5.1. Impacts of paddy cultivation and fields on local environment

Water ponding for rice production needs much water and also irrigation and drainage system to supply and withdraw much water to and from the fields. While the system, of course, should function well for local rice production, it could also perform for improvement of local environment. It is called as "multi-function" of paddy cultivation or paddy irrigation. The functions are fundamentally based on (1) widespread establishment of stable and shallow water body for some specific period, (2) stable water supply, and (3) adjustment of local hydrological regime.

The outcomes of the multifunction include the followings [3]:


These are the outcomes of paddy fields as the artificial wetlands, which are the land with surrounding ridges and the infrastructures for irrigation and drainage, as well as their management institutions and organizations in local society.

While there are many exact cases of the multifunction in the world rice cultivation areas, as the typical case with the function No. 3, the paddy fields in the Kumamoto Region, Kyushu of Japan, are to be introduced. The Kumamoto is famous as a "Groundwater City," where almost 1 million local residents depend their daily lives on the groundwater, which also enables irrigation and industry in the region. It is the fact that the groundwater is a treasured resource to support regional activities, and the stable groundwater is recharged by the percolation from the paddy fields located in the upper basin (see Figure 1). Now, 11 municipalities in the region share this groundwater.

the Lake Biwa that is one of the Ramsar sites of Japan, are working as the areas for feeding the migratory birds Buick Swan. According to the detailed field observation, birds fly only to the

Figure 1. Paddy fields in the Kumamoto region of Japan recognized as water resource for the regional groundwater

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In the dry region of the world, paddy fields have been developed extensively. There, paddy cultivation and irrigation might create local "water rich condition" in regional dry environment. This impact of the artificial modification on local hydrological regime could be much larger and critical to the sustainability of cultivation and irrigation development. This is to be the typical case of the artificial and temporal wetland and suitable opportunity to reevaluate

5.2. Impacts of paddy fields in the dry region: the cases of Egypt and Kazakhstan

paddy plots with water ponding, after harvesting (see Photo 1) [14].

Photo 1. Buick swans flying onto paddy fields in the Kohoku region of Japan.

the implication of paddy fields.

(source: Hama et al. [13]).

In 2012, to conserve the hydrological system, the local residents, private sector representatives, and the local municipal governments established the organization "Kumamoto Groundwater Foundation." There, the function of paddy fields for stable groundwater recharge is widely recognized, and then the conservation of paddy cultivation is one of the main challenges for sustainable groundwater management. For these challenges and outcomes, the Kumamoto City received the "Water for Life Award" from the United Nations in 2013.

Paddy fields are providing wild lives with their habitats, as shown as the function No. 6 above. As one of the examples, the paddy fields in the Kohoku region of Japan, the northern shore of

Figure 1. Paddy fields in the Kumamoto region of Japan recognized as water resource for the regional groundwater (source: Hama et al. [13]).

Photo 1. Buick swans flying onto paddy fields in the Kohoku region of Japan.

5. Implication of paddy fields in local hydrological regime

Water ponding for rice production needs much water and also irrigation and drainage system to supply and withdraw much water to and from the fields. While the system, of course, should function well for local rice production, it could also perform for improvement of local environment. It is called as "multi-function" of paddy cultivation or paddy irrigation. The functions are fundamentally based on (1) widespread establishment of stable and shallow water body for some specific period, (2) stable water supply, and (3) adjustment of local hydrological regime.

1. reduction of flood damage in a region or basin with water storage in the fields and

3. stable groundwater recharge with continuous percolation from water layer on the fields, 4. mitigation of local climatic variability especially drastic temperature changes based on

These are the outcomes of paddy fields as the artificial wetlands, which are the land with surrounding ridges and the infrastructures for irrigation and drainage, as well as their man-

While there are many exact cases of the multifunction in the world rice cultivation areas, as the typical case with the function No. 3, the paddy fields in the Kumamoto Region, Kyushu of Japan, are to be introduced. The Kumamoto is famous as a "Groundwater City," where almost 1 million local residents depend their daily lives on the groundwater, which also enables irrigation and industry in the region. It is the fact that the groundwater is a treasured resource to support regional activities, and the stable groundwater is recharged by the percolation from the paddy fields located in the upper basin (see Figure 1). Now, 11 municipalities in the region

In 2012, to conserve the hydrological system, the local residents, private sector representatives, and the local municipal governments established the organization "Kumamoto Groundwater Foundation." There, the function of paddy fields for stable groundwater recharge is widely recognized, and then the conservation of paddy cultivation is one of the main challenges for sustainable groundwater management. For these challenges and outcomes, the Kumamoto

Paddy fields are providing wild lives with their habitats, as shown as the function No. 6 above. As one of the examples, the paddy fields in the Kohoku region of Japan, the northern shore of

5.1. Impacts of paddy cultivation and fields on local environment

The outcomes of the multifunction include the followings [3]:

2. control of soil erosion with bunds of flat fields,

higher specific heat of water ponded in the field, 5. establishment of conditions for fish cultivation, and

agement institutions and organizations in local society.

6. establishment of habitats for wildlife including aquatic flora and fauna.

City received the "Water for Life Award" from the United Nations in 2013.

acceptance of flood water,

150 Irrigation in Agroecosystems

share this groundwater.

the Lake Biwa that is one of the Ramsar sites of Japan, are working as the areas for feeding the migratory birds Buick Swan. According to the detailed field observation, birds fly only to the paddy plots with water ponding, after harvesting (see Photo 1) [14].

