Miharu Dam Management Office

Transport and, Japan

Miharu Dam Management Office

Transport and, Japan
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Kumazawa K.,OYO Corporation | Osugi T.,Chiyoda Corporation | Nishita M.,OYO Corporation | Azami K.,OYO Corporation | And 9 more authors.
Ecology and Civil Engineering | Year: 2012

In Japan, some of introduced exotic fish such as largemouth bass (Micropteraus salmoides) and bluegill (Lepomis macrochirus) are highly competitive over indigenous fish species, causing loss of biodiversity and degradation of aquatic ecosystem in a site. As this issue became apparent, many strategies have been implemented to control the exotic species. In a breading season of largemouth bass and bluegill, from May to June, they flock to shallow areas for spawning. In a front reservoir of Miharu dam, encircling nets were placed parallel to shores in order to lock the exotic fish in the target sites. As the reservoir level was lowered by a drawdown operation, fish in the areas were inescapably driven into the nets. This drawdown capturing method has been carried out from 2007 to 2011. Among the fish captured, the invasive exotic species, largemouth bass and bluegill, were eliminated and the others were released. Large sized individuals of largemouth bass were collected more in a joint area (about 5m width) between the front and main reservoir. Bluegill does not migrate around the reservoir, but they gather in shallow areas in spawning season. As a result of the consecutive practice, abundance of the largemouth bass and bluegill (2nd year and older) have been decreased. Whereas, the number of indigenous juveniles seen, such as Carassius auratus langsdorfii, has increased and increase of the indigenous populations has been affirmed.

Azami K.,OYO Corporation | Fukuyama A.,Saitama University | Asaeda T.,Saitama University | Takechi Y.,Miharu Board of Education | And 2 more authors.
Landscape and Ecological Engineering | Year: 2013

In limited-water-level reservoirs, areas along the reservoir shoreline are often exposed within the drawdown zone when water levels are reduced from normal to limited levels during the flood season. To prevent erosion and conserve the landscape, test plantings and landscaping along the shoreline have been implemented at some dam reservoirs. The establishment of vegetation within the drawdown zone contributes to both landscape and wildlife habitat conservation. Distribution, habitat, and seed-dispersal period of willows such as Salix subfragilis were investigated at Miharu Dam reservoir in northeastern Japan. Eight willow species were found around the dam, but S. subfragilis dominated within the drawdown zone. Field survey results beginning in 1995 indicate that the size of the S. subfragilis community increased after initial impoundment. Although many other Salix species disperse seeds prior to the drawdown period, S. subfragilis disperses during and after drawdown in the spring; thus, when water levels are lower than normal, its seeds are supplied to the newly exposed zones that provide suitable habitat for Salix seedling establishment. Our results suggest that S. subfragilis dominated because of water-resistant properties and timing of the seed dispersal period. © 2012 International Consortium of Landscape and Ecological Engineering and Springer.

Azami K.,OYO Corporation | Takemoto M.,OYO Corporation | Otsuka Y.,OYO Corporation | Yamagishi S.,Yamashina Institute for Ornithology | Nakazawa S.,Miharu Dam Management Office
Landscape and Ecological Engineering | Year: 2012

The immediate impact of damming appears most notably at the first filling of water, when the dam blocks the river and a lake suddenly forms. In this review, the changes in meteorology, plant communities, birds and fishes surrounding initial impoundment of Miharu Dam, constructed in an Asian Monsoon region, are summarised based on previous papers and subsequent field research. Although wind and temperature changes were investigated, land and lake wind occur due to the different thermal properties between the land and lake, and this type of wind often occurs at large lakes such as Glen Canyon Dam Reservoir or Lake Biwa. The size of Miharu Dam Reservoir (ponding area 2.9 km 2) was insufficient to cause land-lake air differentials. Therefore, wind direction and air temperature were unaffected. Mountain winds weakened at the lake centre and near the dam body. Changes in vegetation were especially diverse at the drawdown zone (the slopes above and below the normal water level). On slopes above this zone, trees died and species composition changed due to submergence. Within the drawdown zone, the pre-existing plant community disappeared, and flood-resistant plants such as Salix subfragilis increased. The natatorial bird population continued to grow for 4 years after dam reservoir emergence and stabilised thereafter. Every year, the majority of natatorial birds utilising the dam reservoir as a resting area were ducks, but populations of diving ducks fluctuated depending on water level and iced area. After impoundment, the fish populations increased. As in most dam reservoirs in Japan, populations of invasive fish species such as Micropterus salmoides and Lepomis macrochirus increased. However, spawning grounds dried up during low-water-level seasons, suggesting that regulating water levels may help reduce invasive species. © 2011 International Consortium of Landscape and Ecological Engineering and Springer.

Kato E.,OYO Corporation | Azami K.,OYO Corporation | Takemoto M.,OYO Corporation | Okitsu J.,OYO Corporation | And 2 more authors.
Ecology and Civil Engineering | Year: 2013

Before the first infilling of Miharu Dam reservoir, a population of vulnerable species, Adonis ramosa, was found in 1996 on a shore slope that was supposed to be submerged by the initial impoundment. The main area of A. ramosa community was on a shore slope between the normal water level and surcharge water level of the reservoir. It was obvious that the initial impoundment would cause a devastating impact on the A. ramosa population. For the conservation purpose, we transplanted the most of A. ramosa individuals to another 4 places before the initial impoundment. In additon, for the examination purpose, we left a part of the community on the original habitat and monitored it. To examine the effect of transplant and influence of submersion, we monitored at 5 sites during 14 years since 1996, of which the first 2 years were taken as the pre-first filling and 12 years were done as the post-first filling. At all sites, A. ramosa individuals were observed after 12 years, though juveniles and blooming individuals were not observed at one transplant site. At the other 3 sites and the original habitat, juveniles and blooming individuals existed. It was suggested that re-production were continued at each site. Future prospect of the populations in the next 50 years were calculated using a Leslie matrix. It suggested that A. ra-mosa communities would be continued at site D and the original habitat, whereas they would be extinct at the other 3 sites. However, the conservation of A. ramosa population was succeeded since the total number of individuals and distribution in recent years were recovered and became larger than the previous time before the initial impoundment. The future populations will be sustainable for a long time at least 2 sites.

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