IJERD – International Journal of Environmental and Rural Development (2019) 10-2

Research article
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GIS-based Analysis for the Energy Potential and Social
Feasibility of Small-Scale Run-Off-River Hydropower inYahagi River, JapanYURI YAMAZAKI*
Faculty of Regional Environment Science, Tokyo University of Agriculture, Tokyo, Japan
Email: yy206792@nodai.ac.jp

KIICHIRO HAYASHI
Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya, JapanNOBUKO KAWAGUCHI
Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya, Japan

HIROMU OKAZAWA
Faculty of Regional Environment Science, Tokyo University of Agriculture, Tokyo, Japan

FERDINANDO VILLA
Basque Centre for Climate Change, Leioa, Spain
Received 15 January 2019

Accepted 20 October 2019(*Corresponding Author)

Abstract Due to the increase in international energy demand and the focus on therealization of a decarbonized society, small-scale hydropower plant is attracting attention in
Japan as an important supply of renewable energy. While Japan has a significant amount ofprecipitation and mountains, it is suitable to establish hydropower plants; however,hydropower energy currently represents only about 10% of the total energy mix. Generally,a small-scale hydropower facility has relatively little impact on the environment and is
expected to play a role as a distributed power source. However, it has not been included in
the survey of hydropower potential, and a study on its viability and the development ofpotential sites is limited. Here, we created an electricity generating capacity map for smallscale run-off-river hydropower plant of the Yahagi River system in Aichi, Japan. We
calculated the river flow rate and potential electricity generating capacity at every 10 m on
the river line of the Yahagi River system using the digital elevation model, published by the
Geospatial Information Authority of Japan. We overlapped various kinds of social
conditions and risks on the map of electricity generating capacity and proposed a suitablesite where the development of potential small-scale run-off-river hydropower plant is high.
Keywords small-scale run-off-river hydropower plant, renewable energy, GIS,
Yahagi River

INTRODUCTION
Due to rapid increase in the number and degree of natural disasters in Japan, the dissemination andpromotion of renewable energy and distributed power sources have become a more critical policy
issue (Agency for Natural Resources and Energy, 2018). In recent years, the following three
conditions have been identified for energy supply: (1) securing small-scale and distributed
generation functions to mitigate the risk of a sudden drop in power supply in the event of a disaster,(2) enhance base-power supply capacity to respond to peak demand in summer and winter, and (3)a generator that is self-sufficient and does not emit greenhouse gases (Ueda et al., 2012). Smallscale hydropower is generally considered to create a low environmental load and a high degree ofaffinity for distributed power supply.
However, there are few noticeable cases of mini and micro hydropower projects that target theⒸ ISERD