#### 5.2. Impacts of paddy fields in the dry region: the cases of Egypt and Kazakhstan

In the dry region of the world, paddy fields have been developed extensively. There, paddy cultivation and irrigation might create local "water rich condition" in regional dry environment. This impact of the artificial modification on local hydrological regime could be much larger and critical to the sustainability of cultivation and irrigation development. This is to be the typical case of the artificial and temporal wetland and suitable opportunity to reevaluate the implication of paddy fields.

Here, brief overviews of the cases of Egypt and Kazakhstan are introduced including the summary by GRiSP in the following [1].

water resource in this dry region. This large quantity of diversion is recognized as the main

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Considering the limited availability of water resources, generally, it is reasonable to recognize that paddy cultivation in dry region is not realistic or acceptable in terms of sustainability of economics and environment in many cases. Actually, most of the paddy fields are developed in the humid region with much rainfall and much available water resources. It brings that paddy fields are suitable to humid condition. This is not wrong, while it simultaneously brings

The Japanese paddy fields have been reclaimed and developed historically and recently improved much with large investments for advanced irrigation and drainage system (see [18]). With advanced farming techniques including the introduction of modern cultivars, nutrients, chemicals, machineries, and so on, they are proud of higher yield and productivity of rice production as well as the qualities. It needs, however, much lasting investments and labors to maintain the systems. They are always facing risks of flood and drought damages, and the cool and hot weather damages during rice growing season. There, the paddy fields and the system are maintained by everlasting human activities as hard as possible, which have developed the infrastructures, institutions, and interconnectedness in the society. This situation has been developed under the condition of climate and small-scale topography and river system, which are relatively controllable comparing with the continental conditions. Thinking over these history and present system, we can ask "Are the paddy fields in Japan suitable to its natural condition?" Some paddy fields in other regions can produce considerable yield without any hard invest-

ment, while its yield is not so high. This could be recognized as "naturally" suitable.

6.2. Impacts of reduced paddy fields on local environment

The point to be recognized here is just that the "suitability" of the paddy fields to the natural, and climate condition is not to be evaluated absolutely. It needs comprehensive conclusion, especially assessment in terms of sound hydrological cycle of the region or basin. Paddy cultivation and fields are to be arranged appropriately in the hydrological regime of the region. Then, consequently, we might find "suitable" and "sustainable" development of paddy fields in each region including dry area, which are to be located in right place in the local hydrolog-

In the past few decades, in some developed countries and regions with long history of rice production, like Japan, Taiwan, and Korea, the area of paddy fields has been reducing, due to the changes of dieting system according to economic development and globalization, as shown in Figures 2 and 3. This reduction of paddy area might result in losing their multifunction with

reason for serious desiccation of the Aral Sea.

6.1. Paddy fields in local hydrological regime

another question on significance of "suitability."

ical system.

reduced rice production.

6. Significance of paddy fields in the environment

Egypt is one of the typical countries that produce rice in dry area. It has a fast growing population with 82.5 million in 2011 leading to increased food demand. Almost all of water demand in Egypt is supplied by the Nile River, of which water is used extensively to irrigate crops including rice. Rice is one of the staple crops in Egypt and consumed 38.6 kg milled rice per person per year in 2009. Rice is grown in the summer on about 600,000 ha, mainly in the northern Nile Delta. The yield is quite high, about 9 t/ha in 2000, due to abundant solar energy and fertile alluvial soils.

The area for rice is officially regulated by the government due to limited water resources, while farmers prefer cultivating rice for its higher profit. The areas for rice producing located in the northern Nile Delta have potential risk of soil salinization. Paddy cultivation has been functioning to leach out accumulated salts in the soil profile. Salt leaching in arable soils can be supported by prevailing sub-surface drainage systems (e.g., [15, 16]).

In Kazakhstan, of which most of the land is classified as steppe or desert with annual average precipitation of 100–200 mm, wheat is a predominant crop in the northern part, whereas rice, cotton, fodder, and fruit are produced in the southern part in summer season. Its cropped area had increased due to rapid land reclamation mainly in the Syr Darya Basin since the 1950s to the 1980s, and the irrigated land became one of the big food supplying sources of the Soviet Union and Eastern Europe in that period. While rice occupies only 5–6% of the irrigated area, its water requirement is about 15% of the total irrigation requirement in that period. Most of the rice cropping area in Kazakhstan is distributed mainly in the Kzyl-Orda area of the Lower Syr Darya River Basin and some in the Ili River basin. The present total rice area is about 113,000 ha, which is equivalent to 17% of the total irrigated area. In the irrigated area in Kazakhstan, the crop rotation system is dominantly practiced with several rotation patterns, and rice is grown usually in this crop rotation system.

In Kazakhstan, large-scale irrigated agriculture has been developed since the 1960s with crop rotation including rice. In the irrigation scheme, water is applied only to paddy fields, which consists about 30% of the total scheme, and paddy fields are continuously ponded. Basically upland crop is not irrigated directly, while water required in upland fields is supplied through much percolation from paddy fields. The efficiency of conveyance and distribution is quite low due to not lined canals running through sandy soil.

Water requirement of paddy fields is around 3000 mm. Seepage from irrigation canals and deep percolation from paddy fields raise local groundwater table, and it functions as water source for upland fields surrounding the paddy fields. According to the study of the Tottori University Group, this water distribution system induces soil salinization (see [17]). In upland fields, salts accumulate during crop production with upwards water movement, while most of them are leached out when that field is cultivated with rice and flooded continuously for the rice growing season.

The large amount of water requirement for the large irrigation schemes, including much loss from the systems, needs much water diversion from the Syr Darya River, which is the main water resource in this dry region. This large quantity of diversion is recognized as the main reason for serious desiccation of the Aral Sea.
