About two million years ago, in the area now on the eastern side of the lake, there were many swamps and wetlands. Waterside-loving plants grew there, such as Japanese alder (Alnus japonica), willow (Salix sp.), bulrushes (Scirpus hotarui), three-leaf arrowhead (Sagittaria trifolia), and water caltrop (Trapa japonica).
This is a restoration of a forest typical of the region two million years ago. The then extensive wetlands and marshes were surrounded by large deciduous conifers, the dawn redwood (Metasequoia glyptostroboides) and Chinese swamp cypress (Glyptostrobus pensilis), with trunks reaching over 150 cm in diameter.
Uplands and mountainous regions were covered with other conifers, such as spruce (Picea jezoensis), Japanese fir (Abies firma) and southern Japanese hemlock (Tsuga sieboldi), various broadleaf trees, including Japanese wingnut (Pterocarya rhoifolia), beech (Fagus sp.), oak (Quercus serrata), and maple (Acer sp.), and Wisteria.
Here, aspects of the local climate (temperature, humidity, rainfall, wind direction and velocity etc) are measured. The data collected are fundamental for research on lake water conditions and the fauna and flora in the area around the museum.
In the mountains, many springs and seeps discharge groundwater into steep valleys. The water subsequently collects and flows between the rocks and boulders, forming fast-flowing streams.
In addition to sections of the stream where the flow is rapid, there are also places that are deeper with a slower flow, and where fallen leaves and mud accumulate. This step-like alternation of rapids and deep pools is characteristic of a stream in its upper reaches. The life found in the rapids is different from that found in the deeper pools.
Downstream from the upper reaches, the stream reaches wider, lower valleys or a plain, and the flow becomes slower.
River beaches of small stones replace the large rocks and the alternating step-like rapids and deep pools of the upper reaches. Deep pools do form where the flow strikes the bank, or when floodwater gouges out the streambed.
Downstream from these pools, the flow can get gradually faster and shallower, forming riffles. The pools harbor different types of life than the faster flowing riffles.
6. Stream and its life (lower reaches)
As the river flows for a long distance through open plains, its flow gradually becomes slower to the point where only small particles of mud and fine sand can be carried along. The banks are characteristically covered with thick growths of trees and grass.
As the river meanders across the plain, the flow slowly erodes some areas and deposits sediment in others, and over time this process changes the course of the river; the old route can sometimes been seen as oxbow lakes.
Because the flow of the river in its lower reaches is sluggish, conditions are similar to those of lakes and wetlands, resulting in a similar fauna.
Buried Cryptomeria japonica forest
In March 1992, these stumps of Cryptomeria japonica trees (Japanese cedar) were found buried in the grounds of Shiga-cho elementary school. Several dozen stumps like this were excavated from three layers.
Radio carbon dating revealed an age of approximately 3000 years, the late Jomon Period. Other buried stumps of these conifers have also been found in South Komatsu (on the west side of Lake Biwa) and Mikatagoko (to the north-west of Lake Biwa).
Data suggests that from the Jomon Period (5000 - 900 BC) to around about the Yayoi Period (900 BC - 250 AD), the area west of the lake was covered with flourishing Cryptomeria japonica forests. Today these trees are still found in the Kinki District, but not in such abundant numbers.
Would you like to experience life in former times?
Fuel for cooking or heating was collected from the forests and riverbanks; water was taken from rivers, wells, or Lake Biwa; and food was produced in fields. From the houses, garbage, ash and urine from people and domestic animals were taken to be used as fertilizers for growing crops. The forest, river and rice fields were the children's playgrounds.
By experimentally re-enacting the lifestyle and play from previous times, the connection of people with water, fauna, and nature can be experienced.
9. Forests of the Jomon and Yayoi Periods
Quercus gilva forest
Currently, within Shiga prefecture there are only two localities where the tree Quercus gilva (a type of oak) occurs naturally: at Hassho Shrine on the west side of Lake Biwa, and at Sayuu Shrine on the east side of the lake. However, evidence suggests that in the past this tree was much more widely distributed around the lake.
At the Late Jomon Period (2000 - 900 BCE) archeological site at Anou, Otsu City, many tree roots of this species have been unearthed, and the Awazu shell mound (Middle Jomon Period) in the southern part of the lake contains large quantities of nuts and acorns of Quercus gilva in layers of freshwater 'shijimi' clam shells.
As the acorns of Quercus gilva are low in tannins they can be roasted and eaten, so were used as a food resource by people during the Jomon Period.
Persea thunbergii forest
Usually, Persea thunbergii forests are distributed along the coasts of Japan, but exceptionaly in Shiga Prefecture Persea thunbergii forests are found in various places around the lake. In similar landscapes in Kyoto and Nara there are no Persea thunbergii, and in the case of Shiga Prefecture, the presence of Lake Biwa and local climate is important; the summers are not too dry and the lowest temperatures in winter are comparatively high.
Japanese chinquapin forest
From the Jomon (2000 - 900 BCE) and Yayoi (900 BCE - 250 CE) periods until recently, the plains and hills around Lake Biwa were covered by broad leaf trees. Today the distribution of this type of forest from the coast of the Sea of Japan to more inland areas is very patchy.
In the Awazu shell mound (approximately 5000 years old) of the Middle Jomon Period, however, many acorns of the oak Quercus gilva have been recovered, and the remnants of forests found within the grounds of shrines contain Japanese chinquapin (Castanopsis cuspidata).
In order to reconstruct the Japanese chinquapin forests of the Jomon and Yayoi periods here, the present-day remnants were used as models.
12. Observation Pond
When this pond was dug in 1996, no animals or plants were deliberately introduced into it so that the natural colonization process of the pond could be monitored.
Other attractions of the Karasuma Peninsula include a large area of lotuses in the lake. During the last half of July and first half of August the lotuses bloom creating a spectacular view.