Journal of Hydrologic Engineering

Urbanization and population growth result in an increase of insufficient groundwater recharge. In order to overcome the adverse effects of urbanization, low impact development (LID) best management practices (BMPs) are introduced. LIDs are nature-based solutions, also called green infrastructures, that have the ability to control both the amount and the quality of stormwater runoff. Rain barrels, vegetative swale, green roofs, bioretention, permeable pavement, and detention ponds are among the examples of LIDs. Within this context, the infiltration trench is also one of the important LID types and is widely implemented in settlement areas. Field-scale experiments may not be sufficient in determining the design criteria of infiltration trenches. Controlled experiments should be conducted in order to identify the optimum design criteria of infiltration trenches for best practices. In this study, the hydrological performance of the infiltration trench is investigated by conducting experiments using an open-lab large-scale rainfall-watershed-infiltration trench (RWI) experimental setup. The RWI experimental setup is built at the Avcılar Campus of Istanbul University-Cerrahpaşa and consists of an artificial rainfall system, an impermeable drainage area, and an infiltration trench. The effect of gravel size, berm height, and rainfall type on the hydrological behavior of the infiltration trench is tested by conducting several experiments. During these experiments, the overflow rate and the drainage rate are measured at the exit of the pipes, located on the front wall and on the base of the infiltration trench, respectively. Results show that the magnitude and lag time of the overflow rate hydrograph are affected by rainfall intensity, gravel size, and berm height significantly. On the other hand, minor changes on the drainage rate hydrograph are observed under different rainfall intensities, gravel sizes, and berm heights. Based on the outcomes of this study, the engineering design guidelines of infiltration trenches are elaborated.

Estimated extreme precipitation and floods provide crucial information for both the design of large hydraulic structures and water resources management. This study aims to estimate, in a series of numerical experiments, the probable maximum precipitation associated with extreme rain events over seven watersheds in the central/southern Sierra Nevada. To this end, a total of 249 extreme 72-h rainfall events, extracted from the historical reconstructions from 1852 to 2014, were maximized by means of the atmospheric boundary condition shifting (ABCS) method in meridional (north/south) and zonal (north/south and east/west) shift directions. Furthermore, optimization of relative humidity along atmospheric river (AR) corridors was applied to 20 significant storms, which were identified from the ABCS results. The meridional shifting exhibited a significant increase compared to historical conditions, with an additional slight increase by the zonal shifting method. Then, the relative humidity optimization exhibited a further significant increase in precipitation over the seven watersheds. The proposed method can generate numerous events at various shifting quantities and relative humidity intensities along the AR. The selected events can then be used as inputs for hydrologic simulations to estimate probable maximum flood (PMF) events.

Vadose zone well (VZW) injection is an effective method of managed aquifer recharge (MAR), and it plays an important role in semiarid and arid regions. Accurate estimation of the recharge of VZW injection remains a challenge in the field of hydrology due to the nonlinear nature of the process in the vadose zone. To improve knowledge of VZW injection, a finite-element numerical model was developed by COMSOL Multiphysics to evaluate the soil property and subsurface heterogeneity control on the recharge of VZWs. Several numerical experiments were conducted to estimate the characteristic arrival time and cumulative recharge volume of injected water for different subsurface conditions. Simulation results indicate that soil properties have a profound influence on the recharge of VZWs and saturated hydraulic conductivity plays a more important role than the Van Genuchten –Mualem soil constitutive model parameters $\alpha$ and $n$ in the influences on the recharge. Subsurface heterogeneity has large impacts on the recharge of VZWs as well. The presence of a low permeable layer in the aquifer hinders the infiltration of injected water and reduces recharge rate $Q_{wt}$ and cumulative recharge volume $V_{wt}$. These influences are affected by depth $D_c$, lateral extension $R_c$, thickness $B_c$, and hydraulic conductivity $K_s$ of the low permeable layer. Whether the well screen cuts through the low permeable layer is a factor that influences the effects of these parameters in two forms. When the well screen cuts through the low permeable layer, $Q_{wt}$ and $V_{wt}$ decrease substantially as $D_c$ increases, and the change of $B_c$ has a greater impact on recharge than $K_s$; when the low permeable layer is below the well screen, the change of $D_c$ only has slight influence on recharge, and the cases with the same hydraulic conductance value of $K_s/B_c$ have similar $Q_{wt}$ and $V_{wt}$. For the low permeable lens, when the well screen cuts through it, the increase of $R_c$ leads to slight decrease of $Q_{wt}$ and $V_{wt}$, which are more obvious in the later stage of VZW injection. When the low permeable lens is below the well screen, the increase of $R_c$ makes $Q_{wt}$ decrease in the early stage of VZW injection, and then $Q_{wt}$ for different values of $R_c$ reach similar asymptotic values in the later stage. Understanding the influences of soil properties and subsurface heterogeneity on the recharge of VZWs provides physically based guidance for the design and management of VZWs.

