For integrated and sustainable water resource managements, it is essential to understand water balance of river basin. Infiltration (groundwater recharge), a balance calculated by subtracting evapotranspiration and runoff from precipitation in a water balance analysis, is a key factor for groundwater resources developments and 3D groundwater flow analyses. Concerning precipitation and evapotranspiration, it became possible to accurately estimate the distributions, because of recent progress in monthly climate grid data, such as radar AMeDAS data. For estimation of runoff, on the other hand, it is the great challenge to establish method for runoff in ungauged basins, because the gauging stations are usually set up in only limited main rivers.
In this paper, focusing on close relation of topography and runoff, the runoff of ungauged catchments in Shimokawa area, Hokkaido, was estimated by the "runoff index" derived from the geomorphometry and statistic analysis using DEM data. Comparison between the runoff index obtained from DEM data and the observed runoff data, dated on August of 2008, show a clear positive correlation. The result of the study proves that the runoff index is reasonably useful for estimation of runoff, showing that it is possible to estimate runoff of ungauged basin from runoff index by linear regression equation.

View full abstract

Paired catchment experiments are a useful method for determining the relationship between vegetation cover and water yield. We collected the results and detailed information of 69 watershed experiments on deforested treatments from all over the world. We characterized each catchment according to the following four aspects: vegetation type, treatment, condition of forest soil, and annual rainfall. The effects of these catchment characteristics on annual water yield changes were evaluated using the Type I Quantification Method proposed by Hayashi (1952), which is a type of multivariate regression analysis. The results showed that annual water yield changes were affected by annual rainfall, treatment, forest soil condition, and vegetation types in this sequence of degree of effect. In particular, the effect of annual rainfall was very strong. The effects of treatment and forest soil condition also had a significant influence on annual water yield changes.
Among vegetation types, the coniferous forest category showed slightly higher water yield changes compared to the hardwood forest category. An additional analysis was conducted for the same 69 watershed experiments to assess the following factors: biome and vegetation type, treatment, and condition of forest soil. We classified each of the 69 watersheds by 11 combinations of biome and vegetation type, including taiga (coniferous), temperate rainforest (coniferous), temperate rainforest (hardwood), temperate forest (coniferous), temperate forest (hardwood), temperate forest (scrub), open forest (coniferous), open forest (hardwood), open forest (scrub), Mediterranean forest (scrub), and tropical monsoon forest. The effect of each category on the annual water yield was shown as a category score. The results showed that the category score of each biome type differs. Each vegetation type in the same biome type had a different category score. In temperate rainforest and temperate forest, the category score of coniferous forests was larger than that for hardwood forests. However, in sparse woodland, the category score for coniferous forests was smaller than that for hardwood forests. We conclude that the effect of vegetation on the annual water yield depends on the type of biome.

View full abstract

A life of a river ecosystem is great influenced the erosion and the accumulation of the sediment with increasing river regime by a large flood of a typhoon and a frontal rain. For this reason, the flood impact on a the habitat of aquatic animals that live in the river bed, and change the community. There is the data of aquatic animals in the upper TONE river, Gunma Prefecture from 1979 to 2004. We have studied river regime control that have an effect on aquatic animals in a river ecosystem. In this article, we have studied the spectrum period and the density which are related to the river regime and aquatic animals used by fast fourier transform in the planning point of TONE river in Yattajima, Gunma Prefecture. We show our success in decrease of aquatic animals affected by variations in river regime. Moreover, it is not transformed the life type of gliding into that of net-spining which is the study of succession and climax advocated by Dr. Matsunae TSUDA. In addition, it is confirmed the dominant species of creeping and burrowing aquatic animals that are abjusted to the life cycle changed by river regime.

View full abstract

We compared snow depths in a Cryptomeria japonica forest of the Nagasaka experiment with a thinned slope, skid trail, unthinned slope, and meteorological station in Akita prefecture during the winter season of 2008/9. Snow depth was measured with a calibrated steel rod and estimated with temperature sensors installed at 0, 25, 50 and 75 cm height. The snow depth during the deposition period was in order: meteorological station > skid trail > thinned slope > unthinned slope. Snow depth declined quickest in order: meteorological station > thinned slope and skid trail > unthinned slope during the snowmelt period. It was suggested that snow depth depended on the canopy openness, which affected the interception of snowfall and radiation balance. We also observed a remarkable decline in snow depth caused by subsurface flow during snowmelt runoff in the skid trail. A snow depth recorder of the thermometer type was effective to measure snow depth in the forest and to identify snowmelt runoff.

View full abstract