Ado River Research Articles

River Water Level and Droughts in Ado River, An Inlet Stream of Lake Biwa, Central Japan

River Water Level and Droughts in Ado River, An Inlet Stream of Lake Biwa, Central Japan

Upstream migration of Cottus reinii (Cottidae) from Lake Biwa to the Ado River, central Japan, in spring and early summer

Upstream migration of Cottus reinii (Cottidae) from Lake Biwa to the Ado River, central Japan, in spring and early summer

Factors characterizing phosphate oxygen isotope ratios in river water: an inter-watershed comparison approach

We compared the oxygen isotope ratio of dissolved phosphate $$\left( {\delta^{{{18}}} {\text{O}}_{{{\text{PO}}_{{4}} }} } \right)$$ in two rivers with different land-cover and geological features (Ado River and Yasu River) within Lake Biwa basin, central Japan, to explore what factor primarily characterizes the $$\delta^{{{18}}} {\text{O}}_{{{\text{PO}}_{{4}} }}$$ . Mean values of $$\delta^{{{18}}} {\text{O}}_{{{\text{PO}}_{{4}} }}$$ in river water were 19.0 ± 2.4‰ (n = 7) in Ado River and 13.1 ± 2.3‰ (n = 15) in Yasu River, which were significantly different. Comparisons of $$\delta^{{{18}}} {\text{O}}_{{{\text{PO}}_{{4}} }}$$ between river water and potential sources of phosphate revealed that in the Ado River, the $$\delta^{{{18}}} {\text{O}}_{{{\text{PO}}_{{4}} }}$$ was similar to that in rocks from the accretionary complex and decreased with increasing sedimentary rock coverage. In the Yasu River, the $$\delta^{{{18}}} {\text{O}}_{{{\text{PO}}_{{4}} }}$$ was low in the upper forested areas, but increased with paddy field coverage. These results demonstrate that river $$\delta^{{{18}}} {\text{O}}_{{{\text{PO}}_{{4}} }}$$ strongly reflects inputs from geological substances, but is also impacted by land-use activities and varies with anthropogenic land coverage in the watershed. Thus, river $$\delta^{{{18}}} {\text{O}}_{{{\text{PO}}_{{4}} }}$$ relates to land or bedrock coverage differentially in each river. Regression analysis showed that residuals of the $$\delta^{{{18}}} {\text{O}}_{{{\text{PO}}_{{4}} }}$$ tended to converge to zero with increasing drainage area, suggesting that river $$\delta^{{{18}}} {\text{O}}_{{{\text{PO}}_{{4}} }}$$ more explicitly reflects land-cover and geological features on a larger watershed scale.

Assessing alpha and beta diversities of benthic macroinvertebrates and their environmental drivers between watersheds with different levels of habitat transformation in Japan

Little is known about differences in species diversity among ecological communities subject to different levels of human-caused habitat transformation and how this disturbance contributes to diversity through symbiotic dependencies with the environment in freshwater ecosystems. We estimated α and β diversities of benthic macroinvertebrates and relationships between diversity and environmental variables in Ado River (natural) and Yasu River (intermediately disturbed) watersheds, Japan. Alpha diversity was consistently slightly higher in the natural river watershed than in the intermediately disturbed one, but the spatial distribution was not equivalent. The opposite pattern was found for β diversity. Significant differences in environmental variables existed between the two river watersheds, with especially high chlorophyll-a concentrations detected in the intermediately disturbed watershed. Alpha diversity was not correlated with specific environmental variables, whereas water temperature and chlorophyll-a concentrations were the two most significant environmental variables influencing β diversity across sites in the two watersheds. These results suggest that diversity patterns in freshwater benthic macroinvertebrates are differentially influenced by levels of human-caused habitat transformation, especially that intermediately disturbed habitats may benefit species turnover, and further understanding how they relate to environmental variables is essential for protecting local to regional diversity and can provide useful information for conservation planning to maximise biodiversity at the watershed scale.

The relative importance of substrate conditions as microhabitat determinants of a riverine benthic goby, Rhinogobius sp. OR (orange form) in runs

We examined the microhabitat determinants of the benthic goby Rhinogobius sp. OR (orange form) in runs by measuring fish density, and substrate and hydraulic variables at four sites in the middle and lower reaches of the Ado River, Japan. One of the four sites was located below a bridge pier in the lower reach and had coarser substrate than was typical there. This contributed to the elimination of the correlation between substrate condition and hydraulic variables by providing anomalous combinations of substrate and hydraulic variables. Using principal component analysis, the variables were divided into substrate and hydraulic components. A multiple regression analysis revealed that substrate variables explained more of the variance in fish density than hydraulic variables. We concluded that the density of this goby is determined by substrate conditions in runs, where the current velocity is lower and the stone shelter is scarcer than in riffles. The importance of substrate conditions, which can be easily masked by current velocity in natural settings, should not be neglected.

