Q1 How was it formed?
Q2 Where does its name come from?
- Its official origin is uncertain, but it is thought that it was left as
a residual pond after flooding of by the early Ishikari River.
Q3 How big is the marsh?
- It relates to the name of the farm that was run by Sajiro Miyajima, founded
in 1893 (Meiji 26), on the west edge of the marsh. Local people also called
the marsh simply, “Ohnuma” (lit. big marsh), because the marsh was the
largest of a number in the area.
Q4 Where does the water come from?
- Officially: Circumference: 2.7 km, Surface Area: 0.36 km2, Volume: 600,000m3
, Maximum Depth: 2.4 m, Average Depth: 1.7 m
- The surface are of the marsh used to be 120,000 tsubo (≒40 ha), but is now only about 30 ha. Furthermore, according to actual
measurements, the maximum depth of the marsh was just 123 cm, and the average
depth 86 cm.
Q5 What lives and grows in the water?
- Spring water used to come from the bottom of the lake, but now melting
snow and rainwater form the marsh.
- The water usage association, formed by local farmers, uses water drawn
from the Ishikari and warmed in the marsh via a water channel in the east
edge for irrigation, but only when they are planting rice.
- Plant : Himebishi, Pond weed, Yellow Pond Lily, etc.
- Fish: Carp, Cyprins, Japanese Dace, Lakeminnow, Asian Pond
- Loach, Ten-spined Stickleback, Pond Smelt, etc.
- Crustaceans: Swan Mussel, GoldenAppleSnail, Monoaragai
Q6 What lives and grows around the marsh?
Q7 Who owns the marsh?
- Grasses & Herbs: Wild-Rice, Reed Grass, Reedmace Sagebrush sp., Giant
Knotweed, Gloden Rod, etc.
Trees: Alder, JapaneseWillow, Kamtschatica,PanicleHydranger, Japanese Angelica
Birds: Great Reed Warbler, Black-Browed Reed-Warbler, Stonechat, Grey-Capped
Greenfinch, Siberian Rubythroat, Reed Bunting, etc.(detail of waterfowl
is as follows)
Animals: Ezo Red Fox, Mink, Rat, etc.
- It belongs to the state, the Ministry of Construction, and it’s treated
as a normal river.
- In the autumn and the spring, Miyajima-numa becomes a stop-off point for
waterfowl, mainly anatidae, during their migration to wintering or breeding
- Among those birds are the white-fronted geese which use the marsh as a
place to roost for about a month every spring and autumn, and eat fallen
rice left in the surrounding rice paddies.
- Miyajima-numa has been used by generations of geese as the largest first
gathering point in the autumn and the last in the spring in Japan, and
their numbers now exceed 40,000.