IJERD – International Journal of Environmental and Rural Development (2015) 6-1

Research article
erd

Evaluation of River Water Quality in Agricultural
Watershed with the Environmental Standards
TOSHIMI MUNEOKA*
Obihiro University of Agriculture and Veterinary Medicine, Hokkaido, Japan
Email: muneoka@obihiro.ac.jp

YURI YAMAZAKIThe United Graduate School of Agricultural Science, Iwate University, Iwate, JapanSACHIYO WAKOU
Ibaraki Prefectural Government, Ibaraki, Japan

MASATO KIMURA
Obihiro University of Agriculture and Veterinary Medicine, Hokkaido, JapanOSAMU TSUJI
Obihiro University of Agriculture and Veterinary Medicine, Hokkaido, Japan
Received 20 January 2015

Accepted 25 April 2015(*Corresponding Author)

Abstract Japan has general environmental standards for organic matter in its public water
bodies. However, there are no environmental standards for nutrient salts such as phosphorus(P) and nitrogen (N) in river water. In this study, the water quality of rivers at normal waterlevel was evaluated in agricultural watersheds by focusing on water quality standards. The
investigated sites are in the Tokachi area (24 watersheds; upland and dairy farming) and theNemuro area (11 watersheds; large-scale dairy farming), which are in Eastern Hokkaido.
The investigations were carried out in the two agricultural areas in 2005, 2006 and 2012.
Electrical conductivity (EC) and water temperature were measured at the same time as riverwater samples were collected in the two areas. Water quality was analyzed for potential ofhydrogen (pH), biochemical oxygen demand (BOD), suspended solids (SS), totalphosphorus (T-P), total nitrogen (T-N) and other values. Most of the values associated withorganic matter, such as pH, BOD and SS, in river water were within the thresholds for thestandards of The Environmental Standards Concerning the Conservation of the Living
Environment (Rivers). In contrast, some values of nutrient salts (N and P) exceeded thethresholds (T-P≦0.1 mg/L, T-N≦1.0 mg/L). Many of the watersheds in the Tokachi area
had T-N concentration in excess of 1.0 mg/L. This suggests that the concentrations ofnutrient salts (P and N) increase with increases in agricultural land development in awatershed. For the evaluation of river water quality in agricultural watersheds, it was foundto be necessary to measure both organic matter and nutrient salts as indices of water quality.
And it was found that controlling the runoff of P and N from agricultural land is essential
for water quality conservation in public water bodies.
Keywords organic matter, nutrient salts, agricultural watershed, environmental standard

INTRODUCTION
In countries around the world, the river water quality is seriously worsening. As is well known,
agriculture has been pointed out as a cause.
The authors have long been researching the concentration of nitrogen in river water at normal
water levels by targeting two areas with different agricultural land use (Yamazaki et al., 2013;Muneoka et al., 2013; Yamazaki et al., 2014; Muneoka et al., 2014). This research has been underway in Eastern Hokkaido, which has precious regional characteristics in the Asian monsoon region,Ⓒ ISERD

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IJERD – International Journal of Environmental and Rural Development (2015) 6-1

with consideration of study results pertaining to the concentration of nitrate nitrogen in river waterfrom the study performed by Tabuchi et al. (1995). Based on the accumulation of these basic data,
it is expected that study and research will make further progress toward measures for controlling
the runoff of nitrogen into rivers in agricultural and forest watersheds.
Japan sets general environmental standards for organic matter in its public rivers. However,there are no environmental standards for nutrient salts such as phosphorus (P) and nitrogen (N) inriver water. Therefore, while the evaluation of land use in agricultural and forest watersheds thatuse nitrogen concentration in river water as an index has progressed, there are few cases that use
other nutrient salts (e.g., P) as well as organic matter as indices for evaluating the water quality ofrivers.
In this report, the present condition of river water quality at normal water levels in Eastern
Hokkaido was evaluated within agricultural watersheds, with reference to water quality standards.
METHODOLOGY
General Description about the Studied Watershed and the Study on River Water Quality
The maps of study sites are shown in Fig.1. The Tokachi area, which has 24 watersheds on theTokachi River system and the Shikaribetsu River system (No. 1 to 24), is located in thenorthwestern part of the Tokachi General Sub-prefectural Bureau, and it is an area with upland anddairy farming. The Nemuro area, which has 11 watersheds on the Shibetsu, the Tokotan and theNishibetsu River systems (A to K), is located in the western part of the Nemuro Sub-prefecturalBureau, and it is an area mainly of dairy farming. In both of these areas, large-scale farming has
been operated, and there have been no considerable changes in agricultural land use in either area
since 1985.

