One of the busiest men in Edo is the mizu-bugyo (the water "mayor") -- the man in charge of Edo's water supply. It is a huge job to keep the water system in Edo working properly. Since all the pipes are made of wood, they need to be replaced once in a while. Earthquakes are not uncommon in Edo, and even a small quake may cause pipes to crack or start to leak. In times of drought, the supply of water needs to be carefully controlled, to make sure that it is distributed fairly to all parts of the city. The job of managing the city's water system is handled by the mizu-bugyo and a staff of mizu-bannin (water technicians).
The mizu-bugyo is one of the few top officials in the bakufu who is appointed to his position, rather than inheriting it. He and his assistants, the mizu-bannin, are responsible for handling all of the repair work on the banks of the canals, as well as maintaining the distribution systems through the city.
Before Tokugawa Ieyasu moved to Edo in 1590, the town was still very small, and the people living in Edo got all the water they needed from the small streams flowing down from the hills of the Yama-no-te into Edo Bay. The main streams were the Koishikawa (Koishi River) in the north, and the Megurogawa (Meguro River) in the south. When the Tokugawa family moved to Edo, with all of his warriors and retainers, it quickly became clear that the traditional sources of water would not be enough to supply all the people in the growing town. Therefore, Ieyasu started the first of many water supply projects, or josui , to bring water to the city. ("jo-sui" literally means "lifting water" or "water inflow")
The first thing Ieyasu did was to build an extensive network of wells throughout the city, which were supplied with water from the main streams -- mainly the Koishi River. Wooden sluices and pipes were built to carry water underground from the river to each of the wells. This ensured that people living in every part of the city had access to fresh water. However, it did not increase the supply. After Ieyasu became Shogun, in 1603, Edo started to grow even more rapidly, and soon there was not enough water to supply all of the wells in the city.
The second major josui project that the Tokugawa shoguns carried out was the Kanda josui . To increase the volume of water supplied to the city wells, two large canals were built to redirect the flow of several smaller streams. Before, they used to flow into the Tama river, but once the canals were built the water flowed straight through the center of Edo. This new man-made "river" was named the Kanda-gawa (Kanda River) because it joined up with the Koishi river at a point near Kanda.
The main branch of the Kanda river starts at a small lake, which was named "Inokashira" (the head of the well), because it supplies all of the wells in Edo. This lake is about ten kilometers west of the city. A smaller branch starts in an area of marshes near Zenpukuji temple, so it was named the Zenpukuji river. The Kanda josui runs east through the hilly Yamanote area until it reaches Yotsuya. At Yotsuya, the water flow is divided. Part of it enters the main outer moat surrounding Edo Castle, and the rest of the water is directed into the main pipes that supply water to all of the city's wells.
An important part of the Kanda josui water project was to build the underground piping system that would carry water from the main intake at Yotsuya to each of the wells in the city. It took a huge effort to dig the trenches, build wooden pipes to carry the water to the wells, and then rebury all the pipes under the city streets. By the time this project was complete, there were about 67 kilometers of underground pipes supplying water to over 3600 wells in the city. At one point, one of the main water pipes crosses back over the Kanda River on top of a large bridge. This bridge is named Suido-bashi, or "Water-works Bridge".
The Kanda josui and a few smaller canal projects were able to provide enough water for the city for several decades. But Edo continued to grow. By the mid-1600s the population was already well over half a million people, and once again there were water shortages as the current supply system was insufficient to meet the needs of all the people. The third Shogun, Iemitsu, realized that water shortages could soon cripple the economy of Edo, so he ordered the most ambitious water supply project yet; a canal to carry water from the Tama river -- 50 kilometers west of the city -- to downtown Edo.
Work began on the Tamagawa josui in February 1653. A small dam was built on the river near the town of Hamura, and workmen began digging a canal across the hills to carry the water to Edo. At that time, there were only a few small villages located in the hilly, wooded region between the northern suburbs of Edo and the Tama river. Apart from one or two small streams, there were few good sources of water in the area, and certainly not enough to support rice farming.
It was rough work digging the huge canal -- in some places, the workers had to dig a channel as much as 18 meters deep -- through the heavily wooded hills. However, as the digging work proceded, and the canal reached further and further towards the city, people began to move into the cleared areas where the workers built their camps, and soon small towns began to spring up along the banks of the canal. The Shogun assigned such a large group of workmen to the Tamagawa josui project that they were able to complete the canal in just seven months. Once the water began flowing through the canal, many areas to the west of the city were transformed from woodlands into small farming towns, which grow vegetables to sell in the city.
The Tamagawa josui links up with the Kanda josui just to the west of the city, and the underground piping system was redesigned and extended to cover an even wider area of the city. Today, there are more than 150 kilometers of pipes in the Edo water systems, and the wells that are connected to this water system supply over 60% of the citizens with water for drinking, bathing and washing.
However, there are still some parts of the city where it is impossible to build wells and waterworks, particularly in the low-lying areas along the coast of Edo Bay, in Fukagawa and Kiba. Whenever you dig a well, it quickly fills up with salty water. People who live in these areas cannot get their drinking water from the wells, although they do use well water for bathing and washing. Drinking water must be carried into these areas of the city in special boats called mizu-bune (water boats).
A large pipe from the main water system empties into the Nihonbashi River at a point near Edo Castle. The mizu-bune load up with water at this pipe, and then travel to the areas of the city that have no wells. Water salesmen, or "mizu-ya", meet the boats at one of the piers in this area, and fill large buckets with water. Then they walk from door to door carrying their water buckets and sell drinking water to the people who live there. Although this system is somewhat inconvenient, the cost is very low.
The water-sellers store water in large casks and tanks in each neighborhood, so the people who live in these areas can always find water nearby when they run out. The system of mizu-bune and mizu-ya is managed by the government. This system allows thousands of people to live in an area that would otherwise be almost uninhabitable.