Surface Runoff Rates Research Articles

Effect of bedrock permeability on runoff and soil loss in soil-mantled karst slopes under successive rainfall conditions

Soil-mantled karst slopes exhibit rapid surface-belowground hydrological responses to rainfall because thin soil layers cover the bedrock. Bedrock features may play important roles in surface-belowground hydrological processes; however, the underlying mechanisms remain unclear. Herein, the effects of impermeable (no fissures) and permeable (3 % fissure rate) bedrock (BS1 and BS2, respectively) on the surface and belowground runoff and soil loss processes were investigated during three successive rainfall events. During each event, the surface runoff (SR), subsurface runoff (SBR), soil–rock interface flow (SRIF) and bedrock fissure permeation flow (BFPF) were recorded. The results showed that the SR and SBR rates for the BS1 slope were significantly greater than those for the BS2 slope (P < 0.05) under all rainfall events. During rainfall, the SR and SBR accounted for ∼ 19 % and 8 %-12 % of the rainwater on the BS1 slope, respectively, and both were less than 5 % of the rainwater on the BS2 slope. Approximately 40 %-55 % of the rainwater was partitioned into SRIF on BS1 slope, and 54 %-74 % of the rainwater was partitioned into the BFPF on the BS2 slope. Furthermore, the BFPF on the BS2 slope was 33 % greater than the SRIF on the BS1 slope at the 1st rainfall and it increased to 50 % at the 3rd rainfall, suggesting that the successive rainfall increased the difference in rainwater loss from the bedrock surfaces between the slopes with different permeabilities. The surface soil loss rate was very low (< 0.01 g·m2·s−1) due to the low SR, and a significant positive correlation was found between the SR rate and surface soil loss rate (P < 0.01) for both slopes. Compared with that on the BS2 slope, the soil loss on the BS1 slope was greater because of the higher SR rate. The belowground soil loss curves were discontinuous, indicating that the belowground soil loss process was very different from the surface soil loss. Therefore, bedrock permeability has a strong influence on runoff and soil loss in soil-mantled karst slopes, and this effect further increases with successive rainfall events.

Impact of Refined Boundary Conditions of Land Objects on Urban Hydrological Process Simulation

Urbanization has led to an increase in impervious areas and, consequently, an increase in the surface runoff volume and runoff rate. This has exacerbated urban flooding and highlighted the importance of modeling urban hydrological processes. The Waterview Community of Hangzhou City (WCHC) was taken as the study area, and three scenarios were developed: the original scenario, the rough description scenario, and the fine description scenario. The urban hydrological processes were simulated through a coupled model incorporating actual measurements and four design precipitation events (1-year, 5-year, 10-year, and 20-year return periods). The results show the following: (1) The refined depiction scenario has the highest accuracy in terms of measured precipitation, with an average error of 0.54 cm. (2) During different precipitation return periods, the refined depiction scenario shows the smallest range of accumulated water, with a more realistic distribution. On average, it differed from the original scenario by 21.45% and from the rough depiction scenario by 32.18%. (3) The simulation results after the refinement of the feature boundaries are more reasonable in terms of the flow rate and flow direction, indicating that the simulation results have better dynamics. The results showed that refined boundary conditions improved the accuracy and dynamics of urban hydrological simulations, especially in terms of their reflection of actual water accumulation under varying precipitation conditions.

Surface Runoff Estimation in Kubaisa Watershed Using SWAT, Western Desert, Iraq

Surface runoff significantly impacts the region's ecosystem and is closely linked to sustainable development and human well-being. The mathematical model SWAT running in an ArcGIS environment was used to estimate surface runoff in the Kubaisa watershed. The period simulated in this model is 31 years, sufficient to give good results regarding surface runoff volume and water yield contribution from each sub-watershed. The Kubaisa watershed has an area of 2485.50 km2 and comprises six sub-watersheds. The watershed consists of 172 HRUs distributed among sub-watersheds depending on the variation in soil layers, land use, vegetation, and slope. The volume of water calculated from the annual surface runoff rate for the simulation period was about 2699 million cubic meters, and its value was higher than the volume of water calculated from surface runoff due to lateral flow, groundwater discharge, and the contribution of each sub-watershed to the water yield. The highest value in water yield was in 2012, and the largest contribution was made by the sixth sub-watershed; thus, the difference is temporal and spatial in terms of water yield. Finally, through the analysis of multiple scenarios, the difference in hydrological response units is controlled by the difference in surface runoff, discharge, and water yield to the watershed. For this purpose, the SWAT model divides the watershed into many different units and starts the simulation on their basis.

