??To investigate changes in tidal current arising from infilling a sea caldron and their influence on seaweed and seagrass bed habitats, numerical simulations of tidal current before and after infilling the sea caldron were carried out using a multi-level flow model. Separate simulations were conducted for stages of infilling to clarify stepwise changes in flow field, and changes in horizontal and vertical velocity distributions at the sea caldron were examined. Effects of changes in flow field on the seaweed and seagrass bed habitats around the sea caldron were also investigated. The results indicated that velocity distributions at both ends of the sea caldron changed in the final stage of infilling, while those at the center gradually changed as the filling progressed. The changes in flow field at the seaweed and seagrass beds were found to remain within the inhabitable range for the species present.
??In this study, we propose a grid-based distributed runoff model based on the spatial distribution of rainfall and land use in Dau Tieng River watershed, Southern Vietnam. In the model, the inflow/outflow matrix was integrated to effectively represent water flow between meshes, simplify programming, and shorten calculation time. Model accuracy was almost satisfactory even though rainfall and discharge observations were limited. The model was then applied to predict future changes in runoff resulting from a number of rural development and global warming scenarios. Results of the scenario analyses showed that land use changes due to rural development led to increased runoff and a more peaked hydrograph, and that variations in runoff were proportional to the rainfall variability rate associated with changes in rainfall due to global warming.
??Erratic rainfall as an effect of climate change has become a serious problem for agricultural development in Indonesia. Rainwater harvesting technology (RWH), which has been successfully applied in several areas in the world, exhibits great potential as a method of addressing this issue. In the present study, we analyze the benefit-cost ratio (B/C) of two lining materials, tarpaulin and concrete to evaluate the suitability of four small farm reservoirs (SFR). The results are as follows. (1) Applying SFR is economically beneficial, as indicated by the income increase through the rise of yield possibility in the 2nd crop season. (2) It is important to estimate the optimum irrigation area in order to obtain the maximum B/C value. (3) The relationship between the B/C value, the catchment area, and the SFR volume is clarified for the optimum irrigation area. (4) SFR concrete is more acceptable than tarpaulin in terms of the B/C value due to its longer depreciation period with less running cost.
??This paper presents a study on the impact of meteorological parameters on alpine rangeland vegetation. In Yushu, China, where rangeland degradation has been an issue of concern, vegetation condition was analyzed using Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery and ground-measured weather data. MODIS Normalized Difference Vegetation Index (NDVI) was assumed to represent the vegetation condition of the alpine rangeland, and the impact of weather parameters was analyzed statistically by multiple linear regression. The duration of the study was the 14 years from 2001 to 2014. The weather parameters included air temperature, precipitation, wind speed, air pressure, and snowfall. The results of the statistical analysis indicated that alpine pasture grows better in conditions of weaker wind, lower atmospheric pressure, smaller number of snowfall days, larger precipitation, and smaller difference of day-night air temperatures, where most of these weather conditions are regarded as “bad weather.” These results imply that water availability in summer, rather than energy availability, has greater impact on the growth of alpine pasture in the region. In addition, lower snowfall in winter resulted in better growth of grass in summer, implying that the negative impact of snow on vegetation growth exceeds its positive impact.
??Quantitatively clarifying bio-chemical water quality dynamics as affected by anaerobic microorganisms such as denitrifying bacteria, iron-reducing bacteria and sulfate-reducing bacteria plays an important role in understanding the mechanism of water environment deterioration that accompanies organic pollution. Accordingly, beaker-scale laboratory experiments were conducted in order to obtain basic knowledge concerning water quality dynamics such as ORP, nutrient salts, sulfides, and so on, near bed material under anoxic conditions. Assuming that denitrification initially caused by anaerobic respiration impacts the reduction half-reactions that later occur in phases, the purpose of this research was as follows: based on the impact of the concentration of nitrate (NO3-N) at the point when an anoxic state was reached with the increase of phosphate (PO4-P), ammonium (NH4-N), and sulfides under anaerobic conditions, their water quality dynamics were quantitatively assessed in relation to change over time of ORP. As a result, the dynamic properties of ORP under anaerobic conditions could be characterized in five steps, suggesting that the rate of decrease of ORP at each step is influenced by the initial NO3-N content, and the higher the initial NO3-N concentration, the longer ORP took to reach equilibrium of the minimized electric potential. Also, the characteristics of increases in PO4-P, NH4-N, sulfides, and DOC can be explained in relation to the transition between ORP steps, and that their water quality dynamics were modeled with either linear or non-linear regressions. Thus, it was concluded that we were able to estimate the dynamics of PO4-P, NH4-N, sulfide and DOC conveniently through monitoring of ORP while considering the influenced of initial NO3-N levels on theses water quality items.