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An understanding of turbulence and mixing is essential to the knowledge of turbulent dissipation, sediment transport, advection of nutrient-rich and organic effluents, and stormwater runoff in prototype water systems, as well as in laboratory channels used for physical modeling of geometrically-scaled full-scale water bodies and for validation of computational models. The acoustic Doppler velocimeter (ADV) system is a robust instrument well suited for such turbulence measurements in open channel flows. The application of acoustic Doppler velocimeter to transient free-surface flows is reviewed in this paper. Based upon field applications and laboratory experiments, the intricacy and inherent difficulties are discussed. The experience and expertise in transient flows highlighted the importance of the signal processing and precise synchronization. Finally, we stress a major benefit of the acoustic Doppler velocimetry for its capability to be used in both field and laboratory, in turn providing some level of confidence in the comparison between full-scale and laboratory data. [ABSTRACT FROM AUTHOR]

The management of landscapes and agricultural activities significantly impacts phosphorus (P) and nitrogen (N) losses, directly influencing eutrophication risk. This study quantifies the eutrophication potential of different land covers through in-situ measurements and analysis of runoff and inorganic substances. The research was conducted in two sub-catchments in the Bedřichovský stream basin, Novohradské hory, Czech Republic: a forest-dominated upper sub-catchment (UFS) and an agricultural lower sub-catchment (LAS). Water flows and surface water samples were measured over a hydrological year (November 2017 to October 2018) to determine runoff and concentrations of nitrate (N-NO3−) and phosphate (P-PO43−). The ReCiPe 2016 method, as a tool for LCIA, was used to quantify the eutrophication potential, converting N and P concentrations into nitrogen equivalents (N eq ha−1 sub-catchment) for marine eutrophication and phosphorus equivalents (P eq ha−1 sub-catchment) for freshwater eutrophication. The potential loss of species (species·yr ha−1 sub-catchment) was assessed as follows. Results indicate UFS has about 60% lower freshwater and 80% lower marine eutrophication potential compared to LAS, along with about 60% lower potential for biodiversity loss. This highlights the role of forest and grassland covers in mitigating eutrophication and protecting water sources. These findings can guide landscape management practices to reduce eutrophication potential, enhancing environmental quality and biodiversity conservation. [ABSTRACT FROM AUTHOR]

This study aims to investigate the impact of forest exploitation methods on monthly discharge and hydrological indices of river flow using graphical methods in a forested watershed in North Iran. To achieve this, 10 hydrological index changes related to river flow regime influenced by the Shelterwood/clear cutting, Femel cutting, and the Near Nature approach forest cutting methods were assessed. According to the results, it can be stated that the Shelterwood/clear cutting method influenced monthly flow indices by increasing the coefficient of variations and intensifying runoff production, while the Femel cutting and the Near Nature approach methods contributed to regulating the flow regime and sustaining river flow. The influence of various tree-cutting techniques on river flow values and fluctuations is more evident during the wettest months compared to low-water months. The period of Shelterwood/clear cutting disrupted the natural correlation between precipitation and runoff production. Furthermore, the shift from Shelterwood/clear cutting to Femel cutting and the Near Nature approach progressively diminished the slope of the curve, indicating a reduction in monthly runoff at both measurement stations. In conclusion, opting for an appropriate method, such as the Near Nature approach, is preferable from both ecological and hydrological perspectives when managing forest areas in the study region and similar conditions involving comparable topography, climate, soil, and forest stands. The index-based coupled with graphical methodology employed appropriately demonstrates the influence of logging techniques on monthly flow patterns, which provides valuable insights into evaluating the repercussions of alternative management interventions on river flow dynamics. [ABSTRACT FROM AUTHOR]

Infiltration-runoff-slope instability mechanism of macropore slope under heavy rainfall is unclear. This paper studied its instability mechanism with an improved Green-Ampt (GA) model considering the dual-porosity (i.e., matrix and macropore) and ponding condition, and proposed the infiltration equations, infiltration-runoff coupled model, and safety factor calculation method. Results show that the infiltration processes of macropore slope can be divided into three stages, and the proposed model is rational by a comparative analysis. The wetting front depth of the traditional unsaturated slope is 17.2% larger than that of the macropore slope in the early rainfall stage and 27% smaller than that of the macropore slope in the late rainfall stage. Then, macropores benefit the slope stability in the early rainfall but not in the latter. Macropore flow does not occur initially but becomes pronounced with increasing rainfall duration. The equal depth of the wetting front in the two domains is regarded as the onset criteria of macropore flow. Parameter analysis shows that macropore flow is delayed by increasing proportion of macropore domain (ωf), whereas promoted by increasing ratio of saturated permeability coefficients between the two domains (μ). The increasing trend of ponding depth is sharp at first and then grows slowly. Finally, when rainfall duration is less than 3 h, ωf and μ have no significant effect on the safety factor, whereas it decreases with increasing ωf and increases with increasing μ under longer duration (≥ 3 h). With the increase of ωf, the slope maximum instability time advances by 10.5 h, and with the increase of μ, the slope maximum instability time delays by 3.1 h. [ABSTRACT FROM AUTHOR]

Accurately characterizing rainfall runoff processes in plain farmland, especially at the plot scale with significant micro-topographic features, has presented challenges. Integrated surface–subsurface flow models with high-precision surface flow modules are appropriate tools, yet open-source versions are rare. To address this gap, we proposed an open-source integrated surface–subsurface flow model called the FullSWOF-Plain model, in which the one-dimensional subsurface module Hydrus-1D was integrated with a modified two-dimensional surface water flow module (FullSWOF-2D) using the sequential head method. Various experimental scenarios were simulated to validate the model's performance, including two outflow cases (i.e., 1D and 2D) without infiltration, a classical one-dimensional infiltration case, and two typical rainfall events at the experimental field. The results demonstrate the accuracy of this proposed model, with the Nash–Sutcliffe efficiency (NSE) of the simulated discharge exceeding 0.90 in the experimental field case and the root mean squared error (RMSE) values for soil moisture at five depths consistently below 0.03 cm3/cm3. However, we observed a lag in the simulated response time of soil moisture due to the neglect of preferential flow. The micro-topography significantly influenced ponding time and ponding areas. Lower local terrain normally experienced earlier surface ponding. Scattered surface ponding water first occurred in the ditch and followed in the relatively low areas in the main field. The concentration process of surface runoff exhibited hierarchical characteristics, with the drainage ditch contributing the most discharge initially, followed by the connection of scattered puddles in the main field, draining excess surface water to the ditch through rills. This quantitative study sheds light on the impact of micro-topography on surface runoff in plain farmland areas. [ABSTRACT FROM AUTHOR]

Precise long-term runoff prediction holds crucial significance in water resource management. Although the long short-term memory (LSTM) model is widely adopted for long-term runoff prediction, it encounters challenges such as error accumulation and low computational efficiency. To address these challenges, we utilized a novel method to predict runoff based on a Transformer and the base flow separation approach (BS-Former) in the Ningxia section of the Yellow River Basin. To evaluate the effectiveness of the Transformer model and its responsiveness to the base flow separation technique, we constructed LSTM and artificial neural network (ANN) models as benchmarks for comparison. The results show that Transformer outperforms the other models in terms of predictive performance and that base flow separation significantly improves the performance of the Transformer model. Specifically, the performance of BS-Former in predicting runoff 7 days in advance is comparable to that of the BS-LSTM and BS-ANN models with lead times of 4 and 2 days, respectively. In general, the BS-Former model is a promising tool for long-term runoff prediction. [ABSTRACT FROM AUTHOR]

