Now showing items 2741-2760 of 3826

    • Evapotranspiration: Concepts and Future Trends 

      Luis S. Pereira; Alain Perrier; Richard G. Allen; Isabel Alves (American Society of Civil Engineers, 1999)
      Past research on evapotranspiration has provided sound theoretical knowledge and practical applications that have been validated through field measurements. Many different approaches have been used; however, when primary ...
    • Subirrigation Systems to Minimize Nitrate Leaching 

      J. Wambua Kaluli; Chandra A. Madramootoo; Xiaomin Zhou; Angus F. MacKenzie; Donald L. Smith (American Society of Civil Engineers, 1999)
      Nitrate leaching from corn production systems and the subsequent contamination of ground and surface waters is a major environmental problem. In field plots 75 m long by 15 m wide, the writers tested the hypothesis that ...
    • Controlling Irrigation Water Flow to Mole Drains 

      E. W. Christen; G. Spoor (American Society of Civil Engineers, 1999)
      Subsurface drainage in irrigated agriculture presents an interesting challenge in that rapid drainage is required after an irrigation or rainfall event to alleviate any waterlogging, but during irrigation events drainage ...
    • Effects of Temperature Changes on Emitter Discharge 

      Leonor Rodríguez-Sinobas; Luis Juana; Alberto Losada (American Society of Civil Engineers, 1999)
      Working on the assumption that temperature affects water viscosity and emitter geometry, the writers have developed a dimensional analysis approach to the potential pressure-discharge relationship to estimate discharge ...
    • Problems of Irrigation in Developing Countries 

      Phillip Z. Kirpich; Dorota Z. Haman; Stuart W. Styles (American Society of Civil Engineers, 1999)
      This paper describes the crucial importance of irrigated agriculture to developing countries and to the world as a whole. This is followed by a summary of key problems that restrict and diminish the benefits of irrigated ...
    • Discussions and Closure: Volume Balance Irrigation Advance Equation: Variation of Surface Shape Factor 

      B. L. Maheshwari; M. Esfandiari; Joaquin Monserrat; Javier Barragán; John D. Valiantzas (American Society of Civil Engineers, 1998)
    • Discussion and Closure: Analysis of Flow through Lateral Slot 

      Masoud Ghodsian; Chandra Shekhar P. Ojha; Damireddy Subbiah (American Society of Civil Engineers, 1998)
    • Rating Adjustment for Settlement of Cutthroat Flumes 

      Steven R. Abt; Bryan C. Ruth; Eric M. Skowron (American Society of Civil Engineers, 1998)
      A study was performed to examine the effects of flume settlement on the accuracy of discharge measurements, using the cutthroat flume in a free-flowing condition. A series of 111 tests was performed on 10.2 cm × 0.91 m, ...
    • Explicit Time of Advance Formula for Furrow Design 

      John D. Valiantzas (American Society of Civil Engineers, 1999)
      The behavior of the dimensionless advance curves obtained numerically for various values of infiltration parameter is systematically analyzed. It was found that when the advance problem is expressed in terms of new variables ...
    • Choke-Free Flow in Circular Channels with Increase in Bed Elevations 

      Subhasish Dey (American Society of Civil Engineers, 1998)
      Physical solutions for the flow through circular channels due to increase in bed elevations are obtained, satisfying the condition of choke-free flow. In this analysis, three different cases of channel transitions, commonly ...
    • Simulating Furrow Irrigation with Different Inflow Patterns 

      A. A. Alazba (American Society of Civil Engineers, 1999)
      Simulation of sloping furrows with free outflow was accomplished to assess the effect of inflow pattern on maximum application efficiency. For five inflow hydrograph patterns, the maximum application efficiency was predicted ...
    • Discussion and Closure: Evaluation of Time-Rated Infiltration Families for Noncracking Soils 

      Albert J. Clemmens; B. L. Maheshwari (American Society of Civil Engineers, 1998)
    • Converting from Pan Evaporation to Evapotranspiration 

      N. S. Raghuwanshi; W. W. Wallender (American Society of Civil Engineers, 1998)
      Evapotranspiration is an essential component of the hydrologic cycle, and its accurate estimation is necessary for many hydrologic studies. Via the pan coefficient (
    • Discussion and Closure: Idealized Automated Control of Sloping Canals 

      Albert J. Clemmens; Eduardo Bautista; John B. Parrish (American Society of Civil Engineers, 1998)
    • Semianalytical Solution to Richards' Equation for Layered Porous Media 

      Fred Marinelli; Deanna S. Durnford (American Society of Civil Engineers, 1998)
      Traditional finite-difference and finite-element solutions to Richards' equation can exhibit stability problems and mass balance errors when sharp saturation fronts migrate across material interfaces. Several semianalytical ...
    • Discussion and Closure: Mobile Prisms for Flow Measurement in Rectangular Channels 

      Prabhata K. Swamee; A. Peruginelli; F. Bonacci (American Society of Civil Engineers, 1998)
    • Soil Hydraulic Models Selection Based on In-Situ Measurements 

      Uri Shani; Rachel Gordin-Katz (American Society of Civil Engineers, 1998)
      Soil hydraulic properties are usually expressed as functional relationships between the soil hydraulic conductivity and water content or matric potential, and between the matric potential and water content. Both functions ...
    • Scouring in Long Contractions 

      Siow-Yong Lim; Nian-Sheng Cheng (American Society of Civil Engineers, 1998)
      Based on the continuity of flow and sediment, an analysis on scouring in long contractions is conducted with a formula obtained from measured sediment discharge in long contractions and a formula for the flow resistance ...
    • Analytical Approach for Direct Drip Lateral Hydraulic Calculation 

      John D. Valiantzas (American Society of Civil Engineers, 1998)
      In application of previous analytical approaches for drip lateral hydraulic computation, it is generally assumed that the emitter outflow along the lateral is constant. This basic assumption may cause significant errors ...
    • Solutions of Boussinesq Equation in Semiinfinite Flow Region 

      A. Upadhyaya; H. S. Chauhan (American Society of Civil Engineers, 1998)
      In a semiinfinite flow region, prediction of the water table profile due to an abrupt rise or drop in the canal or drain water level in the cases of recharging and discharging aquifers has been done for times equal to 1.0, ...