Assessment of environmental nitrogen pollution load potential from sewage treatment water in the Tedori River Alluvial Fan Area, Japan

An evaluation of the nitrogen pollution load potential (NPLP) arising from several sewage treatment systems in the Tedori River Alluvial Fan Area was evaluated by determining the removal percentage of nitrogen as a result of sewage treatment and amounts of nitrogen lost from the different treatment systems. These data were applied to the entire area resulting in an estimated total NPLP of 734 t year⁻¹ (10³ kg year⁻¹), of which 548 t year⁻¹ discharges into the Japan Sea and so does not contribute to the pollution of the environment considered here. The residual 186 t year⁻¹ of the NPLP has a high probability of causing groundwater or downstream pollution, with 58% of the NPLP being contributed from septic tanks not connected to public sewage systems. Rural sewage system accounted for about 18% of the NPLP. Material directly flowing into the middle stream of the Tedori River together with sewage water from small companies and untreated sewage water from local family dwellings made up about 3–12% of the NPLP. To improve water quality due to sewage effluent, it is essential to increase the number of connections to public sewage systems from septic tanks.     

Effects of different application timings of methane fermentation digested liquid to paddy plots on soil nitrogen and rice yield

Treatment of animal and food wastes using a methane fermentation technique is drawing considerable public attention as a suitable option for the utilization of biomass resources. The application of a fermentation byproduct (methane fermentation digested liquid) as an agricultural fertilizer has been investigated. Determining the appropriate timing required for applying digested liquid on a rice (Oryza sativa L.) paddy plot is important. The concentrations of soil nitrogen (N) components and rice yield should be considered because digested liquid contains both inorganic and organic N. This study compares the N transformation and the rice yield and growth at different application times over a period of 3 y. The effects of the timing of basal application on soil N were different and the timing that maximized the rice yield was different in each year. Days before ponding (DBP) affected soil N before mid-summer drainage, and rice growth rates at the panicle formation stage and the ear emergence stage. The effects of DBP disappeared before harvest. The results indicated that sufficient potentially mineralizable N existed regardless of DBP, and the effect of DBP lessened after the mid-summer drainage, which coincides with the period when N uptake is most active.     

An H5N1 highly pathogenic avian influenza virus that invaded Japan through waterfowl migration

In 2010, an H5N1 highly pathogenic avian influenza virus (HPAIV) was isolated from feces of apparently healthy ducks migrating southward in Hokkaido, the northernmost prefecture of Japan. The H5N1 HPAIVs were subsequently detected in domestic and wild birds at multiple sites corresponding to the flyway of the waterfowl having stopovers in the Japanese archipelago. The Hokkaido isolate was genetically nearly identical to H5N1 HPAIVs isolated from swans in the spring of 2009 and 2010 in Mongolia, but less pathogenic in experimentally infected ducks than the 2009 Mongolian isolate. These findings suggest that H5N1 HPAIVs with relatively mild pathogenicity might be selected and harbored in the waterfowl population during the 2009-2010 migration seasons. Our data provide "early warning" signals for preparedness against the unprecedented situation in which the waterfowl reservoirs serve as perpetual sources and disseminators of HPAIVs.     

Relationship between increment of groundwater level at the beginning of irrigation period and paddy filed area in the Tedori River Alluvial Fan Area, Japan

There are many paddy fields and large amounts of groundwater in the Tedori River Alluvial Fan in Ishikawa Prefecture, Japan. Water infiltration from paddy fields during irrigation may significantly contribute to groundwater recharge. Groundwater recharge is known to be one outcome of paddy farming, and in general is usually related to land use. However, a decreased area of paddy fields because of socioeconomic factors such as urbanization and increasing area of fallow fields has possibly affected the groundwater environment. Evaluation of the quantitative effect of paddy fields on groundwater is necessary for groundwater conservation. This study examined the relationship between differences in the depth of groundwater from just before the irrigation period to just after the first irrigation of paddy fields (increments of groundwater levels) in observation wells and the area of paddy fields around each well. The paddy areas within circular buffer zones, which were delineated at 0.2 km intervals between 0.2 and 2.0 km centered on each observation well, were calculated. A positive relationship was found between the rise in groundwater and the area of paddy field within different buffer zones at most wells. In addition, in the middle or upper part of the fan, the effect of changes in the area of paddy fields surrounding the well on the groundwater level rise was greater than that on the lower part of the fan.     

Investigation of irrigation performance at the tertiary canal level in the Nile Delta of Egypt

Paddy and Water Environment - One of the objectives of the Irrigation Improvement Project (IIP) in the Nile Delta, Egypt, is to facilitate equitable water distribution and improve on-farm...     

Analysis of water balance in the Tedori river alluvial fan areas of Japan: focused on quantitative analysis of groundwater recharge from river and ground surface, especially paddy fields

Water balance in the Tedori River alluvial fan areas was analyzed for all components of the hydrological cycle based on exchange of the channel/soil surface and aquifer horizon fractions with river water. The results were summarized on an annual basis, as well as for the irrigation and non-irrigation periods. The study area received 6.28 mm/day of precipitation and had an outflow of 2.32 mm/day as direct runoff, resulting in 3.96 mm/day of water being supplied to the soil surface. The channel/soil horizon fraction received this 3.96 mm/day, as well as 9.12 mm/day intake water from the head works. Conversely, 2.74 and 2.85 mm/day were lost by evapotranspiration and percolation, respectively. Thus, surface runoff of 7.49 mm/day flowed from the study area to the Sea of Japan or drainage canals near the river mouth. In the aquifer horizon fraction, 2.85 mm/day of water was supplied from the channel/soil horizon fraction and 2.15 mm/day was supplied from the Tedori River, while 1.73 mm/day was extracted by groundwater. Thus, 3.27 mm/day of groundwater flowed out to the Sea of Japan or into downstream drainage canals. An outline of the water balance of the irrigation and non-irrigation period is also shown. Because various hydrological components are closely related to each other, planning and management of water resources for individual goals are not adequate, but require the integrated aspect of water balance for sustainable water use.     

