Small-scale hydropower generation at Kawai Water Purification Plant, City of Yokohama

A. Case Study Overview

1. Activity/ Project Title:
Small-scale hydropower generation at Kawai Water Purification Plant, City of Yokohama
2. Themes:
Climate Change, Infrastructure, SDGs
3. Summary:  

Yokohama Waterworks Bureau promotes the effective installation of renewable energy such as solar and small-scale hydropower generation facilities. As one of the efforts for renewable energy utilization, Kawai Water Purification Plant (WPP) in City of Yokohama installed small-scale hydropower generation facilities which effectively harness hydropower produced from the difference of elevation between water levels. In FY2018, the facilities produced 1.78 million Wh and contributed to CO2 emission reduction of approximately 847 tons.

4. Sector:
City : Yokohama Waterworks Bureau
5. Implementation Period:

Construction : FY2009 – FY2010 Operation : Since FY2010 – Present

6. Project Site :
Kawai Water Purification Plant, Yokohama Waterworks Bureau
7. Stakeholders&Partners:

B. Objective:

8. Objectives:
Effectively harness hydro-power generated from the difference of elevation between water conveyance facilities.
(For energy efficiency and energy cost saving)

C. Activities

9. /Activities:

In this project, the difference of elevation (approximately 21.5m) between Sagamihara sedimentation basin located upstream and Kawai water purification plant is effectively used to generate power in the WPP. The benefit of hydro-power is that it is less affected by weather changes and can expect stable power generation because of uninterrupted water flows into the WPP.

The following is the details about power generation facility.
The number of power generation facilities: 2
Power generation method:Dam and conduit type
Water wheel type: Horizontal-tubular-type propeller water turbine
Maximum water use: 2.4㎥/s per a facility
Power generation capacity: 135KW per a facility

D. Challenges and solutions:

10. Challenges and solutions:

By constructing hydro power station in a WPP and utilizing the generated power for the operation of the WPP, CO2 emission and energy cost were reduced.

E. Outcomes and Impacts:

11. Outcomes&Impacts:

The installation of small-scale hydropower stations resulted in the following impacts.


Power generation amount:1.78 million kWh per a year (FY2018)

*Equivalent to the annual power consumption of 598 Japan’s ordinary households

CO2 emission reduction: Approximately 847 tons

*Equivalent to the Co2 absorption of 60,500 cedar trees.

(Calculated based on the standard of Ministry of Agriculture, Forestry and Fisheries, Japan, which sets 0.014 tons for annual absorption of one cedar tree as a standard.
(JP only)


– Total 6 small-scale hydropower stations are installed in the overall Yokohama’s water supply system, which include the installation in distribution reservoirs. As of 2017, the projected power generation of these facilities amount to approximately 4 million kWh, and this contributes to the reduction of 1,956 tons CO2 emission.

– Yokohama effectively uses solar power as well. The energy generated through solar power is used to cover a part of energy required to purify water in the WPP. Furthermore, covering sedimentation basin and filtration basin with solar panel is beneficial to prevent the generation of algae causing musty odor problem.

F. Budget:

12. Budget:

343 million JPY.

13. Source:
Revenue from water tariff and subsidies