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power generation output of around 100 kW. Hydropower plants are mainly of two types of namely,
reservoir and run-off-river hydropower plants. While reservoir-types such as dams can generate
medium to large-scale hydropower, the places where power plants can be installed are limited, andthe installation costs are relatively high. Conversely, a run-off-river type can generate small-scalehydropower and the installation of plants is relatively easy. Also, power generation is possible evenin complex terrain conditions such as mountainous areas. Recently, European attractive policies arefavoring the construction of new small-scale hydropower plants, i.e., in most cases, correspond to
run-of-river hydropower plants (Garegnani et al., 2018).
While estimating the feasibility of renewable energy development projects, a fundamental
challenge is to determine the availability of the natural resources. In the planning process, further
restrictions in the exploitation of natural resource (e.g., technical, environmental, legal, and social)should be considered (Moriarty et al., 2012; Resch et al., 2008). For example, in Japan, theMinistry of the Environment Government of Japan estimates the medium to small-scalehydropower energy potential values in rivers and agricultural water by prefecture (the Ministry of
the Environmental Government of Japan, 2011). Also, the potential of small hydropower isestimated around the world (Cuya et al., 2013; Kusre et al., 2010; Yah et al., 2017).
In this study, the development of a potential estimation method for small-scale hydropower,
which can be applied more simply and on a global scale in the future, is considered by assuming a
run-of-river type and low-drop type power plants. Also, the electricity generating capacity of smallscale hydropower and the amount of power required were compared.
METHODOLOGY
Study Sites
In this case, the Yahagi River system was targeted for the case study (Fig. 1). The Yahagi Riversystem flows down to Nagano Prefecture, Gifu Prefecture, and Aichi Prefecture, which has a total
stream length of 117 km and a catchment area of 1,830 km2.
Creation of Potential Estimation Point for Small-scale Hydropower
The ArcGIS (Ver.10.4 and Ver.10.6) calculated the stream length and the catchment area, and theDigital Map 10 m Grid (Elevation) published by the Geospatial Information Authority of Japan(GIS) and the Hydrology analysis tools of Spatial Analyst (ArcGIS) were used. The streamline wasselected using the Digital Map, and the point data were created on the streamline at 10-meterintervals as a potential estimation point of hydropower (Fig. 2). We calculated the watershed area
at each point.
Estimation of the River Discharge
The river discharge at each potential estimation point was estimated. A specific discharge rate wasused to calculate the river discharge. The actual river discharge values obtained from six
observation sites of Water Information System (MILT of Japan, 2018), i.e., Sumigase, Kugyudaira,Yonedu, Kido, Takahashi, and Iwadu, were then corrected. At these sites, normal flow rates were
calculated using the river discharges per day from January 1st, 2016 to December 31, 2016. A
normal flow rate represents river discharges that do not fall below this value for 185 days
throughout one year. There was a significant correlation between the watershed area and a normal
flow rate at these six observation sites (correlation coefficient (r) = 0.93, p values of significancetest (p) < 0.01). In addition, the potential estimation points correspond to the six observation sitesof Water Information System. There was a significantly strong correlation of watershed areas
between of the potential estimation points and of the six observation sites (r = 0.99, p < 0.01).
From these results, the specific discharge rate of the Yahagi River system (0.0254) was calculated,Ⓒ ISERD

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and the river discharges at each potential estimation point was calculated by multiplying awatershed area by the specific discharge rate.
Calculation of Electricity Generating Capacity
The electricity generating capacity of a small-scale hydropower is expressed by the formula (1).
𝑃𝑒 = 9.8 × 𝑄 × 𝐻𝑒 × 𝜂(1)3

where Pe is the amount of power generated (kW), Q is the river discharge (m /s), He is the height
difference between inlet and outlet of stream (m), and 𝜂 is a dimensionless efficiency of theturbine.
Out of these, the height difference can be adjusted according to the local topography or theamount of electricity. In this study, since the target is the small-scale and low-drop hydropower
plants, the He is uniformly set to 5 m at each point. Furthermore, in this study, we targeted on the
power generation amount ranged from 30 to 500 kW, and values less than 30 kW and greater than
500 kW were excluded from the potential estimation analysis.
Extraction of a Social Condition(1) Spatial duplication in a nature reserve area:
Since the artificial development practices are regulated in the area designated as the nature reserve
are, the points located in the nature reserve area among the potential estimation points were
excluded. The potential estimation points were excluded in the Natural park areas (MILT of Japan,
2015a), Nature conservation areas (MILT of Japan, 2015b) and Wildlife management areas (MILT
of Japan, 2015c) and within their 100 m buffer areas.

