Geographical Review of Vol. 60 (Ser. B), No. 1, 41-65, 1987

Irrigation Systems in Japan

Aklra TABAYASHI*

This paper portrays the distribution pattern of irrigation systems in Japan and then analyzes the pattern with respect to elements of the natural environment and of the irrigation development process. Irrigation systems in Japan are classified into (1) river, (2) pond, (3) lake, (4) ground water, (5) torrent, and (6) other systems. River irrigation systems dominate overwhelmingly and occur widely, but especially in eastern Japan. Pond irrigation systems are important in western Japan, centered on the Inland Sea. Various types of irrigation systems exist together in the Kanto district, and torrent systems are common in mountainous areas. The basic features of irrigation systems in western Japan were formed during the Kofun and Nara periods (300 to 800 A. D.). On the other hand, the main systems in the east were built largely in the Sengoku and Edo periods (1450 to 1867 A. D.). In the large systems, a hierarchical structure of water management coopera tives and water delivery methods that accords with the branchlike network of canals was established in the Edo period (1600 to 1867 AD.).

hold economy. Irrigation systems not only I. Introduction influenced cultivation but also production of crops other than rice. Farmers' life styles Rice cultivation has long been the core of and cultures were similarly affected by irriga agricultural activities in Japan. The high tion systems. Although rice cultivation is productivity of rice per hectare of fields in a much less important in rural life and the humid and temperate environment has made farming economy today, irrigation systems it possible to support a large population on a play a major role in shaping the structures of small land area. That Japanese rice cultiva Japan's agricultural regions. tion enjoys high yields in comparison with As an agricultural geographical study seek other Asian countries owes also to sophisticated ing to describe and explain spatial variations irrigation systems created by huge labor and in agricultural activity on the earth's surface capital investments for land improvement (GRIGG,1984, pp. 13-18), an analysis of rural works over many centuries (NAGATA,1971, regions from the viewpoint of areal differences pp. 24-33). in irrigation systems has a significant meaning. The evolution of rice producing regions has This paper classifies irrigation systems in been closely related to progress in the develop Japan, and describes and analyzes the dis ment of irrigation systems, for irrigation tribution patterns of the main types of systems. systems have played an important role in It also examines the development processes supporting successful rice production in Japan. of the main types of irrigation systems. Although about 86 percent of all farm house holds are part time farmers today, and farm II. Main types of irrigation systems ing itself is not an important source of income in Japan. for them, until the 1950s most farm households 1. Classification of irrigation systems lived on farming, especially rice cultivation. In contrast to crops grown on dry fields such Geographers have described and explained as peas, beans, , millet, barley and sweet regional characteristics of irrigation systems in potatoes, the higher monetary value of rice Japan by examining such features of the per hectare was very important for the house systems as their sources of water, their water

* Institute of Geoscience , The University of Tsukuba, Ibaraki 305, Japan. 42 A. TABAYASHI

carrying and water division structures, their divided into ones with several ponds and ones customary water use practices, their water with a single pond. Pumping irrigation sys management organizations, and their land tems encompassed those using groundwater scape locations. However, in Japan the type and those using surface water. Creek and of water source often strongly influences other ganat systems belonged to the category of features of an irrigation system (TAMAKIand other irrigation systems. HATATA,1974, pp. 228-229). Therefore, the Geographers YAMAGIWA(1928), INOKI(1935), present study focuses attention on water MATSUI(1964) and others discussed river, sources, and irrigation systems are classified pond, groundwater and spring irrigation sys on the basis of their water sources. Terms tems. Books recently published by TAKEUCHI such as river irrigation, pond irrigation and (1980, 1984) describe pond, groundwater,lake, groundwater irrigation are common in the and river irrigation systems. They also ex Japanese literature because they connote more amine rain-fed terraced paddy fields and creek information than simply the source of water. irrigation systems in the Saga plain of Kyushu For example, groundwater irrigation is almost along the . HORIUCHI(1983) has always small scale because the area served by been engaged in research on various types of a well is small. As such, groundwater irriga irrigation systems in the Kinki district and tion systems are managed by single farmers in particular has analyzed river, pond and or small groups of farmers, and water manage groundwater systems. In addition, he has ment procedures are simple. On the other described features of a system pumping water hand, many river irrigation systems are large. from Lake Biwa to nearby paddy fields. ARAI Their main canals gradually decrease in size (1986) classified irrigation systems as they are tapped by branch canals. A part into river, pond, vertical well and horizontal of a branch canal may serve most or all the well systems. land of an entire village. Thus, a single river The present study classifies irrigation systems irrigation system is commonly managed along in Japan into categories called (1) river, (2) parts of its branch canals by villages, along pond, (3) lake, (4) groundwater, (5) torrent, branch canals or parts of its main canal by and (6) other (Table 1). River irrigation groups of villages, and along its main canal systems include subtypes on alluvial fans and at its water source by a municipality. where water flows by gravity, and on deltas Within such a large irrigation system, all where gravity irrigation is impossible. Creek farmers have an interest not only in the pattern irrigation systems are essentially a variation of water flow in their local branch canal but of the delta subtype. In addition, river also in the main canal and the water source. systems are subdivided according to the size Water management procedures at the system of rivers, small, medium or large, from which or district level may be extremely complex they take water. because of competition among subdistricts Pond irrigation systems encompass two sub (TAMAKI,1983). types, parent-child pond systems in which a The Department of Agricultural Land of the large pond distributes water to smaller ponds, Ministry of Agriculture and Forestry in 1960 and single pond systems. Water in both sub classified irrigation systems into river, pond types flows by gravity. Traditionally, lake and creek systems, and rain-fed paddy fields. irrigation systems involved small scale water NAGATAet al. (1982) discussed recent agricul tapping using such devices as buckets handled tural changes in areas irrigated by rivers, by two persons, dragon pumps and foot pro ponds and creeks. HIRASHIMA(1984) divided pelled water wheels to irrigate fields within irrigation systems into categories called river, just a few meters of the lake. However, large pond, pumping and other. He further sub scale pumping stations that have appeared divided river irrigation systems into those mainly since the 1920s enable water to be with a diversion dam and reservoir on a river lifted and then transported several kilometers and those diverting water directly from the upcountry from a lake. The groundwater river. Pond irrigation systems were sub category of irrigation systems has two sub Irrigation Systems in Japan 43

Table. 1 Types of irrigation systems in Japan

Table. 2 Hectarage of paddy fields by main sources of irrigation water (1000 hectares)

* included in others Source: K. NAGATA,1971; Nogyo suiri kenkyukai,1980

types, an ordinary vertical well and a hori are low enough to reach groundwater level and zontal well. Formerly, sweep-well buckets rain fed paddy fields. and windmills were used for pumping water Table 2 shows the hectarages of paddy from vertical wells, but they were replaced fi elds in Japan by main source of irrigation by motorized pumps mostly after world War water in the years 1907, 1942, 1955, and 1977. II. The horizontal well called manbo is a All irrigation types mentioned above are not long tunnel-like excavation on a natural in represented in the table owing to lack of data. cline in which ground water is collected for The figures indicate that about 75 percent irrigation purposes. Torrent irrigation sys of all paddy fields now depend on river irriga tems utilize small mountain streams as sources tion, followed by pond irrigation which sup of water. Terraced paddy fields on steep plies water for about 14 percent of paddy slopes may be supplied with water by such fi elds. Groundwater and torrent irrigation systems. In a sense, torrent systems are a systems together serve about one percent. subtype of river systems. However, they The total area of irrigated land has grown by are considered a separate category here be about 20 percent and the area of river irrigated cause special facilities and methods are required fi elds has increased by about 35 percent in to catch the water torrents and direct them to this century. In 1970, over 60 percent of all fi elds. The category of other irrigation systems villages were served mainly by river irrigation includes dug down paddy fields whose surfaces systems, 15 percent by ponds, and 10 percent 44 A. TABAYASHI

Table. 3 Number of villages by main source of irrigation water

Source: Agricultural Census, 1955, 1970

by torrent systems (Table 3). The numbers of the Hakusan Diversion Dam at the apex of villages mainly depending on lakes, dams, of the fan. The water is first used by the wells, and other systems are small. Not re Hakusan hydropower station and then divided fl ected in Table 3 are secondary sources of so that three-quarters goes to the northern irrigation water. About 40 percent of the sector of the fan and the remainder to the villages have two or more types of irrigation southern sector through a syphon crossing the water sources. (Figure 1). The main canals and division works of the northern sector are 2. River irrigation systems controlled by the Tedori River Seven Canals Rivers are the most important source of Land Improvement District (Tedorigawa Shi irrigation water in Japan and have been since chika Yosui Tochikairyoku). About 6,000 the middle of the Edo era in the early eigh hectares of paddy fields are served by the teenth century (OGAWA,1953). As mentioned district, and about 5,600 farmers are its above, there are two subtypes of river irriga members (Tedorigawa Shichika Yosuishi Hen tion systems, the alluvial fan subtype in which sanshitsu, 1972, pp. 353-395). The main tasks water flows from the river to canals by gravity, of the district are to obtain the necessary and the delta subtype in which water must be irrigation water from the diversion dam, to pumped from the river into the canals. supply it properly to the seven main canals, 1) Alluvialfan subtypeof river irrigationsystems: and to manage and maintain the irrigation Japan is blessed with abundant rivers with rich facilities. Rotation irrigation occurs in time discharges and many plains consist entirely of drought. Then the whole area is divided or largely of alluvial fans with modest gra into two sections. One section comprises the dients. Water flows by gravity efficiently three upstream main canals, the other the on the fans. Water diverted from a river by four downstream main canals. Water is sup means of a diversion dam enters a main canal plied at time intervals of 24 or 48 hours. and is delivered into secondary and lesser Each area served by a main canal is con canals one after another by gravity. Finally trolled by a subdistrict organization called a the water arrives at each paddy field. Rep bunku. The bunku manages the proper supply resentative of this type of irrigation is a of water to its fields. Executive members system on the Tedori alluvial fan in the of the bunku control diversion gates and carry Hokuriku district along the out rotation irrigation. The areal unit of (TABAYASHI,1978). rotation is the go, a political subdivision The Tedori alluvial fan, which covers about established in the Edo period. Each bunku 150 square kilometers, was formed by the area is divided into three go, the kami go or Tedori River whose length is about 71 kilo upstream unit, the naka go or midstream unit meters. The fan is almost completely covered and the shimo go or downstream unit. In with paddy fields. About 12,000 hectares addition, the bunku organizes the cleaning and of paddy fields on the fan are irrigated by a minor repairs of canals. Major repairs and fi ne network of irrigation canals basically com construction efforts are completed by the pleted in the Edo period. All water for irriga district. Irrigation in the southern sector of tion is drawn from the Tedori River by means the Tedori alluvial fan is controlled by the Irrigation Systems in Japan 45

