pollutant load influences the Ishikari River water quality,
which consequently affects downstream aquatic biota. This study was conducted toevaluate the influences of agricultural land and water use activities on Shinotsu Canalwater quality. The Shinotsu Canal is 25 km long and contains a 10,864 hectare catchment
area, which is divided into 10 sub-catchment areas. The proportions of major land uses
such as paddy fields, uplands, and forests were categorized by the supervised classification
method using satellite data for each sub-catchment area. Water samples were collectedmanually from 11 points (P1~P11) upstream to downstream from May 2006 to April 2009.
The suspended sediment (SS) concentration was analyzed by suction filtration; nitrate
nitrogen (NO3-N) was measured by ion-chromatography; and total nitrogen (TN), total
phosphorus (TP) were measured by UV-spectrophotometry. The SS, TN, and TP
concentrations were highest during the puddling period (PP), whereas the highest NO3-N
concentration occurred during the snow melting period (SMP). There was a positive
significant relationship between accumulated paddy field area (APA) and SS (r = 0.94)
and between the accumulated upland area (AUA) and SS (r = 0.96) at <0.001significancelevel during the PP. The TP concentration was also significant during the SS. TN was
highly correlated with APA (r = 0.94, P <0.001) and AUA (r = 0.98, P <0.001) during the
SMP. The SS, TN, and TP concentrations were higher downstream (P11) than upstream(P1) at all periods except for TN during the normal irrigation period. We conclude thatland and water use for agriculture, seasonal meteorological characteristics, and fertilizer
management affect Shinotsu Canal water quality.
Keywords land and water use, water quality, agricultural area, Hokkaido

INTRODUCTION
Shinotsu Canal in the Shinotsu district is 25 km long with both inlet and outlet on the Ishikari
River, Hokkaido, Japan. The canal basin is covered by paddy fields, upland fields, and forests.
Agriculture is the main land use activity in this district. It is well known that agricultural non-point
source pollution from watersheds is a major cause of water quality degradation. Intensive
agriculture emits significant amounts of nutrients, particularly nitrogen, phosphorus, and sediment(Monaghan and Smith, 2004). The water quality of streams, rivers, and lakes is highly related toland use in the catchments, which can affect the quantity and quality of runoff during and after
precipitation. Tong and Chen (2002) examined the hydrologic effects of land use in Ohio anddiscovered a significant relationship between land use and stream water quality, especially withrespect to nitrogen and phosphorus contamination. Tachibana et al. (2001) reported that non-point
pollution greatly influences the water quality of the Ishikari River. Reuse water may contain higher© ISERD

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IJERD – International Journal of Environmental and Rural Development (2010) 1–1

levels of pollutants from surface runoff, i.e., sediments, pesticides, and nutrients, than natural
streams. Water reuse is one of the most important factors for water quality degradation downstreamof the Shinotsu Canal. Polluted water also affects the downstream agricultural watersheds andaquatic biota of the Shinotsu Canal. However, some natural and agro-environmental problems
associated with water use and quality, land use, and management of the Shinotsu Canal still remain
to be solved. The objective of this study was to evaluate the influences of agricultural land andwater use activities on the water quality of the Shinotsu Canal.
MATERIALS AND METHODS
The investigation was conducted on the Shinotsu Canal in the Shinotsu district of the southern partof the Ishikari River basin in the west-central part of Hokkaido, northern Japan (Fig. 1). Its
agricultural catchment area (CA) is 10,864 ha, and the main crops are rice, wheat, maize, onion,
vegetables, etc.
Sampling point