Fig. 1 Outline of the Tokachi and Nemuro areasⒸ ISERD76

IJERD – International Journal of Environmental and Rural Development (2015) 6-1

For the years 1981 to 2010, the annual mean air temperature and the yearly precipitation were5.9 °C and 840.7 mm at Komaba in the Tokachi area, and 5.4 °C and 1158.0 mm at Nakashibetsu
in the vicinity of the Nemuro area. Both areas have a relatively cold climate with low rainfall.
The investigation of the river water quality was conducted at the normal water level at 35
sampling points. Electrical Conductivity (EC) and water temperature were measured at sampling
points. And discharge was also measured on the rivers in small watersheds (varied between 22 and25 by year). Items analyzed to determine water quality varied with each year. This study used
potential of hydrogen (pH), biochemical oxygen demand (BOD), suspended solids (SS), totalphosphorus (T-P) and total nitrogen (T-N) and other values as indices of water quality. The
investigations were carried out during late August to early September in 2005, 2006 and 2012.
Environmental Standards for River Water in Japan
Water quality in Japan is regulated by the Environmental Water Quality Standards Concerning theConservation of the Living Environment (Rivers), which uses organic matter as indices (Table 1).
The standard values are divided into 6 stages (Type-AA to Type-E) according to the suitable use ofthe water, with each acceptable range specified as follows: pH (always between 6.5 and 8.5), BOD(between 1 mg/L and 10 mg/L) and SS (between 25 mg/L and 100 mg/L).
Table 1 The Environmental Water Quality Standards Concerning the Conservation of theLiving Environment (Rivers (Extract))
Standard values
TypepHBOD

SSAAA
BCDE

between 6.5 and 8.5
between 6.5 and 8.5
between 6.5 and 8.5
between 6.5 and 8.5
between 6.5 and 8.5between 6.5 and 8.5

1 mg/L or lower
2 mg/L or lower
3 mg/L or lower
5 mg/L or lower
8 mg/L or lower
10 mg/L or lower

25 mg/L or lower
25 mg/L or lower
25 mg/L or lower
50 mg/L or lower
100 mg/L or lower※※ No floating matter on the surface of the water

Table 2 Some water quality standards on the nutrient salts (N and P)(a) The Environmental Quality Standards
Concerning the Protection of the Human Health (Extract)
Combined concentration of NO3-N and NO2-N

10 mg/L or lower(b) The Environmental Quality Standards
Concerning the Coservation of the Living Environment
Standard values
TypeT-NT-P

Lakes（Appendix 2)

ⅠⅡⅢⅣⅤ

0.1 mg/L or lower
0.2 mg/L or lower
0.4 mg/L or lower
0.6 mg/L or lower
1.0 mg/L or lower

0.005 mg/L or lower
0.01 mg/L or lower
0.03 mg/L or lower
0.05 mg/L or lower
0.10 mg/L or lower

Seas（Appendix 2)

ⅠⅡⅢ
Ⅳ

0.2 mg/L or lower
0.3 mg/L or lower
0.6 mg/L or lower
1.0 mg/L or lower

0.02 mg/L or lower
0.03 mg/L or lower
0.05 mg/L or lower
0.09 mg/L or lowerⒸ ISERD77

IJERD – International Journal of Environmental and Rural Development (2015) 6-1

In Japan, there are two major water quality standards that use nitrogen, and nutrient salts, asindices. The Environmental Quality Standards Concerning the Protection of Human Healthspecifies the highest acceptable combined concentration of nitrate nitrogen (NO3-N) and nitrite
nitrogen (NO2-N) as 10 mg/L (Table 2(a)).
As shown in Type-V in Table 2(b) of Appendix 2 of the Environmental Water Quality
Standards Concerning the Conservation of the Living Environment (Lakes) and Type-IV in Table2(b) of Appendix 2 of the Environmental Water Quality Standards Concerning the Conservation ofthe Living Environment (Seas), acceptable concentration of total nitrogen (T-N) is regulated at 1mg/L or lower.
Further, in Type-V in Table 2(b) of Appendix 2 of Environmental Water Quality Standards
Concerning the Conservation of the Living Environment (Lakes), which is the water quality
standard that uses phosphorus as an index, the acceptable concentration of total phosphoru s (T-P)
is regulated at 0.1 mg/L or lower, and in Type-IV in Table 2(b) of Appendix 2 of said standards(Seas), the acceptable concentration of total phosphorus (T-P) is regulated at 0.09 mg/L or lower.
However, there are no environmental standards for nutrient salts in river water of public waterbodies. In this report, by referring to the water quality standards mentioned above, "thresholdlevels" that use nutrient salts (N and P) as indices were established by specifying T-P as 0.1 mg/Lor lower and T-N as 1.0 mg/L or lower to evaluate water quality.
RESULTS AND DISCUSSION
Evaluation of Water Quality using Organic Matter as an Index
In Table 3, the pH of river water was within the range of 7.1 to 8.0 for the Tokachi area and 7.3 to
7.7 for the Nemuro area, both of which satisfied the standard values in Type-AA (betwee 6.5 and8.5). BOD was within the range of <0.5 to 3.1 mg/L in the Tokachi area, which exceeded thestandard values of Type-B (3 mg/L or lower) at only 1 spot. BOD was within the range of <0.5 to
1.2 mg/L in the Nemuro area, which satisfied the standard values of Type-A (2 mg/L or lower). SSwas within the range of <1 to 39 mg/L in the Tokachi area, and <1 to 13 mg/L in the Nemuro area,
which exceeded the standard values of Type-AA to B (25 mg/L or lower) at only 1 spot.
Therefore, the indices of organic matter for river water at normal water levels in agricultural
watersheds in Eastern Hokkaido were mostly within the standard values in every year when thestudy was carried out, regardless of differences in size of watershed area or the area of upland andpasture as a share of the watershed.
Evaluation of Water Quality using Nutrient Salts as Indices
The T-P concentration in river water was within the range of 0.024 to 0.39 mg/L in the Tokachi
area, which exceeded the threshold level at 9 spots, and 0.060 to 0.23 mg/L in the Nemuro area,
which exceeded the threshold level at 5 spots (Table 4).
Next, T-N concentration was within the range of 0.25 to 10 mg/L in the Tokachi area, which
exceeded the threshold level at 17 spots. In the Nemuro area, it was within the range of 0.19 to 3.2
mg/L, which exceeded the threshold level at 6 points (Table 4).
Therefore, the spots where the values exceeded the "threshold level" of nutritional salts saw arelatively high share of upland field and pasture in watersheds (22 to 95%), and runoff had highconcentrations of T-N.
The authors consider that it is necessary to measure both organic matter and nutrient salts as
indices to evaluate river water quality in agricultural watersheds. In addition, it was found that
controlling the runoff of P and N from agricultural land is essential for water quality conservationin public water bodies. To accomplish these, systematic watershed management is required thatgives consideration to both agricultural land use and farming.