Fig. 1 Irrigation system of the Tedori alluvial fan in 1976 (After TASAYASHI,1978)

Miyatake Irrigation Canal Land Improvement rotation irrigation, the head of the village District (Miyatake Yosui Tochikairyoku). Most directs water delivery to all paddy fields. secondary canals and ditches on the fan were The smallest ditches bringing water to the rebuilt and rearranged as straight channels inlets of paddy fields are controlled by small during an arable land reorganization project groups of farmers, and the ditches are often in the early 1900s. Kanbayashi village, for considered parts of the paddy fields they serve. example, has a regular pattern of secondary The alluvial fan type river irrigation system canals and ditches (Figure 2). Secondary thus comprises several levels of irrigation chan canals tap water from diversion works on the nels. Water use organizations exist at each main canals. Water distribution from a sec level so that the entire system has a hierarchical ondary canal is managed by a village. With management structure. During periods of 46 A. TABAYASHI

Fig. 2 Secondary canals and ditches on the Tedori alluvial fan in 1976 (After TABAYASHI,1978)

water scarcity, competition is strong among bunku, go and village level management units and many complicated water use practices have evolved. 2) Delta subtypeof river irrigation systems: Low and wet deltaic plains exist near the mouths Fig. 3 Irrigation canals and patterns of paddy fields of most large rivers such as the Shinano, in Magabuchi on the lower Tone (After Tone, Kiso and Chikugo. Naturally poorly TABAYASHI,1983) drained, the plains were marshes or parts of 1. Houselot 2. Publicbuilding lot 3. Dry field4. Rice5. W asteland6. FarmerA's land 7. Dike8. Boundaryof sub shallow bays several hundred years ago. Since sectionsof a village9 . Farmroad 10. Canal(Creek) 11 . Irri the gradient of the plains is too gentle for gationpump 12. DiversionDevice 13. Bridge14 . Shallows 1 5. River16. Farmhouse17 . Houseother than farmhouse water to flow by gravity, pumps are indis 18.Public building lot 19. Shop20. Parkinglot 21. Factory 22. Kitchengarden 23. Greenhouse24 . Wheatand Barley pensable. At the same time, drainage controls 25. Flower26. Fallow27 are also very important in the plains. An . Grass28. Rice29 . Wasteland30. V acant lot 31. FarmerA's land 32. Dike33. Farm road34 . C example of a delta type river irrigation system anal 35.River is found near the in the Kanto district (TABAYASHI,1983). Every year in March, just before the beginning Magabuchi village in Ibaraki Prefecture on of rice cultivation, at least one member of each the delta of the Tone River has 57 farm house farm household joined in the communal work holds and 88 hectares of paddy fields. Until of cleaning and dredging the canals. the 1950s there were few farm roads, and the The canal network extending widely over highly developed canal network was used for the area of paddy fields supplied irrigation transportation as well as for irrigation and water to paddies and received discharge from drainage. The width of the canals averaged them. A main canal leading from the Tone 5 to 7 meters, and the depth 0.5 to 0.6 meters. River was the key facility for obtaining irriga- Irrigation Systems in Japan 47 tion water (Figure 3-a). The counter flow also to pump water out of their fields. of the Tone River during high tide in the The irrigation procedure changed drastically nearby ocean was utilized to draw water. following an agricultural water use project When in need of water, the intake gate on the in the area after world War II. The national main canal was opened at high tide time and project first constructed dikes bordering Lake fresh water from the surface layer of the Tone Kasumigaura and the Shintone River by which River automatically flowed into the network the water level external to the area of Maga of irrigation canals. Discharge of surplus buchi village was fixed. Then drainage and water from paddy fields occurred by opening irrigation channels were completed, and pumps the gate at low tide times. A person called installed, some for drainage purposes, others the shioban, or observer of the tide, operated for irrigation (Figure 4). Once the construc the gate and no one else could touch it. When tion works for the basic irrigation and drainage water obtained by means of counter flow was systems were finished, farmland consolidation insufficient to meet needs, the pumping of proceeded for Magabuchi village and other water started. Before 1932, this meant that villages in the area. This included consolida households cooperated using foot propelled tion of farmland into regular parcels of 20 ares, water wheels. Thereafter electric pumps were straightening water distribution and drainage introduced. In late March and April just channels, and construction of farm roads so before the period for plowing and cultivation, that each parcel abutted a road. Irrigation drainage canals were closed and the drawing and drainage canals were separated and and pumping of water from the Tone River arranged along farm roads (Figure 3-b). A started. Individual farmers accomplished the few years thereafter, the irrigation canals were irrigation and drainage of their fields with changed into pipes which conducted water their own portable foot propelled wheels. Each from pump houses to spigot valves in each fi eld was irrigated by lifting water from an paddy field (IsHu and KAGAMI,1983). adjacent channel. Sometimes high levels of With the spread of pumps and advances in water in the adjacent channel forced farmers civil engineering, rapid development of delta

Fi g. 4 Irrigation and drainage systems on the lower Tone (After ISHIIand KAGAMI,1983) 48 A. TABAYASHI

tinuous creek dredging both to lower the level of the bottom and to provide fertile soil for paddies, and on careful tilling and bunding to reduce water seepage back into the creek (TANAKA,1979). The introduction of electric pumps in 1922 resulted in a tremendous reduction of working hours for rice cultivation, and the possibilty of careful manipulation of water intake and discharge. In addition, chemical fertilizers took the place of soil dressings. During the 1930s, the Saga plain enjoyed the highest yields in Japan (KAMAGATA,1947, pp. 25-32). Government projects for the improvement of irrigation and drainage in the 1950s and for land consolidation in the 1960s created many modern farming systems similar to those in fi g. 5 Networks of creek irrigation canals in the Saga plain, northern Kyushu. This area was the Tone River delta. developed early and the Jori grid pattern can 3. Pond irrigation systems be found. (Photograph by the National Insti tute of Geography, KU-85-5X, C5A-20) Ponds are small man made reservoirs that store water for irrigation. Much money is type river irrigation systems took place. The invested in their construction and maintenance, deltaic plains of the Tone, Shinano and Kiso and without continuous maintenance they are Rivers, once relatively unimportant for rice, are easily devastated by floods and persistent now leading rice producing regions in Japan. leaks (TAKEYAMA,1958, pp. 39-77). In order However, they still face danger of flooding. to supply irrigation water by gravity flow they The traditional method of water manage are located at elevations higher than the surface ment in delta type river irrigation systems, as of the paddy fields they serve. There are described for Magabuchi village, is termed two kinds of ponds. One is located at a "creek irrigation ." The best known example valley head and constructed by dividing off of creek irrigation is in the Saga plain along the valley mouth with an earthen dike. The the lowest stretch of the Chikugo River in other, called saga ike, is located on a plain Kyushu (Figure 5). Creek irrigation consists and surrounded by banks (FURUSHIMA,1967, of a few main canals delivering water from a pp. 42-67). In areas irrigated by ponds, river to many small, man made creeks. In restrictions on water use are generally severe the creeks there is virtually no flow, so they and elaborate customary water use practices function as ponds to store water. The area have evolved because of limited volumes of occupied by creeks in the Saga plain varies water (NAGATA,1971, pp. 174-195). Charac from 5 percent in some localities to 19 percent teristics of pond irrigation systems vary with in other localities (JINNAI,1984). the size of ponds and their storage capacity. All paddy fields front on creeks, but draw Ponds with a large storage capacity commonly ing water from the creeks for the paddy fields have long and widespread irrigation canal net was long a major problem because the creeks works similar to those of river irrigation sys are lower than the paddy land by 0.3 to 1.0 tems. In some cases a large pond is a "parent" meters. Until the middle of the Edo period, pond and has several or more "child" ponds bucket tapping by one or two persons was the connected to it. Single ponds mostly have only method used. Foot pedal water wheels have little storage capacity and small canal were introduced around 1780. An extremely networks. intensive form of rice cultivation then develop 1) Single pond irrigation systems: The Nara ed based on the foot pedal pumps, on con basin has many examples of single pond Irrigation Systems in Japan 49