Fig. 1 Location of the Yahagi River

Fig. 2 The potential estimation points ofsmall-scale hydropower(2) Spatial duplication in disaster risk areas:
Since the establishment of small-scale hydropower facilities in areas designated as disaster risk
areas are not realistic, the points located in the disaster risk area of the potential estimation points
were excluded. Sediment disaster hazard areas (MILT of Japan, 2010) and landslide special
warning areas (MILT of Japan, 2017) are targeted in a 50 m buffer area, and the flood eliminate
area (MILT of Japan, 2012) excluded points that were included within a 100 m buffer area.
(3) Distance from the existing road:
When constructing a small-scale hydropower facility, its distance from the existing road influences
the installation cost. Therefore, the linear distance from the newly-installed power generation
facility to the existing road was calculated using the Road Edge data published by Geospatial
Information Authority (GSI, 2017), assuming the necessity of laying the power distribution for theⒸ ISERD

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construction and management of roads. Out of the estimated linear distances, the potential value
was calculated as the maximum value of 1.0 in the case of 100 m or less, and the potential value
using formula (2) when it was larger than 100 m.
100

𝑃𝑛 = 𝐷(2)𝑛where Pn is a potential value of the potential estimation point’s number n, and Dn (m) is the nearest
distance from the potential estimation point. The potential value decreased as the distance from thepotential estimation point to the existing road increased.
Estimation of the Required PowerThe amount of power required per year was calculated by multiplying the number of houses,
included in the concentric circle at center of the potential estimation point, by the power usage perhousehold at each potential estimation point. With respect to the number of houses, assuming one
urban area cell (10 m) as one household from the JAXA (2016) High Resolution Land-Use andLand-Cover Map (Ver. 16.09; 10 m × 10 m spatial resolution), the total number of urban area cells
included in the 1.0 km circles are used to obtain the potential estimation point. An average value((kWh / h / household) of electricity consumption in the five years from 2005 to 2010 is calculated
from the "Trend of power consumption per household" provided by The Federation of ElectricPower Companies of Japan (2017), which is multiplied by the number of households to calculate
the power requirement.
Reclassifying of the Potential Estimation Points into Sections
The consecutive points, excluding spatial duplication points in the nature reserve and disaster risk
areas, were grouped as one section. Using neighbor analysis of ArcGIS, the points adjacent in eight
directions from the potential estimation point were reclassified as a single section.
Site reconnaissance:
We investigated the local conditions of the potential estimation points created and excluded by GIS.
On December 21, 2018, seven locations in Ena City and Toyota City were surveyed. Survey items
included river width, seawall structure of riverbed, right bank and left bank, and the presence oftransmission line.
RESULTS AND DISCUSSION
In the Yahagi River system, the potential estimation points were created at 10 m intervals. Then we
excluded the potential estimation points by the spatial duplicated area of the nature reserve and thedisaster risk areas. Moreover, where the amount of power generation is less than 30 kW and greaterthan 500 kW were also excluded. The potential estimation points were narrowed down to 4,038
points from 106,494 points (Fig. 3).
The minimum value of power generation at 4,038 points was 30.1 kW, the maximum value
was 397 kW, and the average value was 113 kW. Besides, 57% of the 4,038 points had a microscale power generation of 50 kW or less (Fig. 4). When classifying the points as connected in eight
directions out of a potential estimated number of points, 4,038 points were sorted into 125 sections.
Moreover, 125 sections were located in five areas of the Yahagi River system.
Based on the distance of the existing road from the small-scale hydropower facility, we
determined the cost of installation of this facility. The distance to the existing road at 4,001 points
out of 4,038 points was 100 m or less. Hence, it is possible to install and manage the facilities using
existing roads at most potential estimation points.
The amounts of required power generation within 1 km from the potential estimation point
were compared. In this instance, the power generation amount and the required power amount wereconverted into annual values. The annual power generation amount at 4,038 points ranged fromⒸ ISERD141

IJERD – International Journal of Environmental and Rural Development (2019) 10-2

264 to 3,480 MW/y, and the average value was 996 MW/y (Fig. 5). The number of points where
the ratio of the power generation amount to the required amount was less than 100% (except 0%)
was 1,186 points, i.e., 51 sections. Among these points, the points below 10% of the ratio of thepower generation amount to the required amount were 402 points, i.e., 24 sections, and these
sections were located in the population concentrated areas within Toyota City (Fig. 6). The
population within 1 km from these potential estimation points is relatively large; the required
amount is also large compared to the amount of power generation. For this reason, the installationof small-scale hydropower facilities in this section can be considered unsuitable.

