We surveyed and discussed the nature-oriented fishway constructed in the Oshino River in northern Gunma Prefecture, 15 years after its completion. The fishway was improved from a head construction in 1998 because high head constructions become serious obstacles for fish in migration. After the improvement, a fish release experiment was conducted using Yamame Oncorhynchus masou. The fishway had a history of receiving medium-scale or greater runoff , including runoff approaching the designed flood discharge. We surveyed the sediment deposition condition and changes in the main body 14 structure such as stones and wooden stakes, and conducted a biological survey on fish and benthic fauna, additionally taking into consideration the habitat of organisms. Sediment deposition had progressed overall in the fishway, and although some stones had washed away, the basic fishway structure and function were maintained, and we confirmed that the wooden stakes were in fair condition without rot. The presence of fish and benthic fauna was also confirmed from the results of the biological survey, and the existence of pools and dead water areas were thought to provide a diverse habitat for fish and benthic fauna.

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 Produced water is the largest waste stream in oil and gas production activities. Management of produced water and cost reduction of its treatment are important issues in Oman, particularly when considering its arid environment and limited water resources. In this study, the utilization of treated produced water as a new water resource is considered. Operational costs of proposed treatment and theoretical revenues resulting from treated water utilization were calculated based on the assumption that treated produced water is used for irrigation at a particular site where water is currently being disposed into deep wells with only primary treatment.
 Secondary coagulation/flocculation/flotation and advanced filtration/adsorption treatment method developed earlier, resulted in treated water meeting Omani wastewater irrigation reuse standard in terms of oil concentration. The cost of secondary coagulation/flocculation/flotation treatment was found to depend upon the quality of produced water.
 For utilization of treated produced water for irrigation, additional desalination and boron removal treatments would be required to reduce treated water salinity and boron concentrations to also meet the wastewater irrigation reuse standard. Although these additional treatments would increase overall treatment cost, this increased overall cost could be covered through theoretical revenue from sales of higher value irrigation products. In addition, reusing treated water lead to cost saving from reduction of water volume going to deep well disposal.
 While actual utilization of treated produced water for irrigation of products entering the food chain, would require confirmation of the safety of the consumption of such products, and the cost calculations in this study would change depending on the quality of actual produced water to be treated and agricultural conditions at the actual irrigation site; the results of this study clearly indicate the potential feasibility of treating and utilizing produced water as a water resource in such or similar manner in Oman.

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