Fi g. 6 Distribution of ponds for irrigation in the Nara basin of the Kinki district. This area is one of the oldest rice producing regions in Japan. The Jori grid pattern still exists here. However, many paddy fields are now being con verted to urban land uses. (Photograph by the National Institute of Geo graphy, KK-83-IX, C15-5) irrigation systems. Over 70 percent of all utilizing its advantage of being in the most irrigation water in the basin comes from nearly upstream position. 14,000 ponds, 1,600 with a surface of more With pond irrigation, rotation is effected than 5 hectares (NOZAKI, 1986). Villages during periods of low water. Rotation pat sharing the operation of a pond form a water terns are based on volume of water, hours of use organization called ikego. The average water flow or irrigated area. For example, irrigated area served by 32 ikegos that HORIUCHI irrigation water for the village of Ota in Sakurai investigated in 1970 was 52.2 hectares, and City comes from Ota pond, and irrigation by each organization was composed of three rotation starts on the 8th of June every year. villages. Kodaiji pond has a surface area of Four mizugashiras, leaders of irrigation elected about 11 hectares and is managed by an ikego from among farmers who own a certain mini of 6 villages named Hieda, Imaichi, Kami mum area of farm land, manage the flow of mitsuhashi, Shimomitsuhashi, Minosho and water. The cultivated area of 4.8 hectares is Ikeda (Figure 6). Among the villages, Hieda divided into four sections, and each section is the leader and claims the greatest irrigation receives water for a fixed time under the control rights because it was the home of a powerful of the mizugashiras. The average length of family and controlled neighboring villages for time of water supply is about 18 minutes per many years during the medieval period. Ac 10 ares. The order of water supply among the cording to records dating from 1666, irrigation four sections is first decided by lot and then water was supplied for three days to Hieda, rotates so that the first section becomes the for two days to Minosho and for one day each last, the second becomes the first, and so on to Shimomitsuhashi, Kamimitsuhashi and Ima (HORIUCHI,1983, pp. 149-171). Rotation periods ichi, after which the pattern was repeated. have also been measured by the time required Then Hieda, because it was located quite far to burn a fixed number of incense sticks. This from the pond, asked Ikeda to manage the method of measuring time, called senkomizu, pond in exchange for rights to draw water was found in places where planting restrictions from the pond. This condition has continued were imposed on some paddy fields during to the present (KITAMURAand HORIUCHI,1950). severe drought periods to force their farmers Ikeda has gradually enlarged its authority by to plant dry field crops. 50 A. TABAYASHI

2) Parent-child pond irrigation systems: Man on the parent pond. The third is child ponds noike pond in northeast is the largest which depend entirely on the parent pond for man-made pond used for irrigation in Japan. their water. The dependency of child ponds Its total storage capacity is 15.4 million cubic on the parent pond generally increases with meters and it serves an area of 4,600 hectares. proximity to the parent pond. In recent The pond is said to have been constructed years, irrigation in northeastern Shikoku has during the Taiho period (701-703). Its banks been improved with construction of a major failed in the year 818, after which a Buddhist canal. priest named Kukai repaired it. When the banks failed again in 1184, it was abandoned 4. Lake irrigation systems for a long time and some villages were even Lake irrigation systems take water from established on its bottom. It was again re natural lakes or ponds. They need pumps paired in 1631. The present pond was estab because the surfaces of lakes and ponds are lished by improvement work carried out in lower than some or all of the paddy fields 1959. Each November Mannoike pond started irrigated. The Koto plain along Lake Biwa collecting water by canal from the Haji River, includes a low and wet deltaic area adjacent and by June was almost full. Irrigation to the lake. Here farmers dug ditches from extended from the 20th of June to the 30th of which they lifted water using buckets called September. When the gate was opened on the taoke and also buckets called furitsurube with 20th of June, water flowed by gravity for almost ropes handled by two persons. Later they 20 kilometers, branching off into secondary and used dragon pumps, called ryukkoshi, and foot tertiary canals. Rice planting began in the propelled water wheels (TAKEUCHI,1941, pp. upstream area and proceeded downward. This 106-111). Two people could provide 10 ares was called regular water distribution. When of paddy fields enough water for rice planting rice planting was over, the gate of Mannoike in 2 to 5hours with the ryukkoshi and in 1.5 pond was closed. Thereafter, water was distri to 3hours with the foot propelled water wheels. buted according to requests from areas that Motor pumping began in the Koto plain needed irrigation water (INOKI,1937). with the introduction of steam pumps in 1885, Although water from the pond flowed down and electric motor pumps became popular three main canals to many villages at first, during a severe drought in 1922. The motori water delivery became limited largely to the zation of pumping further developed after highest 15 villages nearest Mannoike pond when World War II, encouraged by labor shortages. water in the pond droped to the level of the Construction of a modern lake irrigation system second of five drain gates. The 15 villages were called Azuchi Gyakusui started in 1940 and then irrigated by turns in accordance with was completed in 1949. In the main canal, their hectarages of paddy fields in an eight water was pumped through four steps to the day cycle (KITAMURA,1973, pp. 432-453). Some height of 29 meters above lake level. It then 60 child ponds also received water from Manno irrigated nearly 2,500 hectares (HORIUCHI,1959). ike pond. When delivery from Mannoike The Lake Kasumigaura area of Ibaraki Pre pond by canal directly to the lower villages fecture included traditional lake irrigation stoped, they relied largely upon the child ponds systems using buckets and foot propelled and obtained only supplementary water from water wheels in the 1920s. Many motorized the parent pond. pumps were installed by villages and munici The characteristics of child ponds vary palities between 1910 and 1930, however, depending on their situation. Three broad (Ibaraki Daigaku Chiiki Sogo Kenkyusho,1984, types can be identified. One is child ponds pp. 98-108). After World War II several which can irrigate their service area for almost large lake irrigation facilities were constructed all periods of rice cultivation and get parent (KOBAYASHI,1981, pp. 202-222). One, in pond water only during severe drought periods. Tsuchiura City and 15 neighboring munici The second is child ponds which have enough palities completed in 1968, lifts water 32 meters water for rice planting but otherwise depend and irrigates nearly 4,000 hectares. Irrigation Systems in Japan 51

5. Groundwater irrigation systems 1) Ordinary well irrigation systems: Farmers traditionally lifted water from wells using sweep-well buckets. Wells were distributed mostly in areas where there was not enough irrigation water from rivers or ponds to satisfy farmers' needs. In the upper parts of the Fi g. 7 Structure of a horizontal well, manbo Koto plain many wells were dug for irrigation where lake and river water were unavailable. metropolitan regions have been developed The diameter of the wells was between 1 and 2 into highly intensive horticultural lands pro meters and their depth was less than 10 meters. ducing such crops as melons, cucumbers and The volume of water pumped from the wells strawberries. Completion of their irrigation was small, and an average well could only and drainage facilities and the fact they are irrigate 10 ares of paddy fields. 1Iotor pump large and flat fields enabled farmers to start ing took the place of buckets beginning in horticulture (YAMAMOTO,et at.,1985). about 1910 (HORIUI, 1959). In addition, 2) Horizontal well irrigation systems: A special wells served paddy fields in ravines and narrow kind of groundwater well is the manbo. It is valleys and on natural levees. a horizontal well that collects groundwater In places, windmills pumped water from from a depth of a few meters (ODA,1984). Al wells. According to NAKAJIMA(1984), wind though its structure is similar to the ganat mills were used along the southern shore of in Southwest Asia, the manbo does not conduct Lake Suwa, in areas near Sakai City, on the water from a mother well. Instead, it collects Chita, Boso and Atsumi peninsulas, on the leakage water from the paddy fields on the alluvial plain along the Sakura River in Ibaraki surface above it and delivers the water to and in other places where land and sea breezes paddy fields farther downslope (Figure 7). generally occurred, where land productivity The tunnels that are the horizontal wells are was relatively high, and where labor shortages about a meter high and half a meter wide. existed. Windmills for wells appeared in the They have shafts at 20 to 30 meter intervals 1920s and disappeared in the early 1950s when for ventilation and carrying out soil (KAYANE, motor pumping became widespread. et at., 1973). Manbos are concentrated in In the late 1950s, the area of paddy fields alluvial fans at the foot of the Suzuka expanded in some areas of Japan, especially mountains in Mie Prefecture, and in addition in the Kanto district. Forests were cleared are widely distributed in the Tokai, Hokuriku and unirrigated fields leveled. Then wells and Kinki districts. were dug to irrigate the fields. Such fields, newly cultivated to rice with pumped water, 6. Torrent irrigation systems are called yikuden. The expansion of yikuden Torrent irrigation occurs in terraced paddy occurred as a result of the high price of rice field locations in mountains, sometimes on and diffusion of advanced technologies for rice landslide areas (TAKEUCHI,1984, pp. 80-261). cultivation, and because of the availability of Small streams are dammed and the water is motorized pumps (SATO,1966). conducted through small canals usually for Where water leakage from sandy soils would short distances and on gentle slopes. Where have been considerable, vinyl sheets were laid slopes become steep, water flows to the paddy under the surface soil layers of the fields. fi elds through vinyl pipes. Until the 1950s Many such paddy fields in southeastern Kanto farmers used bamboo pipes (NAKAJIMA,1974). are irrigated by wells 8 to 15 meters deep. Many of the paddy fields were formerly rain Each well can supply water to 50 ares of fields fed. Torrent irrigation systems were built (TABAYASHIet at., 1986). Some yikuden have largely during the Meiji period when farmers been changed into dry fields since rice produc suffered from severe drought. The scale of tion adjustments beean in 1970. Some in torrent irrigation is small, in most eases con- 52 A. TABAYASHI

Fig. 8 Terraced paddy fields served by torrent irrigation in Hoshino-mura, northern Kyushu. Each field is very small. The settlement is located upstream.