Slope has an important effect on the runoff production process. Slope correction of runoff curve number in the SCS-CN runoff production model is important to improve the model prediction accuracy, In order to conduct an investigation of the effect of average watershed slope in the runoff production process, in this paper, based on Huang's slope modification formula, the first 40 out of 70 rainfall runoff measurements in the study area from 1955 to 1981 were used as the validation data, and a1 and a2 parameters in Huang's slope modification formula were re-determined, so as to propose the slope modification formula of the CN value for the study area under three different antecedent moisture conditions, and then the SCS-WJG method, which is of good applicability to the region, was established and compared to the SCS-CN look-up table method, and the SCS-Huang method, which is a direct transfer of the Huang's slope modification formula. The conclusion is as follows: the λ-value of the initial rainfall loss rate determined using the ergodic method is 0.09, so the standard value of 0.2 is not applicable to the study area. After comparing the size of the CN values obtained by the three methods, it is found that the CN value obtained by the SCS-Huang method is the largest, followed by the SCS-CN look-up table method, and the smallest is obtained by the SCS-WJG method, so the CN value obtained by the SCS-WJG method is more suitable for the study area as shown in the simulation results. Comparison of the SCS-CN lookup table method and the SCS-Huang method reveals that the NSE of the SCS-Huang method is lower and the RMSE is higher; therefore, it is necessary to propose a slope correction formula for the CN value applicable to the study area and establish the SCS-WJG method. When λ = 0.09, the NSE of the SCS-CN lookup table method, and the SCS-Huang method are -2.85 and -3.25, respectively, while the NSE of the SCS-WJG method is increased to 0.86, and the RMSE of the SCS-WJG method is reduced by 77%, and 78%, respectively, compared with the first two methods. The simulation accuracy of the SCS-WJG method is significantly better than that of the remaining two methods, indicating that the SCS-WJG method has good regional applicability and can provide a reference for the simulation of runoff production in small watersheds. [ABSTRACT FROM AUTHOR]

Macroscale hydrological/land surface models are important tools for assessing historical and predicting future characteristics of extreme hydrological events, yet quantitative understandings of how these large-scale models perform in simulating extreme hydrological characteristics remain limited. Here we evaluate simulated high and low flows from 23 macroscale models within three modeling experiments (i.e., 14 climate models from CMIP6, 6 global hydrological models from ISIMIP2a, and 3 land surface models from GLDAS) against observation in 633 unimpaired catchments globally over 1971–2010. Our findings reveal limitations in simulating extreme flow characteristics by these models. Specifically, we find that (i) most models overestimate high-flow magnitudes (bias range: from +15% to +70%) and underestimate low-flow magnitudes (bias range: from −80% to −20%); (ii) interannual variability in high and low flows is reasonably reproduced by ISIMIP2a and GLDAS models but poorly reproduced by CMIP6 models; (iii) no model consistently replicates the observed trend direction in high and low flows in over two-thirds of the catchments, and most models overestimate high-flow trends and underestimate low-flow trends; and (iv) CMIP6 and GLDAS models show timing biases, with early high flows and late low flows, while ISIMIP2a models exhibit the opposite pattern. Furthermore, all models performed better in more humid environments and noncold regions, with model structure and parameterization contributing more to uncertainties than climatic forcings. Overall, our results demonstrate that extreme flow characteristics simulated from current state-of-the-art macroscale models still contain large uncertainties and provide important guidance regarding the robustness of assessing extreme hydrometeorological events based on these modeling outputs. Significance Statement: Macroscale hydrological and land surface models represent crucial tools for assessing historical trends and making predictions about future hydrological changes. Nevertheless, our current understanding of the quantitative performance of these large-scale models in simulating extreme hydrological characteristics remains limited. Here, we evaluate simulated high and low flows from 23 state-of-the-art macroscale models against observation in 633 unimpaired catchments globally over 1971–2010. Our results reveal important limitations in the extreme flow characteristics simulated from these models and provide important guidance regarding the robustness of assessing extreme hydrometeorological events based on these modeling outputs. The model evaluation performed herein serves as a pivotal, offering valuable insights to inform the development of the next generation of macroscale hydrological and land surface models. [ABSTRACT FROM AUTHOR]

The prediction of the water film depth (WFD) on the road surface can help with road skid resistance research and reduce the risk associated with driving on rainy days. At present, there are many empirical and analytical models based on drainage length, slope, rainfall intensity and other parameters. Considering the influence of road surface runoff and starting from the Reynolds number formula of road surface water flow, a new road surface WFD calculation formula that considers the movement state of laminar water flow is derived. The results show that the changing trends of various parameters in the prediction model (drainage length, rainfall intensity, road slope) affecting WFD are consistent with those of the existing model. It is also found that the initial water film depth, initial speed of rainwater, and rainfall angle have little impact on WFD. The predicted value of the model has a suitable matching degree compared with the classical empirical model, which provides a new approach to the prediction of road water film depth. [ABSTRACT FROM AUTHOR]

Different types of plants in the vegetation community near the surface of the basin coexist, forming a layered vegetation distribution with high and low plants in the morphology. In order to research the characteristics of flow resistance generated by layered vegetation on slope runoff, a flume experiment was carried out by simulating layered vegetation. The Manning roughness coefficient n was used to characterize the flow resistance of vegetation. Three kinds of vegetation with height combinations of 5 and 7 cm, 6 and 8 cm, and 7 and 9 cm were used for this experiment. By studying the relationship between Manning roughness coefficient n and water depth, it is found that the change of flow resistance of layered vegetation is closely related to the submerged state. The distribution of n shows an inverted "J" type with the increase of water depth. Under the condition of nonsubmerged state and transitional submerged state, n increases with the increase of water depth. The critical point n values of the two states will plummet, and the growth rate of n in the nonsubmerged state is greater than that in the completely submerged state. In the transitional submerged state and completely submerged state, the higher the plant height below the water surface, the higher the corresponding n value and the greater the change rate of n. Formula for predicting overland flow resistance of layered vegetation was established by considering the influence of combined vegetation height and Reynolds number. [ABSTRACT FROM AUTHOR]

The concept of integrated forest management offers a framework for understanding how forest ecosystem services interact with efforts to conserve natural resources. Forests face various disturbances stemming from human activities, management approaches, and shifts in climate patterns. This study aims to explore how forested watersheds respond to diverse silvicultural practices amidst changing climate conditions. The research is centered in the Bonis catchment, situated in the mountainous region of Sila Greca (latitude 39°25′15″ N, longitude 16°12′38″ W) within Southern Italy's Calabria region. Nearly 93% of the catchment area is cloaked in a forest dominated by approximately 50-year-old Pinus laricio Poiret stands. To model the catchment's response to various climate and management scenarios, the FEST-FOREST eco-hydrological model, which is distributed and based on physical principles, has been employed. This model accounts for the dynamic interactions between vegetation and the watershed's hydrological processes. The monitoring of the basin has been ongoing since 1986, with runoff measurements collected at the catchment outlet using dedicated gauging structures. These data have been utilized to calibrate and validate the model, ensuring its accuracy in simulating future scenarios. These simulation results offer stakeholders some qualitative and scientifically based recommendations for the sustainable management of the catchment. In fact, thinning intensity affects hydrological processes, with a 50% stand density reduction identified as a threshold for significant impact on processes like rainfall partitioning and evapotranspiration. Under heavy thinning scenarios, runoff can change by over 60%, and the impact decreases with larger thinning intervals. Furthermore, different climate scenarios influence stem yield levels, with higher production under RCP 4.5 and RCP 8.5 compared to the base climate scenario. In particular, the RCP 8.5 scenario produces the highest yield due to better forest growth under different climate scenarios. This implies the idea that in regions with a Mediterranean climate and coniferous forests, amidst climate change, meticulous forest management involving precisely calibrated thinning schedules and intensities, tailored to unique biotic and abiotic factors, could potentially enhance carbon sequestration while positively influencing runoff rates. [ABSTRACT FROM AUTHOR]

