Odai Water Source (Okaya City, Nagano Prefecture) Complete Guide | History, Water Quality, Access and Role as Water Supply Source
The Odai Water Source located in Minato, Okaya City, Nagano Prefecture is an important spring water that has supported the region’s water supply system for over approximately 90 years. Selected by the Ministry of the Environment as one of “Nagano Prefecture’s representative spring waters,” this water source has been carefully managed as an indispensable part of Okaya City residents’ lives. This article comprehensively explains the history, water quality, current management status, and role of the Odai Water Source in Okaya City’s water supply system.
Odai Water Source | Overview of Nagano Prefecture’s Representative Spring Water
The Odai Water Source is natural spring water that emerges in the Minato district of Okaya City, Nagano Prefecture, and is one of the main water sources supporting the city’s water supply system. Located in a natural environment surrounded by forests, the clear water that emerges from underground has been used as domestic water for local residents over many years.
Basic Information and Location Conditions
The basic information about the Odai Water Source is as follows:
- Location: Minato (minato), Okaya City, Nagano Prefecture
- Water source type: Spring water
- Planned daily water intake: 1,700 cubic meters
- Administrator: Okaya City Water Supply Department
- Access restrictions: Prohibited entry due to water supply facilities
Okaya City is located in the northeast section of Lake Suwa and is surrounded by mountains. This topographical characteristic provides abundant groundwater and spring water, and the Odai Water Source benefits from such natural environment.
Positioning as Ministry of the Environment-Selected “Representative Spring Water of Nagano Prefecture”
The Odai Water Source was selected as one of “Nagano Prefecture’s representative spring waters” in a spring water survey conducted by the Ministry of the Environment. This selection is based on a comprehensive evaluation of water quality, water quantity stability, and regional importance.
However, since it is currently managed as a water supply facility, general public entry is prohibited. This is a necessary measure to supply safe and reliable drinking water, and strict management is carried out from the perspectives of water quality management and risk response.
History of Odai Water Source | Progress as a Water Supply Source from the Early Showa Period
The history of the Odai Water Source is closely linked with the history of water supply development in Okaya City during the early Showa period.
From Start of Water Intake to Transfer to Municipal Water Supply
August, Showa 5 (1930), water intake from the Odai Water Source officially began. This period was a time when modern water supply systems were being developed throughout Japan, and in Okaya City as well, securing safe drinking water was an important issue.
Initially, water supply was provided mainly to the Minato district in the region, but October, Showa 30 (1955), the Minato water supply was officially transferred to Okaya City’s municipal water supply. Through this transfer, the Odai Water Source was positioned as part of the water supply system for the entire Okaya City, making it possible to supply water to a wider area.
Role as a Water Source Over 90 Years
Even now, more than 90 years after the start of water intake, the Odai Water Source continues to function as an important water source for Okaya City. This long-term stable supply is the result of the excellent characteristics of the water source and an appropriate management system.
As the times have evolved, the entire water supply system has progressed and water quality management methods have become more sophisticated, but the value of the clear water that emerges from the Odai Water Source remains unchanged, continuing to support the lives of Okaya City residents.
Positioning of Odai Water Source in Okaya City’s Water Supply System
Okaya City has built a water supply system that combines multiple water sources, and the Odai Water Source plays a central role in it.
Water Source Composition and Water Supply Situation in Okaya City
As of April 1, 2015 (Heisei 27), Okaya City’s water supply system was as follows:
- Water supply population: 51,405 people
- Water supply coverage rate: 99.7%
- Planned total daily water intake: 32,200 cubic meters
Okaya City has 17 groundwater and spring water sources and 1 surface water purification facility (Oigawa Purification Plant), and combines these to achieve stable water supply.
Odai Water Source as a Major Water Source
The planned daily water intake from the Odai Water Source is 1,700 cubic meters, which corresponds to approximately 5.3% of Okaya City’s total water intake. Together with the Kosaka Water Source (300 cubic meters), it occupies an important position among spring waters.
Okaya City’s major water sources by planned daily water intake (top 5):
- Oigawa Purification Plant (surface water): 5,800 cubic meters
- Kawarahaguchi (groundwater): 3,600 cubic meters
- Higashihori (groundwater): 3,100 cubic meters
- Kawagishi Daini (groundwater): 3,000 cubic meters
- Hanaoka (groundwater): 2,500 cubic meters
The Odai Water Source contributes to the stability and diversity of Okaya City’s water supply system as an important water source next to these.