Longitudinal changes in bacterial community composition in river epilithic biofilms: influence of nutrients and organic matter

Epilithic bacterial communities play a major role in biogeochemical cycles of rivers; however, distributional patterns and controls of epilithic communities remain unclear. The objective of the present study was to examine possible environmental factors that affect longitudinal distri- butional patterns of epilithic bacterial communities in 2 rivers (Yasu and Ado Rivers) draining the Lake Biwa basin, Japan. Phylogenetic analyses were conducted using denaturing gradient gel electrophoresis (DGGE) of 16S rRNA genes and fluorescence in situ hybridization (FISH) with oligonucleotide probes targeted to small subunit rRNA. Non-metric multidimensional scaling and canonical correspondence analysis of the DGGE profile indicated that a clear shift in community composition occurred at the middle reach of the Yasu River. This shift was most closely related to variation in the nitrogen stable isotope ratio (δ 15 N) of epilithic materials (BIOENV analysis, ρw = 0.512), which is an indicator of the extent of anthropogenic nitrogen loading. The concentration of dissolved organic carbon (DOC) also affected community composition (ρw = 0.510 for the combina- tion of δ 15 N and DOC). The longitudinal pattern of the DGGE profile was less evident in the Ado River. In both rivers, FISH results indicated that Alphaproteobacteria and Betaproteobacteria gener- ally accounted for a large fraction (37 to 71%) of total bacterial abundance, indicating that species and clones affiliated with a limited number of the major phylogenetic groups occupy diverse epilithic habitats. Our results are consistent with the hypothesis that nutrients and organic matter of anthropo- genic origin are major determinants of epilithic bacterial community structure in rivers.

Distribution of dioxins in surface soils and river-mouth sediments and their relevance to watershed properties

The dioxins toxic equivalent (TEQ) concentration in surface soils, river sediments and river-mouth sediments was measured by the CALUX assay in the Yasu and Ado River basins around Lake Biwa, Japan. In order to examine the distribution of dioxins in each watershed, we evaluated and compared the correlation between the dioxins TEQ concentration and the solid characteristics (i.e. organic carbon content and particle size distribution) of all samples. In both basins, the dioxins TEQ concentration in forest soil correspondingly showed a very good linear relationship to organic carbon content. On the other hand, the dioxins TEQ concentration in paddy field was significantly high, although organic carbon content was relatively low. Generally, the smaller particles have the higher dioxins TEQ concentrations in surface soils, and river sediments were composed of very coarse particles and had relatively low dioxins TEQ concentration. Therefore, we expected high dioxins TEQ concentration in river-mouth sediment, which was, however, not the case. Although the dioxins TEQ concentration in river-mouth sediments is low, the degree of dioxins pollution was different in each basin. The difference was considered to come from the difference of watershed properties including land use, river-slope, dam construction as well as the surface soil pollution.

Distribution of dissolved organic carbon and dissolved fulvic acid in mesotrophic Lake Biwa, Japan

The dissolved organic carbon (DOC) concentrations in mesotrophic Lake Biwa were determined by a total organic carbon (TOC) analyzer, and DOC molecular size distributions were determined by size exclusion chromatography (SEC) using a fluorescence detector at excitation/emission (Ex/Em) levels of 300/425 nm with the eluent at pH 9.7. The fluorescence wavelengths for detection were chosen from the result of excitation–emission matrix spectrometry (EEM) analysis for dissolved fulvic acid (DFA) extracted from Ado River (peak A, Ex/Em = 260–270/430–440 nm; peak B, Ex/Em = 300–310/420–430 nm). Ado River DFA was eluted with a retention time (RT) of 7.4–8.9 min and the apparent molecular weight was estimated at 22–87 kDa based on the elution curve for the spherical protein molecular weight standard. A DFA peak eluted at the same retention time as Ado River DFA also appeared in all the samples of Lake Biwa water. From the linear relationship between the peak areas with an RT of 7.4–8.9 min by SEC analysis and DOC values of DFA by TOC analysis of a series of DFA samples (r 2 = 0.9995), the concentrations of DFA in the lake water were roughly calculated. DFA was distributed within the range 0.25–0.43 mg C l−1 and accounted for 15%–41% of DOC, with the highest ratios observed at a depth of 70 m in August and the lowest at 2.5 m in May.

