Farmers in the dryland regions of Northern India irrigate farmlands with high-salinity groundwater and salinity accumulation causes extensive damage to cultivated agricultural crops, thereby reducing crop productivity. The authors have been standardizing irrigation technologies using saline groundwater for sustainable crop production in Hisar, Haryana, India. The main objective of this study was to quantify the field-scale salinity reduction effect of cut-soiler (CS)-constructed preferential shallow subsurface drainage (PSSD), which refers to drainage mechanisms in which saline groundwater flow is mainly associated with the subsurface drainage network that was built by CS. For this purpose, the groundwater level and electrical conductivity were monitored fortnightly, and the volume of drained saline groundwater was estimated. Furthermore, electrical prospecting was conducted to obtain the resistivity distribution, and a higher resistivity was recorded near the CS drainage lines. Groundwater observations in the subplot quantitatively revealed that CS removed shallow saline groundwater. It was found that the PSSD resulted in a saline groundwater reduction ranging from 54 to 324 m³ and an increase in resistivity exceeding 3.0 Ωm. Thus, CS can contribute to a reduction in saline groundwater.

  Open channel experiments were conducted to investigate influences of bed roughness conditions on the detachment of attached algae by sediment transport. The experimental results showed that sediment deposition was observed between gravels in a hemispherical gravel riverbed and that the presence of sediment deposition significantly affects the amount of detachment of algae. In the case that sediment is deposited, the detachment was not significant because there was a small area where the sediment acts to detach algae from the gravels. The detachment characteristic values, exponents to evaluate detachment rate, also decrease with an increase in dimensionless deposition height. By introducing a sedimentation coefficient, the effective amount of work was calculated considering the effect of sedimentation. This enables the estimation of the detachment characteristics of the hemispherical gravel beds.

  Various countermeasures against water hammer pressure in the event of an emergency pump stoppage include no countermeasures, check valves, rapid and slow closure of discharge valves, two-stage closure, and one-way surge tanks. In this report, numerical models were developed to evaluate the effectiveness of these water hammer pressure countermeasures, either alone or in combination, in deterring the occurrence of water hammer pressure, reducing water hammer pressure in the pipeline, and reducing water hammer pressure. In this report, numerical models of these countermeasures against water hammer pressure, either alone or in combination, were developed to evaluate their effectiveness in deterring the occurrence of water hammer pressure. The effects of these countermeasures alone or in combination were compared and evaluated using a numerical model to determine the optimal countermeasure for long-distance, high-head pumped water pipelines. As a result, it was confirmed that the water hammer pressure countermeasure that combines "allowing reverse pump flow," "loose closure by two-stage operation of the pump discharge valve," and "one-way surge tank," all of which are used in current water delivery systems, is effective.

  The water quality of Shigenobu River, which is the important river in Ehime prefecture, has been improved. However, the factors of the water quality improvement are not clarified until now. In this study, we evaluated the long-term changes of water quality, land use, population density and sewage coverage rate in Shigenobu River basin by water quality data and GIS (Geographic Information System) analysis. In addition, we examined the factors affecting the water quality changes by calculation of pollutant load unit and multiple regression analysis. From 2000 to 2018, BOD, TN and TP concentrations in Shigenobu River basin had decreased. In particular, the concentrations in Ono River basin had largely decreased. As for BOD, TN and TP load, Ono River had the highest contribution to the total load in Shigenobu River basin, which suggested that measures in Ono River basin would be important for reducing the total pollutant loads in Shigenobu River basin. As a result of multiple regression analysis, BOD, TN and TP concentrations were affected by population density, paddy field ratio and sewage coverage rate. Among these factors, sewage coverage rate was the most influential variable. Therefore, it was considered that the increase of sewage coverage rate in the river basin would contribute to the water quality improvement in Shigenobu River.

  Ecosystem-friendly agriculture, which aims at both biodiversity conservation and rice production, has not yet been widely adopted. This paper summarizes the issues in the diffusion of ecosystem-friendly agriculture based on previous studies. The results are as follows. (1) Biodiversity conservation technologies can be broadly classified into environmentally friendly facilities and farming management technologies, and various examples have been reported; however, scientific verification of the effectiveness of these technologies is lacking. (2) Establishment of a certification system and a mechanism to utilize cross-compliance, which will lead to producers' decision to adopt this farming method. (3) While incentives for consumers are limited, the use of the hometown tax payment system may encourage the diffusion of the method. (4) Contribution to solving social issues beyond the framework of agriculture through cooperation with various stakeholders. The above four points were summarized as trends or issues.