Makoto Nakatsugawa
Muroran Institute of Technology
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Featured researches published by Makoto Nakatsugawa.
Archive | 2016
Tadaoki Itakura; Makoto Nakatsugawa; Hikaru Sugimoto; Yasuharu Watanabe
The variation of the water level at Palangka Raya is well described by the Nearest Neighbor Method (NNM) and the prediction can be made with 1-month lead time. A rainfall runoff model, traditional Tank Model, is applied to analyze the rainfall runoff to predict the water level at Palangka Raya using the data of several rainfall gauging station. The water balance is evaluated at Palangka Raya from the rainfall, the discharge and the evaporation.
Journal of Japan Society of Civil Engineers | 2013
Naoki Hayashishita; Makoto Nakatsugawa; Tomohide Usutani
This study discusses the feasibility of maintaining storage capacity for small-scale hydropower generation by operating flood control dams flexibly. Currently in Japan, shortages in electrical supply have been a concern. It is hoped that this study will mitigate such shortages. For flexible dam operation, it is necessary to recover the dam’s flood control capacity by releasing dam water ahead of predicted flooding. To obtain water for small-scale hydropower, a flexible dam operation using the cumulative forecasted rainfall for pre-releasing was considered. We examined such release by using the flood data of previous years. It was found that recovering flood control capacity of a dam is possible before the start of storing flood water. It was found that by using appropriate dam operation, there is a possibility for securing dam water for small-scale hydropower.
Journal of Japan Society of Civil Engineers | 2012
Koki Sugihara; Makoto Nakatsugawa
In the Barato River, eutrophication has been occurring because of urban effluent and river cutoff improvements. To improve the water quality, additional water has been conveyed into the Barato River since 2007. This study aims to evaluate the effects of such conveyance on water quality. At the Jyobukobon, BOD was found to increase by conveyance from the Sosei River and to decrease by conveyance from the Ishikari River. At the Tarukawa-Goryumae, BOD was found to decrease slightly by water conveyance from the Sosei River but to show no clear changes in the year after conveyance from the Ishikari River. To evaluate the effects of water conveyance, an ecosystem model was developed that enables year-round predictions, including for the freezing season. A water quality simulation for four consecutive years estimated a decrease in BOD by about 1.0 mg/L at the Jyobukobon and about 0.6 mg/L at the Tarukawa-Goryumae. Also, nitrogen density was estimated to decrease by water conveyance.
Journal of Japan Society of Civil Engineers | 2012
Terumasa Nishihara; Makoto Nakatsugawa
For better estimation of snow water equivalents for dam basins in cold snowy regions, snow depth distribution was investigated in relation to both elevation and aspect of slope using a high-resolution digital elevation model (DEM) created from an airborne laser scanning survey conducted on a certain day in the snowy period and another one in the snow-free period. Based on the results, a snow water equivalent estimation model was developed. The model was used to estimate snow water equivalents in six dams, and resulted in estimates with a higher level of accuracy than those based on snow surveys and existing models.
Doboku Gakkai Ronbunshuu B | 2005
Tomohide Usutani; Makoto Nakatsugawa; Keisuke Kudo
For comprehensive water management and water environmental planning in large river catchment areas, the longterm hydrologic cycle need to be understood. In cold, snowy regions, the snow process (falling, accumulation, and melting) plays an important role on the hydrologic cycle. An understanding of snow cover volume and snowmelt volume is essential. Analysis of the water balance of the catchment area also requires accurate estimation of evapotranspiration, which is affected by soil and vegetation.This report applies a two-layer model toward estimating the evapotranspiration, snow cover volume, and snowmelt volume of 1-km meshes. The model incorporates heat balance between the air, the vegetation layer, and the ground surface. Observed values for evapotranspiration, snow cover volume, and snowmelt volume were compared with estimates generated by the model. These estimates were used to reproduce long-term runoff, in order to examine the validity of the estimates. The estimates were found to accurately reproduce the measurements. This has enabled the quantification of long-term hydrologic factors for cold, snowy regions.
