Editor’s Note

This issue of the Journal of Irrigation and Drainage Engineering consists of 10 papers, three technical notes, four discussions and a closure. The papers cover irrigation, salinity, evapotranspiration, infiltration, drainage, and storm-water management. The first three papers deal with drip irrigation. The first paper, “Real Local Losses Estimation for On-Line Emitters Using Empirical and Numerical Procedures,” by Palau-Salvador et al., presents a general formula to calculate directly the local losses of on-line emitters as a function of the number of emitters, the average emitter discharge, and the ratio between the protrusion area and the pipe’s cross-sectional area. The second paper, “Soil Hydraulic Properties Affecting Discharge Uniformity of Gravity-Fed Subsurface Drip Irrigation Systems,” by Lazarovitch et al., presents a new approach for predicting the discharge of subsurface drip irrigation. The procedure couples models of head loss in laterals and soil impacts on the dripper discharge. In the third paper, “Hydraulic Analysis and Direct Design of Multiple Outlets Pipelines Laid on Flat and Sloping Lands,” by Yıldırım, an analytical direct design procedure for a single multiple-outlets pipeline is presented. The equations can be used to design laterals and manifolds in both drip and sprinkler irrigation systems.

The fourth paper, “Development of a GIS-Based Model to Estimate Relative Reductions in Crop Yield due to Salinity and Waterlogging,” by Garcia et al., introduces a model to predict relative reductions in crop yield caused by salinity and waterlogging at a field-scale. The model uses GIS and incorporates spatially and temporally variable crop, climatic, and irrigation data to simulate crop yields.

The fifth paper, “Sensitivity Analyses and Sensitivity Coefficients of Standardized Daily ASCE-Penman-Monteith Equation,” by Irmak et al., describes a study in which the sensitivity of the standardized ASCE grass-referenced Penman-Monteith evapotranspiration equation is correlated with climate variables in different regions of the United States. In general, potential evapotranspiration was most sensitive to vapor pressure deficit followed by wind speed at 2-m height in semiarid regions during the summer months. Solar radiation was the most dominant variable in humid locations during the summer months.

The sixth paper, “Managing Irrigation for Better River Ecosystems—A Case Study of the Middle Rio Grande,” by Oad and Kullman, describes a case study that uses an ecological approach to identify water and ecosystem conservation options. The research recommended changing the practice of continuous canal water delivery to rotational water delivery to irrigation water users in the Middle Rio Grande Valley. After these recommendations were adopted since 2002, irrigation water users have reduced their diversions by more than 30%.

The seventh and eighth papers deal with infiltration and drainage. The paper “Modified Kostiakov Infiltration Function: Accounting for Initial and Boundary Conditions,” by Furman et al., presents a methodology to account for changes in water levels and initial soil moisture when applying the Kostiakov infiltration equation.

The eighth paper, “Considerations for the Design of Intercepting Drainage for Collecting Water from Seep Areas,” by Bucur and Savu, presents a design method for establishing the positions of the first row of interceptor drains as well as the number of drains and the distance between successive rows of drains for draining seep areas on sloping lands.

The last two papers deal with storm-water management. The paper “Evaluating Bioretention Hydrology and Nutrient Removal at Three Field Sites in North Carolina,” by Hunt et al., describes a field study of three bioretention sites that measured their pollutant removal abilities and hydrologic performance. The sites varied in fill media type or drainage characteristics. The last paper, “Considerations for Storm-Water Outfalls off Exposed Coasts,” by Grace, discusses the design, planning, and installation of storm-water ocean outfalls that discharge well offshore.

The first two technical notes, “Seepage to a Drainage Ditch and Optimization of Its Shape” and “Capillarity and Evaporation Exacerbated Seepage Losses from Unlined Channels,” by Kacimov, deal with the mathematical development of seepage equations for two different situations. The third technical note “NRCS (SCS) Synthetic Curvilinear Dimensionless Unit Hydrograph,” by Jeng, describes the development of a continuous time function with two parameters for a curvilinear dimensionless unit hydrograph from the unit hydrograph in the form of a gamma probability density function.