Fig. 9 Horisageda, dug down paddy field, in the Kashima area of eastern Kanto. It is made by digging down for about 0.3 to 3meters. Pine trees are planted on the levees to protect the fi eld against salt sea breezes and'sand storms. Irrigation Systems in Japan 53

trolled by a single farmer or several farmers, piled on levees around the paddy, the horisageda occasionally by a village. Generally a canal looks deeper. Pine trees are planted on the irrigates only a few hectares of fields, and each levees to protect the paddies from wind and fi eld is very narrow owing to locating on a sand storms, and to prevent the collapse of steep slope. For example, 12 hectares of the banks (TABAYASHIet al., 1986). paddy fields in Kiwa town are divided into more than 1300 fields. Settlements are often III. Regional patterns of irrigation systems placed in the most upstream areas of terraced paddy field locations as shown in Figure 8. Data on irrigation systems in various parts of Japan have been collected in a variety 7. Other irrigation syytems of ways using various criteria, and are avail The category of other irrigation systems able in a variety of publications. For the encompasses two general procedures by which national agricultural census, however, data paddy fields obtain water; but some researchers are collected in a standard way by munici will feel that neither represents an irrigation palities in all parts of the country. Thus it is system. A few paddy fields in many kinds of appropriate to use the census data for a study areas depend on rainfall, flows from small, of regional irrigation patterns. The most temporary springs, and general surface runoff. recent census with data on types of irrigation Whether located on steep mountain or hill systems was taken in 1970. It enumerated slopes, in ravines, in basins or on gentle slopes, fi ve types of water sources for irrigation, as the fields often suffer drought. Farmers may follows: (1) rivers, including natural lakes and dig small channels to encourage more of the man made reservoirs, (2) ponds, (3) torrents, nearby surface water to flow into a field. They (4) groundwater and (5) other. For the present may also build up the dike around a field to study, Japan was divided into 305 statistical capture more melting snow water. However, units formed by agglomerating several munici they have little real influence on the amount palities into each unit. The percentage of all and timing of the water received. villages in a statistical unit that depended on The same is true of dug down fields, called each type of water source was calculated for horisageda (Figure 9). Horisageda is made by each unit. Those calculations allowed prepa removing a half to 2 or 3meters of subsoil ration of maps that show the relative de under the surface of a field in order to bring pendence of localities in Japan on each type of the surface close to the level of the ground irrigation water source. water table (NAKAJIMA,1966). For fields that River irrigation is of great importance in commonly experience water shortages, farmers all parts of Japan except some areas near the may repeat the dig down procedure during Inland Sea and other smaller isolated areas winter, their off season. As soil dug up is (Figure 10). It prevails on the alluvial plains

Fi g. 10 Dependence of villages on river irrigation (Data source: Agricultural Census of Japan, 1970) 54 A. TABAYASHI

Fi g. 11 Dependence of villages on pond irrigation (Data source: Agricultural Census of Japan, 1970)

of major rivers, especially the plains facing water exploitation generally occurs where the Sea of Japan. It prevails too in the basins surface flows are small and water infiltrates of eastern Japan where precipitation is stored river beds and alluvial fans. on neighboring mountains in the form of snow Irrigation systems in the other category to be released in spring and summer. occur in places in the Kanto district, south Pond irrigation is significant in the Inland eastern Tohoku, parts of the Hokuriku and Sea area, including northern Kyushu and parts Tokai districts, western Chugoku and the of the Kinki district, where river irrigation is western coast of Kyushu. These are places less important (Figure 11). In 1979, the with rain fed paddy fields located in ravines, number of ponds in Japan with a surface area on steep mountain slopes, and on level surfaces of more than one hectare was 97, 564, and about near the water table. The productivity of the 69 percent of them were located in the Inland places is low and the total area of the paddy Sea area. Ponds are significant also in small fi elds utilizing irrigation systems in the other areas such as the southern part of Boso penin category decreased remarkably after rice pro sula, the western part of the Kanto plain, the duction adjustments began in 1970. Noto peninsula and the coastal plains of both In order to depict on a single map a typology southwestern and northeastern Tohoku. In of irrigation systems in Japan, the component general, pond irrigation has developed where ratio of the sources of irrigation water (river, precipitation is generally low, rice cultivation pond, groundwater, torrent and others) was has been well developed for centuries, and calculated for each statistical unit. The ir rivers are small but the ratio of paddy field rigation type in each statistical unit was to total land area is very high (TAKEUCHI,1939). determined by employing WEAVER'Smethod Torrent irrigation occurs mostly in southern as modified by K. Doi (1970). Figure 12 shows Shikoku, western Chugoku, central Kyushu, the regional pattern of irrigation systems. the Kui peninsula, the central part of , River irrigation extends overwhelmingly the northeastern part of Tohoku and the across wide areas especially in eastern Japan, small islands of western Japan. These places although even in western Japan it can be seen have few large plains and many terraced paddy in Sanin and southern Kyushu. On the other fi elds on hill and mountain slopes. hand, pond irrigation is of major significance Groundwater irrigation is mainly distributed in Kagawa, Hiroshima, Hyogo and Osaka in central Kyushu, northern Shikoku, the Prefectures, and river-pond irrigation borders coastal plain around Lake Biwa and the areas of pond irrigation. The general area in southern part of Kanto. Horizontal wells which pond irrigation is important thus ex have been constructed.dorj the alluvial fans at tends from northern Kyushu through the the foot of the Suzuka mountains and on Inland Sea area into the Kinki district. alluvial fans of basins in central Japan. Ground Elsewhere, river-groundwater irrigation and Irrigation Systems in Japan 55

Fig. 12 Typology of irrigation systems in Japan (Data source: Agricultural Census of Japan, 1970)

Fi g. 13 Annual precipitation in Japan (After the National Atlas of Japan, 1977) river-torrent irrigation are located. Although on the Inland Sea, areas of mixed irrigation in eastern Japan pond irrigation is found only types such as the Kanto district and scattered in the Boso peninsula, river-pond irrigation torrent irrigation regions in some mountainous occurs over the area from northern Kanto to and hilly areas. southeastern Tohoku, in the Noto peninsula Regional differences in the relative impor of Hokuriku and on the Noshiro plain in tance of the several types of irrigation systems northwestern Tohoku. are caused by various factors. Annual pre In the Kanto district, river irrigation pre cipitation is an important factor. The dis vails on alluvial plains along the major rivers, tribution of annual precipitation in Japan, as while both river-groundwater irrigation and shown in Figure 13, corresponds well to the river-other irrigation extend over diluvial up regional pattern of irrigation systems, except land and hills. River-torrent irrigation is in . Precipitation of 1,500 milli distributed in hilly and mountainous areas of meters or less is coincident with such areas as northeastern Tohoku, Hokuriku, Tozan, the the Inland Sea area where pond irrigation is Kui peninsula, western Shikoku and east dominant, and the Kanto district and south central Kyushu. eastern Tohoku where several types of irriga Fi gure 12 suggests that Japan is dominated tion are found. The torrent irrigation regions by river irrigation regions. In addition, how generally have annual precipitation of more ever, it depicts a pond irrigation region centered than 2,500 millimeters. Parts of the country 56 A. TABAYASHI with precipitation of 1,500 to 2,500 milli 1986). In addition, pollen analyses on un meters are mostly classified as river irrigation earthed domesticated rice suggest the possi areas. bility of rice cultivation around 1700 B. C. and But natural conditions such as precipita of a wide distribution of rice cultivation over tion, landforms and soils are not alone in western Japan in 300 B. C, at the end of Jomon influencing the regional pattern of irrigation. period (NAKAMURA,1982). It is possible that The age of agriculture in the various parts rice cultivation began in Kyushu before 1000 of the country, the intensity of agriculture, B.C., diffused into western Japan within the ratio of paddy field area to total land area, several decades and reached northern Tohoku technological traditions and economic con by 200 or 100 B. C. (ITO, 1984). ditions also are influential. The regional The total area in paddy fields increased pattern of irrigation systems has been formed rapidly during the Kofun and Nara periods partly through the historical processes of from about 300 A. D. to 800 A. D. According development. to ANDO(1969), paddy fields occupied about 1,050,000 hectares in the middle of eighth IV. Development of irrigation systems century, a number equivalent to one-third of in Japan the present paddy field hectarage. There after, the area of paddy fields remained fairly 1. Expansion of rice cultivation and the stages stable until the Edo period, when rapid land of irrigation development development occurred. As a result, paddy Agronomists, botanists, archaeologists, his fi elds occupied 2,590,000 hectares in 1881, torians and geographers have shown concerns double the hectarage at the beginning of the for the origins of rice cultivation. Recent Edo period (KIKUCHI,1977). The paddy Studies by MORINAGA(1972), WATANABE(1977) fi eld area increased further after the Meiji and NAKAGAWARA(1985) suggest that rice was Restoration (1868), and reached 3,420,000 probably first domesticated in Yunnan of hectares in 1970. In particular, substantial southern China or in Assam or the Himalayas development of rice cultivation, in terms both of northern India, and then spread into the of yield and of hectarage, took place in north alluvial plains of the Chang River. From eastern Japan. Between 1890 and 1970, the southern China rice came into northern Kyushu rice area in the Tohoku district increased by either directly or via southern Korea (ANno, 60 percent. In Hokkaido, rice fields increased 1951, pp. 12-52). from 3,000 hectares in 1880 to 290,000 in Until recently, rice cultivation was thought 1970 (TABAYASHI,1985). to have started in northern Kyushu in the As rice growing expanded and rice cultiva third century B. C. (SUGIHARA,1977, pp. 25 tion practices developed, so too did irrigation 36). It was believed then to have diffused into practices. The development stages of irriga the southwestern part of Honshu, and to have tion systems in Japan are summarized in reached the Nobi plain in central Honshu by Fi gure 14. The first stage extended from the 100 B.C. Further, rice cultivation was thought beginning of rice cultivation to the end of the to have begun in the southern part of the about 300 A. D. The second Tohoku district by the first century A. D. stage lasted through the Kofun and Nara (SATO,1971, pp. 33-100), and to have reachedd periods (approximately 300 to 800 A. D.). the northernmost areas of Honshu in the The third stage was the medieval period (ap third century A. D. proximately 800 to 1450 A. D.). The fourth In the past few years, prehistoric sites of stage began with the Sengoku period of civil paddy fields have been discovered in all parts wars and continued to the end of Edo period of Japan except Hokkaido. Important sites (approximately 1450 to 1867 A. D.). The are in northern Kyushu dated near the end fifth stage began with the Meiji Restoration in of the Jomon period around 1,000 B. C. and 1868 and extends to the present. in northernmost Honshu dated in the middle Yayoi period, 100 B. C. to 100 A. D. (TAZAKI, Irrigation Systems in Japan 57

