Pingping Luo

Spatial and temporal trends in estimates of nutrient and suspended sediment loads in the Ishikari River, Japan, 1985 to 2010.

Nutrients and suspended sediment in surface water play important roles in aquatic ecosystems and contribute strongly to water quality with implication for drinking water resources, human and environmental health. Estimating loads of nutrients (nitrogen and phosphorus) and suspended sediment (SS) is complicated because of infrequent monitoring data, retransformation bias, data censoring, and non-normality. To obtain reliable unbiased estimates, the Maintenance of Variance-Extension type 3 (MOVE. 3) and the regression model Load Estimator (LOADEST) were applied to develop regression equations and to estimate total nitrogen (TN), total phosphorus (TP) and SS loads at five sites on the Ishikari River, Japan, from 1985 to 2010. Coefficients of determination (R(2)) for the best-fit regression models for loads of TN, TP, and SS for the five sites ranged from 71.86% to 90.94%, suggesting the model for all three constituents successfully simulated the variability in constituent loads at all studied sites. Estimated monthly average loads at Yishikarikakou-bashi were larger than at the other sites, with TN, TP, and SS loads ranging from 8.52×10(3) to 2.00×10(5) kg/day (Apr. 1999), 3.96×10(2) to 5.23×10(4) kg/ day (Apr. 1999), and 9.21×10(4) to 9.25×10(7) kg/day (Sep. 2001), respectively. Because of variation in river discharge, the estimated seasonal loads fluctuated widely over the period 1985 to 2010, with the greatest loads occurring in spring and the smallest loads occurring in winter. Estimated loads of TN, TP, and especially SS showed decreasing trends during the study period. Accurate load estimation is a necessary goal of water quality monitoring efforts and the methods described here provide essential information for effectively managing water resources.

Impact assessment of rainfall scenarios and land-use change on hydrologic response using synthetic Area IDF curves

In combination with land use change, climate change is increasingly leading to extreme weather conditions and consequently novel hydrologic conditions. Rainfall Area intensity-duration-frequency (IDF) curves, commonly used tools for modeling hydrology and managing flood risk can be used to assess hydrologic response under extreme rainfall conditions. We explore the influence of land use change on hydrologic response under designed extreme rainfall over the period 1976 to 2006 in the Kamo River basin. Run-off for all six designed rainfall shapes under 2006 land use is higher than that under 1976 land use, but the timing of peak discharge under 2006 land use occurs at roughly the same time as that under 1976 land use. Results indicate that run-off under 2006 land use yielded higher discharge than under 1976 land use, and rainfall shape six leads to the most extreme hydrologic response and most dangerous conditions from the perspective of urban planning and flood risk management. Future hydrologic response will differ from present due both to changes in land cover and changes in extreme rainfall patterns requiring modification to Area IDF curves for catchments.

Impact of forest maintenance on water shortages: Hydrologic modeling and effects of climate change

The importance of water quantity for domestic and industrial water supply, agriculture, and the economy more broadly has led to the development of many water quantity assessment methods. In this study, surface flow and soil water in the forested upper reaches of the Yoshino River are compared using a distributed hydrological model with Forest Maintenance Module under two scenarios; before and after forest maintenance. We also examine the impact of forest maintenance on these variables during extreme droughts. Results show that surface flow and soil water increased after forest maintenance. In addition, projections of future water resources were estimated using a hydrological model and the output from a 20km mesh Global Climate Model (GCM20). River discharge for the near-future (2015-2039) is similar to that of the present (1979-2003). Estimated river discharge for the future (2075-2099) was found to be substantially more extreme than in the current period, with 12m3/s higher peak discharge in August and 7m3/s lower in July compared to the discharges of the present period. Soil water for the future is estimated to be lower than for the present and near future in May. The methods discussed in this study can be applied in other regions and the results help elucidate the impact of forests and climate change on water resources.

