Many models to assess the impact of agricultural activities for the environment have been developed recently. And the accurate soil characteristics are important in applying these models. However, measuring the all soil characteristics costs and takes long time and is not efficient. Therefore, many models have pedotransfer functions (PTFs). It was confirmed that the performance of the PTFs depends strongly on the data that has been used for the development of the PTFs. So, in this study, we examined influences of the bulk density for the retention curve and the hydraulic conductivity of Shimajiri maji soil at first, and applied the PTFs (ROSETTA) to evaluate the practicality. As a result, it was confirmed that there were some errors in applying the ROSETTA to estimate the retention curve of the Shimajiri maji soil.

  Groundwater resources at Dalad, Inner Mongolia were investigated by groundwater metering in 2013 as supplementary investigation during 2002-2006. Since Dalad is located in the middle reach area of the Yellow River basin and classified as arid or semi-arid area with less than 360mm precipitation and more than 2,200mm potential evaporation, the river water is not sufficiently supplied to the area and therefore, irrigation and industrial waters inevitably depend on groundwater resources. As a result of the investigation, groundwater levels at almost of all the observation wells have descended remarkably since 2005 and especially the decreases in the southern part of the objective area are severe by a range of 0.8-5.4m. The groundwater amount in the southern part in 2013 is roughly estimated to be 2.91×10⁷m³, which proves a distinct downward trend. According to the autoregressive-like forecasts, including the Holt-Winters method, the unconfined groundwater in the southern part would be unavailable in the middle of 2030’s. The groundwater amount of the objective area is also decreasing severely and the increase in irrigation and industrial waters must be its potential reasons, except the decrease in the precipitation during 2005-2013. The change of the groundwater usage and flows might decrease the discharge of the Yellow River through the groundwater seepage and it is not only a water resources problem in this area, but also in the basin scale. Therefore, the groundwater management in this area is a pressing issue and should be done by local government or some water-utilization association against both irrigation water and industry water users. The water resources are inherently including uncertainty, so continuing observation is essential to maintain the water resources at Dalad.

  We clarify the effect of volcanic activity on the succession of woody vegetation and growth environment, and water infiltration rate on the northern flank of Sakurajima Volcano, Japan. We made survey quadrants at slope distances 2.1 km, 2.3 km, 2.8 km, 3.3 km and 3.6 km from the Minami-dake crater of the volcano and conducted field investigations. The number of trees and tree species, breast height cross-sectional area, Fisher-Williams index of diversity, forest soil thickness, and water infiltration rate all increased with distance from Minami-dake. However, thickness of the volcanic ash layer deposited since the 1914 Taisho eruption and pH of the forest soil surface layer decreased with distance. Because of long-term volcanic activity, woody vegetation in the survey quadrants was poorer than the climax forest. Moreover, the rate of succession of that vegetation, water infiltration rate, and forest soil development were much slower than those of the climax forest.

  The objective of this study is to evaluate absorptive abilities of nitrogen and phosphorus by natural material for slope protection. Hedge bamboo (Bambusa multiplex) was introduced as a test material in this study. To quantify the absorbed nitrogen and phosphorus by hedge bamboo, logistic model described as a function of cumulative temperature was introduced. Water tank experiments with high and low concentration water were performed to optimize the parameters of this model. The experimental results indicated that the absorptive abilities of nitrogen and phosphorus by hedge bamboo changed with time and initial concentration. Using the experimental data, the parameters of logistic model were identified. The calculated absorption of nitrogen and phosphorus had good agreement with the measured data. The changes of absorbed nitrogen and phosphorus could be predicted using this model.

  Prompt gate control of diversion weirs is required to flow the excess water under the flood condition. It is also important for gate opening method of diversion weir to ensure safety and simplicity to prevent the water accidents and human errors. The aim of this study is to develop the optimal method of gate opening method of diversion weir under the flood condition. A simulation model describing one dimensional unsteady flow was introduced to evaluate the effect of the gate opening of multiple diversion weirs on the downstream current. Using this model, the surface water profile was estimated under the different patterns of gate opening procedure. The simulateds result indicated that the fluctuation of water level and extent of impact by gate opening varied with the speed of the gate opening. The appropriate speed of the gate opening was clarified to reduce the fluctuation of water level by gate opening under the flood condition. The method introduced in this study is effective to develop the optimal gate control method of the diversion weirs for not only prompt flood protection but also safety.

  Central polder in Isahaya Bay in south-west Japan was reclaimed in 1997. Farming was started in 2008 after improvement of soil salinity and hydraulic conductivity conditions. Although the present soil conditions in the root zone are favorable and agricultural productivity has been increased, the crop stress due to wetness and drought is still concerned. The aim of this study is to predict risk of the water stress on crop due to wetness and drought. Annual changes of the soil moisture condition and soil water balance in the crop field were simulated with SWAP (Soil-Water-Atmosphere-Plant) model. In the simulation scenario, potatoes were grown from 20 February to 30 June and from 10 August to 20 December. Simulation results indicated that the soil moisture condition varied with the precipitation and the stress due to wetness was concerned under frequent and heavy rainfall. However the effect of the wetness decreased relatively quickly because of prompt drainage of excess surface and subsurface water. Drought stress was remarkable during the continuous dry weather days. To reduce the stress due to the drought, a scenario analysis was performed assuming the intermittent irrigation. The simulated results indicated that proper irrigation and drainage management is necessary to prevent stress due to wetness and drought.