Fig. 14 Evolution of irrigation systems and expansion of farmland and population (Data source: KITO,1983; ANDO, 1969)

ravines served for irrigation. Archaelogists 2. The development stages of irrigation systems have unearthed intake dams that once stretch 1) Through the Yayoi period (before 300 A.D.): ed across streams 10 meters wide, and irriga The first paddy fields probably were located tion canals with diversion devices (MASAOKA, in backmarshes behind natural levees and on 1983). Each paddy field was small, one or two wet lands in shallow valleys. fields appeared ares, and its circumscribing dike included a next on gentle slopes near the marshes. Then water intake structure. Excavations at Toro paddy fields requiring irrigation facilities ap in Shizuoka Prefecture uncovered third century peared on natural levees and diluvial uplands paddy fields totaling 7.5 hectares and irrigated (HACHIGA,1968; KONDO,1985, pp. 95-101). by a canal more than 370 meters long. The The remains of paddy fields uncovered in fi elds, located a little higher than nearby Itazuke, northern Kyushu, date from the ninth marshes, averaged a large 14 aces in size. century B. C. Located on marsh land, they Marshes around the paddy fields remained were divided into parcels by wide dikes edged uncultivated (SUGIHARA,1968). with wooden pickets. A drainage ditch abut 2) The Kofun and Nara periods (300 to 800 ted the fields. Because the early paddy fields A.D.): During the Kofun and Nara periods, lay on wet lands which at times had excessive marshlands were replaced by dry land or amounts of water, drainage facilities were upland surfaces as the favored locations for required and farmers practiced water control paddy fields, and they expanded widely to (YAMAZAKI,1982). fill alluvial plains and basins along small and After the second century B. C., paddy fields medium size rivers (HACHIGA,1987). Strong gradually were expanded from the marshes intercommunity organizations mobilized many onto bordering uplands. Small streams from laborers for construction of canals 20 to 30 58 A. TABAYASHI

