Journal of Hydrologic Engineering

A comparative study concerning dynamic, local, and zero inertia variants of volume-averaged depth-integrated porous shallow water equations has been presented. The first two hyperbolic models are resolved through an explicit augmented approximate Riemann solver, and the diffusive parabolic model employs an implicit formulation. Three benchmark tests are simulated and compared through all three counterparts. The diffusive wave model offers a wide range of time-step choices and, subsequently, lesser computational cost when the temporal variation of flow depth/velocity is relatively small. However, explicit hyperbolic models outperform in the case of rapidly varied flow interaction with granular media.

Extreme rainfall in midwestern United States has gotten more common over the last half century, thus increasing flooding events across the region. As a result, traditional flood mitigation measures are commonly overwhelmed by highwater events, illustrating the need for new solutions. Of the 91,000 dams in the US, the vast majority are small and go unused for flood mitigation. Among those that are utilized in flood peak reduction, few are actively managed in which outflows are manipulated through a gated outlet. Instead, small storage locations typically use passive control, allowing impounded water levels to fluctuate without the use of a gated outlet, possibly squandering some of their flow-reduction potential. In this paper, we have evaluated actively managed storage within a distributed network of 130 small dams in a $660\text{-}{\mathrm{km}}^2$ watershed in southeastern Iowa using three operation schemes to increase storage utilization and reduce downstream flows. We developed a module to simulate the dam operation into a distributed hydrologic model that is forced with soil conservation service (SCS) 24-h design storms distributed uniformly across the watershed with 0.2, 0.1, 0.02, and 0.01 exceedance probabilities to evaluate flow reductions. When compared with passive operation, outlet flows were reduced under each proposed iteration of the 24-h design storm. Using the most aggressive operation scheme, outlet flows were reduced by over 70%. These results showcase the need for better understanding of activated flood storage across midwestern watersheds and encourage further work in optimizing this technique for real-time management.

A new measure of entropy based on incomplete information theory has been proposed in the literature for deriving velocity profiles in open-channel flow. This entropy is a one-parameter generalization of the Shannon entropy, which can be recovered through the entropy index value as unity. The approach considered a specific range for the entropy index and determined its value close to 1 by carrying out a data analysis procedure. However, this choice for the index may not justify the applicability of this entropy over the Shannon entropy as it is a particular case for this entropy. The present study extended this approach to both one- and two-dimensional cases for wide and narrow open channels, by considering the index as a varying parameter and calculating it using the second-order moment constraint, which physically represents the hydrodynamic transport of momentum. The derived velocity profile was validated using laboratory and field data and compared with the existing equation. The proposed velocity profile showed a slight improvement over the existing one in the case of wide channels, while for narrow channels, it shows superiority to the other entropy-based equations. The slight improvement for the one-dimensional case can be attributed to the available formulae for the momentum distribution coefficient that are used. Indeed, the proposed approach conceptually justifies the applicability of the modified entropy over the Shannon entropy, as the index takes on non-unity values. The effects of the entropy index on the wide and narrow channel velocity profiles are discussed, which reveals the possible physical explanation of the index through its relationship with shear stress values. Also, for practical purposes, regression equations are proposed, which relate the index with the momentum distribution coefficient. Moreover, the analytical derivation of the velocity profile is based on the series approximation of the Lambert function, which is verified for the considered data sets.

As a consequence of global warming, extreme weather events are becoming more prevalent, which influences socioeconomic development. It is vital to reveal the variations of regional extreme precipitation for flood prevention and mitigation. This research presents a comprehensive analysis of spatiotemporal variation and segmentation trend of extreme precipitation indices (EPIs) from the spectrum of intensity, frequency, and duration in the Lixia River Basin (LRB), China, from 1960 to 2019. The influence of global warming [global mean near-surface temperature (GSTEMP)], atmospheric circulation [e.g., multivariate ENSO index (MEI), and East Asian summer monsoon index (EASMI)], and local effects (e.g., relative humidity and local temperature) are examined to explore the dominant driving factors on the trend of EPIs. Results show that the intensity and frequency of EPIs increase across the LRB, whereas the durations of extreme precipitation are decreasing. And the lower reach has more frequent extreme precipitation than the upper reach. And most stations in segmentation trend analysis of EPIs show UUD (i.e., increasing from 1960 to 1980, increasing from 1981 to 2000, and decreasing from 2001 to 2019). What is more, the intensity and frequency of extreme precipitation are more actively related to local temperature and relative humidity than others, with local temperature being the primary negative impact while other factors are positive. And relative humidity and GSTEMP have a greater impact on the duration of EPIs than others. The findings will help figure out how regional global warming affect the trends of extreme precipitation, and can be used on a regional scale for the development of socioeconomic activities.

This study investigates lithologic control on parameters of the conceptual rainfall-runoff model and runoff characteristics through the construction of Xinanjiang rainfall-runoff models in different subwatersheds with different lithologies located in the Xiangxihe River watershed. The Xinanjiang models are calibrated based on a genetic algorithm and validated using the observed data. All the simulations for these four subwatersheds have NSE values larger than 0.8 during the calibration period and NSE values larger than 0.7 during the validation period. Root mean square error (RMSE) values range from 0.030 to $2.780{\mathrm{m}}^3/\mathrm{s}$. Compared with the other three subwatersheds dominated by limestone and dolomite, Gaojiaping subwatershed mainly composed of granite is characterized by the significantly smaller areal mean free water storage capacity and larger outflow coefficient of free water storage to the interflow. Gaojiaping subwatershed has a dramatically higher-level surface runoff proportion and a remarkably lower-level groundwater runoff proportion than the other three subwatersheds-Sanchakou, Cangpinghe, and Xiangguxi subwatersheds. The concept of a geological characteristic value of watershed is proposed to reflect the water-bearing property of rock stratum for the whole watershed through an area-weighted average. This geological characteristic value in the karst subwatershed is larger than that of the nonkarst subwatershed. The relationships between the parameters of the Xinanjiang model and the geological characteristic values are obtained, and the variation of four categories of parameters with the geological characteristic values is analyzed. The surface runoff proportion and groundwater runoff proportion are negatively and positively correlated with the geological characteristic value, respectively. The established empirical equations can well reflect the relations between the geological characteristic values and runoff proportions. The importance of this finding emerges from the direct link between the index of hydrogeological survey in hydrogeology and proportions of different runoff components, providing a simple and effective way for water resources assessment in ungauged watersheds.