Journal of Hydrologic 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.

Lateral and vertical migration capacity of faults has been studied for applications related to fluid extraction and injection from and into the subsurface. Fluid exchange between formations connected by a fault can cause pressure perturbations in nonoperating formations. An analytical model was previously developed to evaluate the leakage rates through a fault in a multilayer system. However, the effect of the fault’s lateral resistance to flow was neglected and therefore the model was not applicable in evaluating the pressure changes caused by fault leakage. Pressure perturbations induced by fault leakage are important to determine the safety of injection operations near faults and/or in characterizing and remediating fault leakage. Here, the previous model on fault leakage to evaluate the pressure changes is extended by accounting for the lateral resistance to flow in all modeling components. As a result, the leakage rates at the two sides of the fault are no longer identical. Also, the model presented here allows for well perforation in any layer compared with the previous model where perforation must be in the bottom layer of the system. This modification is important to enable estimation of pressure changes in multilayer operation [e.g., injection in one or more aquifers while producing from other aquifer(s)]. Hence, the model can be used to determine basin-scale pressure changes considering multiple injection or production wells in multiple layers. The semianalytical solution presented here involves obtaining a set of coefficients to determine the pressure changes in Laplace and Fourier domains followed by numerical Fourier-Laplace transforms inversion. The model is applied to two example problems. In the first example, the model is verified against results of a two-layer system and compared to pressure perturbations in a three-layer system where the solution behavior is investigated. In the second example, the model is applied to investigate pressure management close to a critically stressed fault zone using relief wells, which is of interest in ${\mathrm{CO}}_2$ sequestration and/or waste disposal applications.

The estimation of distribution algorithm (EDA) is a new evolutionary algorithm developed as an alternative to the traditional genetic algorithm (GA). The EDA guides the search by avoiding the crossover and mutation operators of the GA in favor of building and sampling probabilistic distributions of promising candidate solutions. By increasing the probability of generating solutions with better fitness values, the EDA locates the region of the global optimum or its accurate approximation. In this study, EDA was used to calibrate the parameters of the soil and water assessment tool hydrologic model for the Xunhe River Basin in China. The EDA was compared with three other algorithms: (1) the Multistart Local Metric Stochastic Radial Basis Function algorithm (a surrogate optimization method), (2) the Shuffled Complex Evolution algorithm, and (3) the GA. Four metrics are presented to assess the performance of the algorithms: (1) efficiency in terms of the average best objective function value in a limited number of function evaluations, (2) variability in terms of standard deviation and the box plot, (3) reliability in terms of the empirical cumulative distribution function, and (4) accuracy in terms of the Nash–Sutcliffe efficiency coefficient and overall volume error. Results indicated that the EDA is more efficient and could provide more accurate solutions with a relatively high probability, at least for this case study.

Coupling rainfall-runoff and one-dimensional (1D)/two-dimensional (2D) hydrologic models provides the current state-of-the-art approach for predicting the extent of urban inundation, although the computational cost for running 2D models is still a major concern. This paper presents a procedure to dynamically reshape 2D numeric domain according to flooding extent evolution. The numeric domain is updated at each selected time step for reshaping (TSR) and includes grid elements directly connected to the 1D stormwater network, flooded grid elements, or grid elements within a buffer distance threshold (BDT) identified in both previous criteria. Results for an urban catchment in South Brazil are presented considering two spatial resolutions and three return-period rainfall events. An optimal relation between TSR and BDT was found and resulted in runtime savings greater than 86% in comparison to adopting a fixed boundary as catchment limits, and greater than 69% in comparison to using a fixed boundary below the 70-m elevation (which represents the maximum elevation reached by the 100-year flood). The major concepts of the proposed algorithm are straightforward and could be tested in similar 2D models.

The aim of this paper is to propose a new geomorphologic method for deriving the complete shape of instantaneous unit hydrograph (IUH) in ungauged watersheds by calculating the mean travel time of excess rainfall in overland and channel segments. All required parameters for the calculations of travel time of sheet and channel flows for different hydrologic orders are determined based on geomorphologic data of a watershed. In the proposed model, IUH is obtained using the exponential probability density function (PDF) of mean travel time of possible flow paths in a watershed. In this method, the excess rainfall is determined using the National Resources Conservation Service) NRCS curve number (CN) method (SCS-CN). To investigate the performance of the proposed IUH model, it is applied for daily rainfall-runoff simulation in two separate watersheds with different climate conditions (i.e., cool-humid and semiarid) in Iran. Also, other geomorphologic IUH (GIUH) models are utilized as benchmark models for comparing their results with those obtained using the proposed model. The goodness-of-fit criteria show that the proposed GIUH model practically provides direct runoff ordinates in ungauged and partially geomorphologically homogeneous watersheds with an accuracy slightly better than one of the other GIUH (especially in terms of estimating peak flow) and much better than the other GIUH model. Additionally, the proposed model is beneficial to estimate the travel time of overland and channel flows in different orders of watershed, which can be worthwhile for flood management and designing flood warning systems in each segment of the watershed.