meters wide and several kilometers long on but water use practices advanced with new alluvial uplands. They drew water from methods of water delivery based on time dura diversion dams constructed across rivers as tion and new forms of diversion structures, wide as 50 to 70 meters (SUGAWARA,1980). some of which were used until very recently. At the same time, a technology evolved for Irrigation devices such as buckets handled by building ponds and small reservoirs by shutt two persons and water wheels were newly ing off the heads of ravines with small earthen introduced (HOGETSU,1943, pp. 23-48). dams. In the fifth century, advances allowed 4) The Sengoku and Edo periods(1450 to 1867 construction of ponds completely surrounded AD.): The political and economic authority by man made banks (KAMEDA,1973, pp. 24 of some of the prominent families and some 36). Pond irrigation was commonly superior of the influential farmers gradually grew to to river irrigation because ponds often had a the point where they became powerful lords more stable water supply. called sengokudaimyo during the civil wars of In the Kinki, Setouchi and northern Kyushu the mid-fifteenth century. As sengokudaimyo, districts, areas of alluvial plains were laid out they utilized the advanced technologies of with the well ordered Joni grid pattern of rural castle building and mining to construct irriga paths, ditches and fields. The interlacing tion facilities along the upper and middle networks of paths and ditches divided an stretches of large rivers. In particular, they area into units approximately 109 meters created huge areas of new paddy fields in square, each further divided into 10 subunits western Kyushu and the districts of Chubu called allotments (KINDA,1986). Ponds con and Kanto with the completion of irrigation structed or rebuilt were adapted to the pattern, systems based on large rivers. Many river and irrigation water passed through canals irrigation systems constructed during the Sen and ditches whose locations were defined by goku and Edo periods were on alluvial fans. the patterns (TANIOKA,1964, pp. 25-41). The Various engineering technologies for irriga nation owned all land at that time, and offered tion and for river flood control were developed free of charge two allotments of paddy fields, by the sengokudaimyo. The technologies have about 24 ares, to every male six years of age come to be called river training methods. or older. Females received two-thirds of that Among them, the Kamigata method developed amount. Only a strong government could in the Kinki district, the Mino method from carry out such an ambitious program and also the Tokai district and the Koushu method construct and maintain the facilities. figures from the Yamanashi Prefecture area were 5 and 6 show areas of modern Japan that famous. Important parts of the methods reflect the Joni grid pattern. were integrated into the Kanto river training 3) The medieval period (800 to 1450 A.D.): method in the early seventeenth century and With the medieval period, the influence of the the Kishu river training method in the early national government decreased so that it no eighteenth century (KIKUCHI,1986). The longer carried out major water utilization and Kanto method attempted to control flood river flood control projects, and the area of waters by widening river beds, by lengthening paddy fields did not increase much. On the rivers through the creation of meanders, by other hand, lords of manors, locally prominent sending excess water into holding basins, and families and influential farmers redeveloped by altering the paths of rivers. Its techniques farmland and engaged in small scale land re strongly affected development of the Tone clamation projects. For example, they built River watershed, particularly regarding flood small ponds in ravines to irrigate narrow strips control in the Tokyo area and expansion of of paddy fields and opened terraced paddy arable land through diversion of the Tone fi elds on hill and mountain slopes. The de and Ara Rivers to their present paths (OKUMA, velopment of irrigation systems proceeded in 1981). The Kishu river training method con terms of efficient usage of irrigation water. trolled floods by constructing high and con Paddy fields and canal networks defined by tinuous dikes along rivers, straightening the Joni grid pattern continued functioning, meanders, and leading flood waters to the sea Irrigation Systems in Japan 59 as directly as possible. Additional irrigation Hensan Iinkai, 1982, pp. 51-132). Another, water was obtained by tapping major rivers in the Nasu canal project completed in 1884, more places, and wider irrigation canals were reclaimed an alluvial fan area in northern built. Construction of the Minumadai irriga Kanto. tion canal and reclamation of Minuma pond in Until about 1890, it was individual farmers Saitama constituted major accomplishments of who created small paddy fields in Hokkaido this method. The pond was drained and about and dug the wells to irrigate them. Then 10,000 hectares of paddy fields were reclaimed. several irrigation canals were built by villages Then the fields were irrigated by the new canal to create a few hundred hectares of paddy (SHINZAWA,1955, pp. 241-358). fi elds. With the turn of the century, the Even the deltaic plains of large rivers could government supported reclamation associa be reclaimed by the technologies of the river tions called Doko Kumiai established to training methods. In addition, construction expand the paddy field area in Hokkaido of continuous dikes along rivers encouraged (SHICHINOHE,1984). They constructed some extension of deltaic plains and beaches. The important river irrigation systems with long deltas of such rivers in eastern Japan as the canals that served thousands of hectares of Iwaki, Kitakami and Tone experienced major fi elds. Partly as a result of their work, rice development, as did marshes and beaches fi elds increased in Hokkaido from 3,000 hec along the bays of Ise, Osaka and Ariake and tares in 1880 to 200,000 hectares in 1930 along the Inland Sea (KIKUcHI,1977). The (KAWAGUCHI,1935). farmland area expanded. However, some of In many localities over Japan, private the newly cleared arable lands suffered drainage individuals such as wealthy landowners en problems beginning 70 to 80 years after re gaged in irrigation and drainage development clamation because of sand and mud deposited works. They conducted the reclamation of at the mouths of drainage canals and because Lake Junichogata in Toyama Prefecture, the of rises in river beds owing to siltation. Some repairing of Iruka pond in Aichi Prefecture and major problems of poor drainage were not the improvement of drainage in Kuse village, solved until the introduction of motor pumps Kyoto Prefecture, for example. They also in the Meiji period. built a number of large irrigation works in In general, land development efforts during the Tokai district. Among them was the the Edo period brought a rapid expansion of Meiji irrigation canal, completed in 1884. It paddy fields and of rice yields. The paddy obtained irrigation water from the Yahagi fi eld area doubled and rice production tripled. River, and irrigated 8,800 hectares of newly Cultivation of rice on alluvial plains along cleared paddy fields on diluvial uplands large rivers was widespread and the essential (AONoand BIRUKAWA,1969, pp. 252-258). pattern of Japanese irrigation, with river A distinctive land improvement activity of irrigation as the center, was established in the Meiji period came to be known formally the Edo period. Where pond irrigation pre in 1899 as the Arable Land Reorganization dominated, isolated ponds were in places con Program. It aimed at consolidation of farms nected with one another to create bigger by land exchange, regularization of fieldshapes, systems of parent-child ponds. land reclamation, conversion of unirrigated 5) The Meiji Restoration to the present (from farmland to irrigated paddy fields and con 1868): In the late 1800s the government con struction of irrigation and drainage facilities ducted a number of land development projects. (LATZ, 1986, p. 33). Before the law that One was construction of the Asaka canal in created the formal program was enacted, there Fukushima Prefecture, Tohoku district, in were groups of farmers in many parts of the 1882. The 53 kilometer canal took water nation who wanted to consolidate the widely from Lake Inawashiro to irrigate about 2,000 scattered fields that comprised their individual hectares of new paddy fields and to supply farms, to straighten their irrigation ditches, supplementary water to 3,200 hectares of or to change their irregularly shaped fields other paddy fields (Asakasosui Hyakunenshi into rectangular shapes. Some of the groups 60 A. TABAYASHI worked on their own, using traditional Japanese arable land reorganization projects often fol techniques to accomplish such tasks in their lowed the prefectural projects. own villages. There was straightening of Use of motorized pumps for irrigation and farm roads and irrigation ditches in Shizuoka drainage expanded rapidly during the 1920s Prefecture, for example. Then when in and 1930s. In the very low and poorly formation on European ways of accomplishing drained parts of the deltas of the Shinano, those tasks became available in the 1880s, Tone and Kiso Rivers, drainage pumps allowed farmers in Ishikawa Prefecture used the paddy fields waterlogged by siltation of gravity European technology to adjust the boundaries drainage channels to produce rice effectively of their fields. This sort of farmer interest again. Small electric pumps became popular led to enactment of the Arable Land Re to tap water from creeks in many areas but organization Law in 1899. Arable land re especially in the Saga plain of Kyushu (KAMA organization was strongly desired by some GATA,1950, pp. 16-28). landowners so that the total area of improved Early hydroelectric power companies made paddy fields amounted to about 247,000 hec agreements with irrigation cooperatives to use tares in 1911, with an additional 214,000 the heads of irrigation canals for power genera hectares by 1917. In the 1920s, the hectarage tion. In return, the power companies re of improved paddy fields amounted to about constructed and repaired old irrigation facil 15 percent of the total (Suiri Kagaku Kenkyu ities. In some places, a power company would sho,1962, pp. 16-33). combine the headworks of several irrigation The Meiji period also saw irrigation and systems in order to create a large canal with a drainage works accomplished as parts of river larger flow of water that would generate more fl ood control projects. Floods were generally power. Then the company agreed to send more destructive along segments of rivers water from the large canal into each of the where several irrigation diversion dams several irrigation systems in accordance with stretched across them than where there was the amounts of water the systems had formerly only one dam. Thus, where a major flood received (SHINZAWA,1962, pp. 129-146). The destroyed a series of dams and their associated spread of hydroelectric and other power com water intake structures, the rebuilding process panies made electricity widely available for sometimes included consolidation to create only pumping. one new dam and one river intake. That In the 1930s and 1940s the national govern meant, of course, a restructuring of the upper ment demonstrated renewed interest in irriga parts of the main canals of the irrigation tion for purposes of enhancing food production systems served by the dams. The first major during the worldwide economic depression intake consolidation occurred on the Joganji and the war and of providing empolyment for River in Toyama Prefecture in 1881 on the demobilized soldiers and repatriates follow advice of J. D'RIKE. A few years later, seven ing the war. The Farmland Development old water intakes were amalgamated into one Public Corporation, instituted in 1941, engaged on the right bank of the Tedori River when in a number of large scale construction pro the prefecture repaired dikes and irrigation jects. Responsibility for projects not com facilities destroyed by a big flood in 1886. pleted in 1949 was conveyed to prefectural The national government began supporting governments and other national government half the cost of irrigation and drainage pro agencies. Most all projects were consum grams sponsored by the prefectures in 1923, mated by the 1960s. but only for projects that benefited an area During the 1950s, 1960s, and 1970s, irriga of more than 500 hectares. This program tion activity generally took three forms: had a wide ranging impact on irrigation irrigation of areas of dry crop fields, competi systems all over Japan. Modern headworks, tion for water with cities and industry, and including improved diversion dams and intakes, improvement of irrigation facilities in associa and main canals of advanced design came into tion with farmland consolidation projects. The wide use. Secondary canal improvements and availability of small pumps and the abundance Irrigation Systems in Japan 61 of ground water in Hokkaido and the Tohoku subsoil of fields was compacted. Where district encouraged individual and cooperative needed, undersurface drainage structures were enhancement of the productivity of dry fields provided (SHIRAI,1977, pp. 284-300). The in those areas by making them irrigable projects reached a peak in the mid 1970s. (M0T0KI,1982). Such development work also Almost all facilities for agricultural water use occurred elsewhere, including the prefectures ranging from major to minor were improved; of Saitama, Tochigi and Ibaraki in the Kanto modernized and unified irrigation and drainage district. In addition, canals such as the Aichi systems were completed (TABAYASHI,1981). and Toyokawa canals were built to supply The necessity for regulation and management water to dry fields on uplands. The area of agricultural water use by groups of farmers served by the latter, in particular, has grown disappeared almost everywhere. Except in into one of the most productive and profitable some areas, each farmer may take water freely. horticultural regions in Japan (NAKAJIMA, In place of the farmers' own control of irriga 1980 and 1986). tion systems, managers of authorized land At the same time, water for agricultural improvement districts now simply maintain use faced strong competition from cities, in the physical facilities (TABAYASHI,1982). Many dustry and hydroelectric power plants that customary water use practices have disap grew rapidly and had tremendous appetites peared from use. for water (MORITAKI,1982). Conversion of land from agricultural to urban use often V. Conclusion caused malfunctions in nearby irrigation sys tems and occasionally the destruction of such The development of rice cultivation regions systems (SHIRAI,1971). In western Japan in Japan has been closely related to progress where pond irrigation is important, many in the development of irrigation systems. ponds were polluted or destroyed by urban Irrigation systems have played an important expansion (KAWAUCHI,1983). role in forming the essential features of Japa With the advance of industrialization and nese rice producing regions. In this paper, urbanization, the character of farming changed. irrigation systems are classified according to Farmers generally were able to find non-farm source of water, and their regional patterns employment at attractive wages so that the within Japan are examined. The historical number of part time farmers increased greatly, development of irrigation systems is described especially during the most rapid growth period in order to explain some of the regional from the early 1960s to the early 1970s. A features. major desire of the part time farmers was to Irrigation systems in Japan can be classi reduce the amount of labor devoted to farm fi ed into (1) river, (2) pond, (3) lake, (4) ground work. The government, recognizing that de water, (5) torrent, and (6) other. River irriga sire and also wanting to achieve higher levels tion systems encompass alluvial fan and delta of agricultural productivity, engaged in activi subtypes. Pond irrigation systems include ties to streamline farming. The activities single ponds and parent-child ponds. Within were incorporated in Farm Consolidation Pro the groundwater category are ordinary vertical jects begun in 1963..The intent of a project wells and horizontal wells. River irrigation was to increase the productivity of paddy systems are most important in total hectarage fi elds by improving the qualities of local and number of villages served. The other features of the agricultural infrastructure. The types are locally important. layout pattern of field boundaries, land pro River irrigation systems extend overwhelm perty boundaries, irrigation and drainage ingly across wide areas, especially in eastern channels and farm roads in a village area was Japan. Pond systems prevail in parts of altered to create a rectangular pattern with western Japan, especially near the Inland Sea. farmland blocks of 30 ares, and with a road, Various types of irrigation systems exist an irrigation channel, and a drainage channel together in the Kanto district. Torrent sys adjacent to each block. Where desirable, the tems are common in mountainous and hilly 62 A. TABAYASHI

