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Theses

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1996 - 19984
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Subject: Land and Water Management Engineering × End date: 1999 × Start date: 1996 ×
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    ThesisItemOpen Access
    Mathematical model for sediment yield in agricultural watershed
    (Department of Land and Water Resources and Conservation Engineering, Kelappaji College of Agricultural Engineering and Technology, Tavanur, 1998) Babu, V; KAU; Remadevi, A N
    The knowledge of temporal distribution of sediment yield is required in the design and operation of soil and water conservation programmes on watershed basis. For the project planning purposes, the estimates made are mostly based on experience. Such estimates are very approximate and grossly inadequate for engineering analysis. Therefore there is an urgent need for , rational analysis of erosion data from catchments, inorder to obtain relationship for erosion rate. Therefore a mathematical daily sediment yield model is developed for Thuthapuzha drainage basin (940 km2 ) of Bharathapuzha basin, corresponding to Muskingum routing equation. The model is based on combined approach of translation and routing for simulating sediment graphs. Thirty seven selected storm events of the drainage basin observed during 1986- 92 are used for estimation of model parameters by Lagrange multipliers method and three storm events of 1993 are used for verification of the model. The model is used to compute temporal distribution of suspended sediment yield on storm basis and their performance is evaluated both qualitatively and quantitatively. Mathematical relationships of mobilized ~ sediment with effective rainfall; computed sediment flow rates with observed sediment flow rates and observed and computed sediment flow with effective rainfall and mobilized sediment were also established. The Correlation Coefficient of all those equations are found to be close to one. The statistical measures of Percentage Absolute Error in peak sediment flow rates, Absolute Prediction Error, Integral Square Error, Correlation Coefficient and Coefficient of Efficiency of the model are obtained as 3.9934, 9.0007, 5.3286, 0.9951 and 0.9659 respectively. The study reveals that the developed model is a very effective tool in the real time forecasting of sediment yield in Thuthapuzha drainage basin.
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    ThesisItemOpen Access
    Effect of different types of mulches on growth and yield of drip irrigated vegetables
    (Department of Land and Water Resources and Conservation Engineering, Kelappaji College of Agricultural Engineering and Technology, Tavanur, 1997) Gilsha Bai, E B; KAU; Jobi V Paul
    The present project was to study the effect of drip irrigation along with two colours of plastic mulching on the growth and yield of summer season vegetable. Two types of irrigation methods, drip and surface, and two colours of plastic mulches, black and transparent, were used in the experiment. Three levels of irrigation water, v, 0.8V and 0.6V volume, were applied in drip treatments. Mulches increased the soil temperature. High soil temperature was developed under transparent mulch compared to black mulch. Black mulch increased the soil temperature in the root zone by 3 to 4°C compared to non-mulched plots. This increase in soil temperature under the black mulch was advantageous to the crop. Presence of mulch sheet over the soil reduced the evaporation from the soil. Hence, moisture depleted from the non-mulched plots were more than mulched plots. Water saving obtained by the use of plastic mulch was about 30 to 35% in the different treatments. Black mulched and non-mulched treatments did not show significant difference in the plant height. Maximum plant height was observed in the non-mulched drip irrigated treatment with O. BV volume of water. Maximum plant spread was observed in the surface irrigated black mulch treatment. Surface irrigated treatments gave more plant spread than drip irrigated treatments. Use of mulch sheets reduced the weed growth in the field. Practically, there was no need of weeding from the plastic mulched plots. Earlier flowering and maturity of fruits were observed in the mulched plots. All treatments with black mulch increased the yield compared to the control. Treatment with black mulch and drip irrigation with O.BV volume of water gave 76.5% more yield than the control. Most of the treatments with transparent mulch reduced the yield. This reduction in yield was due to the high soil temperature developed under the transparent mulch. Yield was increased with the soil temperature upto an optimal level of about 46°C and then decreased with the increase in soil temperature. In drip method O.BV volume of irrigation water level was the best. It gave highest yield and growth in mulched as well as non-mulched treatments. Drip irrigation along with mulching in summer vegetable can reduce the cost of cultivation through efficient water management. Also the area of cultivation can be increased with the available water in the water scarce areas.