Sustainability and Life Span of Japanese Reservoirs-Statistic analysis of sedimentation condition in Japan

The sedimentation condition directly affected the sustainability of reservoirs which are as long as they offer sufficient water storage for their objectives such as electric power and water supply. Statistic analysis of sedimentation condition could give a measure of the sustainability and life span of reservoirs. In this study, we built a database of 421 reservoirs in Japan from 1994 to 2003. First, this paper describes the Mann-Kendall trend analysis of sedimentation in terms of total amount and annual average. Spatial distribution of sedimentation condition for each dam is presented by using geographic information systems (GIS). Most of 421 dams had a significantly increasing trend of total sedimentation with more than 2.0 in terms of Z test value. Most decreasing trend of total sedimentation are found at Chubu region, the west of Kyushu region and Tohoku region. For the annual average sedimentation, most of 421 dams show the significant decreasing trend, especially in the Chubu region (Higashiyama area and Tokai area), Kinki region and the northwest of Kyushu region. On the other hand, the significant increasing trend of annual sedimentation is presented at Hokuriku region, the west of Kanto region and the west of Shikoku region. The life span of all 421 dams are calculated by using a simple statistical method based on the Mann-Kendall trend analysis of sedimentation condition. The life span in Chubu region, Hokkaido region and Kyushu region had the shorter life span than other regions with 335, 473 and 559 years in average. In Chugoku region, there are eight dams that the life spans are over 5000 years. The relationship between the life span and watershed characteristics is estimated in this study. The average slope of watershed may have the high relationship with the sediment production. This study could give a direct information for the policy maker to conduct the best management on dams.

Assessment of hydrological extremes in the Kamo River Basin, Japan

ABSTRACT A suite of extreme indices derived from daily precipitation and streamflow was analysed to assess changes in the hydrological extremes from 1951 to 2012 in the Kamo River Basin. The evaluated indices included annual maximum 1-day and 5-day precipitation (RX1day, RX5day), consecutive dry days (CDD), annual maximum 1-day and 5-day streamflow (SX1day, SX5day), and consecutive low-flow days (CDS). Sen’s slope estimator and two versions of the Mann-Kendall test were used to detect trends in the indices. Also, frequency distributions of the indices were analysed separately for two periods: 1951–1981 and 1982–2012. The results indicate that quantiles of the rainfall indices corresponding to the 100-year return period have decreased in recent years, and the streamflow indices had similar patterns. Although consecutive no rainfall days represented by 100-year CDD decreased, continuous low-flow days represented by 100-year CDS increased. This pattern change is likely associated with the increase in temperature during this period. EDITOR D. Koutsoyiannis ASSOCIATE EDITOR E. Gargouri

Applying a water quality index model to assess the water quality of the major rivers in the Kathmandu Valley, Nepal

Human activities during recent decades have led to increased degradation of the river water environment in South Asia. This degradation has led to concerns for the populations of the major cities of Nepal, including those of the Kathmandu Valley. The deterioration of the rivers in the valley is directly linked to the prevalence of poor sanitary conditions, as well as the presence of industries that discharge their effluents into the river. This study aims to investigate the water quality aspect for the aquatic ecosystems and recreation of the major rivers in the Kathmandu Valley using the Canadian Council of Ministers of the Environment water quality index (CCME WQI). Ten physicochemical parameters were used to determine the CCME WQI at 20 different sampling locations. Analysis of the data indicated that the water quality in rural areas ranges from excellent to good, whereas in denser settlements and core urban areas, the water quality is poor. The study results are expected to provide policy-makers with valuable information related to the use of river water by local people in the study area.

Numerical Assessment of Shallow Landslide Using the Distributed Hydrological–Geotechnical Model in a Large Scale

Kyushu is the third largest island of Japan. The natural hazards accompanied with geomorphic changes like landslides and debris flows occur at many places in Kyushu region. In this study, a hydrological–geotechnical modelling system was applied in Kyushu using observed rainfall for a regional shallow landslide prediction system. The physically based distributed landslide model has been developed by integrating a grid-based distributed kinematic wave rainfall-runoff model with an infinite slope stability approach. The resulting time-invariant landslide susceptibility map shows good agreement with the spatial patterns of observed landslides in Kyushu region. Application of the model to calculate the shallow landslides shows that the model can successfully simulate the effect of rainfall movement and intensity on the spatiotemporal dynamic of hydrological variables that trigger shallow landslides. The results of this study can be used to develop the potential applicability of the modelling system for shallow landslide disaster predictions and warnings.