areas. The regional patterns of irrigation are obliged to Professor Shozo Yamamoto at the Univer importantly defined by natural conditions such sity of Tsukuba who guided me with endless patience as precipitation and landforms but have also in every stage of my study on agricultural water use been influenced by economic and cultural in Japan. I owe gratitude to Professor Canute conditions. VanderMeer at the University of Vermont who helped Early paddy fields probably evolved in my study with many ideas and suggestions. I also would like to express my thanks to Miss Wendy marshy locations. Later, irrigation water was Rainford for her reading the manuscript. drawn from small streams. Then ponds were constructed, especially in western Japan, and (Received March 12, 1987) (Accepted May 16, 1987) diversion weirs on small and medium size rivers came to be utilized. These develop ments encouraged rapid expansion of paddy References fi elds from about 300 to 800 A. D. Although little land reclamation occurred in the medieval ANDO, H. (1951): Nihon kodai inasahushi zatsuho (Essays on the history of rice in Japan). Chikyu period from 800 to 1450, improvement of Shuppan, Tokyo, 163p. irrigation facilities and rationalization of water ANDO,H. (1969): Origin and disperse of Japanese rice, use practices proceeded. In the west, the In K. YANAGIDA,et al. (eds.): me no nihonshi patterns of irrigation networks based on small (Japanese history of rice). 269-330, Chikuma-Shobo, and medium size rivers came to reflect the Joni Tokyo, 374p. (J) grid pattern. With the 1500s, developments AONO, H. and S. BIRUKAWA,(eds.) (1969): Nihon in construction techniques including dike chishi, Aichi-ken, Gifu-hen (Geography of Japan, building enabled cultivators to use first the Aichi and Gifu Prefectures). Ninomiya-Shoten, upper and middle parts of large rivers as Tokyo, 603p. sources of irrigation water, and then the deltas, ARAI, S. (1986): Tochi, mizu, chiiki: nogyo chiri and to establish fine irrigation networks on gahu josetsu (Land, water and region: Introduction to agricultural geography). Kokon-Shoin, Tokyo, 137p. extensive areas of plains along the large rivers. Asakasosui Hyakunenshi Hensan Iinkai (1983): Asa The development of rice production after the kasosui hyahunenshi (Hundred year history of the Meiji Restoration in 1808 also depended on Asaka canal). Asakasosui tochi kairyoku, Kori execution of irrigation and drainage projects. yama, 623p. The basic features of irrigation systems in Department of Agricultural Land, Ministry of Agri western Japan were formed in the Kofun and culture and Forestry (ed.) (1960): Nippon nogyo to Nara periods, by about 800 A. D. On the other mizu riyo (Agriculture and water use in Japan). hand, the main irrigation systems in eastern Suiri Kagaku Kenkyusho, Tokyo, 391p. Doi, K. (1970): The re-examination and the modifica Japan are river systems developed in the Sengoku and Edo periods, from about 1450 tion of Weaver's method of combination analysis. to 1807. Most irrigated land in Japan today The Human Geography, 22, 1-18.(J-E) FURUSHIMA,T. (1967): Tochini kizamareta rekishi is served by river irrigation systems. Agri (History printed on the land). Iwanami-Shoten, cultural water use projects carried out afterr Tokyo. 222p. the Meiji Restoration improved and modified GRIGG,D. (1984): An introduction to agricultural geo all facilities from diversion dams and main and graphy. Hutchinson, London. 204p. secondary canals to minor ditches and the HACHIGA,S. (1968): The development of irrigation in inlets of paddy fields. Strongly unified and ancient Japan: its relation with the nature of soil. efficient irrigation and drainage systems have Journal of Japanese History, 96, 1-24. (J) been established, and regulation of water has HIRASHIMA,S. (1984): The view point of irrigation become unnecessary nearly everywhere. Almost development, In A. TAMAKI,et al. (eds.): Suiri no all farmers in Japan can take water freely shakai kozo (Social structure of irrigation). 255-308, from their modern systems. Tokyo-Daigaku Shuppankai, Tokyo, 327 p. (J) HOGETSU,K. (1943): Chusei kangai no kenkyu (Research on the history of irrigation in the medieval period). Acknowledgements Unebi-Shobo, Tokyo, 416p. HoinucHI, Y. (1959): A geographical study of reserve In relation to my present study, I am especially stream irrigation on the plain to the east of Lake Irrigation Systems in Japan 63

Biwa. Geographical Review of Japan, 32, 70-82. KITAMURA,T. (1950): Nihon kangai suiri kanko no (J-E) shiteki kenkyu: soron hen (Historical research on HORIUCHI,Y. (1970): On the distribution of the water Japanese irrigation customs: General volume). utilization groups and the utilization regulations in Iwanami-Shoten, Tokyo, 503p. the Nara basin. Geographical Review of Japan, 43, KITAMURA,T. (1973): Nihon kangai suiri Kanko no 171-182. (J-E) shiteki kenkyu: kakuron hen (Historical research on HORIUCHI,Y. (1983): Nara bonchi no kangaisuiri to Japanese irrigation customs: Case studies volume). sonraku kozo (Irrigation systems and village stru Iwanami-Shoten, Tokyo, 624p. cture in the Nara Basin). Nara Bunka Kenkyusho, KITO, H. (1983): Nippon nisennen no jinkoshi (Two Yamatotakada, 282p. thousand year history of population in Japan). PHP Ibaraki Daigaku Chiiki Sogo Kenkyusho (1984) Kenkyusho, Kyoto, 206p. Kasumigaura: shizen, rekishi, shakai (Lake Kasumi KOBAYASHI,M. (1981): Kasumigaura niokeru nogyo gaura: nature, history and society). Tokyo, 300p. suiri ken (Water right for irrigation in Lake Kasumi IMAMURA,N. et al. (1973): Tochikairyo hyakunenshi gaura). Bujin-Shobo, Tokyo, 315p. (Hundred year history of land improvement works). KONDO,Y. (1985): Nippon kodaigaku kenkyu josetsu Heibon-Sha, Tokyo, 415p. (Introduction to ancient ). Iwanami INOKI, H. (1937): A geographical study on the irriga -Shoten, Tokyo, 353 p. tion system in the Marugame plain. Otsuka Chini LATE,G. (1986): Contemporary and historical irrigation Gakkai Ronbunshu, 5, 1143-1189.(J) in Japan: Selected terminology and illustrations. IsHII, H. and M. KAGAMI,(1983): Changes of landscape Toyota Foundation, Tokyo, 85p. and land use in Azuma-mura, Ibaraki Prefecture. MASAOKA,M. (1983): Irrigation and paddy fields in Area Research Papers, 5, 7-27. (J) the Yayoi and Kofun periods: Cases of western ITO, N. (1984): Formation of rice cultivation in Aomori Japan. Kodaigaku Kenkyu, 99, 1-21. (J) Prefecture. Tohoku Bunka Kenkyusho Kiyo, 16, MATSUI,I. (1964): Irrigation system of paddy field in 1-26. (J) the Nasu basin: A problem of the regional division. JINNAI, Y. (1984): Creek irrigation and society, In Ochanomizu University Studies in Arts and Culture, A. TAMAKI, et al., (eds.): Nogyo suiri no shakai 17, 153-183. (J) kozo (Social structure of irrigation), 169-208, Tokyo MORINAGA,T. (1972): Origin of rice in Japan, In. H. - Daigaku Shuppankai, Tokyo, 327p. (J) KIHARA,(ed.): Reimeiki Nihon no seibutsushi (History KAMAGATA,I. (1947): Sagaken nogyo no tenkaikatei of creatures at the daybreak of Japan). 69-73,Yokendo, (Development of agriculture in ). Tokyo, 436p. (J) Norinsho Nogyo Sogo Kenkyusho, Tokyo, 389p. MORITAKI,K. (1982): Gendai Nikon no mizu shigen KAMEDA,T. (1973): Nihon kodai yosuishi no kenkyu mondai (Water resource problems of modern Japan). (Research on ancient history of irrigation in Japan). Chobun-Sha, Tokyo, 379p. Yoshikawa Kobunkan, Tokyo, 416p. MOTOKI,Y. (1982): A study of paddy fields reclamation KAWAGUCHI,T. (1935): Rice-culture in Hokkaido, its after World War II, especially on the reclamation northern boundary of Japan (second reports). of paddy field irrigating underground water in the Geographical Review of Japan, 11, 1-23, 155-196. (J) Tsukidate hill land area, northern part of Miyagi KAWAKAMI,K. (1983): The abandonment of irrigation Prefecture. Water Science, 26(2), 88-112. (J) reservoirs in Matsubara city. The Human Geography NAGATA,K. (1971): Nikon nogyo no suiri kozo (The 35, 328-344. (J-E) structure of irrigation in Japanese agriculture). KAYANE,I. et al. (1973): On the "Manbo", an under Iwanami-Shoten, Tokyo, 337p. ground aqueduct, in Mie Prefecture. Geographical NAGATA,K. et al. (1982): Nogyo suiri no gendaiteki Review of Japan; 46, 600-604. (J) kodai (Recent subjects of agricultural water use). KIKUCHI, T. (1977): Shinden kaihatsu (Development of Norm Tokei Kyokai, 373p. new settlements). Kokon-Shoin, Tokyo, 538p. NAKAGAWARA,M. (1985): Ine to Ine no furusato (Rice KIKUCHI, T. (1986): Zoku shinden kaihatsu (Develop and its origin). Kokon-Shoin, Tokyo, 234p. ment of new settlements, second series). Kokon NAKAJIMA,M. (1966): The management of the "Dug Shoin, Tokyo, 758p. down paddy fields" and the cultivation of dry KINDA, A. (1986): The Joni plan in ancient and med fi elds on the Kasumigaura coastal sand dune, ieval Japan. Geographical Review of Japan, 59, (Ser. Ibaraki Prefecture. Geographical Review of Japan, B), 1-20. 39, 84-102. (J-E) KITAMURA,T, and Y. HORIUCHI,(1950): Two special NAKAJIMA,M. (1974): A geographical study of rice water rights and social structures in Yamato. The terraces region in Japan. The Scientific Research, New Geography, 4(8), 28-38. The School of Education, Waseda University, 23, 64 A. TABAYASHI