Runoff Control Performance of Three Typical Low-Impact Development Facilities: A Case Study of a Community in Beijing

The development of sponge cities advocates for sustainable urban rainwater management, effectively alleviating urban flood disasters, reducing non-point-source pollution, and promoting the recycling of rainwater resources. Low-Impact Development (LID) serves as a key strategy in this context, providing essential support for urban rainwater control and pollution reduction. To investigate the runoff control effects of LID measures and to reveal the relationship between facility runoff control performance and installation scale, this study focuses on a sponge community in Beijing. A SWMM model was constructed to analyze the rainwater flood control and pollutant load reduction effects of different LID facilities, including bio-retention cells, green roofs, and permeable pavements. Using evaluation indicators such as surface runoff, node overflow, and pollutant control rates, this study examined how facility performance varies with installation scale under different rainfall conditions. The combination scheme of LID equipment optimal configuration is designed by using multiple criteria decision analysis (MCDA) and cost–benefit theory. The results indicate significant differences in performance among the various LID facilities across different rainfall scenarios. Specifically, the optimal installation proportion for runoff and overflow control of permeable pavements were found to be between 30% and 70%. Green roofs demonstrate superior performance in handling extreme rainfall events, while bio-retention cells exhibit significant effectiveness in controlling Total Suspended Solids (TSSs). Through comprehensive performance evaluation, this study identified the optimal combination scale under a 3-year rainfall recurrence interval as 30% permeable pavements, 20% green roof, and 60% bio-retention cells. This combination effectively leverages the strengths of each facility, ensuring system stability and efficiency while also demonstrating optimal management efficiency in cost–benefit analyses. The findings of this research provide valuable insights for future urban water management and infrastructure development.

Rainfall Runoff and Nitrogen Loss Characteristics on the Miyun Reservoir Slope

Rainfall intensity and slope gradient are the main drivers of slope surface runoff and nitrogen loss. To explore the distribution of rainfall runoff and nitrogen loss on the Miyun Reservoir slopes, we used artificial indoor simulated rainfall experiments to determine the distribution characteristics and nitrogen migration paths of surface and subsurface runoff under different rainfall intensities and slope gradients. The initial runoff generation time of subsurface runoff lagged that of surface runoff, and the lag time under different rainfall intensity and slope conditions ranges from 3.97 to 12.62 min. Surface runoff rate increased with increasing rainfall intensity and slope gradient; compared with a rainfall intensity of 40 mm/h, at a slope of 15°, average surface runoff rate at 60 and 80 mm/h increased by 2.38 and 3.60 times, respectively. Meanwhile, the subsurface runoff rate trended upwards with increasing rainfall intensity, in the order 5 &gt; 15 &gt; 10°. It initially increased and then decreased with increasing slope gradient, in the order 5 &gt; 10 &gt; 15°. Total nitrogen (TN) loss concentration of surface runoff shows a decrease followed by a stabilization trend; the concentration of TN loss decreases with decreasing rainfall intensity, and the stabilization time becomes earlier and is most obvious in 5° slope conditions. TN loss concentration in subsurface runoff decreased with increasing rainfall intensity, i.e., 40 &gt; 60 &gt; 80 mm/h. The surface runoff rainfall coefficient was mainly affected by rainfall intensity, a correlation between αs and slope gradients S was not obvious, and the fitting effect was poor. The subsurface runoff rainfall coefficient was mainly affected by slope gradient, the R2 of all rainfall intensities was &lt;0.60, and the fitting effect was poor. The main runoff loss pathway from the Miyun Reservoir slopes was surface runoff, which was more than 62.57%. At the same time, nitrogen loss was subsurface runoff, more than 51.14%. The proportion of surface runoff to total runoff increases with the increase of rainfall intensity and slope, with a minimum of 62.57%, and the proportion of nitrogen loss from subsurface runoff also decreases with increasing rainfall intensity but does not change with slope gradient. The order of different runoff modulus types was mixed runoff (surface and subsurface runoff occur simultaneously) &gt; surface runoff &gt; subsurface runoff. The surface and mixed runoff modulus increased significantly with increasing rain intensity under different rain intensities and slope gradients. Overall, rainfall intensity significantly affected slope surface runoff, and slope gradient significantly affected nitrogen loss.

