International Journal of Agricultural Engineering

D. Sai Gangadhara Rao ¹, T. V. Satyanarayana ¹, H. V. Hema Kumar ¹

Affiliations
1 Department of Agricultural Engineering and Technology, College of Agricultural Engineering, Bapatla, Guntur A.P., IN

Abstract

Critical flow in control sections prevents the downstream water level and flow conditions from affecting the flow through the critical sections, and the discharge can be computed as a function of the measured upstream head. Measurements of irrigation water flows in field channels have usually been expensive, too often of questionable accuracy and otherwise difficult to apply to all field situations. The techniques available in open channel hygrometry are the use of hydraulic structures (devices), velocity-area methods, dilution techniques and slope-hydraulic radius and area methods. Considering the constraints in the measurements of low discharges in open channels, hydraulic structure technique is best suited. Crest height had been increased from 10 cm to 25 cm then the C_d values also decreased from 0.82 to 0.50 for discharge decreased from 24 to 6 Ls^-1 under free flow conditions. The co-efficient of discharge for the different weirs under 60 per cent submergence conditions, if the increased crest height was from 10 cm to 25 cm then the C_d values also decreased from 0.75 to 0.43 for 24 to 6 Ls^-1 discharge. Under 75 per cent submergence conditions, if the increased crest height was from 10 cm to 25 cm then the C_d values also decreased from 0.7 to 0.42 for discharge decreased from 24 to 6 Ls^-1. Under 90 per cent submergence conditions, if the increased crest height was from 10 cm to 25 cm then the C_d values also decreased from 0.69 to 0.42 for 24 to 6 Ls^-1 discharge. For 24 Ls^-1 discharge, the co-efficient of discharge has been decreased from 0.72 to 0.62 for increased submergence levels from 60 per cent to 90 per cent due to increase in contact surface area and friction and less discharge have low velocity of approach.

Keywords

Flume, Weirs, Co-efficient of Discharge, Crest Height, Discharges.

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R. Ganesh Babu ¹, G. Ravi Babu ¹, H. V. Hema Kumar ²

Affiliations
1 Department of Soil and Water Engineering, College of Agricultural Engineering, Bapatla (A.P.), IN
2 Department of Agricultural Structures, College of Agricultural Engineering, Bapatla (A.P.), IN

Abstract

Land and water resources are the basic needs of agriculture and for the economic development of any country. As water becomes increasing scare and increasing demand for irrigation water, everywhere, has now focused national attention and public interest on utilization of existing water supplies, integrated irrigation water conservation and management policy and practices. Accurate quantification of evapotranspiration is crucial for better management and allocation of water resources. It is important that the water requirements of crops are known at different management levels within the irrigated area to accomplish effective irrigation management. Estimation of the evapotranspiration and effective rainfall are extremely useful for operation planning and management issues. CROPWAT is a computer model, was used to estimate the reference evapotranspiration, effective rainfall, crop water requirement and irrigation water requirement for the Bapatla region in Andhra Pradesh state, India. Daily meteorological data including rainfall, maximum and minimum temperatures, relative humidity, wind speed and sunshine hours were collected for the period of 2009 to 2013 and used as input data for CROPWAT. Average peak monthly ET₀ was observed to be 8.09 mm/day for the month of June and followed by the 7.55 mm/ day for the month of May. Whereas average minimum ET₀ were observed as 3.85 and 3.92 mm/day in the months of December and January, respectively. The average effective rainfall was estimated for the study area as 769.3 mm out of 1060.3 mm annual rainfall. The crop water requirement (ETc) and irrigation water requirement were estimated for vegetable crops during Rabi season in the study area (Bapatla) as 516.3 mm and 470.4 mm, respectively.

Keywords

CROPWAT, Effective Rainfall, ET₀, Crop Water Requirement, Bapatla Region.

