Hajime Tanji

Updating an Input–Output Matrix with Sign-preservation: Some Improved Objective Functions and their Solutions

This paper presents an easy-to-use method for updating input–output (IO) matrices with sign-preservation by combining Lagrangian multipliers and penalty functions. Biproportional methods such as the representative RAS are very simple and popular because a target matrix can be obtained simply by iterative computation. However, they cannot reasonably deal with matrices that include negative entries. Although a generalized version, GRAS, can do so, its objective function is questionable. In contrast, some non-biproportional methods such as those that take weighted or unweighted squared differences between the target and original matrix as objective functions can deal with negative entries, but it is difficult to guarantee the signs of entries. In this study, GRAS and some conventional objective functions were improved and their solutions for preserving the signs of entries are presented. Comparisons of applying these objective functions to a simple example show that both the Improved Normalized Squared Differences (INSD) function and the Improved GRAS (IGRAS) function yield a good target matrix and are close to each other; we suggest that INSD or IGRAS be used for updating IO transaction matrices in practice.

Performance diagnosis of Mae Lao Irrigation Scheme in Thailand (I) development of unsteady irrigation water distribution and consumption model.

The Mae Lao Irrigation Scheme is one of the largest irrigation projects in Northern Thailand. According to the field reconnaissance, water shortage usually occurs during the dry season. And it is very difficult to equally distribute available water to the paddy fields from the upstream to the downstream parts of the system. To understand and identify the causes of the problems, the measurement of water level and flow rate along all canals may be effective. However, it is not easy to achieve this in such a large-scale irrigation system. Thus, the numerical simulation becomes the second option. The objective of this study is to identify and quantify the real water shortage causes by developing an Unsteady Irrigation Water Distribution and Consumption model which can simulate the water movement and consumption in the whole irrigation system. The beneficial area of the right main canal is modeled based on the physical aspect of the system. The components of the model consist of canal networks, control structures, and paddy fields. A canal is divided into several portions called reach. The Saint-Venant equations are applied to describe the unsteady water movement in each reach. Flow movement at the control structure is expressed by the boundary condition. The paddy fields are modeled to make paddy block and connected to each reach. The water consumption in each paddy block is estimated by Paddy Tank model. The numerical model is successfully developed showing the ability to simulate the water movement and consumption properties in this irrigation system.

Performance diagnosis of Mae Lao irrigation scheme in Thailand (II). Application of the UIWDC model for water distribution system analysis

The Unsteady Irrigation Water Distribution and Consumption (UIWDC) model is applied to analyze causes of uneven water distribution between the upstream and downstream beneficial areas of the Mae Lao Irrigation Scheme (MLIS). The uneven water distribution may be caused by inadequate water distribution facilities or improper operation rule; therefore, its causes are examined systematically and quantitatively from the aspects of “water allocation” and “operation rule”. The water allocation is considered focusing on the dry season irrigation, where equity and efficiency should be especially balanced because of the scare water resources. The “EQTY index” (the equity index) is defined to widen the range of consideration between the equity and the efficiency, instead of alternative judgment of which has a priority. The operation rule for facilities in the MLIS is assumed considering their capacities, and two coordinate values of “ineffective spillage” and “water deficit” in the scheduled areas are incorporated into operation rule to quantitatively diagnose the system performance. As a result, the original causes of uneven water distribution will presumably be identified. The informative and quantitative results are utilized to set a new benchmark performance of the MLIS for the water distribution. It can be described by the “Expected Ratio of Irrigable Area” (ERIA) and “Present Ratio of Irrigable Area” (PRIA). Based on this standard, the general recommendations can be more concretely proposed to raise the water distribution performance of the MLIS such as by improving distribution facilities and/or by installing vertical pumps.

