Editor’s Note

This edition of the Journal of Irrigation and Drainage Engineering has nine papers, three technical notes, and a discussion. The first three papers deal with irrigation. “Calibration of Electromagnetic Induction for Regional Assessment of Soil Water Salinity in an Irrigated Valley” by Wittler et al., should be of interest to a wide range of readers. The paper describes a study in the Lower Arkansas River Valley in which calibration models for salinity assessment over a regional scale related apparent soil electrical conductivity measured with an EM-38 electromagnetic induction meter to traditional laboratory-measured saturated paste electrical conductivities. A total of 414 randomly selected sites were used for the calibration. The next two papers will interest international readers. The paper by Romero et al., “Set Sprinkler Irrigation and Its Cost” is from Spain. Annual water costs per unit area were analyzed for set sprinkler irrigation that is designed with different pipe material. The paper by Cornejo et al. “Irrigation Potential of the TRASVASE System (Santa Elena Peninsula, Guayas, Ecuador)” describes a study in Ecuador. The purpose of this study was to determine the total irrigable area in the Santa Elena Peninsula under several land-use scenarios on the basis of a water budget model requiring estimation of crop water requirements, irrigation efficiency, and dams and canals evaporation. CROPWAT was used to calculate the irrigation water requirements.

The next three papers deal with hydrologic modeling. The fourth paper, by Sridhar et al., is “Assessment of Soil Moisture Dynamics of the Nebraska Sandhills Using Long-Term Measurements and a Hydrology Model.” It used a hydrological model to investigate major water-balance components at six Nebraska Sandhills locations over a six-year period. The fifth paper, by Geem, is entitled “Parameter Estimation for the Nonlinear Muskingum Model Using the BFGS Technique” and estimates the parameters in the nonlinear three-parameter Muskingum model by using the Broyden-Fletcher-Goldfarb-Shanno mathematical technique. The sixth paper, by Cleveland et al., “Instantaneous Unit Hydrograph Evaluation for Rainfall-Runoff Modeling of Small Watersheds in North and South Central Texas,” uses data from more than 1,600 storms at 92 stations in Texas to evaluate an instantaneous unit hydrograph model (IUH) for rainfall-runoff models. The IUH model is compared with two other unit hydrograph models. A sum of squared errors function and an absolute error function at the peak discharge were used to fit observed data to the IUH model.

The seventh paper, by Ramamurthy et al., “Nonlinear PLS Method for Side Weir Flows,” describes a multivariable nonlinear partial least squares (PLS) method to determine the empirical equation relating the discharge coefficient to the dimensional weir parameters. The last two papers both deal with open channels. The eighth paper, by Yu and Tan, “Errors in the Bed Shear Stress as Estimated from Vertical Velocity Profile,” systematically analyzes one-point velocity, two-point velocity and a group of velocity measurements within the log-velocity region by regression analysis to determine the error in estimating bed shear stress.

The ninth paper, by Chanson, “Minimum Specific Energy and Critical Flow Conditions in Open Channels,” describes the development of a new analytical expression that characterizes depth for ideal-fluid flow conditions with nonhydrostatic pressure distribution and nonuniform velocity distribution. The new equation may be used to predict discharge more accurately on weir and spillway crests.

The first technical note, by Terzi et al., entitled “Estimating Evaporation Using ANFIS,” summarizes a study from the southwestern part of Turkey in which an ANFIS was applied to daily meteorology data that included evaporation, solar radiation, air and water temperatures, and relative humidity. The second technical note, “Flow Depletion Induced by Pumping Well from Finite Length of Stream,” by Singh, describes the development of an analytical expression to calculate flow depletion from a stream when pumping occurs in a well of an adjacent aquifer. The last technical note, by Bhattacharjya, is “Optimal Design of Open Channel Section Incorporating Critical Flow Condition.” It describes a nonlinear optimization model to design an optimal channel section incorporating critical flow conditions.