Just Enough. Azby Brown

      The relationship between irrigated fields and those for non-irrigated crops is defined by local geography. With all of the flat land devoted to rice, other crops, such as vegetables, dry grains (wheat, millet, and barley), yams, and cash crops such as cotton and hemp, are usually planted on the lower slopes of the surrounding mountains. Even steeper slopes can support orchards and crops such as tea, with the result that agriculture is practiced in a stratified manner that conforms to the local environment. Except in the widest of valleys or the rare expanses of coastal lowland, the farmhouses themselves are likely to be nestled in clusters against the nooks and hollows of the hillsides, often somewhat distant from the family’s fields.

      approaching the village

      As we approach the village, we are passing through a very green but very human-influenced landscape. Certainly the largest environmental effect has been on the valley floor, where the previously existing ecosystem has been selectively dismantled and replaced with paddy agriculture. Trees have been cut down and the ground subdivided into shallow pockets. These paddies provide a ripe environment for other species that benefit from the changes humans have brought: frogs and fish flourish, feeding on insects whose numbers have increased with the new food source that rice represents. The frogs and fish in turn attract ducks, egrets, and other predators, and so on up the food chain.

      What have declined are many weeds, bushes, grasses, and other botanical species, as well as boars, foxes, rodents, snakes, and other animals that seek dry ground during the summer. The result could be considered damage from the purely natural point of view. But by designing the agricultural process in a manner that makes the fullest possible use of naturally existing features, by seeking to maintain the fertility and productivity of the forests, and by the secondary effect whereby the paddies and other fields become ideal environments for other species, the farmers have developed an agricultural ecology that replicates the purely natural one in several of its most essential aspects. The balance has been altered, true, but humans are being supported in large numbers without degrading their environment.

      Irrigation is a major undertaking. Waterworks in general have achieved a high degree of technical sophistication, with well-engineered aqueducts supplying major urban areas and ambitious river works easing navigation and lumber transport. Rice field irrigation is similarly sophisticated and well engineered, while often using simpler technical means; it is implemented with the same attention to social cooperation and environmental monitoring that distinguishes forest gathering activities. A new rice paddy cannot be built unless its impact on the shared water supply is acceptable to all concerned, and the actual construction of the dams and dikes is a cooperative effort. The farmers manage their water supply precisely and with foresight.

      Gravity is made to do the work of moving water from source to destination wherever possible. While in some cases the geography makes this relatively easy, more often than not the choice is between expending resources and energy to construct an aqueduct to provide a gravity-fed water supply from a distant source, or to implement a system of human-powered pumps and lift systems to bring water from a low-lying source to paddies above. The former is a vastly preferred solution. The earliest irrigation systems in Japan, developed shortly after the beginning of paddy agriculture around 400 bc, utilized catchment basins to collect water until it was needed to flood the paddies, and this method is still widely practiced. Although in some situations it is necessary to dig artificial ponds for this purpose, for the most part naturally occurring ponds can be made to serve beautifully with the addition of weirs, sluices, and gates.

      In cold parts of the country, sun shining on the pond water warms it to the optimal temperature for use before it is released to the crop; in other cases long, serpentine irrigation ditches serve an identical function. The design process is essentially one of augmentation—reinforcing and shaping naturally occurring features and forces. Natural ponds have the tremendous advantage of having evolved symbiotically with their watersheds and possess naturally occurring inflow sources as well as natural outflows; they are balanced with their local ecosystems in a way that is difficult to replicate through engineering alone. Larger projects such as levees and dikes, intended to limit damage from seasonal flooding, are usually based on similar principles. The meanders of the rivers are left untouched, but the riverbed is broadened, and low levees are built that allow natural flooding to pour into a wide catchment beyond.

      One commonly used design that originated in nearby Koshu uses separate, discontinuous levees that are angled to the direction of flow to guide the flood-waters. They are planted with trees and bamboo to anchor and consolidate the earthwork and to encourage further natural growth. Riparian works like these undertaken during the previous century allowed a considerable increase in arable land through reclamation of otherwise dangerous flood plains, but there are few opportunities for similar gains now.

      Although the dynamics of steeply terraced and lowland irrigation differ, in both cases the result is a gravity-fed cascade. From original sources such as rivers and streams, water flows into a catchment, and from there it is released into the paddies at prescribed intervals; it flows from one level to the next, and excess water can be released back into the waterways. This cascade captures sludge and organic matter and has a filtering and purifying effect on the water. For this reason it can be argued that these systems actually improve the local water supply, with benefits to those downstream.

      sharing the wealth of water

      At every step, from planning to construction and utilization, cascade irrigation requires very close cooperation among community members, and often among members of different communities. This is particularly true because—due to successive projects of clearing and reclamation as well as inter-marriage and redistribution of assets—a single family’s fields are likely to be scattered and interspersed with those belonging to others. Consequently, simply deciding the order in which fields will be flooded requires tremendous coordination and agreement, and the earthen dams separating one paddy from another must usually be considered assets shared by more than one family. The canals, ponds, sluices, and other major components of the irrigation system require the mediation and guidance of village headmen and possibly government representatives, and they are therefore assets shared by the village as a whole, under the jurisdiction of the village’s suiri kumiai, or water-use association.

      The effort expended on constructing, maintaining, and intensively farming the extensive rice paddies goes far beyond what would be needed for self-sufficiency on a local scale, and beyond what would be necessary to secure a good living through open-market sales, because the government has saddled the peasantry with a large tax burden. Officially discouraged from eating the rice they grow, the peasants surrender a third or more as tax, sell some, put some in communal emergency stores, and keep a portion for consumption despite the prohibitions. Through their taxes, the 80 percent of the population that are farmers support the entire ruling class and subsidize the feeding of the remaining 10 percent who live in cities.

      The lower slopes of many of