Niiza-shi

In the latest Population Census the population is about 166,000 (166,017 in 2020). Its course is a consistent increase. From 149,511 in 2000, through 153,305 in 2005, 158,777 in 2010, and 162,122 in 2015, to 166,017 in 2020, it added about sixteen thousand over twenty years.

Looking inside, the figure of a plateau city where people commuting to the city center live appears. The share aged 65 and over rose from 11.6% in 2000 to 25.4% in 2020, but, while many regional cities approach four in ten, it stays at about a quarter, keeping youth. The household-with-children share is 20.4% in 2020, and the Childcare Waitlist was 8 in 2024 and 22 in 2025, increasing somewhat in recent years. The Fiscal Capacity Index was 0.87 in fiscal 2023, a comparatively high level covering nearly nine-tenths of expenditure with its own tax revenue. A town that drew water onto the plateau, consistently increasing its population while keeping youth, appears in the numbers. Why it took this form cannot be read without going back over the history of the channel and the coppice.

This town’s skeleton is set by the single irrigation channel that drew water onto a dry plateau, and by the coppice, temples and new fields that the water raised. The opening layer is the channel. In the Edo era, this area was a dry plateau where volcanic ash had piled up, an unreclaimed land where water was hard to obtain. A domain lord who had completed a great aqueduct drawing the water of a Tama river to Edo was, as a reward, permitted a branch flow from that aqueduct, and to open this plateau lying midway between Edo and his own castle town, he had a single channel dug. His retainer, foreseeing the leak-prone stratum of volcanic ash, dug along the ridge, and the channel is said to have brought water onto the plateau in just a forty-day work period, in the mid-1650s.

This channel set life upon the plateau. The plateau that gained water was planted with Musashino coppice, and new fields fertilized by the woods’ fallen leaves were opened, and a life of farming and woodland together was carried on. In this land was placed a temple tied to the house of the lord who had the channel dug, which continued as a place for the requiem of a daimyo house, together with broad precincts that preserve the Musashino coppice. The path by which it became a city mirrors this town too. This land became a city in the 1960s, and since then the plateau where the coppice remains has changed into a town where people commuting to the city center live. The irrigation channel that drew water onto the plateau, the Musashino coppice, a daimyo house’s family temple, and the new fields — this town’s form stands upon the history of the channel that the dry Musashino plateau held.

What characterizes Niiza-shi is that, while bearing the history of an irrigation channel that drew water onto the plateau, it consistently increases its population and keeps youth. From 149,511 in 2000 to 166,017 in 2020, it added about sixteen thousand over twenty years. Behind this town increasing while many regional cities lose population, one can read its position in the southern part of Saitama Prefecture, easy to commute to the city center, with housing spread across the plateau the channel opened and households raising children staying in the town. That the share aged 65 and over stays at about a quarter at 25.4% in 2020, keeping youth, is its expression.

On the other hand, the Childcare Waitlist was 8 in 2024 and 22 in 2025, increasing somewhat in recent years. It can be read as the expression of households raising children flowing into the residential area and childcare demand increasing. A Fiscal Capacity Index of 0.87 is a comparatively high level covering nearly nine-tenths of expenditure with its own tax revenue. The income of the many households living on the plateau can be read as supporting the tax source comparatively high. The population consistently increases, the aging is about a quarter, and the fiscal stamina is comparatively high. Traced to their root, these figures arrive at the point that a single irrigation channel made life possible on a dry plateau — behind them lies one connected chain: housing spread there, people stayed, and they support the tax source.

Niiza, as a town opened on the edge of the dry Musashino plateau, holds several functions of its own. One is the history of a single irrigation channel that drew water onto a dry plateau of volcanic ash in a work period of just forty days, its water raising the Musashino coppice and the new fields. Another is the character of a temple tied to the house of the lord who had the channel dug, continuing as a daimyo house’s family temple together with broad precincts that preserve the Musashino coppice. And the landform of a dry plateau called in the channel that drew water, and that water raised the coppice and new fields, and later the housing.

Niiza is a town where an irrigation channel that drew water onto the plateau holds coppice and housing. From a channel that opened a dry plateau, to the Musashino coppice, a daimyo house’s family temple, and the housing of people commuting to the city center — the geography of “opening on the edge of the dry Musashino plateau” called in the channel that drew water, and called in the coppice and housing. The dry plateau where volcanic ash had piled up was originally a land hard to set human life upon. Because water ran through there, the coppice, the new fields and the housing all came to stand. That a single condition — water — was met has become the premise of all of today’s Niiza.