Journal of Irrigation and Drainage Engineering

Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing speculation, on a civil engineering topic of general interest and relevance to the readership of the journal. The views expressed in this Forum article do not necessarily reflect the views of ASCE or the Editorial Board of the journal.

Hydraulic design and environmental permitting require the knowledge of ordinary high water marks (OHWMs) because they determine the federal jurisdictional limits over nontidal waters. The U.S. Army Corps of Engineers (USACE) uses OHWMs for regulation of the “Waters of the United States” as well as for authorizing activities such as stream restoration and bank stabilization. Current methods to determine OHWMs are based on detailed on-site surveys to identify physical characteristics like scouring, deposition around the banks, absence of vegetation, and water staining. These characteristics are site specific so there are fluctuations in measurements based on the water body, weather conditions, channel morphology, slope, fluvial patterns, and size of the channel. This study proposes an objective approach to determine OHWMs in the absence of clear physical indicators. This study uses hydrologic and hydraulic modeling to relate OHWMs to storm return periods by analyzing hydraulic and hydrologic parameters corresponding to design streamflow events for 26 watersheds in Indiana. The results show that OHWMs correspond to discharges that have return periods ranging from 0.7 to 1.1 years with a mean return period of about 0.92 years. The OHWM discharges are then related to 100-year discharges to enable the use of this relationship in approximately estimating the OHWM discharge when the 100-year discharge is known. For Indiana, it is found that the ratio of OHWM discharge and 100-year discharge has an average value of 4.99% for the northern part, 3.60% for the central part, and 5.49% for the southern part. The regression equations and range of OHWM attributes developed in this study can be used as a guide for OHWM determination for ungauged sites that do not have physical indicators for OHWMs.

The present study investigates the accuracy of five different data-driven techniques in estimating oxygen transfer efficiency in baffled chutes: feedforward neural network (FFNN), radial basis neural network (RBNN), generalized regression neural network (GRNN), adaptive neuro fuzzy inference system with subtractive clustering (ANFIS-SC), and adaptive neuro fuzzy inference system with fuzzy c-means clustering (ANFIS-FCM). Baffled apron chutes or drops are used on channel structures to dissipate the energy in the flow. A baffled chute design is effective both in energy dissipation and in aerating the flow and reducing nitrogen supersaturation. There is a close relationship between energy dissipation and oxygen transfer efficiency. This study aims to determine the aeration efficiency of baffled chutes with stepped ($S$), wedge ($W$), trapezoidal ($T$), and $T$-shaped ($T\text{-}S$) baffle blocks. The performances of the FFNN, RBNN, GRNN, ANFIS-SC, and ANFIS-FCM models are compared with those of multilinear and nonlinear regression models. Based on the comparisons, it was observed that all data-driven models could be successfully employed in modeling the aeration efficiency of $S$, $W$, and $T\text{-}S$ baffle blocks from the available experimental data. Among data-driven models, the FFNN model was found to be the best.

The electrical conductivity of saturated soil-paste extract (${\mathrm{EC}}_e$) has been extensively used as the standard index for soil salinity assessment. However, this method is time-consuming and laborious. A number of research works are therefore attempting to find conceptual or empirical models to correlate ${\mathrm{EC}}_e$ with the soil bulk electrical conductivity ${\mathrm{EC}}_a$, which could be more easily provided in different ways. Dielectric devices, which could provide measurements of the soil dielectric constant and of ${\mathrm{EC}}_a$ simultaneously and for the same volume of soil, could be easily used to provide measurements of the bulk saturated paste electrical conductivity (${\mathrm{EC}}_p$). In the present work, a less time-consuming method of calculating ${\mathrm{EC}}_e$ from the bulk electrical conductivity of saturated paste (${\mathrm{EC}}_p$), as this can be obtained directly by a dielectric sensor (e.g., WET sensor), is examined. The method utilizes a model with two empirical relationships that estimate the solid particle surface charge component of electrical conductivity (${\mathrm{EC}}_s$) and the water content of the continuous liquid current flow-coupling pathway (${\theta }_{wc}$) as functions of the saturation percentage (SP). The appropriateness of the method was tested in 220 soil samples, collected from five different locations across Greece. The model was applied with two different couples of empirical relationships, one developed for U.S. soils and the other for Greek soils. The ${\mathrm{EC}}_e$ prediction in both cases was reliable and satisfactory (RMSE = 1.22 and $1.36\mathrm{dS}·{\mathrm{m}}^{-1}$). More specifically the results showed that in three out of five locations, the performance of the model supported by the empirical relationships for Greek soils was relatively better. In one location with special characteristics, the model with empirical relationships for U.S. soils performed better.