N

Ishikari
HW

Pump station

CA- Catchment area
Drainagechannel

CA2
CA4

CA5
CA7

Japan

P10 0

Shinotsu

CＡ9

P8
P9

ｋｍ

P4
P5

CA6

Ishikari river

P11

CA11

CA10

P2
P3

P6
P7 Shinotsu canal

CA8

Ishikari

P1

CA3

2

Hokkaido

Fig. 1 Location map of study

Fig. 2 Investigated area of Shinotsu

The annual average precipitation is 1024 mm and most of it falls as rain from June to
September. The annual snowfall is 9500 mm and occurs from mid November to April. Maximum
snowfall occurs in January. The annual temperature ranges from a minimum of −7.4°C in January
to a maximum of 23°C in August. The study area is within the temperate zone, so there are four
seasons. However, we divided the study year into five periods: puddling (PP; May), normal
irrigation (NIP; June~August), post irrigation (PIP; September~mid November), snow covered(SCP; mid November~mid March), and snow melting (SMP; mid March~April). Water samples
were collected manually from May 2006 to April 2009 from upstream to downstream at 11 points
along the Shinotsu Canal. Sampling points are indicated by P1~P11 in Fig. 2. Samples werecollected 10 times during the PP, 11 times during the NIP, 11 times during the PIP, 9 times during
the SCP, and 8 times during the SMP. In the laboratory, a portion of each sample was filteredthrough pre-rinsed 0.2-µm filter paper, and the nitrate nitrogen (NO3-N) concentration wasdetermined using ion chromatography.
Water samples were analyzed according to the Japanese Industrial Standard (JIS). SS wasdetermined gravimetrically by suction filtration, and total nitrogen (TN) and total phosphorus (TP)were determined by UV spectrophotometry. The investigated area was determined using ArcGIS
9.2 modeling software. The total catchment area was divided into 10 sub-catchment areas,© ISERD

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represented as CA2~CA11 (Fig. 2). The catchment area for the P2~P11 sampling points was also
represented by CA2~CA11. The catchment and sub-catchment areas were delineated on 1:25,000
scale digital topographic maps, and land use was categorized by the supervised classification
method (Satellite Pourl Observation deta Terra (SPOT) of June 4, 2006, and Advance Land
Observing Satellite (ALOS) data of July 28 and Aug 9, 2006). Simple linear regression was applied
to evaluate the relationships of the paddy and upland fields with SS, TN, and TP for each period.
RESULTS AND DISCUSSION
There was a significant difference in nutrient concentrations among the sampling points. The SSconcentration showed its highest average value of 81 mg/L during the PP at P10 and the lowest
value of 1 mg/L during the SCP at P1 (Fig. 3). During this period, maximum water is irrigated andthere is excess used water runoff through the drains into the canal, which carries a high SS load.
100

3
PP

NIP

PIP

SCP

SMP

TN (mg/L)

SS (mg/L)

80
60
40

2

1
20
0

0
3

0.20

PP
NO3-N (mg/L)

TP (mg/L)