Both the renovation of rainwater pipes and the addition of sponge city facilities in the low-terrain residences of urban fringes were rarely systematically simulated using the Storm Water Management Model (SWMM). With the waterlogging prevention project in an old residential quarter at a fringe of Hefei city being an example, this study used the SWMM to simulate the effect of the renovation of rainwater pipes and sponge city facilities under different return periods. The results showed the key nodes on the main pipes met the drainage requirements based on water depth analysis after renovation below the 20-year return period, and the reduction rate of the maximum water depth at the key node J5 was the greatest, with 87.7%. The four flow parameters (the average flow rate, the peak flow rate, the total discharge, and the percentage of water flow frequency) for the two outlets (PFK1 and PFK2) all improved after renovation under five return periods (2, 5, 10, 20, and 50 years [a]). The addition of sponge city facilities effectively reduced the amount of rainwater runoff from 28.68% to 14.78% during 2 a to 50 a, and the maximum reduction rate of water depth, being 61.15%, appeared in J5 under 20 a. The curve integral area of the depth over the elapsed time was innovatively used to indirectly express the accumulated rainwater volume through the rainwater well. This study verified that the SWMM model can be well applied to old low-terrain residential quarters in urban fringes and broadened the application scenario of the model. [ABSTRACT FROM AUTHOR]

Many landslide events occur during or immediately after rainfall, which is one of the main factors that induce slope instability. In this study, a physical model test was conducted to investigate the hydrological response and failure mechanism of fractured rock slopes with anti-dip and strong weathering characteristics under rainfall conditions. Considering the connectivity and development of fractures, a model slope was constructed using prefabricated rock blocks and joint fillers based on a permeability coefficient of the joint fillers that is much larger than that of the prefabricated rock blocks to embody the preferential flow phenomenon of fractures. Gradient cyclic incremental rainfall events were used in the experiment to reflect the effect of previous rainfall on the slope behavior. The results indicate that during rainfall events, the rock blocks become severely softened, and tension cracks that gradually expand are generated on the slope surface. These cracks then penetrate into the joints and fractures developed in the rock mass, forming preferential paths for rainwater infiltration. The failure of the slope started at the toe and gradually developed into the middle and upper parts. This study may provide a feasible method for the model testing of fractured rock slopes under rainfall conditions. [ABSTRACT FROM AUTHOR]

Soil Conservation Service Curve Number (SCS-CN) method is one of the most widely used, popular, stable, reliable, and attractive rainfall-runoff methods, initially designed for direct surface runoff estimation in small and medium agricultural watersheds. It, in various forms, is now being employed to several areas other than the intended one, such as infiltration, sediment yield, pollutant transport and so on. In this study, the proportionality concept of the SCS-CN method is further extended to the field of flood routing and is shown to either parallel or be analogous to the Muskingum routing method, which is a simplified variant of St. Venant equations. When employed to various real (typical) flood events of four different river reaches available in literature from different sources, and thus, of varying flow and channel settings, the results of SCS-CN concept compare well with those due to Muskingum method in terms of their evaluation for performance through root mean square error (RMSE) for overall hydrograph, and relative error (RE) for peak discharge (Qp) and time to peak (Tp) of all four flood events. It thus underscores not only the efficacy but also the versatility of the SCS-CN concept in application to one more field of flood/flow routing, which forms to be an element of paramount importance in distributed hydrologic modeling. [ABSTRACT FROM AUTHOR]

Sustainable stormwater management in developing countries requires more research, and budget compared to developed countries. Runoff measurement in small urban watersheds is often not carried out; city plans are made without much consideration of the effect of runoff. In this study, the effect of land use decisions on the surface runoff was assessed using land use change scenarios in an urban catchment located in Izmir, Turkey. Answers to the following two questions were sought: (1) how the runoff will be affected if the city plan decisions currently in use are implemented and (2) whether it is possible to control the runoff in an urban catchment by developing rational, sustainable planning suggestions based on water. The main novelty of this study is to show the importance of the maquis cover, as well as the permeability of the built-up environment and the existence of open spaces in lower catchments are vital in meeting the runoff. [ABSTRACT FROM AUTHOR]

Because of the benefits of solar energy, solar photovoltaic (PV) technology is being deployed at an unprecedented rate and the number of photovoltaic panels is sharply increasing. Agrophotovoltaic systems (solar farms) seem to be the most sustainable tools to create renewable energy without compromising agricultural production. However, utility‐scale solar energy development is land intensive and its large‐scale installation can have negative impacts on the environment. Moreover, its impacts on soil and on relative hydrological processes have been poorly studied. This article aims to evaluate the impact of solar panels on the runoff generation process, which is directly linked to the soil erosion process. Using a rainfall simulator, runoff measurements for a rainfall intensity equal to 56 mm/h were carried out by assuming different panel arrangements with respect to the maximum slope direction of the field (cross slope and aligned slope). Results were compared to a control reference of the same plot, with no panels (bare soil). Physical models found in the literature were then applied and calibrated, to upscale the models to a much higher hillslope length. Results showed that solar panels increase the peak discharge by about 11 times compared to the reference hillslope. A moderate effect of PV panel arrangement was observed on the peak discharges (11.7 and 11.5 times higher, for cross slope and aligned slope panels, respectively), whereas the time to runoff was the lowest for aligned slope panels (0.3 h), higher for cross slope panels (0.62 h), and the highest (1.2 h), for the bare soil hillslope. As it would be expected, upscaling the models to longer hillslopes resulted in increases in outlet discharges, and in the time to runoff, with an exception for aligned slope panels. [ABSTRACT FROM AUTHOR]

The measurement of surface runoff holds pivotal significance in the prediction of rainfall and runoff patterns, with the outcomes of these predictive models playing a crucial role in sustainable water resource management. The accuracy and availability of surface runoff measurements considerably influence the level of uncertainty inherent in the model outcomes. Particularly in developing nations, continuous and reliable surface runoff data is often lacking. However, the advantage of satellite imagery lies in its constant and cost-free accessibility, offering a potential avenue for comprehensive measurements of the hydrological cycle. It is noteworthy that previous research has illuminated biases in satellite-based measurements, emphasizing the need for bias removal. This paper introduces an uncomplicated approach for calculating runoff measurements, segmented into three distinct stages. The initial phase involves the mapping of surface water using the Normalized Difference Water Index (NDWI). The subsequent stage entails the adjustment of estimated surface areas through a linear regression mechanism, based on average monthly surface area data. The final stage encompasses the computation of water volumes, facilitated by a storage elevation curve. To rigorously examine the efficacy of the proposed methodology, the study applies the correlation coefficient (CC), mean errors (ME), root-mean-square error (RMSE), and Nash Sutcliffe efficiency coefficient (NSE) to assess the performance at the Jalajil Dam in Saudi Arabia, spanning from March 2017 to September 2021. This timeline is divided into calibration (March 2017–August 2020) and validation (September 2020–September 2021) phases to ascertain the constant and slope of the linear regression. Overall, the methodology demonstrates promising results: Monthly calibrated runoff volumes exhibit a CC of approximately 0.98, the mean of ME settles around − 0.01 MCM, RMSE stands at 0.07 MCM, and the NSE attains a value of 0.91. The outcomes underscore that the proposed approach is well-suited for estimating runoff volumes at the dam, offering a viable option when ground observations are limited or unattainable. [ABSTRACT FROM AUTHOR]