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IJERD – International Journal of Environmental and Rural Development (2015) 6-1

Table 3 Water quality using organic matter as an index (2005, 2006 and 2012)
Measuring values
Measuring values

Investigate area Investigate area
（Sampling spots）（Sampling spots）
pH

BODpH
(mg/L)

BOD(mg/L)SS (mg/L)

SS (mg/L)

Tokachi（24～spots）
Tokachi Area （24spots）Area7.1
8.0

7.1 ～
<0.5
～ 8.0
3.1※

※

<1 ～～ 3.1
39
<0.5

<1 ～ 39

Nemuro(11～spots)
Nemuro Area (11spots) Area 7.3
7.77.3 ～<0.5～7.7
1.2

<0.5
<1 ～ 1.2
13<1 ～ 13※※exceeded
theofstandard
of1Type-B
exceeded the standard
value
Type-Bvalue
at only
spot at only 1 spot

Table 4 Water quality using nutrient salts an index (2005, 2006 and 2012)
Investigate area
（Sampling spots）

Measuring values
T-P (mg/L)

T-N (mg/L)※

Tokachi Area （24 spots）

0.024 ～ 0.39 (9 spots)

0.15 ～10※ (17 spots)

Nemuro Area (11 spots)※
0.060 ～ 0.23 (5 spots)※
0.19 ～ 3.0 ( 6 spots)※

the number which exceeded the threshold level( T-P >0.10mg/L; T-N >1.0mg/L )CONCLUSION
Evaluations of river water quality using the environmental standards in Japan show that organic
matter at normal water levels in agricultural regions in Eastern Hokkaido are within the standard
values. In contrast, it was confirmed that nutrient salts constantly run off at high concentrations. In
order to consider measures for controlling the runoff of nutrient salts (especially nitrogen) withboth sustainable agriculture and environment conservation in mind, constructing comprehensive
watershed management is an urgent issue. In the future, we would like to contribute to measures forthe evaluation of land and water conservation in wide water catchment areas with Asian monsoon
climate by applying the environmental standards in Japan for the evaluation of river water quality
in other agricultural regions.
ACKNOWLEDGEMENTS
We would like to express our gratitude to the research assistance provided by the students, Obihiro
University of Agriculture and Veterinary Medicine.
REFERENCES
Muneoka, T., Yamazaki, Y., Wakou, S., Shimura, M., Yoshino, K., Tsuji, O. and Tabuchi, T. 2013. The
nitrogen runoff characteristics in agricultural watersheds after enforcement of animal waste regulation.
IJERD, 4 (2), 56-61.
Muneoka, T., Yamazaki, Y., Wakou, S., Kimura, M. and Tsuji, O. 2014. Evaluation of Nitrate Pollution inRiver Water at Agricultural Watershed. IJERD, 5 (2), 51-55.
Tabuchi, T., Yoshino, K., Shimura, M., Kuroda, S., Ishikawa, M. and Yamaji, E. 1995. Relation between
land use and nitrate concentration of outflow water from watersheds of agricultural and forest area, Japan.
Trans. of JSIDRE, 178, 129-135 (in Japanese with English abstract).
Yamazaki, Y., Muneoka, T., Wakou, S., Shimura, M., Yoshino, K., Tsuji, O. and Tabuchi, T. 2013. The
difference of agricultural land use in watersheds and long term fluctuation on the river water quality.
IJERD, 4 (1),152-157.
Yamazaki, Y., Muneoka, T., Wakou, S., Kimura, M. and Tsuji, O. 2014. Evaluation of the ion components
for the estimation of total nitrogen concentration in river water based on electrical conductivity. IJERD, 5(1), 160-164.

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