Water Quality Management and Water Safety Plan | Efforts to Deliver Safe Drinking Water
Okaya City has formulated a “water safety plan” and manages the entire water supply system from water source to tap to deliver safe and reliable drinking water to its citizens.
What is a Water Safety Plan?
A water safety plan is a plan that assumes hazards and risks throughout the water supply system from water source to tap and defines response methods to them. This plan is expected to produce the following effects:
- Risk identification and management: Identify potential hazards that may affect water quality in advance and take appropriate measures
- Improved water quality management: Enhance water quality management levels through continuous monitoring and evaluation
- Rapid response: Establish a system to respond quickly when problems occur
- Transparency assurance: Clearly demonstrate the safety of drinking water to citizens
Actual Water Quality Management at Odai Water Source
A dedicated water safety plan has been formulated for the Odai Water Source, and the following management is carried out:
- Regular water quality testing: Conduct testing of water quality standard items based on laws and regulations
- Environmental management around water source: Monitor activities that may affect water quality
- Facility maintenance management: Appropriate inspection and maintenance of intake facilities and water distribution equipment
- Emergency response plan: Establish contact procedures and response steps for abnormal situations
For the Odai Water Source, which utilizes the blessings of nature as spring water, environmental preservation around the water source is particularly important. Okaya City also implements preservation measures based on the Nagano Prefecture Water Environment Conservation Ordinance, including designation of water supply source conservation districts.
Water Quality Characteristics and Use Value of Odai Water Source
The water that emerges from the Odai Water Source becomes high-quality water naturally filtered and containing mineral content as rain and snow that fell in the mountainous areas of Nagano Prefecture pass through geological layers.
Characteristics as Spring Water
Spring water is groundwater that naturally emerges on the earth’s surface and has the following characteristics:
- Stable water temperature: Water temperature fluctuation is minimal throughout the year
- Natural filtration: Impurities are removed as water passes through geological layers
- Mineral content: Contains appropriate levels of minerals derived from geological layers
- Clarity: High transparency and clear water quality
The Odai Water Source’s spring water contributes to improving the quality of Okaya City’s drinking water by taking advantage of these characteristics.
Okaya City Water Quality
Okaya City’s drinking water achieves stable water quality by blending multiple water sources. Spring water like the Odai Water Source plays an important role in improving the overall quality of drinking water in terms of water quality stability and pleasant taste.
In general, Nagano Prefecture’s drinking water is known to be soft water with low hardness and easy to drink. Okaya City’s drinking water has similar characteristics and is suitable water quality for daily drinking and cooking.
Management as Water Supply Source Conservation District
Under the “Nagano Prefecture Water Environment Conservation Ordinance,” Nagano Prefecture designates areas particularly necessary for water supply source conservation as “water supply source conservation districts.”
Purpose of Water Supply Source Conservation District System
This system was established to preserve water supply source water quality and continue supplying safe drinking water for the future. In designated districts, prior consultation and approval from the governor is required for activities that may affect water quality.
Regulatory Content in Conservation Districts
When the following activities are conducted within a water supply source conservation district, prior consultation is required:
- Land form changes (development activities, etc.)
- Construction or remodeling of buildings
- Installation of structures
- Soil and stone extraction
- Waste disposal
- Other activities that may affect water quality
Through these regulations, the environment around the Odai Water Source is properly preserved, and the function as a high-quality water source is maintained over the long term.
Access to Odai Water Source and Visiting
The Odai Water Source is located in the forest area of Okaya City’s Minato district, but is currently strictly managed as a water supply facility, and general public entry is prohibited.
Reasons for Entry Prohibition
The main reasons for restricting access to water supply sources are as follows:
- Water quality preservation: Prevent water contamination risks caused by human entry
- Facility safety management: Ensure the safety of intake facilities and piping equipment
- Maintenance of stable supply: Guarantee stable operation of the water supply system
- Sanitary management: Strictly maintain sanitary standards for drinking water
How to Obtain Information About Water Sources
Information about the Odai Water Source and Okaya City’s water supply can be obtained through the following methods:
- Okaya City Official Website: Water safety plans and water supply status are published on the Water Supply Department page
- Publication of water quality test results: Regular water quality test results are published
- Inquiry to Okaya City Water Supply Department: Detailed information and questions can be inquired directly
While visiting the water source is difficult, it is possible to learn about Okaya City’s water supply system and water quality management.
