Study on Water Management at Paddy Fields with Automatic Taps for Irrigation in a Cold Region

  The aging of farmers and decreases in the number of farming households in Hokkaido has resulted in the farmland consolidation. Thus, the sizes of farms, which are managed by decreasing numbers of farmers, have been rapidly increasing. In view of these circumstances, farmland consolidation and the introduction of automatic taps for paddy-irrigation that utilizes ICT have been promoted to increase labor productivity. Automatic taps for paddy irrigation make it possible to automatically irrigate paddy fields by using a smartphone for remote observation and control, as well as for setting of the irrigation time or the water level. Thus, it is expected that the time necessary for water management in each field will be shortened and extra releases of water will be reduced. At the same time, alterations in the irrigation supply system, the types of waterways, and the rice cultivation method might lead to changes in the timing of high demand for agricultural water, the quantity of water intake at various times of the year, and the time of day for water intake. In order to use an appropriate amount of water at the right timing for farmers, managers of irrigation facilities need to control the distribution of irrigation water while responding to these changes. Water management based on water temperatures is recommended in Hokkaido because of the cool climate. In order to avoid cold damage, ‘night-time or early-morning water intake’ and ‘deep-water irrigation’ are encouraged. ‘Night-time or early-morning water intake’ is conducted to efficiently raise the water temperature in paddy fields by taking in water when the difference between the agricultural water temperature and the air temperature is relatively small, because in comparison to the water temperature at paddy fields, the temperature of water in an agricultural water channel varies less significantly during the day. In ‘deep-water irrigation,’ the depth of ponding is increased when rice plants are at risk of harm from cold weather. Such irrigation aims at increasing the ripening rate by preventing the panicles from getting cold.
  Although the use of automatic taps for paddy irrigation is likely to help farmers take water more flexibly than before, very few studies have been done on the actual use of these taps at paddy fields in cold regions. Thus, for the purpose of understanding and analyzing the utilization of automatic taps for paddy irrigation, the Irrigation and Drainage Facilities Research Team has been conducting research at farms that collectively account for 30 plots of paddy fields in the T district of Sorachi Subprefecture. Specifically, the use of automatic taps has been analyzed and the amount of water intake has been surveyed. One or two automatic taps are installed in each paddy field.

Photo 1 Automatic tap for paddy irrigation

  The research found that the time of day for water intake differs between the fields with automatic taps and the fields where taps are manually controlled. In the fields with manual taps (Fig. 1), water intake tends to be started or stopped during daytime hours. In the fields with automatic taps (Fig. 2), water intake is started or stopped regardless of time, because night-time irrigation is conducted by using an irrigation time setting and because water is supplied to maintain the set ponding depth.
  Fig. 3 shows the percentages of paddy fields that were simultaneously irrigated. It is clear that the percentage of these paddy fields increased when puddling soil or transplanting seedlings was done for transplanting culture, when the initial water intake or shallow-water management was conducted for direct seeding, or when the air temperature was high and rainfall was inadequate.

Fig.3 The percentage of paddy fields that simultaneously took in water during an irrigation season

  The diversion of water from the main irrigation channel to branch channels and the allocation of different flow rates are controlled by the manager of the irrigation facilities in each land improvement district. In the districts where open irrigation channels are used, irrigation water is distributed based on the current trend of demand, to avoid excess or deficiency in supply. By using the research to reduce the amount of water taken from pumps during hours of low demand for irrigation water, the maintenance cost of irrigation facilities can be lowered.
  In addition to the analysis regarding the use of automatic taps, analysis by the Research Team will focus on the following: data on the amount of water intake at representative fields, observation data on the flow rates in the drainage channels around the fields, and demand for irrigation water in the fields under study. Based on the analysis results, the Research Team will propose an efficient technique for water distribution control that responds to changes in the demand for agricultural water in each irrigation district.

(Contact : Irrigation and Drainage Facilities Research Team,  CERI)

Potential of VR Risk Communication Techniques as an Educational Tool for Water Disaster Management

  To reduce evacuation delays and minimize exposure of residents to danger in the event of water disasters, it is necessary to develop risk communication techniques that allow the government to share information with residents in the event of an unusual crisis such as a water disaster and to ensure appropriate evacuation actions. Virtual reality (VR), whereby people can experience a space virtually created by a computer or other means, has also developed in recent years.

  ICHARM is now developing a Virtual Flood Experience System (VFES) whereby people can virtually experience water disasters, which are extraordinary crises, using VR. The VFES overlays information on simulated floods on 3D survey data of mountains, rivers, urban landforms, and buildings to reproduce a virtual experience of floods through avatars, which represent the alter egos of users in virtual space. Not only can residents virtually experience water disasters in their own neighborhoods in advance, but the system also allows them to simulate the circumstances of elderly people and others who cannot easily evacuate by changing the avatar's walking speed and other settings.

  To confirm the effectiveness of the VFES, a water disaster management competition using VFES was held on the occasion of the 9th International Conference on Flood Management in Tsukuba City in Feb. 2023, and junior high/high school and university students of the city also participated. Prospective participants in the competition underwent training about possible water disasters and appropriate evacuation procedures for each school in advance. The students were then divided into two groups: those who experienced operating an avatar on VFES and those who supported the operation while also viewing the administrator screen shown in Figure 1. They then took turns to conduct a virtual evacuation drill using a VFES of potential water disaster areas in Tsukuba City (Figure 2, left photo). After participants in the competition had undergone the prior training, they gathered to experience a water disaster in a common virtual space, and competed based on points and time to reach evacuation shelters while obtaining information and selecting evacuation routes (Figure 2, right photo).

(Contact : Materials and Resources Research Group）