A Laboratory Watershed Model to Study the Effect of Rainfall Intensity and Soil Surface Slope on Surface Runoff Rate of Karbala Desert Soil

Precipitation generating surface runoff is very important in various water resources development and management activities such as flood control and management, irrigation scheduling, irrigation design, and drainage networks. The aim of this study is to indicate the effect of rainfall intensity and soil surface slope on the surface runoff rate of Karbala desert soil. This study was conducted on the soil of the Karbala desert in Iraq, located between the provinces of Karbala and Najaf, extended from the longitude 32o44'186'' E and latitude 44o100'960''N. In this study, a laboratory watershed model was designed and constructed to be used to examine surface runoff of the Karbala desert soil and other hydrological properties, under the influence of different precipitation intensities (1.83 cm/min, 1.67 cm/min, 0.9 cm/min, and 0.64 cm/min) and different slopes of the soil surface (0.0 %, 2.0 %, 3.3 %, and 6.7 %). A Gene Expression Programming model was used to develop an equation of the surface runoff rate for the Karbala desert soil. The results showed that the rate of surface runoff increased with increasing rainfall intensity. The highest surface runoff rate of 101.53 cm/hr was obtained when the rainfall intensity was 1.83 cm/min, while at the rainfall intensity of 0.64 cm/min, the highest value of surface runoff rate of 31.17 cm/hr was obtained. The results also showed that the slope of the soil surface has a clear effect on the surface runoff rates. The highest value of surface runoff rate of 96.82 cm/hr was obtained when the slope of the soil surface was 0.0%, while at the slope of the soil surface of 6.7%, the highest value of surface runoff rate of 101.53 cm/hr was obtained. According to the simulation results, the surface runoff rate equation created using the Gene Expression Programming model did a great job of predicting the Karbala desert soil surface runoff, with a coefficient of determination R2 equal to 0.8812 for training and 0.8155 for testing.

Variations in climate habitability parameters and their effect on Earth's biosphere during the Phanerozoic Eon

Essential insights on the characterization and quality of a detectable biosphere are gained by analyzing the effects of its environmental parameters. We compiled environmental and biological properties of the Phanerozoic Eon from various published data sets and conducted a correlation analysis to assess variations in parameters relevant to the habitability of Earth’s biosphere. We showed that environmental parameters such as oxygen, global average surface temperatures, runoff rates and carbon dioxide are interrelated and play a key role in the changes of biomass and biodiversity. We showed that there were several periods with a highly thriving biosphere, with one even surpassing present day biodiversity and biomass. Those periods were characterized by increased oxygen levels and global runoff rates, as well as moderate global average surface temperatures, as long as no large or rapid positive and/or negative temperature excursions occurred. High oxygen contents are diagnostic of biomass production by continental plant life. We find that exceptionally high oxygen levels can at least in one instance compensate for decreased relative humidities, providing an even more habitable environment compared to today. Beyond Earth, these results will help us to understand how environmental parameters affect biospheres on extrasolar planets and guide us in our search for extraterrestrial life.

Hydrosedimentary behavior of a field combining surface drains and tile drains

In agricultural fields, soil erosion is usually associated to surface runoff. However, in drained fields, tile drains are additional pathways for soil particles. Few studies have quantified erosion in drained fields and they mainly focused on tile drained fields, without considering fields combining surface and tile drainage. These studies show high inter-site and inter-annual variabilities that highlight the need for more annual quantifications of erosion in drained fields. Consequently, it is still difficult to quantify the relative importance of the factors affecting soil erosion in drained fields. In addition to a comprehensive review of the existing studies of erosion through drainage, this study aims at quantifying surface and subsurface erosion in a 5 ha cultivated field combining surface and tile drainage. Suspended sediments (SS) and water fluxes have been monitored during two years (2019–2020 and 2020–2021) at a high temporal resolution (1 min), both at the outlet of the tile drain network and at the outlet of the surface drainage rill. SS yield was 0.49 t ha−1 and 1.08 t ha−1 in 2019–2020 and 2020–2021, respectively. During 2019–2020 and 2020–2021, tile drainage contribution to the total runoff was 46% and 21%, respectively and its contribution to SS yield was 9% and 11%, respectively. High temporal resolution measurements of runoff and SS concentrations showed the suspended sediment concentration in the surface drain runoff only increase by 17% from the first to the second study year. Conversely, for tile drainage, average suspended sediment concentrations increased by 260%. These variations and the increase of surface runoff rate suggest a shift in water and sediment connectivity at the field scale. Cropping practices could have generated a slumping of the soil surface during the second year and, at the same time, the development of a macropore network in the subsoil. Cropping practices induced changes of surface horizon characteristics and their impact on the hydrosedimentary behavior of drained soils need to be further studied. This study confirms previous results concerning the temporal dynamics of SS exports in a drained context under temperate climate and adds a new quantification of hydrosedimentary fluxes in a surface and tile drained field separating surface drains and tile drains contributions.