Virological surveillance and phylogenetic analysis of the PB2 genes of influenza viruses isolated from wild water birds flying from their nesting lakes in Siberia to Hokkaido, Japan in autumn

Recent introduction of H5N1 highly pathogenic avian influenza virus (HPAIV) in wild birds from poultry in Eurasia signaled the possibility that this virus may perpetuate in nature. Surveillance of avian influenza especially in migratory birds, therefore, has been conducted to provide information on the viruses brought by them to Hokkaido, Japan, from their nesting lakes in Siberia in autumn. During 2008-2009, 62 influenza viruses of 21 different combinations of hemagglutinin (HA) and neuraminidase (NA) subtypes were isolated. Up to September 2010, no HPAIV has been found, indicating that H5N1 HPAIV has not perpetuated at least dominantly in the lakes where ducks nest in summer in Siberia. The PB2 genes of 54 influenza viruses out of 283 influenza viruses isolated in Hokkaido in 2000-2009 were phylogenetically analysed. None of the genes showed close relation to those of H5N1 HPAIVs that were detected in wild birds found dead in Eurasia on the way back to their northern territory in spring.     

Evaluation of water resources by snow storage using water balance and tank model method in the Tedori River basin of Japan

We evaluate water resources as the difference between the observed and virtual discharges, defined as discharge without snow storage during the snowfall and snowmelt season, in the Tedori River basin of Ishikawa Prefecture, Japan. The virtual discharge was estimated using the Tank model, in which parameters of calculated discharge were determined when the predictions were consistent with the observed discharges except for those during snowfall and snowmelt periods. Precipitation increase factors, i.e., the ratio of precipitation in the basin to that of a Kanazawa site, ranged from 1.46 to 2.00 with an average of 1.68. Water resources by snow storage (WRSS) during 31 years from July 1976 to June 2006 were estimated to be 400–1,500 mm in depth, which could be considered a significant amount. WRSS gradually decreased over time from 1976 to 2006. We propose the water balance method to estimate WRSS and water resources by snowmelt (WRSM), which easily estimates these parameters without the need for any detailed analysis of hydrograph as that of the Tank model. If snowfall decreases due to global warming, we suggest this area would suffer an irrigation water shortage under the water right, especially in the early spring.     

Effectiveness of cyclic irrigation in reducing suspended solids load from a paddy-field district

The reduction of suspended solids, nutrients, and organic matter loads in drainage water from paddy fields is an important issue for water quality management in closed water areas in Japan. We evaluated the ability of cyclic irrigation to reduce the suspended solids load from paddy fields. In 2006 and 2007, we investigated water and mass balances during the irrigation period in a low-lying paddy-field district neighboring Lake Biwa, which is the largest lake in Japan. We confirmed that cyclic irrigation reduced effluent loads during the puddling season. With cyclic irrigation, 118 kg ha⁻¹ of suspended solids was returned to the paddy fields in 2006 and 199 kg ha⁻¹ in 2007. The effect of cyclic irrigation on the net suspended solids load can be represented by three ratios: the concentration ratio, which represents the ratio of the suspended solids concentration in drainage water to that in lake water; the cyclic irrigation ratio, which represents the ratio of the volume of reused water to that of irrigation water in cyclic irrigation; and the surplus irrigation water ratio, which represents the ratio of the volume of surplus irrigation water to that of irrigation water. The cyclic irrigation ratio and the surplus irrigation water ratio interact to determine the effect of cyclic irrigation on the net suspended solids load. Simultaneously increasing the cyclic irrigation ratio and decreasing the surplus irrigation water ratio will maximize the purification effect on drainage water from paddy fields.     

Genetic characterization and susceptibility on poultry and mammal of H7N6 subtype avian influenza virus isolated in Japan in 2009

From February to March 2009, six strains of H7N6 subtype avian influenza virus were isolated from quails in three farms in Aichi prefecture in Japan. The isolates were shown to be low pathogenic for chicken by the examination performed using the "Manual of Standards for Diagnostic Tests and Vaccines" by World organisation for Animal Health (OIE). The deduced amino acid sequence at the cleavage site was PE (I/Q/L) PKRR (nucleotide sequences were cct gaa (a/c) (t/a) a cc (a/g) aaa aga aga), suggesting persistence in domestic poultry for some time. The direct putative ancestor strain could not be elucidated by phylogenetic analysis of all genome segments of the quail isolates. Diverged date from a putative common ancestor in a non-rooted phylogenetic tree among quail viruses was estimated between March 2002 and July 2004. Three putative N-linked glycosylation sites resided in the vicinity of the receptor binding pocket of HA1 region. They are considered to decrease the reactivity of neutralizing antibody against the virus. Experiments for the infectivity and pathogenicity of a quail strain to poultry indicated that the quail isolate had higher infectivity to quails than chickens and ducks. Direct and dust-borne and/or droplet-borne transmissions among quail were proven in quails with and without direct contact with experimentally infected quails. The virus is seldom transmitted among chickens either directly or indirectly, and indirect transmission from infected quails to chickens was not observed. The pathogenicity of the quail strain for mammalian, pig and mouse was low, although it could replicate in those animals.