Hydrologic connectivity refers to the processes and thresholds leading to water transport across a landscape. In dryland ecosystems, runoff production is mediated by the arrangement of vegetation and bare soil patches on hillslopes and the properties of ephemeral channels. In this study, we used runoff measurements at multiple scales in a small (4.67 ha) mixed shrubland catchment of the Chihuahuan Desert to identify controls on and thresholds of hillslope‐channel connectivity. By relating short‐ and long‐term hydrologic records, we also addressed whether observed changes in outlet discharge since 1977 were linked to modifications in hydrologic connectivity. Hillslope runoff production was controlled by the maximum rainfall intensity occurring in a 30‐min interval (I30), with small‐to‐negligible effects of antecedent surface soil moisture, vegetation cover, or slope aspect. An I30 threshold of nearly 10 mm/h activated runoff propagation from the shrubland hillslopes and through the main ephemeral channel, whereas an I30 threshold of about 16 mm/h was required for discharge from the catchment outlet. Since storms rarely exceed I30, full hillslope‐channel connectivity occurs infrequently in the mixed shrubland, leading to <2% of the annual precipitation being converted into outlet discharge. Progressive decreases in outlet discharge since 1977 could not be explained by variations in precipitation metrics, including I30, or the process of woody plant encroachment. Instead, channel modifications from the buildup of sediment behind measurement flumes may have increased transmission losses and reduced outlet discharge. Thus, alterations in channel properties can play an important role in the long‐term (45‐year) variations of rainfall–runoff dynamics of small desert catchments. [ABSTRACT FROM AUTHOR]

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Rainfall infiltration is one of the main factors inducing landslides. For rock slopes with more developed fractures, the effect of preferential flow cannot be neglected. Thus, this study investigates the effect of preferential flow on the hydrological response and three-dimensional stability of fractured rock slopes under different rainfall conditions. A method combining the numerical solution of rainfall infiltration with the upper-bound theorem of the limit analysis kinematic approach is proposed. In this method, the internal dissipation rate by apparent cohesion in the energy rate balance equation of the three-dimensional rotational failure mechanism is calculated using the discrete summation technique. By considering a rainfall-infiltrated slope case, the infiltration law and hydrological response of the slope based on the dual-continuum model under four rainfall events were examined. Subsequently, the three-dimensional safety factor and failure pattern of the slope were analyzed. For comparison, the results based on the equivalent continuum model without considering preferential flow were also included. It was found that preferential flow can significantly strengthen the hydrological response and reduce the three-dimensional stability of fractured rock slopes. The current study presents a practical method for evaluating the hazard of fractured rock slopes subjected to rainfall infiltration. [ABSTRACT FROM AUTHOR]

The young water fraction represents the fraction of water molecules in a stream that have entered the catchment relatively recently, typically within 2–3 months. It can be reliably estimated in spatially heterogeneous and nonstationary catchments from the amplitude ratio of seasonal isotope (δ18O or δ2H) cycles of streamwater and precipitation, respectively. It has been found that young water fractions increase with discharge, thus reflecting increased direct runoff with wetter catchment conditions. This so-called discharge sensitivity of the young water fraction (S * d ) can be useful for describing and comparing catchments' hydrological behaviour; however, the estimation of S * d can be highly uncertain and unreliable when the streamwater isotope data are sparse and don't capture the entire flow regime. Here, we present a new method that can increase the temporal resolution of the young water fraction estimates, and thus better constrain the estimation of S * d . Our so-called EXPECT method is built upon three key assumptions: 1) the two-component hydrograph separation technique can be used to obtain the portion of young water and old water in a stream by considering EC as a proxy of the water age, 2) the EC value of the young water endmember (ECyw) is lower than that of the old water endmember (ECow), and 3) the mixing of young water and old water fractions is described assuming an exponential decay of electrical conductivity with increasing young water fraction. We calibrate the two endmembers, ECyw and ECow , by constraining the time-weighted and flow-weighted average young water fraction achieved with hydrograph separation to be equal to the same quantities obtained from seasonal isotope cycles. We test the EXPECT method with data from three small experimental catchments in the Swiss Alptal valley by using two different temporal resolutions of Q and EC data: sampling-resolution (i.e., we only consider Q and EC measurements during dates of isotope sampling) and daily-resolution. By leveraging high-resolution and low-cost EC measurements and bi-weekly isotope data, the EXPECT method has provided reliable young water fraction estimates at bi-weekly and daily resolution, from which S * d could be determined with higher accuracy compared to the existing method that uses only bi-weekly isotope data. For proper use of the EXPECT method, we further highlight its main limitations that may vary in their relevance depending on the characteristics of the catchments under study. [ABSTRACT FROM AUTHOR]

The effect of permeable pavement in reducing stormwater runoff is dependent on its infiltration performance. The monitoring and modeling methods were adopted to analyze infiltration performance of permeable pavement and was primarily based on Darcy's law in previous studies. But Darcy's law disregards the changing infiltration rate with the change of water content in permeable pavement medias. Neglecting the infiltration rate change frequently resulted in significant deviation between the monitoring and modeling results. To address these issues, the accuracy of two modeling methods for the infiltration performance of permeable brick pavement system (PBPs) was evaluated. The first is the low impact development (LID) module of the stormwater management model (SWMM), and the second is a new equivalent modeling approach based on the Horton model for PBPs. According to the results, the Horton model accurately described the infiltration performance of PBPs in SWMM. Under high return periods situation, the coefficients of determination (R2) and Nash-Sutcliffe efficiency coefficients (Ens) reach 0.82 and 0.88, respectively, and the simulation error ranges from 6.57% to 8.75%. The experimental and simulation results of the LID module in SWMM were compared in greater detail. The result demonstrated that the LID module of SWMM underestimated the infiltration capacity of PBPs because it ignored the fluctuating infiltration rate throughout the whole PBPs infiltration process. Therefore, the proposed equivalent modeling method is superior to simulating the infiltration performance of PBPs in SWMM , and the Horton model improved the simulation accuracy of PBPs infiltration. [ABSTRACT FROM AUTHOR]

Heavy Precipitation Events (HPE) are the result of enormous quantities of water vapor being transported to a limited area. HPE rainfall rates and volumes cannot be fully stored on and below the land surface, often leading to floods with short forecast lead times that may cause damage to humans, properties, and infrastructure. Toward an improved scientific understanding of the entire process chain from HPE formation to flooding at the catchment scale, we propose an elaborated event-triggered observation concept. It combines flexible mobile observing systems out of the fields of meteorology, hydrology and geophysics with stationary networks to capture atmospheric transport processes, heterogeneous precipitation patterns, land surface and subsurface storage processes, and runoff dynamics. As part of the Helmholtz Research Infrastructure MOSES (Modular Observation Solutions for Earth Systems), the effectiveness of our observation strategy is illustrated by its initial implementation in the Mueglitz river basin (210 km2), a headwater catchment of the Elbe in the Eastern Ore Mountains with historical and recent extreme flood events. Punctual radiosonde observations combined with continuous microwave radiometer measurements and back trajectory calculations deliver information about the moisture sources, and initiation and development of HPE. X-band radar observations calibrated by ground-based disdrometers and rain gauges deliver precipitation information with high spatial resolution. Runoff measurements in small sub-catchments complement the discharge time series of the operational network of gauging stations. Closing the catchment water balance at the HPE scale, however, is still challenging. While evapotranspiration is of less importance when studying short-term convective HPE, information on the spatial distribution and on temporal variations of soil moisture and total water storage by stationary and roving cosmic ray measurements and by hybrid terrestrial gravimetry offer prospects for improved quantification of the storage term of the water balance equation. Overall, the cross-disciplinary observation strategy presented here opens up new ways toward an integrative and scale-bridging understanding of event dynamics. [ABSTRACT FROM AUTHOR]