57-73. (J) fi elds of Toro site. Kakashi, 2, 3-7. (J) NAKAJIMA,M. (1980): The development of upland SUGIHARA,S. (1977): Nihon noko shakai no keisei fi eld irrigation in Japan. The Scientific Researches, (Formation of agricultural society in Japan). Yoshi The School of Education, Waseda University, 29, kawa Kobunkan, Tokyo, 380p. 15-35. (J) Suiri Kagaku Kenkyusho (1962): Nogyo mizu shigen NAKAJIMA,M. (1984): A geographical study on wind (Water resources for agriculture). Chijin-Shokan, mill irrigation in Japan. Geographical Review of Tokyo, 296p. Japan, 57, 307-328.(J-E) TABAYASHI,A. (1978) The irrigation system on the NAKAJIMA,M. (1986): Upland field irrigation made Tedori alluvial fan. Tsukuba Studies in Human available by three irrigation projects in Aichi Pre Geography, 2, 109-130. (J-E) fecture. Journal of Geography, 95(3) 45-65. (J-E) TABAYASHI,A. (1981): Spatial structure of the irriga NAKAMURA,M. (1982): The Jomon and Yayoi periods tion systems in the Hokuriku district. Geographical by pollen analysis. Rekishi Kokon, 74, 71-77. (J) Review of Japan, 54, 295-316. (J-E) Nogyo Suiri Kenkyukai (1980): Nihon no nogyo TABAYASHI,A. (1982): Formation of the spatial struc yosui (Water for agriculture in Japan). Chikyu-Sha, tures of irrigation systems in the Horkuriku district. Tokyo, 342p. Tsukuba Studies in Human Geography, 6, 1-28.(J-E) NOZAKI, K. (1986): Irrigation in the Nara basin, In TABAYASHI,A. (1983): Transformation of a rice growing K. FUJIOKA, (ed.): Shin nihon chishi semina, 5, villages in Azuma-mura, Ibaraki. Area Research Kinhi (New geography of Japan, 5, Kinki). 79-93, Papers, 5, 75-87.(J) Taimei-Do, Tokyo, 189p. TABAYASHI,A. (1985): Development of rice cultivation ODA, T. (1984): Studies of the origin and construction in the northeastern part of Japan. Annual Report of Qanat: a review. The Human Geography, 36, 433 of the Institute of Geoscience, University of Tsukuba, 455, (J) 11, 1.0-14. OGAWA,M. (1953): Increase in arable lands and the TABAYASHI,A. et al. (1986): Changing rural settle beginning of land improvement works, In S. TOHATA, ment in Shari, Hazaki-machi. Area Research Papers, et al. (eds.): Nihon nogyo hattatsushi (Japanese history 8, 95-121. (J) of agricultural development). 119-287, Chuokoron TAKEUCHI,J. (1939): Distribution of irrigation ponds Sha, Tokoy 788p. (J) in Japan (Except Hokkaido). Geographical Review OKUMA,T. (1981): Tonegawa chisui no hensen to suigai of Japan, 15, 285-300, 319-342, 444-457.(J) (Changes in flood control of the Tone River and flood TAKEUCHI,J. (1941): Geographical study of irrigation damage). Tokyo-Daigaku Shuppan Kai, Tokyo, pumps in Japan. Geographical Review of Japan, 17, 393p 35-59, 96-123, 106-111, 161-188.(J) SATO, T. (1966): Development of Rikuden, dry-paddy TAKEUCHI,J. (1980): Nihon no inasaku hatters no kiban: fi elds, along the Tone River. Chin, 11(4), 34-40. tameike to yosuki (Bases for the development of SATO, T. (1971): Nihon no kodai mai (Ancient rice in rice cultivation in Japan: Irrigation ponds and Japan). Yuhikaku, Tokyo, 346p. irrigation pumps). Kokon-Shoin, Tokyo, 452 p. SHICHINOHE,C. (1984): Development of rice cultivation TAKEUCHI,J. (1984): Zoku inasaku hatters no kiban in the area irrigated by the Taisho canal in Hokkai (Bases for the development of rice cultivation in do, In A. TAMAKI,et al., (eds.): Suiri no shakai kozo Japan, second series). Kokon-Shoin, Tokyo, 482p. (Social structure of irrigation). 207-252, Tokyo TAKEYAMA,M. (1958): Tameike no kenkyu (A study on Daigaku Shuppan Kai, Tokyo, 327p. irrigation ponds). Yuhikaku, Tokyo, 358 p. SHINZAWA,K. (1955): Nogyo sum ron (A theory of TAMAKI,A. (1983): Mizu shakai no kozo (Structure irrigation). Tokyo-Daigaku Shuppan Kai, Tokyo, of water society). Ronso-Sha, Tokyo, 257p. 449p. TAMAKI,A and K. HATATA, (1974): Fudo: Daichi to SHINZAWA,K. (1962): Kasen suiri chosei ron (A theory ningen no rekishi (Culture and environment: History of regulation of river water use). Iwanami-Shoten, of land and people). Heibon-Sha, Tokyo, 332p. Tokyo, 511p. TANAKA,Y. (1979): Changes of the paddy farming on SHIRAI,Y. (1971): Urbanization and irrigation water the creek irrigation area. Bulletin of the National use: the case of the Hiroshima Metropolitan Area. Institute of Agricultural Science, Series (H), 52, 60p. Geographical Review of Japan, 44, 284-300. (J-E) (J-E) SHIRAI, Y. (1977): Nihon no kochi seiri (Land im TANIOKA,T. (1964) Heiya no kaihatsu (Development of provement in Japan). Taimei-Do, Tokyo, 372p. plains). Kokon-Shoin, Tokyo, 344 p. SUGAWARA,Y. (1980): Irrigation facilities of the Yayoi TAZAKI,H. (1986): Foods in the . Yayoi period: rice. agriculture. Kodaigaku Kenkyu, 92, 1-18. (J) Archaeology Quarterly, 14, 18-22 (J) SUGIHARA,S. (1968): Reconstruction of the paddy Tedorigawa Shichika Yosuishi Hensanshitsu (1982): Irrigation Systems in Japan 65

Tedorigawa Shichika Yosuishi, Vol. 1 (History of ture in Tokujuku, Hokota-machi, Ibaraki Prefec Tedori River Seven Canals, Vol. 1). Tedorigawa ture. Area Research Papers, 7, 111-153 Shichika Yosui Tochikairyoku, Matto, 910p. YAMAZAKI,S. (1982): Beginning and development of YAMAGIWA,J. (1928): Irrigation agriculture in Osaka Itazuke village of the Yayoi period. Rekishi Koron, Prefecture. Geographical Review of Japan, 4, 1023 74, 51-58. (J) -1042, 1136-1163. (J) WATANABE,T. (1977): me no michi (Diffusion of rice). YAMAMOTO,S, et al. (1985): Development of horticul Nippon Hoso Kyokai, Tokyo, 266p.

日 本 の 灌 漑 シ ス テ ム

田 林 明*

この 報 告 では,日 本 の 灌 漑 シ ス テ ムを 用 水 源 に 基 づ き 弥 生 時 代 に は 天 水 や 溪 流 を 利 用 した 個 別 的 水利 用 が まず 類 型 化 し,そ れ ぞ れ の 類 型 の 実 態 と分 布 状 態 を 説 明 し 始 ま り,こ れ が 小 河 川 の 利 用 に 進 ん だ.古 墳 時 代 に な る た.さ らに 灌 漑 シ ス テ ムの 特 徴 を 明 らか に す るた め に, と さ らに 溜 池 や 中 小 河 川 利 用 が 盛 ん に な っ た.大 河 川 の そ の形 成 過 程 を 検 討 した 。 上 中 流 を 利 用 し扇 状 地 性 平 野 の 開 発 が進 ん だ の は江 戸 時 日本 の灌 漑 シ ス テ ムは, (1)河 川, (2)溜 池, (3)湖 代 前 半 で あ り,江 戸 中 期 か ら大 河川 下 流 の三 角 州 性 平 野 沼, (4)地 下 水, (5)溪 流,そ して(6)そ の 他 の 灌漑 シ の 開 発 が す す ん だ.明 治 期以 降 は灌 漑 シス テ ム の改 善 の ス テ ムに 分 類 す る こ とが で き る.そ の うち最 も重 要 な も 時 期 で あ り,新 しい 施 設 や技 術 が導 入 され た. の は 河 川 灌 漑 シ ステ ムで あ り,溜 池 灌 漑 シス テ ム は そ れ 西 日本 に お い て は 古 代 の条 里 制遺 構 や 中世 の荘 園 制 の に 次 い で い る.日 本 列 島 の 大 半 で は 河川 灌漑 シス テ ム が も とで整 備 され た 小 用 水 路 が 最近 ま で広 く利用 され て お 卓 越 して い るが,特 に 東 日本 に お い て そ の 傾 向 が 強 い. り,現 在 の灌 漑 シ ステ ム の 基 礎 が古 い 時代 に確 立 され て ま た,瀬 戸 内地 方 や 近 畿 地 方 を 中 心 に して 溜 池 灌漑 シス い た と考 え る こ とが で き る.他 方,戦 国時 代 か ら江 戸 時 テ ムが 優 勢 な 地 域 が 広 が って い る.さ らに,よ り局地 的 代 に か け て の大 河 川 を 利 用 した 用 水 創設 と新 田開 発 は, で あ るが,関 東 平 野 で は 多 様 な 灌漑 シス テ ム が併 存 し, 東 日本 で 著 しい 水 田増 加 を もた ら した.河 川 灌 漑 に 基礎 本 州 中 部 や 四 国,九 州 の 山 間部 で は漢 流灌 漑 シス テ ム が を お く 日本 の灌 漑 シス テ ム の基 本 的性 格 は,こ の 時 期 に 多 くみ られ る.こ れ らの地 域 差 は1つ に は,降 水 量 や 地 成 立 した とい え よ う。 こ とに,樹 枝 状 に分 岐 す る水 路系 形 な どの 自然 条 件 の 差 異 と対応 す る が,よ り本質 的 に は 統 を基 盤 と して形 成 さ れ て い る 階層 的 ・重層 的 配 水 シス 社 会 的 ・経済 的 ・文化 的諸 条 件 に規 制 さ れ な が ら歴 史 的 テ ム とそ れ に対 応 す る組 織 体 系 は 日本 の灌 漑 シ ステ ム の 過 程 を経 て形 成 さ れ た も の と考 え る こ とが で き よ う. 特 徴 で あ る が,江 戸 期 に確 立 し今 日に至 って い る とい え そ こ で 日本 の灌 漑 シ ス テ ム の形 成 過 程 を検 討 す る と, よ う.

* 〒305茨 城県新治郡桜村 筑波大学地球科学系