SIMIS (Scheme Irrigation Management Information System) is a personal computer software of integrated databases developed by FAO. It allows data available in the field or the project office to be used effectively for planning, operation, maintenance and management of an irrigation system. Major characteristics of SIMIS that distinguish it from conventional irrigation management softwares are its simplicity and adaptability. The SIMIS program comprises 14 modules related to irrigation system management and operation. The current paper focuses on the “Irrigation Scheduling” module of SIMIS which, the authors were responsible for developing. The module was applied to a model project in Brazil to verify its capability. SIMIS gives guidelines for establishing irrigation schedules taking a demand-oriented approach and canal operation schedules that meet established schedules. Simulations of irrigation scheduling were carried out for twenty weeks to compare the performance of different scheduling methods. It was found that the application of water in response to the specific water demands of crops was needed to minimize possible crop damage and water loss. Various scheduling options available in SIMIS allow users to establish appropriate operation procedures under specific local environments.
A typical small watershed (5.91km2) located in the Loess Plateau (Mizhi County, Shanxi Province, China) was selected for the trial study. The objective of this study was to quantify the amount of soil eroded under current land use and to predict soil loss according to different conservation measurements simulated with pc-ARC/INFO GIS (Geographical Information System) on the principle of the USLE (Universal Soil Loss Equation). Thematic maps of the watershed related to land use, soil, soil erosion, and land type were drawn from aerial photo field surveying, and the slope map was derived from DTM (Digital Terrain Model) analysis. The rill and interrill erosion region where most of the crops are planted was extracted from the watershed based on the concept of the division of geomorphological characteristics and erosive types. Through overlaying of thematic maps, a distributive map unit was generated with an attached attributive data file that consists of all necessary information for soil loss quantification and land evaluation and planning. The amount of soil loss under present land use was calculated and used as the baseline for comparing soil loss under different conservation simulations. Land use planning was conducted with the methodology of linear planning, and it was dependent on the results of land quality evaluation and the possibility of economic development prediction in the village. The potential soil loss was evaluated and compared to simulations of other biological and engineering land conservation practices. The results by computer simulation showed that both biological and engineering countermeasures can effectively protect soil against water erosion. However, the best approach was the combination of terrace engineering and the adjustment of land use pattern, which was based on linear planning of the general development of the watershed.
“Assessing and improving performance of irrigated agriculture” is one of five major research programs of the International Irrigation Management Institute (IIMI). It aims to develop internationally agreed assessment indicators for the comparative study of performance of irrigated agriculture in developing countries. This is a case study of the Muda Irrigation Project focusing on the effective rainfall. A simple method to monitor and assess actual effective rainfall based on field water depth was proposed using commonly obtainable data sets in developing countries and field-tested it using monitored data in the Muda Project in comparison with other methods broadly applied over the world. It was certified that the effective rainfall estimated by the proposed method reflects not only characters of rainfall distribution but also the quality of irrigation system management.
Good farms are required to be sustainable. This is achieved by an appropriate land use method suitable for the natural environment. A sustainable system of land use can be found in the old Japanese style of agriculture. An investigation was carried out to determine the optimum ratio of land use among paddy field, upland field, and woodland within small basins (Yachi) in the Kanto Plain district near Tokyo. The land use pattern in one watershed showed that the share ratio of land use among paddy field, upland field, and woodland was 33:12:55 in an old map published more than 100 years ago. Since urbanization in the Yachi district started 1970's, there has been a significant change in land use. Unused paddy fields are increasing in number in these districts. The current share ratio among actural paddy field, upland field, and woodland is 19:44:37. The unused paddy field emerges mostly around the ratio of 15:50:35. This ratio illustrates a lower criterion of sustainable land use. One form of land use has close connections with the other forms. Therefore, taking into account their inter-connection during land use planning is important for sustainable agriculture.
The spatial distributions of water in the soil under varying sprinkler irrigation uniformities and water application depths were observed to determine how evenly the water was distributed in the soil. It was found that the water was more uniformly distributed in the soil than water applications measured at the surface. The effect of water application uniformity on the uniformity of water in the soil was not as important as originally supposed. The uniformity of water within the root zone after irrigation mainly depends upon the initial soil water content and its uniformity
The productivity of acid sulphate heavy clayey soils of the Central Plain of Thailand is severely hampered by their poor drainage capability. A field-oriented study was conducted to assess the performance of a pipeless drainage system in terms of soil improvement. A total of eight pipeless drains were constructed at 1% slope having drainage base and drainage spacing of 55 cm and 2m, respectively. In addition to the hydraulic assessment of the drains, crack observation (staining test), in situ hydraulic conductivity measurement, and pertinent chemical analyses of drain-effluent were carried out. The individual drain-response time varied considerably among the drains themselves as well as among six observed irrigations. The drain-discharge hydrographs were found to be highly influenced by the surface cracks caused by long-term drying. These cracks enhanced the drain-discharge by about 15 to 20 times the normal draindischarge; such enhanced discharge is not desirable and hence should be avoided. The drainage system in general effectively regulated the water flow through the soil profile. The staining test further confirmed the presence of macropores (cracks/fissures) up to an appreciable depth in the drained plot. Consequently, its hydraulic conductivity increased by a factor of about 4.3. Additionally, the pipeless drainage system provided promising results concerning acidity and/or toxicity attenuation of Bangkok's acid sulphate soil.
This study evaluated the characteristics of soil compaction by measuring the dry density, permeability, unconfined compressive strength, and soil structure of Indonesian latosol soil. The changes in dry density and permeability observed with a normal compaction test were similar to those widely noted in sandy clay loam. The increasing of compaction energy affected dry density, permeability, and soil strength clearly at the dry side of optimum water content, while it had almost no effect at the wet side. Also, the unit of soil structure expressed by using mean mass diameter of aggregates became smaller at the dry side and larger at the wet side when compaction energy increased. The additional compaction of normally compacted soil had more effect on the upper soil layer than on the underlayer. Moreover, it created dry density higher than 1.3 g/cm3 and minimum permeability of 10-7cm/s at lower water content than the optimum obtained by normal compaction test.