Fig. 3 Potential estimation points(red colored points)

Fig. 4 Histogram of power generation

Fig. 5 Power generation of 4,038 ofpotential estimation points

Fig. 6 Ratio of the demand to
the power generation

Conversely, at 784 points, where the ratio of the power generation amount to the required
amount is higher than 10% and less than 100%, small-scale hydropower facility is useful for local
production and consumption.
At around 100% (2,443 points), where the population concentration is low, and the amount of
power generated exceeds the requirement, small-scale hydropower facility can be used for powerselling.
Based on these results, to evaluate the validity of the potential estimation points of small-scalehydropower facility published by GIS, a site reconnaissance was conducted in three areas, as
shown in Fig. 7. These three areas have relatively lower population concentration and are located in
the mountainous regions of Japan.
In the section where the village is near the river, it is generally accepted that the small-scalehydropower facility for the local production and consumption type is sufficient. By site
reconnaissance, roads and power transmission lines are being maintained, the river is also managed,Ⓒ ISERD

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and the flow conditions are stable. From this, it was inferred that even in the mountainous areas, it
is possible to install a power generation facility at a relatively low cost near the settlement, and asmall-scale power generation facility according to the size of the village is suitable.
Conversely, since most of the target sections have few settlements, it is considered that the use
as a power-selling type is suitable.
In these sections, it was confirmed that there is an existing road near the river, but there is no
power transmission line. In addition, there are many natural rivers, including sprawl points, where
flow paths are complicated with big rocks of river beds. At such points, there is a concern that highcosts will be incurred for the installation of power generation plants. In the case of valley terrain,
the distance from the existing road to the river is long, and there is a concern that the installationand management of the power plant are complicated.

Fig. 7 Location of site reconnaissance
However, even if there are no settlements near the points, small-scale hydropower plant withexisting irrigation facilities such as weirs is considered to be effective. In the vicinity of irrigation
facilities, since the river flow is stable, low cost and stable power generation are expected. By
combining existing irrigation facilities with small-scale hydropower facilities, it is possible toallocate administrative expenses for irrigation facilities.
Several tasks remain to apply the potential estimation method of this study in other regions
and on a global scale. In this study, we set the buffer to 100 m in the extraction of social conditions;
it is necessary to verify the proper distance. In the calculation of the distance to existing roads, 100m buffer from the center point of the river was used as the standard. However, it is expected thatthe river width dramatically varies depending on the size of the river. For example, the river width
in the upstream river is small in general, and even if the distance from the center of the river iswithin 100 m, the distance could be far away from the estimation point.
Conversely, when large rivers are included, the river width may be 100 m or more, and it may
be impossible to calculate the distance to existing roads. It is necessary to change the distance tothe existing road for each point considering the width of the river, the topography, and the flow
rate. Based on the results of the site reconnaissance, it showed that the utilization of existing
irrigation facilities is useful. However, position information on small facilities such as weirs isoften not released as GIS data, and it is difficult to estimate the potential considering existing
facilities. Likewise, we have not considered the positional relationship with existing power
generation facilities. However, considering the balance with the demand amount, it will benecessary to consider the necessity of the power generation facilities to be nearby.
CONCLUSION
In this paper, we suggest a potential estimation method for a small-scale hydropower plant. The
results showed a suitable point for small-scale hydropower generation facilities in more detail byⒸ ISERD

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public information. It is necessary to confirm the environmental conditions around the river andnear the field by the site reconnaissance in the mountainous areas where the population is low.
Also, in order to evaluate the more realistic energy potential, it is necessary to identify the locationof existing irrigation facilities and power generation facilities and to examine the relevance ofsmall-scale hydropower generation.
ACKNOWLEDGEMENTS
This research was supported by the joint usage / research program of the Institute of Materials andSystems for Sustainability (IMaSS), Nagoya University.
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