The aim of this study was to investigate the influence of organic mulching on soil temperature and moisture content. An experiment was conducted in a pineapple plantation at Lampung province, Indonesia from July 2001 to September 2002 using tapioca wastes and rice husk. There were 5 treatments namely: control/no mulch, rice husk mulch, cassava bagasse mulch, cassava peel mulch, and black polyethylene film mulch. The results showed that the soil temperatures of the surface layers under cassava bagasse and black polyethylene film mulches slightly increased with the increase in air temperature, while rice husk and cassava peel mulches decreased the heat convection into soil surface by retaining the incoming solar radiation heat within mulches layers. However, soil temperature regimes were greatly ameliorated by the mulching materials and that enhanced water absorption by pineapple, therefore the total wet biomasses and yields were improved. Cassava bagasse mulch enhanced effective rainfall during rainy season, better than the other mulching materials.
This study was carried out during April-May, 2005 to explore the management and operation of the Kumroj FMIS, one of the Farmer Managed Irrigation Systems operating (FMIS) in three village development committees (VDCs) of the eastern Chitwan district, Nepal. The Kumroj FMIS committee is responsible for the operational and managerial affairs of the system while the East Rapti Water Users Association is the apex body that provides major/external financial help for this system including all the FMISs in that area. This system delivers service to the beneficiaries on an unbiased and transparent manner. The rights, rules, and duties related to operation and management are entirely under the control of the water users themselves. In this system, water in each branch canal is allocated depending upon the area and type of land to be irrigated as well as the season. The irregular water supply resulting from the unlined canals is the major constraint encountered in the effective service delivery of this system. Further, the tail users receive less of the irrigation water as compared to the head users. The practice of labor mobilization based on households utilizes little technology. Proper repair and maintenance as well as canal improvement work is of utmost important to reduce the conveyance loss. The administrative work, especially communication, is heavily dependent on Panipale (water guards), hindering the smooth operation of system. Therefore, restructuring the administrative framework as well as improving the canals is of utmost importance for the sustainable and effective functioning of Kumroj FMIS.
Overexploitation of coastal aquifers has become a common issue with many coastal regions experiencing extensive seawater intrusion, resulting in severe deterioration of groundwater quality. When analyzing the freshwater quality extracted from the pumping wells in coastal aquifers, the movement of very low concentrations of the solute is critical in analyzing the level of contamination in pumping wells. This research analyzes the effectiveness of four seawater control measures using a hypothetical steady-state salt distribution model in a representative cross-section perpendicular to the coastline using a two-dimensional density-dependent solute transport model through homogeneous media. It is established that the shallow pumping wells are more preferable than the deep pumping wells as they have relatively lower concentration value in the pumping well. Low permeable aquifers give high concentration values in the pumping well and the extent of seawater intrusion is large than the high permeable ones. The level of contamination in the pumping well is proportional to the extent of seawater intrusion wedge. Pumping wells located further away from the seashore are not affected by the presence of the seawater intrusion wedge; however, this may not be an effective method of controlling seawater intrusion. Deep recharge wells closer to the pumping well seem to be the most effective method of controlling the extent of seawater intrusion and the concentration value in the pumping well. Deep seawater pumping wells located relatively away from the pumping well could be used to control seawater intrusion if proper disposal methods for the extracted saltwater are implemented. Low permeable barrier walls located closer to the pumping well could be used, although the initial cost of construction may be high.
In natural disasters, the agricultural activity sometimes suffers enormous damage such as failure of an irri-gation tank and a water channel. To produce an agricultural commodity in such emergency circumstances, water has to be supplied by temporary works. In many cases, the water supply line is temporarily built from undamaged tanks or head works. In this paper, the selection method of the temporary irrigation water supply line with GIS was presented. The digital elevation model having 2.5 m resolution was used in GIS. The functions of GIS software were used as much as possible because the method has to be easily and quickly operated. Since the facility has to be constructed economically and rapidly, it was assumed that the water supply line would be constructed on the ground surface without excavation works and the gravity irrigation of a closed type pipeline would be adopted. For the siphon design, the location giving the high negative pressure was avoided. To examine the selected routes, the indexes indicating the ratio of positive pressure, the length of the line and the undulation of the route were introduced. It was found that the method using the information of elevation gave the economic route and the method using the gradient and slope direction information gave the safe and easy constructible route.
