## (5) Promoting measures concerning groundwater

As a result of excessive utilization of groundwater for industrial purposes during the period of high economic growth, adverse effects emerged in various locations such as land depression and salination of water supplies. In the Noube plain, Chikugo and Saga plains, and the Northern parts of the Kanto plain, where land depressions have occurred, activities for preserving groundwater and promoting proper usage are being conducted based on the Guideline on Measures for Prevention of Ground Subsidence.

## 4 Realizing amenity by promoting improvements to sanitary drainage

Sewage is the indispensable social foundation for the development of healthy cities, treating waste, and preventing floods. In recent years, new demands are being made of sanitary drainage, including forming a low carbon, recycling society and a healthy water circulation system.

## (1) Dissemination of sewage processing with sanitary drainage

Although the dissemination of sewage treatment plants reached around 88% (dissemination of sanitary drainage systems of around 76%) of Japan as of 2011 (total of 45 prefectures, excluding Iwate and Fukushima due to effects from the Great East Japan Earthquake), there is a large gap between regions. In particular, the dissemination of sewage treatment plants in small to medium communities with populations of less than 50,000 people remain low, only reaching a ratio of approximately 74% (dissemination of sewage systems approximately 48%). Focusing on improvement in areas with high population density, the advancement of efficient development in accordance to condition of communities and the rectification of the gap between communities are seen as being of the utmost importance for developing sewage systems in the future.

**Population Penetration Ratio for Waste Water Treatment**
Penetration ratio for waste water treatment (%) | 1,000,000 or more (%) | 500,000 - 1,000,000 (%) | 300,000 - 500,000 (%) | 100,000 - 300,000 (%) | 50,000 - 100,000 (%) | Less than 50,000 (%)
Population Penetration Ratio for Waste Treatment (%) | 99.4 | 98.9 | 91.8 | 90.9 | 86.7 | 80.2
Population Penetration Ratio for Sewage Treatment (%) | 87.6 | 85.2 | 82.7 | 74.6 | 60.5 | 73.9
Population Penetration Ratio for Waste Water Treatment (%) | 75.8 | 70.0 | 60.5 | 48.0 | 40.0 | 30.0

(Note) Due to the Great East Japan Earthquake, the prefectures of Iwater and Fukushima are excluded from evaluation. The collected data is of the 45 prefectures excluding the two mentioned.

Source) Developed by the MLIT based on documents provided by the MLIT, Ministry of Environment, and Ministry of Agriculture, Forestry and Fisheries

## ① Cooperation between businesses for efficient maintenance of sewage treatment facilities

In regards to the maintenance of sewage treatment facilities, individual disposal by using septic tanks are economical in areas where households are widely distributed throughout a region, while the collective disposal with sewerage systems and drainage facilities for agricultural communities become more economical as the population density rises. For this reason, each prefecture has established a “Prefectural Plan,” a compiled maintenance plan over sewerage treatment which reflects considerations over regional characteristics such as the economic efficiency and importance over protecting water quality. In light of the declining population in recent years, the prefectural plans are undergoing urgent revision to attain increased efficiency in the maintenance of sewage treatment facilities. In addition, efficient means of maintenance are also being actively promoted through the implementation of cooperative schemes between other waste water treatment facilities such as cross-jurisdictional waste water treatment.

Graphic II-8-4-5

Revision of sewerage plans and focused improvement