Optimal selection of cost-effective biological runoff management scenarios at watershed scale using SWAT-GA tool

Study regionStudy region: Hablehrood River (HR) watershed in the northern part of the Iranian Central Plateau. Study focusFinding the most economical management scenarios for implementing biological best management practices (BMPs) in the HR watershed is one way to solve the runoff issue in the study area. As, the best types, quantities, and locations of arid and semi-arid rangeland biological BMPs have not yet been identified or determined using the soil and water assessment tool (SWAT) or genetic algorithm (GA) to maximize runoff reductions at the lowest possible cost in arid and semi-arid rangelands, therefore, to estimate runoff and best identify biological management scenarios at the watershed scale in the current study, the SWAT and a GA model have been used. After determining the hydrological response units (HRUs), eight biological watershed management scenarios were identified through a combination of biological management activities. To determine the best management practice with the highest runoff reduction and the lowest possible cost, optimization was performed by GA based optimization model. New hydrological insights for the regionThe simulation results of this study show that all the developed biological BMPs had a significant effect on the surface runoff rate reduction and reduced the surface runoff from 4.4% to 8.2%. The fifth scenario including seeding using machine (SUM) and seeding without machine (SWM) biological activities as optimal and the best scenario with weighted coefficients of 0.95 and 0.05 for runoff reduction and cost, respectively, was determined to be the optimum practice. The results further indicate that runoff would be decreased by 76.4 million cubic meters compared base scenario runoff volume, at a cost of 469.8 billion IR Rials. The lowest volume of surface runoff, however, was related to scenario number eight, while it had the highest cost (1114.3 billion IR Rials) among all scenarios. Using optimization methods, decision-makers and managers may pinpoint the best biological BMP scenarios in terms of kinds, locations, and amounts that might reduce runoff rates as much as possible at the lowest possible cost.

Fate of fertilizer nitrogen and residual nitrogen in paddy soil in Northeast China

The relationship between the fate of nitrogen (N) fertilizer and the N application rate in paddy fields in Northeast China is unclear, as is the fate of residual N. To clarify these issues, paddy field and 15N microplot experiments were carried out in 2017 and 2018, with N applications at five levels: 0, 75, 105, 135 and 165 kg N ha−1 (N0, N75, N105, N135 and N165, respectively). 15N-labeled urea was applied to the microplots in 2017, and the same amount of unlabeled urea was applied in 2018. Ammonia (NH3) volatilization, leaching, surface runoff, rice yield, the N contents and 15N abundances of both plants and soil were analyzed. The results indicated a linear platform model for rice yield and the application rate of N fertilizer, and the optimal rate was 135 kg N ha−1. N uptake increased with an increasing N rate, and the recovery efficiency of applied N (REN) values of the difference subtraction method were 45.23 and 56.98% on average in 2017 and 2018, respectively. The REN was the highest at the N rate of 135 kg ha−1 in 2017 and it was insignificantly affected by the N application rate in 2018, while the agronomic efficiency of applied N (AEN) and physiological efficiency of applied N (PEN) decreased significantly when excessive N was applied. N loss through NH3 volatilization, leaching and surface runoff was low in the paddy fields in Northeast China. NH3 volatilization accounted for 0.81 and 2.99% of the total N application in 2017 and 2018, respectively. On average, the leaching and surface runoff rates were 4.45% and less than 1.05%, respectively, but the apparent denitrification loss was approximately 42.63%. The residual N fertilizer in the soil layer (0–40 cm) was 18.37–31.81 kg N ha−1 in 2017, and the residual rate was 19.28–24.50%. Residual 15N from fertilizer in the soil increased significantly with increasing N fertilizer, which was mainly concentrated in the 0–10 cm soil layer, accounting for 58.45–83.54% of the total residual N, and decreased with increasing depth. While the ratio of residual N in the 0–10 cm soil layer to that in the 0–40 cm soil layer was decreased with increasing N application. Furthermore, of the residual N, approximately 5.4% was taken up on average in the following season and 50.2% was lost, but 44.4% remained in the soil. Hence, the amount of applied N fertilizer should be reduced appropriately due to the high residual N in paddy fields in Northeast China. The appropriate N fertilizer rate in the northern fields in China was determined to be 105–135 kg N ha−1 in order to achieve a balance between rice yield and high N fertilizer uptake.

