In time rice irrigation water management under limited water supply

In-time water distribution of canal water to the farmers has been a major concern of managers, planners and researchers involved in irrigation. This study analyzed the ways for water distribution and timely water release in a rice growing area during the pre-saturation period and the normal irrigation supply periods. The analyses were carried out using field data collected at the Besut Irrigation Scheme located in the northeastern corner of Peninsular Malaysia in the state of Terengganu. The scheme comprises two sub-schemes, giving a total irrigation area of 5, 164 ha for the overall Besut Irrigation Scheme. Based on field water requirements and available flows at the intake gates, canal simulations were performed and results show that land preparation should not be done continuously unless flow rates are at least 9.00 m3/s and 3.00 m3/s at the Besut Barrage and Angga Barrage respectively. If the respective flow rates fall below these values, then land preparation should be done in two phases. However, when the flow rate is between 5.00 and 5.50 m3/s at the Besut Barrage, land preparation is recommended to be carried out over three phases. During the normal irrigation supply period, flow rates of 6.00 m3/s and 1.75 m3/s for the Besut and Angga Barrage respectively, are to be maintained for the entire irrigation scheme, otherwise selective irrigation or irrigation on a rotational basis has to be enforced. When flow rates are 7.20 - 9.00 m3/s and 1.70 - 3.00 m3/s at the Besut and Angga Barrage respectively, then water should be released two days before the beginning of the pre-saturation period for the filling main and secondary canals. However, water should be released three days before the beginning of the pre-saturation period when flow rates are between 5.00 and 7.00 m3Is at the Besut Barrage. But irrigation water should release 5.00 hours before beginning the normal supply period in order to maintain the in-time irrigation schedule

Modeling of changes in evapotranspiration for an area in Peninsular Malaysia,

A study was carried out to check the sensitivity of evapotranspiration estimation due to changes in climate. The study used 30 years of data from the meteorological station in the FELCRA paddy estate, Seberang Perak, Peninsular Malaysia. The effect of changes in the climatic variables, temperature, solar radiation, relative humidity and wind speed on evapotranspiration were analyzed. Results showed that the mean temperature, mean relative humidity, mean wind speed, and net global radiation have changed by + 0.182 oC, -0.73%, -0.0365 mis, and +0.146 MJ/m2 respectively per decade, while the short wave radiation received has decreased by 0.0037 MJ/m2 per decade. The statistical analysis of the evapotranspiration estimations using selected methods showed that the Penman-Monteith, Blaney-Criddle and Pan evaporation methods give similar estimations (P = 0.05) and are suitable for the study area. When changes to the present climate are imposed for future decades, the over-estimation rate is linear with the Blaney-Criddle and Penman methods whereas for the PenmanMonteith method it is exponential. The overall increment expected after 5 decades is 5.3% and 6.9% with Penman and Blaney-Criddle methods respectively. The Penman-Monteith shows a 74.4% increment in the evapotranspiration over the next five decades.The authors wish to expressive their sincere gratitude to the staff of the FELCRA Seberang Perak Paddy Estate Irrigation Scheme, the Drainage and Irrigation Department, the Malaysian Meteorological Service. The authors would also like to thank The Ministry of Science, Technology and the Environment for the funding of the Project IRPA 01-02-04-0422

Estimating evapotranspiration of irrigated rice at the West Coast of the Peninsular of Malaysia

The correct estimation of ET in the water balance equation allows for improved water management in rice cultivation. Eight evapotranspiration estimation methods (Penman, Penman-Monteith, Pan Evaporation, Kimberly-Penman, Priestley-Taylor, Hargreaves, Samani-Hargreaves and Blaney-Criddle) were tested with 30 years of daily data, in the west coast of peninsular Malaysia. The evapotranspiration estimates by all methods shows the same trend throughout the year. Samani-Hargreaves gives the highest estimates followed by the Priestley-Taylor and Hargreaves methods. The lowest estimates were by Penman-Monteith and followed by the Blaney-Criddle and Pan methods.The Penman-Monteith, Blaney-Criddle and Pan methods estimate lower values of evapotranspiration with no significant difference among them (P = 0.05). All the other methods are significantly different from these three methods. Penman method, though is different from the three methods, estimates reference evapotranspiration close to these three methods. The Penman-Monteith, Blaney-Criddle and Pan are the best methods to estimate evapotranspiration in the study area. The Penman method can be used to get somewhat reasonable estimates though it overestimates the evapotranspiration a little. All other methods, which tend to over estimate evapotranspiration were not suitable. Comparisons of the selected methods against the Penman-Monteith method showed that they have good correlation. The Pan, BlaneyCriddle and Penman gave correlation coefficients 0.87, 0.55 and 0.97 respectively. A simple correlation equation, developed using 30-year daily data, showed that direct measurement of net radiation can be used to estimate reference evapotranspiration with considerable accuracy (r2 = 0.97)

Strength development in fine-grained paddy field soil by lime addition

Due to high population density, the people of Bangladesh are building houses and the government is establishing infrastructure (such as roads, flyovers, bridges) on agricultural land that pose significant settlement issues. Consequently, such development works require prior improvement of the soft soil or improvement during construction to restrict post-construction failures. Soil stabilization, a conventionally used ground improvement method, is often utilized to alter engineering properties of fine-grained soil such as strength, stability, permeability, weathering resistance, etc. to maintain the required construction criteria. Moreover, the addition of lime in the soil is demonstrated to markedly reduce the hydraulic conductivity, which will prevent the vertical movement of pore water. With this in mind, in the current study an attempt has been undertaken to increase the strength of fine-grained soil of agricultural land by adding commercially available hydrated lime, which may in the future be used as foundation material. For this purpose, lime was added at various percentages (0–12%) by weight to soil collected from a paddy field. The study noted the collected soils as being inorganic silts of high plasticity or organic clays of medium to high plasticity. Unconfined compression tests were conducted on cylindrical mold prepared specimens with clayey soil in the presence of lime, and all specimens were cured for 3–90 days for strength development. The study revealed 7% added lime as the optimum content, with the corresponding unconfined compressive strength (UCS) observed to be 344 kPa and 356 kPa at the end of 28 days and 90 days, respectively. The evolution of unconfined compressive strength was higher in hotter and more alkaline environments