Doboku Gakkai Ronbunshuu B | 2005
Ken-ichi Takada; Makoto Nakatsugawa; Yasuhiro Murakami
Basin-wide hydraulic and material behaviors of a river are important factors reflected in basic indicators that are used to form consensus among residents for a river project in both environmental aspects and flood control and water utilization aspects. These indices are used for preserving ecosystem and maintaining river channels, banks and structures. We studied how runoff characteristics and water components of a river relate to the geology, climate and land use in some river basins in Hokkaido using multiple regression analysis. We found that hydraulic parameters tend to vary according to geology, which confirms past studies. We also found that water quality components were greatly affected by geology, such as the distribution of plutonic rock, metamorphic rock and unconsolidated sediment, although the data covers normal time only. This could prove to be an important consideration in river management.
Doboku Gakkai Ronbunshuu B | 2004
Yasuhiro Murakami; Ken-ichi Takada; Makoto Nakatsugawa
The behavior of sediment and other substances in the entire basin is an important factor in maintaining the river channel as well as conserving the aquatic ecosystem at these places. It is especially important to understand transport during flooding, when large amounts of substances are transported. The most recent large-scale flood in Hokkaido, Japan, occurred in August 2003. It struck Hidaka district, causing many injuries and fatalities. The sediment runoff from that flood is still of concern, and examination on its potential effects is awaited. We surveyed dam basins in Hokkaido to study the relationship between the volumes of sediment and water quality components and the geological and vegetation conditions. Sediment transport during flooding is known to have significant impacts on the water environment. To analyze the flood-related runoff characteristics of sediment, the Saru River basin was chosen for its large sediment runoff. This paper summarizes the substance balance of the basin and analyzes the causal relationship between that balance and the conditions of a basin that tends to experience particularly severe damages.
Doboku Gakkai Ronbunshuu B | 2004
Saori Hayama; Makoto Nakatsugawa
In Sarobetsu Mire, the groundwater level has dropped because of drying. There is concern regarding increase in the area occupied by Sasa bamboo and displacement of the original vegetation. The mire basin has seen decreases in snowfall and river water level during the snowmelt season. For mire conservation, it is necessary to understand how changes in the hydrological cycle affect the groundwater in the basin.In this research, to determine howSasabamboo has spread, we employed remote sensing data collected over the last 23 years as well as ground truth data. We separated river runoff components to clarify water balance in the basin and estimated rates of rainfall and snowmelt water recharge into groundwater. These estimates were used as simulation inputs. The simulation was designed to analyze groundwater responses to changes in rainfall, snowmelt water volume, and river water level, toward revealing a causal relationship with the increase inSasabamboo-covered area.
Doboku Gakkai Ronbunshuu B | 2003
Koji Kato; Makoto Nakatsugawa
The Barato River is largely an enclosed water area, the flow tends to become stagnant and the river is subject to the inflow of pollution loads from its surrounding areas. As a result, the growth of green algae and other eutrophication phenomena have emerged in recent years. To prevent the Barato River from becoming eutrophicated, it is necessary to understand the space structure and formation factors of the water quality.In this study, the focus is placed on the topographical classification of upper, middle and lower lake basins in calculating the water and load balances for each of these basins. The water and load balances are clarified in consideration of the complex outflow routes of the river water via urban sewerage. As a result, it was learned that incoming loads at times of rain and the loads from bottom sludge may be the primary supply source of suspended solids in the river. Based on the calculation results, this paper aims to comprehend characteristics related to the formation of water quality of each lake basin, in order to use these characteristics as the basic data for the purification of water quality and the preservation of the water environment.
Doboku Gakkai Ronbunshuu B | 2003
Saori Hayama; Makoto Nakatsugawa; Xiangwei Zhang
In recent years, the Sarobetsu Mire is suffering from aridification allowing for the invasion of Sasa bamboo grass. In order to clarify the cause of aridification, the hydrologic process in the entire watershed must be properly assessed. Specifically, reliability of assessments of the snow accumulation and snowmelt are needed to evaluate the water balance in cold, snowy regions.This paper focuses on the hydrologic process estimated by the two-layer model that deals with the heat balance in the atmosphere, vegetation layer and ground surface as well as the simulations of groundwater. Accordingly, the hydrologic processes including the obscure factors such as snow accumulation, snowmelt and evapotranspiration were properly assessed. Based on such assessment, the characteristics of groundwater are analyzed using FEM. The Proposed method is considered to be proper is assessing water balance in cold, snowy regions and its effect on the groundwater.