Specific power or droplet shear stress: Which is the primary cause of soil erosion under low-pressure sprinklers?

Specific power and droplet shear stress are generally considered to be the most critical indicators of soil erosion in sprinkler irrigation, but there is controversy about which indicator has a greater impact. This creates uncertainty in the optimization design of low-pressure sprinkler irrigation systems. In this study, a commonly used low-pressure sprinkler, i.e., Nelson D3000, was used to carry out in soil box experiments, to study the effects of specific power and average droplet shear stress at the end of a spray jet on soil erosion during sprinkler irrigation under three nozzle diameters (3.97, 5.95, and 7.94 mm), two operating pressures (103 and 138 kPa), and two soil textures (loamy sand and silty loam). Overall, the larger specific power or average droplet shear stress resulted in higher initial and steady runoff rates and a shorter time until runoff occurs and stabilizes. Enlarging the specific power or average droplet shear stress could significantly increase the initial infiltration rate, sediment yield, and surface soil bulk density, but the infiltration depth prior to runoff and surface soil porosity decreased. Furthermore, the specific power was observed to have greater correlations than average droplet shear stress with the surface runoff rate, initial infiltration rate, and increase in the soil bulk density and decrease in the soil porosity after irrigation. However, it was weakly related to the infiltration depth prior to runoff and sediment yield, indicating that the specific power could more accurately reflect the soil erosion with respect to the shear stress. To minimize the risk of soil erosion, a small operating pressure (103 kPa) is recommended in the design of center pivot irrigation systems, especially for the overhang of the system with large nozzle diameters. This research can provide the technical support for soil erosion prevention under low-pressure sprinkler irrigation.

Prioritization of Sub-watersheds for the Categorization of Surface Runoff and Sediment Production Rate Based on Geo-spatial Modeling and PCA Approach: A Case from Upper Beas River, Himachal Pradesh, India

Abstract Studying geo-morphometric parameters using Remote Sensing (RS) and Geographic Information System (GIS) tools is crucial to routing runoff and remaining hydrological processes. A geo-spatial model and principal component analysis (PCA) approach are used in this study to prioritize sub-watersheds of the upper Beas river up to Pandoh dam. Dendritic drainage patterns throughout its sub-watersheds characterized the 6th-order Beas river. The sub-watersheds show a lithological uniformity that indicates that the entire watershed has structurally impermeable materials at both surface and sub-surface levels. Moreover, the aerial and relief aspects of the sub-watershed indicate fine drainage textures, steep slopes, immediate peak flows, a hydrograph with multiple peaks, and a low concentration time. In other words, the sub-watershed may not be able to manage flash floods during the storm period. Surface runoff and sediment production rates (SPR) were estimated in the present study ranged from 3.576 - 5.240 sq. km-cm/sq.km and 0.101 - 0.234 ha-m/100sq.km/year, respectively. Finally, the study concluded that the sub-watersheds in the upper regions produced high runoff and sediments, usually carried into the mainstream. Further, the PCA technique was applied to find the redundant morphometric parameters and then the same results were utilized to determine the effective way to prioritize the watershed. The present study will serve as a basis for developing appropriate policies and practices for peak flooding and promoting the sustainability of the watershed.