Climate change and anthropogenic development considerably influence groundwater resource distribution and conditions. Catchment basin groundwater recharge—discharge computation reliability is needed for effective groundwater management policy formulation and implementation and also for resolving environmental challenges in such a watershed. This paper compares groundwater recharge patterns between urbanized and nearly natural small catchment basins of Israel's Western Mountain Aquifer (WMA). The correlation between precipitation volumes and surface runoff shows that surface runoff volume constitutes 3–4% of the precipitation volume in the Natuf catchment and 1–2% in the Te'enim catchment. These assessments reflect the differences in the land use, outcrop lithology, topography and hydrodynamic properties of the WMA within the model basins. A groundwater recharge assessment based on water balance and water table fluctuation methods was performed for the mountainous karstic Te'enim and Natuf catchment basins for all the available data from 2000 to 2020. The water balance method provided reliable estimates. The groundwater recharge assessment considered land use classification and climate changes during this period. The average multiannual groundwater recharge values for the 2000–2021 period varied from 17.6 × 106–24.8 × 106 m3 to 24.5–29.2 × 106 m3 for the Te'enim and Natuf catchment basins, respectively. For the relatively dry period of the 2013/2014–2017/2018 hydrological years when detailed measurements of the surface runoff were available, the corresponding groundwater recharge volumes were 17.6 × 106 m3 and 24.5 × 106 m3. The corresponding local groundwater recharge coefficients constitute 0.46–0.57 for the mostly agricultural Te'enim basin and 0.29–0.32 for the urbanized Natuf basin. A significant difference in the groundwater recharge coefficients between the studied catchments is caused mostly by the differences in land use. It is suggested that applying such a groundwater recharge estimation for small hydrological sub-basins can improve one's understanding of the groundwater recharge distribution within a major basin, enabling the application of an accurate regional hydrogeological model that may be extrapolated to other similar regions. [ABSTRACT FROM AUTHOR]

The vegetation type and its coverage in forest ecosystems are crucial in soil erosion and surface runoff. Cover crops provide significant protection to the soil aggregates, preventing damage caused by rainfall and runoff that might occur in the absence of these crops. However, changes in land use, such as converting forests into oil palm plantations, have resulted in changes to the land cover, which affect erosion, surface runoff, and, ultimately, the forest ecology of the watershed. This study aimed to provide an overview of erosion and runoff in forest areas and oil palm plantations. This field research was conducted to study erosion, runoff, and nutrient loss using plots measuring 15m x 25m, including oil palm plantation areas and forest areas. After each rain, sediment weighing and runoff volume measurements were carried out. Laboratory analysis was conducted for sediment and surface runoff water samples' N, P, and K elements. The study results showed that five-year-old oil palm plantation areas experience the highest levels of erosion and runoff, followed by three-year-old oil palm plantation and forest areas. Nutrients were found to be lost in sediment across all land cover types, with a minimal amount recorded in surface runoff. [ABSTRACT FROM AUTHOR]

In recent years, climate change has occurred on a global scale, causing frequent flooding in many regions. In response to this situation, watershed-wide flood management is attracting attention around the world as a promising approach. Under these situations, Japan has also made a policy shift to watershed-based flood management, which aims to manage floods and control runoff in the entire watershed. For this management, it is essential to obtain areal hydraulic information, especially flow information, from each location in the watershed. To measure river flow, it is necessary to measure water level and velocity. While it is becoming possible to make area-based observations of water levels using simple methods, various attempts have been made to measure the velocity, but continuous data cannot be obtained using simple methods. Low-cost flow velocity meters would facilitate the simultaneous and continuous accumulation of data at multiple points and enable the acquisition of areal flow information for watersheds, which is important for watershed-based flood management. This study aims to develop an inexpensive, simple velocity meter that can be used to make areal measurements within watersheds, and to make this velocity meter usable by residents, thereby contributing to citizen science. Therefore, experimental studies were conducted on a method of measuring flow velocity based on the simple physical phenomenon of rising water surface elevations due to increased pressure at the stagnation point. First, we placed the cylinders in the river or waterway, observed the afflux, and compared the velocities calculated using Bernoulli's theorem with the velocities at the experimental site. By multiplying the calculated flow velocity by 0.9, the average flow velocity was found to be obtained. Then, by using a large pitot tube with a hole diameter of about 5 mm, the rise in water level in the pitot tube was measured using a pressure-type water level meter, and the flow velocity was calculated using the pitot tube theory and compared with the flow velocity at the location of the hole at the experimental site. By multiplying the calculated velocity by 1.04, the velocity at the location of the hole can be obtained. In addition, the same experiment was conducted using a pitot tube with a slit. The slit tube was placed vertically with the slit facing upstream. Measurements were taken in the same method as for the pitot tube velocity meter and compared to the velocity at that point. By multiplying the calculated flow velocity by 0.99, the average flow velocity at that location can be obtained. These results indicate that a flow velocity measurement method utilizing stagnation points can lead to the development of inexpensive velocity meters. Because of the simplicity of this meter, there is a possibility that citizens can participate in the observation to obtain information on the flow velocity during floods and areal information within a watershed. [ABSTRACT FROM AUTHOR]

Increasing temperatures in Antarctica have resulted in the enlargement of proglacial regions on the Antarctic Peninsula, following glacier melt. This melt has increased river activity yet direct runoff measurements remain scarce in Antarctica, despite it acting as a proxy for glacial ablation. Here, we present discharge and water temperature data from 2013 for three streams on Vega Island and discuss their relationship with air temperature. The average discharge at the largest stream was 0.523 m3s−1 with a maximum of 5.510 m3s−1 – among the highest recorded in Antarctica. The rivers continued to flow even when temperatures dropped to −7°C, indicating that a large proportion of the total runoff originated sub-glacially. This is supported by the one-day time lag between air and water temperatures. Using river discharge as a proxy, we measured 124.5 ± 14.4 mm w.e. of ablation. This indirect measurement proved an effective tool to complement classic glaciological observations. [ABSTRACT FROM AUTHOR]

Wide-grading particles on loose soil slopes will experience scouring erosion under the coupling of runoff and seepage. In this paper, the particle critical incipient velocity was calculated based on an analysis of the rolling dynamics, and a runoff-seepage coupled nonlinear mathematical model was established. In the model, the Navier–Stokes equation and the Brinkman–Darcy equation were used to describe runoff and seepage motion, respectively. The expressions for the interface velocity and safety factor of the incipient particle motion were obtained by introducing a stress-jumping boundary condition where the velocity is continuous and the stress is jumping, with an incipient motion probability distribution. An indoor flume-scouring experiment on the wide-grading gravel particles was conducted, and the absolute errors of the particle incipient probabilities between the theoretical and experimental results were found to be less than 0.14. Furthermore, the existing theoretical model is a special case of the present model when the jumping coefficient is equal to 0. The parameter analysis results show that increasing the runoff depth, jumping coefficient, slope angle, porosity, and permeability aggravates the erosion of wide-grading particles, while increasing the equivalent diameter, unit weight, and exposure angle has the opposite effect. This study can provide guidance on wide-grading soil erosion due to runoff and seepage. [ABSTRACT FROM AUTHOR]

The hydrological model ECOMAG was used to calculate runoff characteristics in the main arctic (Northern Dvina and Pechora) and southern (Don and Kuban) river basins of Eastern Europe using the data from the ensemble of global climate models under the scenario of 1.5 and 2 °C global warming in the 21st century relative to pre-industrial values. Flow generation models were calibrated and validated based on runoff measurements at gauging stations using meteorological observation data. According to the results of numerical experiments, the relative change in river runoff in European Russia increases from north to south and from east to west under global warming of 1.5 to 2 °C. As a result, hydrological systems in milder climate were found to be more vulnerable to climate change. The assessment of flow anomalies in European Russia under the selected climate scenarios revealed the following general features: winter runoff in arctic rivers would increase, spring melt runoff in the Northern Dvina and Don would decrease, and summer–autumn runoff in all studied rivers would decrease to varying degrees. The most negative runoff anomalies are characterized in the southwestern part of the Northern Dvina basin, the middle part of the Don basin, and the lowland part of the Kuban basin, whereas positive runoff anomalies are characterized in the northern and eastern parts of the Pechora basin. Global warming of 1.5 to 2 °C would have the greatest impact on the rate of reduction of Kuban summer–autumn runoff and Don runoff during the spring flood, as well as the increase in Northern Dvina and Pechora winter runoff. [ABSTRACT FROM AUTHOR]

