Water Supply in rural area is still a crucial issue in many countries. Storage in groundwater aquifer is a promising alternative for water harvesting. Rainwater tank system on a household scale is proposed for storing excessive water both in the tank and in the aquifer during rainy season and recovering the recharged water from the aquifer for use during dry season. The design concept is described with a calculation sample for reference. From the data of water level and water quality, obtained through monitoring 400 constructed tank systems, the system proposed is proved to be workable and effective in both quantitative and qualitative aspects, especially in the area with high rainfall and moderately or low yielded aquifer.

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This paper is associated with evaluating the quality of groundwater and its suitability for irrigation use in Jamalpur and Sherpur districts of Bangladesh. Water samples collected from 31 deep tubewells (DTWs) and 1 shallow tubewell (STW) in the Jamalpur district and from 22 DTWs and 2 STWs in the Sherpur district are tested with a view to evaluating salinity, infiltration, toxicity and miscellaneous problems. All of the samples are found free from salinity hazard for irrigation use, and also from toxicity of sodium, chloride and iron. 37.5% of the samples shows boron toxicity problem if very boron sensitive crops are considered. 21.4% and 3.6% of the samples show boron toxicity problem for boron sensitive crops and moderately boron sensitive crops, respectively. If moderately to highly boron tolerant crops are considered, 100% of the samples shows no boron toxicity problem. Ammonium nitrogen and pH values are within their permissible limits. In terms of bicarbonate content, 73.2% of the samples shows slight to moderate restriction on irrigation use. A sever infiltration problem for the 78.6% samples and a slight to moderate infiltration problem for the remaining 21.4% are identified that are mainly caused by the low salinity of the samples. Calcium is so deficient as to reduce infiltration rate. Application of calcium fertilizer may overcome this problem. Compared to the DTWs water samples, some investigated elements from the STWs samples show irregular pattern. Therefore, water quality in shallow aquifer needs to be investigated thoroughly. To see the relationships among different combinations of water quality determining indicators, correlation coefficients are estimated. Only sodium adsorption ratio (SAR) and adjusted sodium adsorption (adj R_<Na>) are found to be highly correlated each other with a correlation coefficient of 0.99.

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This paper deals with a second order accurate Godunov-type numerical model of the two-dimensional shallow water equations discretized using finite volumes. Roe's flux function is used for the convection terms, and a non-linear limiter is applied to prevent non-physical oscillations. The mathematical formulation of shallow water equation, used in this paper, is suitable for cases where the bathymetry is non-uniform. The model is based on hierarchical quadtree grids automatically generated to fit the boundary configuration. A hydraulic jump and a tidal wave propagation into a channel with uneven bottom are simulated as validation tests and then the flows over a cascadetype head work and through a vertical slot-type fishway are computed as applications.

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Small-scale irrigation tanks have been an important source of irrigation in Japan. These contribute nearly 10% of the total irrigated area, controlling the ravages of drought. Since many of the total 246,158 tanks are centuries-old, their rehabilitation and/or modernization are in emerging need. This paper is associated with one of the serious issues envisaged, i. e., excess leakage of impounded water through an earthen embankment. As a case study, an attempt is made to identify leaky embankment transections for an overage tank in Matsuyama, Ehime Prefecture, Japan, which is in real need of rehabilitation to prevent a calamity of the subsequent embankment-break. Using the up-to-date data (tank water level, water level and temperature in the boreholes installed, leaked water amount, etc.) obtained from long-term in-situ observations, their relational analyses are carried out to investigate the hydro-geological aspects of the embankment and find a transection of major leakage-path. The results demonstrate that the leaky transection with extremely high permeability (1.0 × 10^<-2> cm/s) exists closely to the right-bank of the tank, and the flow seeping along the toe of the embankment is indeed a result of leakage of the impounded water.

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We are advancing the development of the new managing system for maintenance of the irrigation earth dam by using two-dimensional resistivity tomography technique, which enables us to supplement the limit of traditional maintenance system by using buried meters. It is expected that we successfully estimate two-dimensional distribution of water contents or porosity in the embankment site. Before applying this system to actual embankment site, we made small model embankment and investigated the possibility of resistivity tomography application. We arranged the electrodes for resistivity tomography in order to surround the embankment. Besides, we arranged open piezometers to acquire actual water behavior in the embankment. Then we conducted resistivity tomography measurement to detect the change of water level in the embankment. From the differences between resistivity distributions before and after water storing, we find resistivity decreasing areas caused by water intrusion. This result is well matched to the permeability of the fill and the values of open piezometers.

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The probability is that the effects of acid rain will be more dramatic in revegetated areas than in forest soil areas due to the greater level of deterioration in the physical and chemical properties of the soil in revegetated areas. For this reason, we measured the pH value of forest-tree stem flow and gathered test samples of revegetated plant characteristics. The results show that for conifers, the pH value is highest in the rainfall outside the tree crown, and generally declined inside the tree crown and in the stem flow. In contrast, for broad-leaved trees, the pH value increases in the following order : outside the tree crown, inside the tree crown and in the stem flow.We are able to predict a small variation in the pH value in the stem flow of all tree species peculiar to this tree type. The internal factors are stand structure, tree from, leaf from, bark structure, and degree of difficulty during eluviation at a particular leaf growth stage. The rainfall is considered as a contributing external factor. The above findings indicate the necessity of determining which revegetated species and methods of planting are to be used for a particular tree characteristic. We must also reduce the load on revegetated areas, given that the majority of rainfall infiltrates via the soil in the form of rainfall inside the tree crown and stem flow.

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The Island of Tobishima, Yamagata Prefecture, has seven small-scale multi-purpose dam reservoirs whose storage capacities are within the range of 1,470 to 17,320m^3. These render great service to the eradication of inherent water scarcity. No or insufficient rain during a dry spell of summer to autumn, however, often causes serious droughts and water shortages. Thus effectively collecting rainwater gifted on their watershed is a sheer need to perennially meet the water demand. In this paper, in order to provide basic knowledge for forest preservation or treatments that are effective means for water conservation, inflow characteristics of the reservoirs are investigated. The run-off reduction curves for the watersheds selected are derived through regarding the increased reservoir water during a no-rain spell as run-off water from the watershed. In addition, by use of the data obtained from field tests, the potential infiltration is evaluated for both the forest soil and the dry-field soil. The results invite us to the conclusion that forestations and reforestations in all possible areas including non forest ones are needed for enhancement of water conservation as well as erosive soil protection.

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Instructions are given to prepare the manuscript of an English paper submitted to the Journal of Rainwater Catchment Systems. Being a model in itself, the document demonstratively prescribes the layout of the manuscript. Manuscripts should be typed on one side of white A4 size paper when they are submitted. Accepted manuscripts will be off-set printed. Titles of papers, names and affiliations of authors, abstracts, main texts, headings, references, equations, mathematical symbols, captions of figures and tables and so on should be in specified fonts. All references cited should be collected together at the end of the paper. Figures and Tables with their captions should be placed appropriately.

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Instructions are given to prepare the manuscript of a Japanese paper submitted to the Journal of Rainwater Catchment Systems. Being a model in itself, the document demonstratively prescribes the layout of the manuscript. Manuscripts should be typed on one side of white A4 size paper when they are submitted. Accepted manuscripts will be off-set printed. Titles of papers, names and affiliations of authors, abstracts, main texts, headings, references, equations, mathematical symbols, captions of figures and tables and so on should be in specified fonts. All references cited should be collected together at the end of the paper. Figures and Tables with their captions should be placed appropriately.

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