Kamafusa Damu-ko (Reservoir) was constructed by the Ministry of Construction on the Goishi River of the Natori River System in 1970 as a multi-purpose reservoir for flood control, irrigation, domestic and industrial water supply, and electric power generation at a cost of 8.72 billion yen. Construction began in 1966 and the reservoir was filled in 1970. The reservoir is located among low hills 25km west of Sendai City. The prevailing climate is characterized by hot wet summers and rather mild winters when the reservoir seldom freezes over. It supplies drinking water for Sendai and its suburban areas and offers an important recreational park area for both Sendai citizens and local residents with various facilities for camping, boating and sport fishing.

The water quality of the reservoir has become seriously eutrophic owing to heavy nutrients loads, particularly from non-point sources, failing to meet the lake water quality standards required by the national law in recent years. Remedial measures have therefore been carried out by Miyagi Prefectural Government, including sediment dredging and installation of intermittent aeration system. The construction of wastewater treatment plants for livestock pens is also encouraged. The Committee for Environmental Conservation in Kamafusa Damu-ko, established in 1989, is responsible for the promotion of conservation works, recreational development, environmental concern of the public and related citizens activities (Q, 12). (1987, revised in 2018)

In 1987 Kamafusa Reservoir was appointed to the seventh designated lake based on the Law Concerning Special Measures for Preserving Lake Water Quality following the first five lakes registered in 1985, and a successive one, Lake Suwa, in 1986. The midterm evaluation of the execution was as follows.

It is being suspected that the water quality of the reservoir is deteriorating. However the investigation of the actual conditions, the analysis of the result and investigating measures for the efforts including the moderate application of fertilizers to the agricultural field and measures against non-point load source like forest thinning which is included in the fourth plan, contamination load reduction from nature and fish-raising industry should be prioritized first, hence the plan is judged to be continued as it is.

For the latter half of the Phase 6 Plan, research and investigation will be conducted with an emphasis on measurements of long term variation and the following five noteworthy view points, that will help prepare the next plan, while continuing the existing measures.
1. Flow characteristics of inflow rivers and water temperature variation, which is suspected to be connected to the global warming
2. Water circulation within the reservoir and water quality variation (including vertical mixing and internal production)
3. Measurement of the load during flood
4. Non-point load characteristics and their curtailing measures
5. Load characteristics of fish farms and their curtailing measures
(February 2018)