To assess the impacts of climate change on water resources, hydrological models are the most commonly used to simulate future flows. Hydrological model calibration is typically based on historical hydrometeorological data, which may not be representative of the future climate. This paper evaluates various calibration strategies to minimize this issue. The impact of these calibration strategies is measured on 921 North American catchments using a lumped hydrological model. Five calibration strategies (warm, low rainfall, high rainfall, low-flow, and high-flow years) were investigated, each using a 5-year (noncontinuous) independent validation dataset maximizing all five studied climate anomalies. The remaining years were used as a pool of calibration years, using targeted subsets of years in multiples of five to assess the impact of the number of calibration years versus the climate anomaly of each calibration subset. Results showed large cross-catchment variability, indicating that no single calibration strategy and number of calibration years were optimal for all watersheds. However, the large number of catchments used in this study allows for some general conclusions to be drawn. For the warm-years calibration strategy, using a large number of years was the approach most likely to succeed, indicating that removing a small subset of cold years was preferable to keeping a small subset of warm years. For the other four calibration strategies, the approach most likely to succeed was the one in which about half of the years in the historical record were kept. For the warm year strategy, keeping a larger number of years for calibration ensures better model robustness to account for precipitation variability in the validation set. For the other four calibration strategies, which are mostly related to precipitation, a larger number of years had to be dropped to account for the much larger differences between wet and dry years.

Two-sided extreme conditional sampling regularly is coupled with copula theory to assess the dependence between flood-risk drivers such as extreme precipitation or river discharge and storm surge. The approach involves many subjective choices, including sampling techniques used to identify extreme events [block maxima or peaks-over-threshold (POT)], whether to account for the fit of marginal distributions, and time-lags considered between the two drivers. In this study, estimates of the potential for compound events at three sites along the Texas Gulf Coast, where the USACE is undertaking coastal storm risk management (CSRM) projects, were shown to be highly sensitive to the setup of the statistical model. A pragmatic approach accounting for marginal fit in a POT framework is proposed and was shown to provide stable estimates of the compounding potential for high discharge and storm surge events. We also explored the effect of using precipitation as a proxy for discharge in the absence of sufficiently long discharge records.

Evaporation is the main outflow of many water bodies. In hypersaline Lake Urmia (LU), which has experienced significant shrinkage during the last 3 decades, evaporation is the only water outflow. The 15-year daily saline water evaporation pan data collected near the lake indicate that approximately 71% of the annual evaporation occurred from May to September, about $4.15\mathrm{billion}{\mathrm{m}}^3/\mathrm{year}$. To reduce this water loss, three self-assembled layer coatings—fatty alcohols of stearyl and cetyl with stearic acid in hexane solvents, stearyl and cetyl alcohols with stearic acid powder, and stearyl and cetyl alcohols in ethanol solvents—were tested on pools and evaporation pans adjacent to LU in July, when the lake had the highest evaporation rate. Results of 60 h of experiments for each test showed that the coating composed of stearyl and cetyl alcohols with stearic acid in hexane had the best performance and could reduce evaporation by about 52%. This suggests that applying this coating to LU for $5\mathrm{months}/\mathrm{year}$ could reduce the lake evaporation by about $1.5\mathrm{billion}{\mathrm{m}}^3$, which is more than the total annual supply of the main river flowing into the lake. A short-term study of Artemia urmiana indicated that the coatings did not have a significant effect on their length and weight. However, long-term side effects on human health and the environment need further investigation.