Water repellent soils represent some of the most responsive natural surfaces from the point of view of overland flow generation. Measurement of the runoff response of such soils can therefore provide characteristics that can help constrain hydrological models or improve the conceptual models of hillslope runoff generation. We have analysed the overland flow characteristics of water repellent sandy soils at three sites with different dominant vegetation (hereafter denoted as the lichen, moss and herb sites) and following vegetation removal (scalping) during extreme rainfall events created by a rainfall simulator (three consecutive sprinklings at 2.1 mm min−1 for 15 min each with a 5 min hiatus between the sprinklings). Despite the extreme water repellency (WR) and rainfall intensity, on average just up to a half of the rainfall left the plots as an overland flow. Whilst the overland flow mostly generated quickly (on average within 50–120 s), the vegetation substantially delayed its appearance (by approximately 100% compared to scalped plots). The median values of the runoff coefficients were 6% and 49% on the soil with and without vegetation, respectively. Good relationships between the overland flow characteristics and soil moisture were found only for the scalped plots. Although the time to runoff and runoff coefficients after each of the three consecutive sprinklings were not substantially different, the differences between the soil with and without vegetation remained substantial. The results indicated: (a) high variability within each of the sites, including the lichen site that appeared homogenous; (b) all vegetated plots retained a higher amount of water than the scalped plots; (c) although all sites exhibited high WR, the combined influence of preferential flow, higher hydraulic conductivity and specific vegetation (soapwort, black locust) mitigated its effects at the herb site; (d) the relatively lower overland flow at that site may point to subsurface flow. [ABSTRACT FROM AUTHOR]

Predicting catchment stormflow responses after tropical deforestation remains difficult. We used 5‐min rainfall and storm runoff data for 30 events to calibrate the Green–Ampt (GA) and the Spatially Variable Infiltration (SVI) models and predict runoff responses for a small, degraded grassland catchment on Leyte Island (the Philippines), where infiltration‐excess overland flow (IOF) is considered the dominant runoff process. SVI replicated individual stormflow hydrographs better than GA, particularly for events with small runoff responses or multiple peaks. Calibrated parameter values of the SVI model (i.e., spatially averaged maximum infiltration capacity, Im and initial abstraction, F0) varied markedly between events, but were statistically significant and negatively correlated with (mid‐slope) soil moisture content at 10 cm (SWC10)—as did the "catchment‐wide effective" hydraulic conductivity (Ke) of the GA model. Using SWC10‐based estimates of F0 and Im in SVI yielded satisfactory to good simulations for 11 out of 17 events with runoff coefficients ≥15%, but failed to reproduce the hydrographs for events with very small runoff amounts (0.25–1 mm) and low runoff coefficients (3%–6%). The median field‐measured near‐surface Ksat (2 mm hr−1) was distinctly lower than the median Im (32 mm hr−1) and, to a lesser extent, Ke (∼8 mm hr−1), suggesting an underestimation of the spatially averaged Ksat by the field measurements. Application of SVI is expected to give the most realistic results for situations where IOF is dominant, that is, where surface conditions are degraded and rainfall intensities high. Plain Language Summary: It is important to be able to predict the streamflow volume and peak flow rate during intense rainfall events. We used rainfall and streamflow data for a small, degraded tropical grassland catchment on Leyte Island (the Philippines) to calibrate two rainfall infiltration models of comparable complexity: the Green–Ampt model (GA), that describes a decrease in infiltration capacity with time, and the Spatially Variable Infiltration (SVI) model for which the infiltration capacity is a function of the rainfall intensity. SVI generally performed better than GA in simulating observed streamflow responses to rainfall, especially for events with multiple rainfall peaks. Values for the two main parameters of SVI (the amount of rainfall required to initiate stormflow, and the maximum infiltration capacity of the soil) were related to the amount of moisture in the top 10 cm of the soil prior to the rainfall event. Using the measured topsoil moisture contents for 26 rainfall events to estimate the SVI parameter values and predict the stormflow response from the measured rainfall intensity produced satisfactory to good results for most of the larger events. However, it failed to reproduce the stormflow patterns for six events with mostly small to very small runoff responses. Key Points: The Spatially Variable Infiltration (SVI) model outperformed the Green–Ampt model, especially when simulating multi‐peaked storm hydrographsSVI‐model parameter values correlated negatively with antecedent topsoil moisture contentModel‐derived catchment‐scale infiltration capacities were higher than field‐measured Ksat, regardless of the model or field method used [ABSTRACT FROM AUTHOR]

This paper presents the permeability of the permafrost active layer determined in the Brattegg River catchment (SW Spitsbergen) for the 6-years interval of 2005-2010. The field permeability measurements technique of weathered rocks on various geomorphological forms allows to assess the value of their hydraulic conductivity (k). High variability of k values, ranging from 6.37 10-9 to 4.0 10-3 m s-1, indicates the permeability of rocks from very low in clay to very high in gravel-rock rubble. Among the geomorphological forms, the best permeability was observed in boulder covers and rock debris, and the lowest one in patterned ground. The obtained results were used to determine the groundwater runoff (qtot), assuming the unit thickness of the active layer aquifer. The qtot value from the Brattegg River catchment was calculated at 130 L s-1, which is from 15% to 47% of the average surface runoff. [ABSTRACT FROM AUTHOR]

Green roofs are increasingly popular in both new and modernised buildings. They significantly reduce the outflow of stormwater from buildings and change its composition. Wherever an urbanised area is equipped with a separate sewage system, usually stormwater goes directly to the receiver without treatment, which may affect the quality of water in the receiver. The article presents results of research carried out on the green roof of a building in Lodz, Poland. During rainfall, the flow rate from the roof was measured. With the use of the US EPA software Stormwater Management Model (SWMM) a model of the green roof was created and calibrated using rainfall data from the city's pluviometric network. Based on the measurements of the roof runoff, as well as SWMM modelling, the degree of outfall reduction was determined. Samples of roof runoff were collected to study the characteristics of rainwater, including pH, electrical conductivity, organic compounds, nitrogen, phosphorus, and suspended solids. The results were compared with the quality of runoff from a traditional roof. Except ammonium nitrogen, values of the examined quality indicators was higher in the case of the green roof but the pollution load of almost all contaminants, except phosphorus, were lower due to a significant reduction in the volume of stormwater outflow (62-91%). The quality of stormwater discharged from the green roof improved with its age. [ABSTRACT FROM AUTHOR]

Sensitivity analysis of model parameters and inputs is an important research method to improve model accuracy and calibration efficiency. The purpose of this paper is to explore the sensitivity of model parameters and model inputs in arid areas, and then to study the linear or nonlinear relationship of model sensitivity taking Erjiama small watershed in Jungar banner, Ordos, Inner Mongolia, China as the research object. Based on the calibration of CASC2D-SED model, four model parameters, including hydraulic conductivity, Manning coefficient, Suction head and vegetation interception, and one model input-river network were perturbed at a variation rate of 25%. The hydrological process is simulated by using the combination of 20 model parameters and model inputs after perturbation, and then the sensitivity analysis of model parameters and inputs is studied. The results show that: 1) The sensitivity of Manning coefficient to peak discharge and peak arrival time is non-linear, while the sensitivity of hydraulic conductivity, Suction head and vegetation interception to peak discharge, peak arrival time, simulated total discharge and infiltration amount is linear; 2) With the increase of hydraulic conductivity, Suction head and vegetation interception, the peak discharge and simulated total discharge decrease gradually, while the peak arrival time and infiltration amount increase gradually; 3) With the increase of Manning coefficient, the simulated total flow decreases gradually, while the infiltration rate increases gradually; 4) With the increase of the number of tributaries, the peak discharge, the simulated total discharge and the total amount of infiltration gradually decrease, while the flood peak arrival time presents a U-shaped change; 5) With the increase of Manning coefficient, hydraulic conductivity, Interception and Suction head, the simulated sediment flow decreases. Manning coefficient is more sensitive to the simulated amount of clay than the other three model parameters. Sensitivity analysis of parameters and inputs of CASC2D-SED model plays a guiding role in model calibration and accurate modeling. This method can be applied to the calibration, structural uncertainty and model application of hydrological models, and has a wide range of application. [ABSTRACT FROM AUTHOR]