For the numerical modeling of invert traps in open channels, earlier investigators used a fixed lid model (assuming closed conduit flow with the top wall as a shear free wall) with a stochastic discrete phase model (DPM). This approximate model was poorly validated with the experimental data. In the present study, experimentation has shown that the free-water surface rises above the central opening (slot) above the invert trap, which cannot be modeled using a fixed lid model. Therefore, in the present study, without making such assumptions, the appropriate computational fluid dynamics (CFD) model for open-channel flow, i.e., volume of fluid (VOF) model along with stochastic DPM has been used. Two-dimensional (2D) and three-dimensional (3D) analyses show that 2D predicts slightly lower trap efficiencies than 3D, which is theoretically justified because in 3D, more sediment falls into the trap due to their low velocity near the walls, as also observed experimentally, giving higher values of trap efficiency, which is contrary to the presumptions of the earlier investigators that the 3D model will predict lower values than the 2D model. Although, 2D predicts the same qualitative results as the 3D one but quantitatively, the 3D model predicts the best results.

The present paper deals with a United States Bureau of Reclamation (USBR) Type II stilling basin, which is characterized by blocks at the end of the chute and a dentated sill at the end of the basin. For this basin, USBR only gives overall design criteria concerning basin length and block dimensions on the basis of the assumption that the hydraulic jump remains confined within the sill. No considerations are provided concerning possible different jump types, pressure regimes, and forces acting on the sill. To comply with such a lack, an experimental campaign was undertaken that focuses on the differences among hydraulic jump types that can occur in a USBR Type II stilling basin. Jump types can range between submerged and spray jump types; accordingly, dimensionless relations are provided to predict jump type and position for assigned boundary conditions, with particular concern about the submerged/nonsubmerged distinction. Considerations about the drag force and drag coefficients are provided, along with estimates of pressure extreme fluctuations. Finally, an evaluation of the dissipation efficiency is presented for both submerged and nonsubmerged jumps, enabling comparisons among different jump types and with classical hydraulic jump.

This paper presents the development of fuzzy set–based performance measures for an irrigation reservoir system to answer questions on how likely a system is to fail (fuzzy reliability), how quickly it is likely to recover from failure (fuzzy resiliency), and how severe the consequences of failure are likely to be (fuzzy vulnerability). The failure/success state of the system is defined as a fuzzy event. A fuzzy set with an appropriate membership function is defined to describe both the working and failed states, to account for the system being in partly working and partly failed state. Failure of the irrigation reservoir system is related to the evapotranspiration deficit of the crops in a period. Application of the performance measures is demonstrated with the case study of the Bhadra Reservoir system in Karnataka, India. The reservoir operation is simulated using three different reservoir operating policy models: steady-state policy obtained using a fuzzy stochastic dynamic programming (FSDP) model, steady-state policy obtained using a classical stochastic dynamic programming (SDP) model, and yearly operating policy using a conceptual operating policy (COP) model. All reservoir operating policy models consider the integration of the reservoir operation policy at 10-day time periods with water allocation decisions on a daily basis by maintaining the storage continuity and soil moisture balance. Inclusion of fuzziness in the performance measure gives realistic solutions by capturing uncertainties in the reservoir operating policy models.

Policy makers in sub-Saharan African (SSA) countries have identified irrigation as a key ingredient to boosting food security and income as well as a precursor for agricultural development. However, most SSA countries have hardly exploited their irrigation potential. The overarching aim of this paper is to critically examine factors constraining exploitation of irrigation potential in Uganda. Lessons learned from previous interventions and successes elsewhere from countries comparable to Uganda are drawn and future perspectives to guide effective irrigation planning and development are recommended. From this paper, it is evident that there is no single blanket solution to constraints of irrigation development in SSA. All strategies should be implemented in a holistic manner dictated by specific local conditions. The key to successful adoption of irrigation lies in building the national irrigation capacity, improving access to reliable water for irrigation in proximity of the farms, streamlining extension services for farmers, addressing economic aspects of irrigation, and streamlining land tenure systems and management. It is recommended to operationalize government policy on irrigation by developing national guidelines on irrigated agriculture.

Land drainage practices represent a suitable technique that can assist managing the water table and control salinity levels. Until the last few decades, mainly the positive aspects of drainage performance have been addressed rather than negative impacts. Despite the positive effect of drainage systems on agricultural land, nowadays, drainage water flow containing too much salt constitutes a serious concern for the environment, including the accumulation of salt deposits and environmental contamination and destruction. Measured data from observation wells drilled around a drainage system were investigated to understand the effectiveness of drains to decrease the salinity level of groundwater using data analysis and simulation. The results indicate that the salinity level of the drained land considerably decreased to $4.4–137.7\mathrm{dS}{\mathrm{m}}^{-1}$ within 3 years (2010–2014). In contrast, annually over $244.3\mathrm{t}{\mathrm{ha}}^{-1}$ salt load has entered into the environment; this is expected to create a salty layer of 10 cm thickness over 1,000 ha, adjacent to the outlet, due to the operation of drainage.

The conventional approach in uniform open channel flow is to express the resistance coefficient in the Manning, Darcy-Weisbach, or Chezy form. However, for practical cross sections, including rectangular and trapezoidal, the governing equation is implicit in the uniform water depth. For these sections, the water depth, corresponding to known values of the flow discharge, slope channel, and resistance coefficient, is presently obtained by a trial-and-error procedure. In this paper, explicit analytical solutions of uniform flow depth for rectangular and trapezoidal sections have been obtained in the form of fast converging power series.