Authors have developed the elastic wave exploration method as a nondestructive investigation to examine the current situation of embankment of irrigation tank. The method applied the concept of impact-echo used for concrete structure. However, the method had a difficulty to identify the resonance frequencies from the Fourier transform of the elastic wave. There might be, therefore, a personal error of investigator. To improve the difficulty, the new procedure for Fourier transform was proposed in this paper. The spectrum at a frequency was added to the one at double the frequency. This concept used the tendency that the resonance vibration had the peak at double the resonance frequency. The spectrum at resonance frequency was, thus, emphasized. The personal error was not included in this procedure. By converting the frequency to the distance, the location having the reflected wave was identified. The proposed method was verified at the laboratory and then applied to the in-situ investigation. In comparison with the previous method and electric exploration, the efficiency of the newly proposed method was examined.
To decide the timing and the method of repair of the irrigation tanks, the method to evaluate the life cycle cost (LCC) of the tank was proposed by using the annual failure probability and the amount of the loss which were derived from the disaster data at Awaji Island in 2004. It was found that as the tank was repaired at the earlier timing, LCC of the tank at the 80th year became lower when a single tank was examined. The effect of LCC was also influenced by the repair cost. As LCC of the multiple tanks in an area, the total LCC became large in the case that the maximum budget became small and the period of repair became long, while the investment effect became high. The uniform annual cost of repair could be planned if the repair of each tank was carried out in a single year or the budget of repair was restrained to relatively small value.
There are many rock slopes in the intermediate and mountainous area. The rainfall and ambient temperature would cause the gradual degradation of the slope, which would become the trigger of the slope failure. In this paper, the degradation process of rock slope was numerically examined by using the damage model considering the expansive strain due to damage progress. The damage parameters obtained from the rock specimen degraded by freezing and thawing were applied to simulate the behavior of hypothetical rock slope suffering from temporal change in rainfall and ambient temperature. The simulation was carried out by the coupled thermal, hydraulic and mechanical model. Three locations having the typical pattern of rainfall and ambient temperature in Japan were selected. It was found from the results that the degradation was progressed most at the top of slope. The location having the large variation of temperature through one year showed the high progress of degradation of the slope. The effect of rainfall on the degradation of soft rock was larger than that of hard rock. It was recommended to monitor the change in Young's modulus and Poisson's ratio by nondestructive investigation to understand the future progress of the degradation of the slope.
Philippines is a country richly endowed with natural resources, including abundant surface and groundwater resources. Its total internal water resource is estimated at 130 km^3/year. However, despite the vastness of this potential supply, the country has a low freshwater availability per capita and experiences water-related problems. Analyzed holistically, the problems will redound to institutional and management failures. The water governance sector is fragmented and the institutional framework is weak, as it is also given less priority by the government. Though there is already the consciousness of solving the seemingly worsening problem and several moves were already undertaken, much has to be done for the country to attain "water supply and demand balance", as there are a lot of things to do to conserve one of the nature's very important resource- water.
This paper presents a 3-D Volume of Fluid method (VOF) applied for the flow in pool-and-weir fishways. In the 3-D VOF, 3-D incompressible continuity equation and Navier-Stokes (N-S) equations are solved incorporated with a convective equation of VOF function. The donor-cell scheme is employed to discretize the convective terms of N-S equations and the donor-accepter scheme characterizing the VOF is applied for discretization of the equation of VOF function. As for other spatial differencing terms, the second order central difference approximation is used. Two types of fishways are investigated; one is a pool-and-weir fishway with no notch and no orifice and the other is an ice-harbor fishway. Results from the former case demonstrated the numerical model used was able to reproduce two typical flow regimes, which are plunging and streaming modes, depending on the parameters. The ice-harbor fishway is a model of the fishway installed at Akaishi Second Headwork in Akaishi River, Aomori, Japan. Field observation of hydraulic structure was also conducted to obtain the data for validation of the numerical results. The numerical model was able to reproduce well the rapid flow over a notch and through an orifice. Circulating flow behind the non-submerged part of the baffle was also reproduced well. For further quantitative evaluation, modeling efficiency (EF) was introduced. The EF value made clear the longitudinal velocity component was reproduced better than transversal and vertical velocity components.
This study used bamboo coal like filter for clarification of turbidity in water and carried out with two laboratory experiments and one in situ experiment. Objectives of the first laboratory experiment were (1) to assess the capability of small, middle and big-sized bamboo coal, and (2) to assess the relationship between inflow volume and turbidity of outflow. The results showed that, the small-sized gave the most decrease of turbidity values; the next were the medium- and big-sized ones. With inflow volume of 2L/min, the turbidity was the least decreased followed by 6, 10 and 14L/min. The second experiment used only small-sized and assessed the relationship between different volume of filter and turbidity of outflow. The results showed that high volume of filter can reduce turbidity more effectively than low volume. In situ experiment showed that turbidity in outflow measure indicated the decrease of 30?90% and depended on concentration of turbidity in inflow and measure time. This study pointed out that bamboo coal can reduce the turbidity of runoff water.