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Purpose: Since surface runoff clogs stormwater grates, leading to deterioration of drainage capacity, and also it is difficult to complete the study with actual dimensions in experiments, a numerical simulation work was established in this study to investigate the surface runoff clogging stormwater grate patterns. The purpose of this study is to describe the mechanisms of storm grate clogging and storm well deposition for different flow rate floods and granular materials. Design/methodology/approach: In the work of this study, the volume of fluid (VOF) method and the discrete element method (DEM) are used to solve the gas–liquid and particle flows. In order to solve the evolution of the gas–liquid interface during surface runoff, the VOF was used. To simulate the rain grate and set up different material particles to represent the surface floating materials, the DEM was utilized. Findings: The research results show that the clogging distribution and clogging rate of the rainwater grate are closely related to the fluid flow velocity and the physical characteristics of the particles, and the higher the clogging rate of the rainwater grate and the higher the number of particles deposited in the rainwater well at the same surface runoff velocity, the higher the density of the clogged particles. The surface runoff velocity (0.5 m/s, 1 m/s) shows that the rapid change of particle movement state at high runoff velocity makes the particle clogging more obvious. Originality/value: A multi-scale CFD-DEM approach was used to simulate the particulate motion of the road surface with different incoming runoff velocities. The innovative use of DEM to model the storm grate simulation ensures the accuracy of the traction model. [ABSTRACT FROM AUTHOR]

Surface runoff is an important factor inducing soil erosion of shallow slope. Due to the complexity of material composition, grain arrangement and porosity structure, however, it is difficult to directly give the critical shear velocity of incipient motion under surface runoff if all matters of cohesive sediment are taken into account. Considering the bonding effect of cohesive sediment, a closed-form solution for critical shear velocity is presented in this work. Three primary assumptions, i.e., slope angle less than 30 deg, laminar for surface runoff and uniform film water around soil particles, are made in deriving the solution. The bonding force of cohesive sediment stemming from film water contact can be embedded in the force analysis of single particle. Laboratory scouring test results validate the present solution. [ABSTRACT FROM AUTHOR]

The storage–discharge (S-Q) relation, widely employed in hydrology and hydraulics, is often derived from empirical data and is found to be hysteretic or looped, although approximated by a straight line or a curve in hydrologic modeling. The nature of hysteresis depends on geometric and hydraulic conditions. Despite its ubiquitous use, an analytical treatment discussing what causes the storage–discharge relationship to exhibit a looped behavior does not seem to have been reported. This study analyzes the S-Q relation analytically using kinematic wave approximation for a watershed represented by a plane, considering simultaneously rainfall, infiltration, and surface runoff or overland flow. For purposes of simplicity and tractability of analytical solutions, both rainfall intensity and infiltration rate are assumed to be constant. Depending on the duration of rainfall, two cases—equilibrium and partial equilibrium—are distinguished. The hysteretic S-Q relationship is different for these two cases and requires close scrutiny, which is pursued in this study. It is emphasized that the assumptions of constant rainfall intensity and infiltration rate, rectangular geometry, and kinematic wave approximation undermine the dynamics of hysteresis. [ABSTRACT FROM AUTHOR]

The spoil dumps are the main sediment sources in the open-pit mining area. The erosion control is of great significance to the high-quality development of the energy zone. This article aims to analyze the gully development and sediment process of spoil dumps. The plot construction of platform-steep slope system and field scouring experiments were also carried out, where the flow rate was ranged from 60 to 80 L/min, and the duration was 45 mins each run. The results showed that: 1) The gully was developed by the combination of different erosion progresses, including the headcut migration, bed incision, and lateral erosion on the platform-steep slope system. Notably, there were the stage differences in the topographic characteristics of gully, due to the variation of dominant process. A three-stage development was experienced for the gully on the platform, including the headcut formation, migration-expansion, and stable stage. In the gully on the steep slope, four developmental processes were divided into the incision of sandy loam layer, expansion of sandy loam layer, incision of clay loam layer, and deceleration of erosion. No significant differences were found between the various flow rates of gully development speed on the platform. Whereas, the transformed time increased with the flow rate between adjacent gully development stages on the steep slope. 2) In terms of sediment process, the migration - expansion stage was the main erosion period on the platform. The incision of sandy and clay loam layer were the main erosion stages on the steep slope, particularly with the accumulated sediment yields accounting for 29.72%~53.36% and 19.06%~48.88%, respectively. Spatially, the runoff shear force and stream power increased by 7.11-120.86 times, and 7.59-239.59 times after the runoff flowed from the platform into the steep slope, and the erosion rate increased by -0.84-66.20 times. Correspondingly, the steep slope was the main sediment source of the platform and steep slope system. The cumulative sediment yield was accounted for 88.15 %-90.16 % of the total amount of platform and steep slope system. Hence, the separation and control of runoff on the platform was a vital way to control the gully erosion in the platform-steep slope system of spoil dumps. 3) In terms of the flow hydraulics, the platform velocity decreased first and then increased with the gully development. Conversely, the slope velocity decreased gradually. Meanwhile, the runoff shear stress and the runoff stream power increased gradually with the gully development on the platform, but increased first, finally decreased on the steep slope. 4) Comparatively, the erosion rate presented a more sensitive response to the stream power than the runoff shear force, where the response regularity was different among the gully development stages. The erosion rate was linearly responded to the stream power in the migration-expansion stage and stable stage of platform. On the steep slope, the responses were still linear in the expansion of sandy loam layer and deceleration of erosion, but the exponential in the incision of sandy and clay loam layer. Therefore, it is necessary to consider the difference of responses in the various gully development stages, in order to improve the applicability of sediment transport model for the gully erosion. As such, the results revealed the staged development of gully and sediment process on the platform-steep slope system of spoil dumps. The finding can also offer the strong reference for the gully process, further to implement the soil and water conservation measures in the spoil dump. [ABSTRACT FROM AUTHOR]

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A sudden surge of data has created new challenges in water management, spanning quality control, assimilation, and analysis. Few approaches are available to integrate growing volumes of data into interpretable results. Process-based hydrologic models have not been designed to consume large amounts of data. Alternatively, new machine learning tools can automate data analysis and forecasting, but their lack of interpretability and reliance on very large data sets limits the discovery of insights and may impact trust. To address this gap, we present a new approach, which seeks to strike a middle ground between process-, and data-based modeling. The contribution of this work is an automated and scalable methodology that discovers differential equations and latent state estimations within hydrologic systems using only rainfall and runoff measurements. We show how this enables automated tools to learn interpretable models of 6 to 18 parameters solely from measurements. We apply this approach to nearly 400 stream gaging sites across the US, showing how complex catchment dynamics can be reconstructed solely from rainfall and runoff measurements. We also show how the approach discovers surrogate models that can replicate the dynamics of a much more complex process-based model, but at a fraction of the computational complexity. We discuss how the resulting representation of watershed dynamics provides insight and computational efficiency to enable automated predictions across large sensor networks. • Process-based models are not designed to ingest large amounts of real-time data. • Machine learning approaches can automatically ingest data to make predictions, but lack interpretability. • A new open-source method automatically creates interpretable models, as validated with data from nearly 400 catchments. [ABSTRACT FROM AUTHOR]