Distribution of CH 4 in the north basin of Lake Biwa and tributary rivers

To determine the origin of CH4, the vertical distribution of CH4 around the thermocline in the north basin of Lake Biwa and the horizontal distribution in the Yasu and Ado rivers were measured. In 1995, CH4 concentrations (ranging from 200 to 1000 nM) exceeding the saturation level were observed just above or in the thermocline in the pelagic region off the Yasu River. These values were higher than those just below the thermocline and in the hypolimnion. CH4 concentrations in the mouths of the Yasu and Ado rivers were much higher than at other stations, around 2500 and 2000 nM, respectively. Due to the drought in 1994 when there was no water from the Yasu River flowing into the north basin, CH4 concentration just above or in the thermocline in the pelagic region off the Yasu River ranged from 49 to 74 nM. It is thus concluded that the high level of CH4 observed in the mouth of the Yasu River is one of the sources of the high CH4 concentrations in the pelagic region off the Yasu River. On the other hand, the CH4 concentration in the pelagic region off the Ado River was about 50 nM. It is thought that water flowing in from the Ado River diffused readily into the lake water because the depth of the lake in the region off the Ado River declines steeply. The maximum concentration of CH4 in the river mouths indicates that these areas are important sites for clarifying the mechanism of the decrease in dissolved oxygen in Lake Biwa and the Yodo River watershed.

Environmental chemistry of rivers and lakes, part v: a comparative study of the chemical and physicochemical characteristics of organic carbon dissolved in river and lake waters

To determine the chemical and physicochemical characteristics of dissolved organic carbon in the Ado River and the Yasu River, the main rivers flowing into Lake Biwa, the adsorption behavior onto hydrous iron oxide (HIO) and the reactivity to KMnO4 oxidant were investigated in parallel with measurement of the distribution profiles of dissolved organic carbon (DOC) along the rivers. In one year of observation at the mouths of the two rivers, DOC concentrations were found to vary in the Ado over the range 0.28–1.21 mg C l−1 and in the Yasu over the range 1.01–2.68 mg C l−1. Act-DOC, one of the fractions separated from the total DOC by its adsorption-active character onto HIO at pH 4, was thought primarily to control the variation of total DOC, as in Lake Biwa. The int-DOC, another fraction separated by its adsorption-inert or -inactive character onto HIO, remained at almost a steady value around 0.18 ± 0.07 mg C l−1 in the Ado, which was lower than that (0.35 ± 0.05 mg C l−1) in Lake Biwa. The act-DOC in river waters was reactive to KMnO4 oxidant, showing a linear relation with the amount of permanganate consumed for the reaction (chemical oxygen demand: COD). In river waters, the relation can be approximated by a straight line expressed as COD (mg O2 l−1) = 0.64 × act-DOC (mg C l−1) − 0.02. In contrast, in the lake water the relation was COD (mg O2 l−1) = 0.97 × act-DOC (mg C l−1) − 0.50.

Behavior and distribution of upstream-migrating juvenile Rhinogobius sp. (the orange form)

Upstream-migration of juvenileRhinogobius sp. OR was studied along the Ado River, a tributary of Lake Biwa. Juvenile gobies, mainly 18–21 mm in standard length, migrated from the lake in a belt of about 3 m wide in lower reaches and about 10–20 cm wide in middler reaches. Their upstream-migration was restricted to places shallower than 20 cm with bottom current velocities less than 20 cm/sec. Individual migration speed varied between 4.2–8.9 m/min at places with bottom current velocity of 8.8–20.0 cm/sec, slowing down with increasing current velocity. Most active migration occurred between 14:00 and 16:00, number of upstream-migrating juveniles decreasing with distance from the river mouth. Riffles in the mid-and upper reaches, having few slow current areas, probably present barriers to upstream-migration of the juvenile gobies, although both adults and subadults of the species are distributed in more upper reaches.

Processes and Factors of Village Desertion: A Case Study of Ogose and Ohmi in the Vicinity of Kyoto