0.15

0.10
0.05

NIP

PIP

SCP

SMP

2

1

0

0.00
P1

P2

P3

P4

P5

P6

P7

P8

P9

P10

P11

P1

Sampling points

P2

P3

P4

P5

P6

P7

P8

P9

P10

P11

Sampling point

Fig. 3 Periodic variations in SS and TP

Fig. 4 Periodic variations in TN and NO3-N

Russell et al. (2001) found that farm fields in agricultural watersheds are the major sedimentsources and determined the rate of soil loss from fields in response to various agricultural practices.
The lowest SS value occurred during the SCP, because the land surface is covered by snow, andthere are no land use activities. We found an increasing trend in the SS concentration in the orderof SCP < NIP < SMP < PIP < PP. The TN and TP concentrations are higher during the PP (Fig. 3,4), because chemical fertilizers are applied during transplanting, resulting in an increase indissolved nutrient concentrations in the drain water and discharge of the nutrients via surface
drainage water into the Canal. It has been reported that the nitrogen and phosphorous
concentrations in drainage water increase during the PP, transplanting, and when fertilizer isapplied (Takeda et al., 1991; Feng et al., 2004). Hiroaki et al. (2009) also suggested that TN and TP
are high during the puddling and transplanting periods in Shimane Prefecture, Japan. During the
NIP, the average TN and TP concentrations were lower than those during others periods, whichmight have been due to the retention time of water in the paddy fields during the growing season
for plants with high nutrient uptake. Tomas et al. (2003) and Braskerud (2002) reported that theretention of water in paddy fields during the growing season induces purification mechanisms, suchas denitrification, plant uptake, or sedimentation, similar to those present in natural and artificial
wetlands. The average SS, TN, and TP concentrations during the PIP, SCP, and SMP wererelatively higher than those during the NIP. Because no agricultural activities are conducted in thisarea during the PIP, SCP, and SMP, it is believed that residual soil nutrients are leached by rain andsnowmelt water, which subsequently flow into the Canal. The NO3-N concentration at P10 during© ISERD

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the SMP was 2.26 mg/L (Fig. 4). During this period, snow melt continuously percolates into thesoil, and nitrogen fertilizer decomposes to NH4+ through nitrification, which oxidizes to NO3under aerobic conditions. Nitrate is water soluble and is lost through leaching in melting water andincreased drainage discharge though the Shinotsu Canal, which had high NO3-N concentrations
during the SMP. A significantly higher NO3-N concentration is found in agricultural streams andrivers during high flow conditions (Castillo et al., 2000). A recent study indicated that the large
loading of nutrients into rivers occurs during the early stage of the snowmelt period in Hokkaido(Hayakawa et al., 2003).
PP

NIP

PIP

SCP

SMP

100

PP
PP, r = 0.94***

SS (mg/L)

80

NIP, r = 0.95***
PIP, r = 0.47

100

***

PP, r = 0.96

SCP

PIP

SMP

NIP

SCP, r = 0.89***

NS
NIP, r = 0.94*** SMP, r = 0.44

80

NSPIP, r = 0.42NS
SS (mg/L)

60

SCP, r = 0.89***
SMP, r = 0.34NS

40

60
40

20

20
0

4
PP, r = 0.81***
NS

NIP, r = 0.00

SMP, r = 094

SCP, r = 0.86***
SMP, r = 0.98***

PP, r = 0.82******

NIP, r = 0.00NS***

PIP, r = 0.97

3
TN (mg/L)

TN (mg/L)

3

0
4

SCP, r = 0.80***

2

PIP, r = 0.95***

2

1

1
0

0
0.3

0.3
PP, r = 0.94 ***NIP, r = 0.84***

SCP, r = 0.51 NS
SMP, r = -0.13

PIP, r = 0.75 **TP (mg/L)

TP (mg/L)

0.2

PP, r = 0.96***
NIP, r = 0.89***
PIP, r = 0.82***

NS

0.1

SCP, r = 0.55NS
SMP, r = -0.01NS

0.2

0.1

0

0
0

500

1000

1500

2000

2500

APA (ha)

0

500

1000

1500
2000
AUA (ha)

2500

3000

3500

Fig. 5 Relationship between APA and nutrients Fig. 6 Relationship between AUA and nutrients

There was a relationship between water quality parameters (SS, TN, and TP) and theaccumulated paddy field area (APA) and accumulated upland area (AUA) during the PP, NIP, PIP,
SCP, and SMP. APA is calculated as in Eq. (1)APA i = ∑ i2 PAi = PA2 + PA3 + … + PAi,

(1)where (i = 2~11). AUA is calculated in the same manner. Linear regression results showed a highly
significant correlation between APA and SS during the PP (r = 0.94), NIP (r = 0.95), and SCP (r =0.89) (P < 0.001; Fig. 5), as well as between AUA and SS during the PP (r = 0.96), NIP (r = 0.94),
and SCP (r = 0.89) (P < 0.001; Fig. 6) due to intensive agricultural activities during the PP and
NIP. There were no such relationships during the PIP and SMP, because agricultural activities wereabsent. Hamill and McBride (2003) reported that lowland stream sediments were highly associatedwith intensive agricultural land use in Southland, a New Zealand province. TP showed a similar
trend of correlations with both APA and AUA as SS did, but not during the SCP. It has been