[Display omitted] • We provide a 10-year data set of soil loss and runoff for five different land covers. • Runoff is more sensitive to changes in land cover and precipitation than soil loss. • LULC changed topsoil composition while deeper depths were less affected. • It was not possible to point out which LULC were the most environmentally harmful. • Agricultural uses have higher erosion and runoff compared to the Cerrado biome. Changes in land cover and land use (LULC) are one of the main drivers of erosion and runoff. How ever, most research has relied on short-term observations and only focused on one or two land cover types. We investigated the long-term trade-off between common agricultural land covers (sugarcane, pasture, and soybean), runoff, and soil loss rates. We compared these to native forest (wooded Cerrado) and bare soil. The field observations were done in 100 m2 experimental plots in Brazil maintained during the past 10 years. The paper provides three main contributions: (1) long-term runoff and soil loss rates of plots under different LULCs, (2) comparison of runoff, soil loss, and pedological characteristics between plots constructed 10 years apart, and (3) analysis of the trade-off between different LULCs. When ranking land covers based on runoff and soil loss rates, there is a shift in ranking positions, making it difficult to determine which one is more environmentally harmful. However, it is evident that whatever agricultural practice is used, there is a significant impact when compared to native forest. For example, the area converted to pasture resulted in almost 20 times higher runoff, while conversion to sugarcane resulted in 5 times higher soil loss. Not only land cover plays a major influencing factor, but also weathering exposing time. Areas under the same land cover and environmental conditions had different rates of soil loss and runoff due to long-term exposure effects such as soil crusting. Our findings have high relevance for the hydrological and agricultural community by demonstrating (i) the magnitude of trade-off in terms of soil loss and runoff due to land cover changes and (ii) that soil loss should not be assumed to be a linear process over time, as it is commonly assumed. [ABSTRACT FROM AUTHOR]

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Recent research explored an alternative energy-centred perspective on hydrological processes, extending beyond the classical analysis of the catchment's water balance. Particularly, streamflow and the structure of river networks have been analysed in an energy-centred framework, which allows for the incorporation of two additional physical laws: (1) energy is conserved and (2) entropy of an isolated system cannot decrease (first and second law of thermodynamics). This is helpful for understanding the self-organized geometry of river networks and open-catchment systems in general. Here we expand this perspective, by exploring how hillslope topography and the presence of rill networks control the free-energy balance of surface runoff at the hillslope scale. Special emphasis is on the transitions between laminar-, mixed- and turbulent-flow conditions of surface runoff, as they are associated with kinetic energy dissipation as well as with energy transfer to eroded sediments. Starting with a general thermodynamic framework, in a first step we analyse how typical topographic shapes of hillslopes, representing different morphological stages, control the spatial patterns of potential and kinetic energy of surface runoff and energy dissipation along the flow path during steady states. Interestingly, we find that a distinct maximum in potential energy of surface runoff emerges along the flow path, which separates upslope areas of downslope potential energy growth from downslope areas where potential energy declines. A comparison with associated erosion processes indicates that the location of this maximum depends on the relative influence of diffusive and advective flow and erosion processes. In a next step, we use this framework to analyse the energy balance of surface runoff observed during hillslope-scale rainfall simulation experiments, which provide separate measurements of flow velocities for rill and for sheet flow. To this end, we calibrate the physically based hydrological model Catflow, which distributes total surface runoff between a rill and a sheet flow domain, to these experiments and analyse the spatial patterns of potential energy, kinetic energy and dissipation. This reveals again the existence of a maximum of potential energy in surface runoff as well as a connection to the relative contribution of advective and diffusive processes. In the case of a strong rill flow component, the potential energy maximum is located close to the transition zone, where turbulence or at least mixed flow may emerge. Furthermore, the simulations indicate an almost equal partitioning of kinetic energy into the sheet and the rill flow component. When drawing the analogy to an electric circuit, this distribution of power and erosive forces to erode and transport sediment corresponds to a maximum power configuration. [ABSTRACT FROM AUTHOR]

Soil preferential flow is an essential process that affects the movement and relocation of soil water and solutes. This study was conducted on cropland in an arid and semi-arid area in Zhongning County, Ningxia. According to the different cracks, rain intensity, rainfall duration, and slope, there were three groups, and 17 dye tracer experiments were conducted in the field. We quantified the characteristics of soil preferential flow by investigating and analyzing the infiltration depth, dyeing area, saturation, runoff coefficient, and rainfall infiltration coefficient using the dye tracer method. The results showed that increasing the rainfall or irrigation intensity could promote the activation of the fracture channel as the preferential flow channel, which is advantageous to the preferential flow formation. The fractures dominated the formation of the preferential flow. The fractures slowed the formation of runoff, reduced the velocity of slope flow, reduced the flow of the slope, and increased the amount of soil water infiltration. These results have theoretical and practical significance for understanding soil water transportation, especially for agricultural irrigation management and improving cropland water use efficiency in arid and semi-arid areas. [ABSTRACT FROM AUTHOR]

Floods are the most disastrous natural hazards, but the prediction of flood hydrographs is hindered due to the lack of Hydro-meteorological data. This paper presents an approach for flood routing of the ungauged basin using rainfall-runoff and Dynamic wave models. Specifically, the SCS-CN rainfall-runoff model is employed to obtain the inflow and lateral inflow hydrographs of the ungauged sub-basins, and a Modified Dynamic Wave Model is employed to anticipate the flood hydrograph at the outlet of the ungauged basins. The Modified Dynamic Wave Model for the parabolic channel (MDWMP) has been numerically solved using an implicit finite difference scheme considering both continuity and momentum equations. The method is tested in hypothetically considered ungauged Kulsi River Basin, a mountainous basin in Northeastern India, and the results obtained are compared with the observed data at the outlet of the Kulsi Basin. The approach is validated by considering four parameters RMSE, Peak flow Error, Peak time Error, and Total Volume Error. A high degree of affinity (i.e. peak flow error below 6%) was observed between the predicted outflow hydrograph and the observed hydrograph, which verified the satisfactory applicability of the developed approach to anticipate the flood hydrograph of an ungauged basin. [ABSTRACT FROM AUTHOR]

Obtaining water quality samples from surface runoff is essential for understanding erosion and pollutant transport processes. Existing water sampling devices are expensive, require installation of extensive infrastructure or power supplies, or have limited ability to collect flow‐weighted samples. We created an inexpensive, nonpowered, flow‐weighted water sampling device that can be incorporated into runoff quantification systems like the Upwelling Bernoulli Tube (UBeTube). Our device, called the Holey Sampler, consists of a standpipe with holes drilled at specific heights. Water enters the standpipe in proportion to the water flow rate through the UBeTube and is routed to an external collection bottle. We built and tested two versions of the Holey Sampler that sampled water at an approximate ratio of 1:250 of the runoff rate. The Standard Opening Holey Sampler (Standard‐OHS) configuration was made with 1.6‐mm‐diam. holes, whereas the Miniature Opening Holey Sampler (Mini‐OHS) configuration was designed to prevent oversampling at low outflows but required drill bit of smaller diameter (0.8‐mm). Laboratory and numerical experiments demonstrated that both configurations obtained accurate flow‐weighted runoff samples when incorporated into the UBeTube. Flow rates in the Mini‐OHS were better correlated with runoff rates under constant‐flow (R2 =.992 vs..965 for the Standard‐OHS) and variable‐flow conditions (R2 =.996 vs..954 for the Standard‐OHS). Further modification of the Holey Sampler could also allow flow‐weighted sampling of other runoff quantification devices like flumes and weirs. Core Ideas: Surface runoff samples are needed to quantify pollutant transport processes.We developed an inexpensive, passive flow‐weighted sampling system for runoff.We tested versions with standard‐ and miniature‐sized sampling holes.Both configurations collected flow‐weighted samples during constant and variable flow.Sampler may be adapted to other runoff quantification systems. [ABSTRACT FROM AUTHOR]