Water Source Conservation Activities in the Community and the Role of Citizens
To protect the Odai Water Source and other water sources in Okaya City for the future, the awareness and actions of individual citizens are important in addition to administrative management.
Citizen Initiatives for Water Source Conservation
Initiatives that local residents can undertake for water source conservation include the following:
- Practice of water conservation: Use water resources carefully and avoid wasteful water use
- Appropriate wastewater management: Do not discharge oil or chemical substances from household wastewater into drains
- Cooperation in forest conservation: Participate in water source conservation forest preservation activities
- Interest in water quality: Take interest in drinking water quality and report any abnormalities
Role of Forests as Water Source Conservation Forests
The forests around the Odai Water Source serve important functions as “water source conservation forests.” Forests protect water sources through the following functions:
- Rainwater storage: Forest soil stores rainwater and allows it to slowly permeate underground
- Water quality purification: Soil layers function as natural filters and purify water
- Water volume regulation: Store water during floods and release it gradually during droughts
- Topsoil erosion prevention: Tree roots hold soil in place and prevent soil runoff into the water source
Proper forest management is essential for maintaining the water quality and quantity of the Odai Water Source.
Comparison with Other Water Sources in Okaya City
Okaya City has many water sources besides the Odai Water Source, each with its own characteristics.
Comparison of Spring Water Sources
Major spring water sources in Okaya City:
- Odai Water Source: 1,700 cubic meters/day (Minato district)
- Kosaka Water Source: 300 cubic meters/day (mountainous area)
The Kosaka Water Source is spring water like the Odai Water Source, but its water intake is about one-sixth that of the Odai Water Source. Both water sources are located in mountain areas blessed with natural environment and supply high-quality water.
Differences from Groundwater Sources
Most of Okaya City’s major water sources are groundwater. The main differences between spring water and groundwater are as follows:
Characteristics of spring water:
- Emerges naturally on the earth’s surface
- Water intake facilities are relatively simple
- Water quality is stable
- Water quantity depends on geological conditions
Characteristics of groundwater:
- Requires pumping to extract
- Water quality varies by depth
- Easy to adjust water intake volume
- Requires energy such as electricity
Spring water like the Odai Water Source has the advantage of low energy costs and small environmental impact.
Future Outlook and Challenges
The Odai Water Source is a water source with over 90 years of history, but several challenges must be addressed to continue stable water supply in the future.
Response to Climate Change
Recent climate change has raised concerns about changes in precipitation patterns and increased extreme weather phenomena. Since the water quantity of spring water is closely related to precipitation, the following measures are necessary:
- Strengthened water quantity monitoring: Understanding long-term water quantity fluctuations
- Use of multiple water sources: Diversification of water sources for risk distribution
- Securing water storage capacity: Water storage in preparation for droughts
Addressing Facility Aging
A long period has elapsed since the start of water intake, and aging of intake facilities and water distribution pipes may be progressing. Planned updates and maintenance management are important.
Advancement of Water Quality Management Technology
Water quality standards have become stricter over time, requiring more advanced water quality management. Through the introduction of the latest testing technologies and management methods, further water quality improvement is necessary.
Sustainable Water Source Management
To pass on quality water sources to future generations, the construction of a sustainable management system is essential. This includes water source conservation, forest management, and collaboration with local residents.
Conclusion | Role and Value of Odai Water Source
The Odai Water Source is a historic spring water located in Minato, Okaya City, Nagano Prefecture, and has supported the lives of Okaya City residents for over 90 years since water intake began in Showa 5 (1930). With a daily water intake capacity of 1,700 cubic meters, it occupies an important position in Okaya City’s water supply system.
This water source, which is also selected as one of the Ministry of the Environment’s “representative spring waters of Nagano Prefecture,” is a good example of sustainable water supply that takes advantage of nature’s blessings. Safe and reliable drinking water supply is realized through strict water quality management and operation based on the water safety plan.
While it is currently managed as a water supply facility and general public entry is not allowed, its existence serves as an important foundation supporting the stability and diversity of Okaya City’s water supply system. The clear water that emerges in the natural environment surrounded by forests will continue to be an indispensable water source for Okaya City residents under appropriate preservation and management.
Understanding the value of the Odai Water Source and recognizing the importance of water resources is the first step toward building a sustainable society. By each of us using water carefully and taking interest in water source environment conservation, we can pass on this precious blessing of nature to the future.