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reported that the concentration of phosphorus is more transport limited because phosphorus adsorbs
on sediments and is therefore lost through runoff and erosion (Heathwaite et al., 2000).
The TN concentration showed a strong and significant relationship with AUA during the SMP(r = 0.98) and PIP (r = 0.95) (P <0.001; Fig. 6). Similarly, APA and TN during the SMP (r = 0.94)
and PIP (r = 0.97) were significantly correlated (P < 0.001; Fig. 5). There was also a highly
significant correlation between TN and AUA during the PP (r = 0.81) and SCP (r = 0.80) andbetween TN and APA during the PP (r = 0.82) and SCP (r = 0.86) (P < 0.001). However, there wasno relationship during the NIP for either APA or AUA. There was a stronger relationship with TN
during the SMP than during other periods because melting water percolates into the soil and thesurplus nitrogen is discharged with melted water. Osborne and Wiley (1988) examined an east
Illinois watershed and found that median nitrate concentrations are correlated with agricultural
practices during the high-flow spring period and are correlated with urban land use during the lowflow summer and autumn. Turner et al. (2001) reported that nitrogen concentrations in streams,
rivers, and lakes are highly related to landscape characteristics and land use.

80
P1

P11

SS (mg/L)

60
40
20

TN (mg/L)

0
3

2

1

0

0.20

TP (mg/L)

0.15

0.10

0.05

0.00
PP

NIP

PIP

SCP

SM P

Sampling periods

Fig. 7 Comparisons of P1 and P11 streams nutrients in each period
The inlet (P1) of the Shinotsu Canal is at the Ishikari River, which flows downward, and theoutlet is at the lower reach (P11) of the Ishikari River. Therefore, P1 is the upstream point and P11
is the downstream point. Thus, P1 represents the Ishikari River water quality and P11 represents
the Shinotsu Canal water quality. The SS and nutrient concentrations, except TN, were higher
downstream than upstream during every period (Fig. 7). The TN concentration had its lowest value
during the NIP, because during that period, paddy plants are in the growing stage and higher
amounts of nutrients are discharged than during other periods (Fig. 7). Especially during the PP, theSS and nutrient concentrations were higher downstream than upstream due to puddling activities in
the paddy field and the frequent re-use of drainage water as irrigation water at the lower-stream
agricultural area of the Shinotsu Canal. Water reuse and land use activities affect water flow fromupstream to downstream, so SS and nutrient concentrations increase downstream and degrade
water quality of the Shinotsu Canal and the lower reaches of the Ishikari River.
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CONCLUSION
This study has shown that there are periodic stream nutrient fluctuations in the Shinotsu Canal. The
SS, TN, and TP concentrations were highest during the PP and lowest during the SCP, except for
TN during the NIP. NO3-N concentration was highest during the SMP and lowest during the NIP.
APA and AUA were significantly correlated with stream SS during the PP, NIP, and SCP, whereas
no relationship existed during the PIP and SMP. The TN concentration was highly associated with
APA and AUA during the entire study period, except during the NIP. The concentration of TP had
no relationship with APA and AUA during the SCP and SMP, but a strong relationship was foundduring the PP, NIP, and PIP. It was also found that nutrient concentrations were higher at P11 thanat P1 during every period, except for TN during the NIP. Though P11 showed higher values ofconcentrations during almost every period, there must be an impact of land use and water
management on the agricultural area of the Shinotsu Canal. Therefore, it can be concluded that land
and water use for agriculture, the seasonal characteristics of meteorology, and fertilizer
management reduced the water quality of Shinotsu Canal and ultimately of the Ishikari River.
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