A combined technique of floodplain storage and reservoir irrigation for paddy rice cultivation

This paper introduces an irrigation system developed in the floodplain of a lake and studies the water management technique of the irrigation system by estimating the total water balance of the whole system. The system is characterized by a reservoir combined with a dike system in the floodplain of the Tonle Sap Great Lake and an irrigation system. Two main models are used for calculating the total water balance. The first model is the water balance of the reservoir. The inputs to the model are water level of the reservoir, precipitation, lake evaporation, infiltration, and area–volume curve of the reservoir. The outputs are inflow and outflow of the reservoir. The supply from the reservoir to paddy fields is computed from the outflow. The second model is the water balance of paddy fields, based on which the water requirement in paddy fields is derived. The reference evapotranspiration needed to calculate the water requirement is simulated for monthly time series using the FAO Penman–Monteith model. Since there is no drainage network in the irrigation system, surface drainage and runoff are not included in the calculation of the water balance, and seepage is considered negligible in the flat floodplain area. The evapotranspiration, rice variety, soil type and irrigated area are used to simulate water consumption in paddy fields. Finally, the two models are connected to produce the total water balance from the reservoir to paddy fields. The total outflow from the reservoir is estimated and the total water consumption for dry season cultivation is also determined. Finally, the efficiency of the whole system is examined.

Estimation of supplementary water to paddy fields in the lower Mekong River basin during the dry season

Efficient management of water resources in paddy fields requires an understanding of the volume of supplementary water used. However, quantifying the volume is laborious due to the large amount of data that must be collected and analyzed. The purpose of our study was to estimate the volume of supplementary water used in paddy fields, based on several years of available statistical data, and to provide information on how much water can be supplied to paddy fields in each target area. In this study, the lower Mekong River basin of northeast Thailand, Laos, and Cambodia was selected as the study area. In the first step, we used agricultural statistics for each country, rainfall data acquired from the Mekong River Commission Secretariat (MRCS), and the value of virtual water required per unit of rice production. Because several years of data were used for dry season harvested areas and rice production in each country, the supplementary water to paddy fields in each province was calculated using virtual water and rainfall. This method made it possible to estimate changes in supplementary water in each province. Through this study, the supplementary water to paddy fields during the dry season in three countries was approximated from the minimum number of data sets. Moreover, for cases in which it is not possible to procure agricultural water use data for a hydrological model simulation, an alternative solution is proposed.

Functions and Cost of Irrigation Service at the Aichi Irrigation Scheme

Because of externalities, it is difficult to study an irrigation service segmented into service receivers. The case study of the Aichi IS shows that irrigation services combine a private good-type service and a public good-type service. This complexity causes problems with cost-benefit relations and the flexible supply of services. The authors propose analyzing functions and cost of actual irrigation services to solve these problems. To achieve a staged solution to these problems, first, core services are selected and, including private–public relations, the benefits of functions and the cost of functions should be well balanced.

Reducing Tsunami Damage to Drainage Pump Stations in Coastal Areas

Measures to mitigate tsunami disaster damage to drainage pump stations in coastal areas were studied by conducting a field survey of drainage pump stations that suffered a great deal of damage from the 2011 Tohoku Pacific Ocean Tsunami, and by performing an experiment with a hydraulic model. The field survey showed that the spatial relationship between the pump house and the water discharge tank greatly affected the level of damage suffered by the drainage pump station from the disaster. The ability of the water discharge tank to dissipate the tsunami energy was examined in a hydraulic model experiment. The result showed that even if the tsunami wave height exceeded the height of the water discharge tank, the wave force in the direction of movement of the tsunami wave was reduced.

Level 2 Performance Based Design of Coastal Drainage Pumping Station

Level 2 performance based design, which considers the probability of design values as normal or lognormal distribution, is introduced for coastal pumping stations. Considering inundation risk, the outer forces are assumed to be the increase of water levels in drainage canals caused by inflow, and counter forces are assumed to be the decrease of water levels in drainage canals caused by pumping discharge and drainage gate discharge. Design rainfall is modeled as lognormal distribution based on data from the Saga Meteorological station. Design tide levels are modeled as the sum of residuals of high tides caused by typhoons and astronomic tides at Oura. Based on a Monte Caro simulation for 100,000 years, the maximum water level data in drainage canals are calculated to evaluate performance.

Data structure analysis of irrigation intakes for database building

For building database of irrigation intake water, especially for paddy-fields, data structure must be made clear. The authors collected printed or manuscript irrigation data of 326 points in Kinu and Kokai River basins. 142 points of them have some measured data. By the analysis of these data, following points come to be clear. 1) Irrigation facilities are historical structure. Therefore random additional information cannot be negligible. Database must have some variable length data structure. 2) Some structures have multi-names. Synonym dictionary must be prepared.