The management of urban channel systems constitutes an important problem in most developing cities of the world. In this study, a deterministic approach was followed to obtain water-diversion function through development of a numerical model that includes main hydrological elements such as stream flow, groundwater flow with stream–aquifer interaction, and evapotranspiration. An application to the city of Eskisehir (Turkey) is presented. The city has an extending channel network lying on an alluvium plain. In developing the new diversion function, three main criteria were taken into consideration: (1) the conservation of ecosystem; (2) flood prevention; and (3) aquifer replenishment. As the aquifer is the main water resource in the basin, a total of 96 boreholes were drilled in the framework of two projects. From these borehole data, stratigraphy and the piezometric head distribution were obtained. The basin was modeled using MODFLOW under Groundwater Modeling System (GMS) software. For calibration of hydraulic conductivities, the parameter estimation model was used. Through steady-state analysis, flood-prone areas were determined. Transient simulations were performed over a period of 650 days covering both low and high flows. A computer code following an iterative procedure was written in order to integrate the diversion function into MODFLOW. Simulation results demonstrated that the proposed function was successful in satisfying all three criteria.

The sharing of water resources across transboundary regions between countries has long been a political problem. Sharing of data among countries is also a significant impediment for both planning and research purposes. In the context of climate change, it is necessary to know about possible future climatic changes and their potential impacts that would be especially crucial to water resources management. This requires data for hydrological modeling and data management, as in the case of river basins. This paper presents a study over the course of the Da River, which flows from China (upstream) to Vietnam (downstream), and it is assumed that rainfall data from China are not available. To overcome data limitation, regional climate model outputs are used as proxy data for this upstream region to study changes over the downstream Da River. The Weather Research and Forecasting (WRF) model was used as the regional climate model, driven by the European reanalysis data for the baseline period of 1961–1987 for a domain covering the transboundary areas, at a resolution of 25 km. Precipitation outputs from this model were used as inputs to the hydrological model and soil and water assessment tools (SWAT) to calibrate/validate the model at data-available gauging station sites. The initial results of this study imply that the regional climate model (RCM) data proxies serve as a good alternative to assess water resources over transboundary regions and are useful tools for assessing future climate changes and their impacts at subregional and local scales.

Three independent analyses establish that the Conestoga River flow published by the U.S. Geological Survey (USGS) for Tropical Storm Agnes in 1972 of $\mathrm{1,420}{\mathrm{m}}^3/\mathrm{s}$ ($\mathrm{50,300}{\mathrm{ft}}^3/\mathrm{s}$) should have been at least $\mathrm{1,660}{\mathrm{m}}^3/\mathrm{s}$ ($\mathrm{58,600}{\mathrm{ft}}^3/\mathrm{s}$), an increase of over 16%. The three analyses included an empirical analysis of the data for U.S. Geological Survey Gauge 01576500, a reanalysis of a 1978 U.S. Army Corp of Engineers Hydrologic Engineering Center (HEC)-2 simulation of the Conestoga River, and a retrofit and minor corrections to a preliminary 2013 HEC-RAS (river analysis system) simulation of the Conestoga River.

Engineered media used in living roofs and bioretention plays a crucial role in determining stormwater mitigation performance. Engineered media with compositions varying in four aggregates, volumetric ratio of compost (0, 10, and 20%) and three amendments (zeolite, paving sand, and topsoil) were prepared in the laboratory. Media basic properties including particle-size distribution (PSD), dry bulk density, particle density, porosity, and saturated hydraulic conductivity ($K_s$), were characterized and investigated as a function of the varying composition. All media are classified as poorly-graded sand (SP), exhibiting porosity greater than 0.51, with magnitudes of $K_s$ ranging from ${10}^{-2}$ to ${10}^{-1}\mathrm{cm}/\mathrm{s}$. Media with pumice-based aggregates have particle densities between 2.21 and $2.48{\mathrm{g}/\mathrm{cm}}^3$. The $K_s$ of a pure aggregate classified as SP is positively related to the particle size corresponding to 50% fines on the cumulative PSD curve. $K_s$ values of four aggregates either remain unchanged or decrease by 73% at most with the addition of the compost. An amendment to an aggregate-compost mixture can alter $K_s$ in different ways, depending on its particle shape, coarseness, and organic material.