This is a comparative study, from a micro-geographical viewpoint, on the village desertion process pattern in the case of two small hamlets-Ogose and Ohmi-in the mountainous tracts of Kyoto City (commonly called the Kitayama district), only 20km north of the center of the city. The examination has been made chiefly in terms of the change in the number of the households in each village that has taken place during the period of more than a century since the early years of the Meiji era.The two hamlets, now deserted and completely extinct, were located in the northern part of Kyoto City, on the eastern edge of the Tamba highland, topographycally a pene-plain, from which the Ado River rises and flows down into the Lake Biwa, the lagest in Japan. A chain of passes lie between the Kyoto basin and these villages.Ogose was situated at the altitude of 660m. above sea level and Ohmi 610m., they were among the highest of all the mountain villages in the Tamba highland. The average temperature is 0.2°C. in January and 25.8°C. in August, those settlements are colder by 7°C. than the Kyoto basin. As to the transportation, there are only two narrow motorable roads leading to the center of Kyoto, both in an extremely bad condition. It is a two or three hours' trudge to the nearest bus-stop.In 1885 the two villages had 15 households each, and after World War II there existed 7 in Ogose and 19 in Ohmi. However, a series of village desertion of the whole household type began in Ogose in 1969 and in Ohmi in 1971, and continued, until the former finally reached a state of complete desertion and extinction in 1972 and the latter in 1973.The difference in the number of households prior to this incident simply reflects the difference of population inflow from outside and branch families; in 1965 the household that had continued to exist ever since the time preceding 1885 untill the day of desertion was 5 in Ogose and 6 in Ohmi.The processes of desertion of settlement can be divided into three stages: the Meiji, the Taisho, and the Showa periods.(1) The Meiji period: 6 households in Ogose and 11 in Ohmi deserted their villages and half of them moved into Kyoto. The social status of the villagers who left their home was the lowest and they had to call themselves “drop-outs”. The ‘absorption power’ of the big city in those days was not yet great enough. Compared to Ohmi, Ogose remained more stable, as it was located further away from the city. It can be said that they were economically subject to Kyoto through charcoal business, whereas culturally they were still under the influence of the lake district with its long, deep-rooted tradition from the Edo period; Ogose rather thrived as a transit place, commercially and culturally.At the close of the Meiji there emerged a new transportation means of raft along a branch of the Ado River to carry out charcoal, which had made them involved in the big Kyoto culture area; Ogose was reduced to an unimportant position placed at the furthest edge of the great cultural and economic sphere of Kyoto.(2) The Taisho period: 6 households deserted each village (totaling 12), and 9 out of those moved into Kyoto. The group included a small number of what may be called positive job change type of desertion by the upper class villagers, but the majority were of the bankrupt type of desertion. This penomenon relates to the cultural and economic expansion of Kyoto, and its urbanizational effects were also felt upon those mountain villages.(3) The Showa period (up to 1965): the impact of Japan's social and economic disturbances was great to those hamlet and the ‘absorption power’ of Kyoto for some time seemed to cease and become less great. An epoch-making huge demand for charcoal and timber checked the trend of the outflowing of village populations.

A Study of Restoration of the Jori System on the Ado River Delta-fan

Jori System is a land system concerning the adjustment of partitions of agricultural land in the ancient times of Japan, and is one of the most principal elements showing phases of that time. The theme I have taken up here in this paper is how this system was applied on the Ado river delta-fan, Takashimagun (Takashima county, Shiga Pref. at present). Fig. 6 shows the locations of “Jo” and “Ri” in this area which I have restored with the help of some historic records of the Middle Ages.These are summings-up:1) The traces of this system still remains clearly in the area surrounded by the two diluvial uplands, Aebano and Taizanjino. However few traces are to be seen in the area along the basins of the Ado river and the Kamo river, or on the old river channels, the lagoons and the backswamps where there occurred frequent floods or submergence of rivers and lakes.2) According to this system, the land was divided along the two different directions: in the south it was divided along the north-south line of N16°E, covering the whole area of the alluvial plain, and in the northern part of the plain, along the line of N6°E.3) Kozu monor under the control of the Enryakuji temple was established during the period of 1135∼40, which occupied the northern part of the alluvial plain along the left hand-side bank of the Ado river and the Aebano diluvial upland. The detailed descriptions of the farm land belonging to this monor are given in “Kozusho-Kenchucho” and “Kozusho-Indencho”. Making a comparative study between the historical evidences given in “Kozusho-Indencho” and Fig.1, the following points have become clear: this farm land now lies under the water of Lake Biwa within 2.5m in depth; although the time when it sank under the water is not quite certain, it is supposed to be from the latter half of the 15th century toward the 16th.4) The Jori System seen on the alluvial plain along the downstreams of the Ado river was like this:The “First-Jo” starts at Uchioroshi in Takashima-cho situated on the southern end of the plain, and the “18th-Jo”, the northernmost one, ends at Kozu, in Shinasahi-cho. In regard to “Ri”, however, its starting points on each “Jo” are not on the straight line. Each starts at somewhere around Aebano or at the foot of Taizanjino diluvial upland in the west and disappears into Lake Biwa in the east. This difference seems to have much to do with the geographical features of this area: the gradient of the slope lying in the western part of the plain varies in different places. Fundamentally, the system applied here belongs to Omi-type Jori System: “Jo” was counted toward the direction of “Tsubo-su” and “Ri” toward the direction of “Tsubo-nami”.