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    ThesisItemOpen Access
    Laboratory studies on soil moisture flow and runoff generation in laterite soil
    (Department of Land and Water Resources and Conservation Engineering, Kelappaji College of Agricultural Engineering and Technology, Tavanur, 1998) Roshni, Sebastian; KAU; Noble, Abraham
    If land and water are to be put to the best use, a full understanding of soil- water relation is necessary. Much of the research on retention and movement of water in soil and the use of water by plants is done with this objective. Modelling of water movement in soils requires knowledge of hydraulic conductivity as a function of volumetric water content or soil water pressure head, and the soil water retention curve. Laterite soils are by far the most important group occurring in Kerala and cover the largest area. A study was conducted to analyse the saturated and unsaturated flow of water in laterite soil under selected precipitation intensities. The objective was to establish a relation between hydraulic conductivity, moisture content and hydraulic head. Runoff generation and relation between runoff and soil moisture status were also considered. A rainfall simulator and a soil trough were fabricated. The design of the rainfall simulator was based on that of Bhardwa] et al (1992). The rainfall simulator comprised of a drop forming mechanism mounted on a supporting frame. A float valve maintains a constant head of water in the drop forming tank to get a desired rainfall intensity. The soil trough had provision for collecting surface and subsurface outflow of water. Provision was also made to incline the soil trough when a sloping plot was required. The experimental set up was installed in the Soil and Water laboratory of KCAET, Tavanur. \1\'.31 The rainfall simulator was tested for different rainfall intensity by changing the head of water in the tank Rainfall intensity increased as the head of water in the tank was increased. At a head of 22 cm, a maximum rainfall intensity of 285.6 rnrn/h was obtained. Drop size determination by flour - pellet method showed that the simulated raindrop size remained almost constant The uniformity coefficient also increased with increase in intensity. The basic soil properties were also determined. The particle size distribution curve showed that the soil was coarse graded. The bulk density of the soil was 1.53 g/cm3. The piezometer readings in the soil trough showed that unsaturated flow takes place through the soil under simulated rainfall. Experiments were done for different rainfall intensities of 20, 40, 90, and 285.6 mm/h and also at 10% and 20% slopes with 40 and 90 mm/h intensity. The variation in moisture content with time was found to increase with intensity of rainfall. Steeper slopes also increased the rate of depletion of moisture with time. Instantaneous profile method was adopted to determine hydraulic conductivity. An exponential relation was observed between hydraulic conductivity and volumetric soil moisture content Matric suction and volumetric moisture content were observed at different depths - 10, 20, 30 and 40 cm. The hydraulic conductivity - moisture content relationships were established. Studies on runoff generation showed that inclination of the bed rock is a major factor controlling subsurface outflow. Variation in intensity of rainfall did not cause considerable variation in outflow. Surface runoff also was affected only by the slope of the soil trough.
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    ThesisItemOpen Access
    Monthly water balance model for lateritic hill slope- a case study
    (Department of Land and Water Resources and Conservation Engineering, Kelappaji College of Agricultural Engineering and Technology, Tavanur, 1996) Beena, Thomas; KAU; Noble, Abraham
    The groundwater balance of K. C. A. E .T. Campus, Tavanur, Kerala has been studied and a deterministic model has been developed for the prediction of depth to water table in this hill slope based on Darcy’s equation. The input data required are the precipitation, evapotranspiration, specific yield, initial water table, elevation of the points under consideration and the distance between the points. The weekly precipitation and evapotranspiration were calculated and from this the recharge to groundwater was estimated. The groundwater recharge was taking place only during the southwest monsoon season. The change in storage divided by the hydraulic gradient for a period without rainfall i.e., from 01 December 1994 to 16 February 1995 were determined. Using these values and other inputs in the model, the depth to water table for a period from 26 May 1994 to 25 May 1995 were estimated from the model. These values were compared with the observed values for the same period. It was found that the estimated values give a reasonable estimate of the depth to water table in the study area. This model can be used to predict the changes expecting in the water level in a particular region. The model has several areas of application in the fields of groundwater resource development and irrigation. The infiltration characteristics of the selected area was evaluated and observed that the infiltration rate was increasing towards the higher elevation. The model was simulated for different percentages of effective rainfall and found that, at 50 per cent it accounts as groundwater recharge and the rest as surface runoff.