Editor’s Note

This issue of the Journal of Irrigation and Drainage Engineering contains eight papers and five technical notes. The first two papers, by Wahlin and Clemmens, are on feedback control of water levels in branching canal networks. The linear quadratic regulator and model predictive control algorithms were used. The first paper presents the theory of the feedback controllers, and the second paper uses the methodology to automatically control a large portion of the branching canal systems operated by the Salt River Project through hydraulic simulation.

The third paper, by de Vries and Anwar, involved modeling irrigation scheduling at the tertiary level to include sequence- dependent travel times between users. The fourth paper, by Prasad et al., is also on irrigation modeling. The model is an optimal irrigation allocation model that allocates available land and water resources in a multicrop and multiseason environment. In the paper, the model is applied to a semiarid region of India.

The fifth paper, by Nandagiri and Kovoor, evaluates seven reference evapotranspiration equations for a range of climates in India. The sixth paper, by Dukes and Evans, involved a water quality study in North Carolina. Surface water was monitored for 5 years in the streams of the coastal plains region, and shallow groundwater was monitored for 3 years in cropped fields and adjacent to drainage ditches.

The seventh paper, by Korkmaz and Önder, presents a numerical finite-difference solution to the equation for seepage from a rectangular ditch to a groundwater table. The problem wasalso investigated experimentally using a sand tank model and compared to the analytical solution.

The eighth paper, by Göğüş et al., describes a series of laboratory experiments to investigate the effects of the width of a main channel and the step height on the value of the discharge coefficient and approach velocity coefficient for broad-crested weirs having rectangular compound cross section.

The first technical note, by Singh, explains the development of a diagnostic curve for identification of dispersivity and injected mass of a soil column with a homogeneous and isotropic soil. The new method will be useful for field application in assessing the pollutant load from point sources.

The second technical note, by Guaraglia and Pousa, discusses the evaluation of a commercial thermal groundwater flowmeter in the laboratory to determine the causes of inaccurate readings in field studies involving high groundwater velocities in a gravel and course sand soil. The third technical note, by Mishra et al., summarizes the results obtained by using a hydraulic tilting flume to investigate the effects of slope and vegetative cover on outflow sediment concentration and deep percolation in channels covered with bermuda grass in an alfisol.

The fourth technical note, by Pagliara and Chiavaccini, summarizes experiments conducted on reinforced block ramps with varying slopes. A new equation was developed that can be applied to block ramps with or without the presence of boulders.

The fifth technical note, by Singh, presents an optimization method to develop an instantaneous unit hydrograph (IUH) from multistorm data. The optimization method uses the Nash IUH or gamma IUH.

Besides the papers and technical notes, this issue also contains discussions and two closures on previously published papers.