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D. Sai Gangadhara Rao ¹, T. V. Satyanarayana ², H. V. Hema Kumar ², K. V. S. Rami Reddy ²

Affiliations
1 College of Agricultural Engineering Bapatla (A.P.), IN
2 College of Agricultural Engineering, Bapatla (A.P.), IN

Abstract

Accurate water measurements systems enable accurate accounting of water use, and permit the available water to be supplied at optimum rates to the areas where it is intended to be used. A perfect understanding of some of the primary principles relating to the subject of water measurement is, therefore, necessary for establishing any water measurement system in the canal commands of irrigated agriculture. All the four weir types have enabled creation of critical flow conditions within the throat section, which indicate their suitability for measurement of water in open channels in general. All the four design crest heights (25 cm (Weir-I), 20 cm (Weir-II), 15 cm (Weir -III) and 10 cm (Weir-IV)) are found to be acceptable excepting for 90 per cent submergence level condition. Critical depth (section) has occurred at only one location in the throat section for all the weirs under all possible conditions. The crest height has increased from 10 cm to 25 cm and then location of the critical section has moved towards the upstream side from 1.6 to 0.8 cm, 1.7 to 1.0 cm, 1.8 to 1.1 cm for 24 Ls^-1 discharge under free flow, 60 per cent, 75 per cent submergence conditions, respectively. For 18 Ls^-1 discharge, crest height has increased from 10 cm to 25 cm, and then location of the critical section has moved towards the upstream side from 7.0 to 3.1cm, 7.1 to 3.3 cm, 7.3 to 3.5 cm under free flow 60 per cent, 75 per cent submergence conditions, respectively. For 12 Ls^-1 discharge, crest height has increased from 10 cm to 25 cm and then location of the critical section has moved towards the upstream side from 8.1 to 4.7 cm, 7.1 to 4.9 cm, 8.3 to 5.0 cm under free flow 60 per cent, 75 per cent submergence conditions, respectively. Crest height has increased from 10 cm to 25 cm and then location of the critical section has moved towards the upstream side from 8.4 to 6.0 cm, 8.6 to 6.1 cm, 6.3 cm for 6 Ls^-1 discharge under free flow, 60 per cent, 75 per cent submergence conditions due to increased the contact surface and friction and not found for 90 per cent submergence levels for all the four weirs.

Keywords

Hydraulic Flume, Semi-Circular Crested Weirs, Characteristics of Semi-Circular Weirs, Open Channels, Point Gauge, Critical Depth, Crest Height, Discharges.

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K. Krupavathi ¹, K. Kishan ¹, H. V. Hema Kumar ¹

Affiliations
1 College of Agricultural Engineering, Bapatla, Guntur (A.P.), IN

Abstract

Accurate discharge measurement in open channels is essential for water resources planning, water and sediment budget analysis, hydrologic modeling, reservoir operation, flood mitigation. Long-throated flumes are coming into general use in discharge measurement because they can be easily fitted into complex channel shapes as well as simple shapes. And also provide cost-effective, practical and flexible capabilities for measuring discharge. 'Winflume' software allows the user to calibrate the existing design and to make new design of long throated flume. Based on channel dimensions and conditions of canal an attempt is made to theoretically design a new flume to measure the discharge accurately. With so many iterations, three acceptable designs were considered with compound cross-sections. The three designs were further studied for hydraulic flow conditions. Among the three flumes, the flume with trapezoidal compound crosssection resulted the best performance.

Keywords

WinFlume, Discharge, Canal.

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K. Kishan ¹, K. Krupavathi ¹, H. V. Hema Kumar ¹

Affiliations
1 College of Agricultural Engineering, Bapatla, Guntur (A.P.), IN

Abstract

For efficient and judicious use of water resources, an accurate design and high quality optimization of the check basin irrigation system is necessary. BASDEV of SURDEV model was used to evaluate the check basin irrigation system of size 30 m × 45 m for medium soils in Bapatla, Guntur District, Andhra Pradesh, India, for an irrigation application depth of 75 mm with a stream size of 10, 20, 30, 40, 50, 60, 70, 80 and 90 lps. To optimize the efficiency of the design, the model was run varying the basin design dimensions and cutoff times. The outputs of BASDEV, is intended to improve the overall efficiency of basin irrigation system, provided optimum field dimensions for border irrigation in medium textured soils.

Keywords

Application Efficiency, BASDEV, Basin Irrigation, Surface Irrigation, Water Management, SURDEV.

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