Reconstruction assessment of historical land use: A case study in the Kamo River basin, Kyoto, Japan

Reconstruction assessment of historical land use can be useful for understanding historical conditions and the impact of long-term land-use change. This study establishes a new method to estimate historical land use based on a set of basic rules generated from the comparison of present land-use and historical documents. This method has been formalized in the paleo-land-use reconstruction (PLUR) program, allowing users to quickly reconstruct historical land use using historical information. The 1843, 1902 and 1927 historical land use conditions were generated using the PLUR model for the Kamo River basin (KRB). Our results show that between 1902 and 1976, three golf courses (Ohara Public course, Kamigamo course and Funayama course) replaced forest land in the KRB. As a result of agricultural development, the area occupied by paddy fields in 1843 was 2.48km^2 less than that in 1902. Urban areas increased from 1843 to 1976, mainly reflecting declining coverage of paddy fields after 1902. The approach presented in this study can be used to support land-use change analyses and reconstruction of paleo-hydrology. This study also provides a discussion of the major drivers of land use change.

Mapping of Japanese areas susceptible to snow cover change

Abstract Many of the Japanese regions subject to seasonal snow cover are characterized by low elevations and relatively high winter temperatures. A small change in winter temperatures could render many of these areas susceptible to snow cover change and consequently affect water resources management. This paper describes a climatological approach combined with an AGCM output to identify the regions and main river basins most sensitive to snow cover change in the case of climate change in Japan. It was found that a 1°C rise in temperature during the winter season could increase the snow-free area of Japan by 6%. The snow cover of Tohoku region and Mogami and Agano river basins was found to be the most sensitive to climate change. The AGCM output for a future scenario presents a reduction in total snowfall and an earlier peak in snowmelt for all regions. Editor Z.W. Kundzewicz Citation Chaffe, P.L.B, Takara, K, Yamashiki, Y, Apip, Luo, P., Silva, R.V., and Nakakita, E., 2013. Mapping of Japanese areas susceptible to snow cover change. Hydrological Sciences Journal, 58 (8), 1718–1728.

Effects of Phytoremediation Treatment on Bacterial Community Structure and Diversity in Different Petroleum-Contaminated Soils

Increased exploitation and use of petroleum resources is leading to increased risk of petroleum contamination of soil and groundwater. Although phytoremediation is a widely-used and cost-effective method for rehabilitating soils polluted by petroleum, bacterial community structure and diversity in soils undergoing phytoremediation is poorly understood. We investigate bacterial community response to phytoremediation in two distinct petroleum-contaminated soils (add prepared petroleum-contaminated soils) from northwest China, Weihe Terrace soil and silty loam from loess tableland. High-throughput sequencing technology was used to compare the bacterial communities in 24 different samples, yielding 18,670 operational taxonomic units (OTUs). The dominant bacterial groups, Proteobacteria (31.92%), Actinobacteria (16.67%), Acidobacteria (13.29%) and Bacteroidetes (6.58%), increased with increasing petroleum concentration from 3000 mg/kg–10,000 mg/kg, while Crenarchaeota (13.58%) and Chloroflexi (4.7%) decreased. At the order level, RB41, Actinomycetales, Cytophagales, envOPS12, Rhodospirillales, MND1 and Xanthomonadales, except Nitrososphaerales, were dominant in Weihe Terrace soil. Bacterial community structure and diversity in the two soils were significantly different at similar petroleum concentrations. In addition, the dominant genera were affected by available nitrogen, which is strongly associated with the plants used for remediation. Overall, the bacterial community structure and diversity were markedly different in the two soils, depending on the species of plants used and the petroleum concentration.