Effect of exposed roots on the erosion characteristics of sloped land based on close-range photogrammetry in a karst rocky desertification region

On sloped land in karst rocky desertification regions, some roots gradually become exposed to the surface due to the low soil-forming rate of the parent rock and shallow natural soil layer. The spatial orientation of these roots varies with the terrain as the plants grow and the surrounding surface erodes. In previous studies, the exposed roots were often used to estimate erosion intensity, but little is known about how exposed roots influence the erosional characteristics of sloped land. In this study, the effects of the orientation of the exposed roots (vertical slope arrangement, parallel slope arrangement, transverse slope arrangement) on the erosion characteristics of sloped land were investigated based on close-range photogrammetry and simulated rainfall experiments. The results showed that there were differences in the responses of the sloped land to erosion based on the different orientations of the exposed roots. In the first four rainfall events, the surface runoff rate was the highest for the parallel slope arrangement, followed by the vertical slope arrangement and transverse slope arrangement. With the occurrence of intermittent rainfall events, this difference gradually decreased. The exposed roots affected the erosional characteristics of sloped land by interfering with the runoff flow path. In most rainfall events, the general trend of eroded sediment yield was parallel slope arrangement > vertical slope arrangement > transverse slope arrangement. The digital elevation model (DEM) constructed by close-range photogrammetry showed that the surface microtopography changed during intermittent rainfall, which resulted in the difference in the relief of sloped land with different exposed root distribution patterns. The volume of soil detached and transported along slopes with parallel slope arrangement was more severe than that on transverse and vertical slopes because the shallow gullies between exposed roots provided a good transport channel for runoff along sloped land. These results provide a reference for understanding the relationship between plant roots and erosion processes in regions of karst rocky desertification.

A Historical–Projected Analysis in Land Use/Land Cover in Developing Arid Region Using Spatial Differences and Its Relation to the Climate

Land resources are under relentless pressure from metropolitan regions, pollution, and climate shifts. The urge to monitor Land Use/Land Cover (LULC) and climate changes based on technology and sustainable management are addressed. This study analyzes the historical land cover maps to calculate growth patterns for the years 1985–2022 and uses Logistic Regression (LR) and Artificial Neural Networks (ANN) to project future dynamics forecasts for the years 2030–2040 in the Amman-Zarqa Basin (AZB). The state of the climate and the extreme indices projections of CMIP5 under RCP8.5 are linked to the corrected historical LULC maps and assessed. Given greater dry covering of large surface runoff, little rainfall, and high evapotranspiration rates, the state of the climate across the AZB notably showed instability in key climatic indices and a major exacerbation of warmth and drier soil in the basin. Both climate change and land use are contributing dynamics, but land-use alterations are much more dramatic changes than climate changes. Since the effects of climate alterations are mostly identifiable through land cover forms, land use practices put the phase that may be influenced by climate change. The results revealed that the daily extremes in 1992 are aligned with the corresponding increase of barren lands and diminished the half area of forest, cultivated, rainfed, and pasture lands in 1995. Rainfed regions were converted to agriculture or shrubland with an accuracy of 0.87, and urban encroachment caused the acreage of woodland, cultivated, rainfed, and grazing fields to decrease by almost half. Predicted land cover maps were created using LR in 2030 (Kappa = 0.99) and 2040 (Kappa = 0.90), in contrast to the ANN approach (Kappa = 0.99 for 2030 and 0.90 for 2040). By combining ANN and LR, decreasing bare soil was anticipated between 325 km2 and 344 km2. As a result, 20% of the total area of the major AZB cities’ urban areas will be doubled. More subjective analysis is required to study and predict drought in the future to improve the resilience of various LULC types.

Quantitative characteristics of surface runoff from railway tracks

Analysis is carried out and the nature of surface runoff filtration in the ballast prism of the railway track is considered, as well as options for water migration in the upper and lower structure of the ballast prism are considered. The formula of flow rate of rain, melt and filtration runoff is obtained. The formula for surface runoff consumption from the railway track was clarified, and the total surface runoff flow rates for the areas of railway transport facilities were determined. It was found that when surface water seeps through the upper and lower structures of the path. Two lateral ejections occur. The proposed methodology for determining the flow rates of surface runoff from railway tracks allows using an adapted methodology proposed not for residential zones, which is relevant for 90% of the railway bed located in the Russian Federation, in particular, the Kuibyshev railway road located in the forest-steppe and semi-steppe zones.

Effects of the Rainfall Intensity and Slope Gradient on Soil Erosion and Nitrogen Loss on the Sloping Fields of Miyun Reservoir.

Environmental loss is primarily caused by soil, water, and nutrient loss, and runoff is associated with nutrient transport and sediment loss. Most existing studies have focused on one influencing factor, namely slope gradient or rainfall intensity, for slope erosion and nutrient loss, but the joint effects of the two factors have rarely been researched. In this context, the impact of slope gradients (0°, 5°, 10°, and 15°) and rainfall intensities (30, 40, 50, 60, 70, and 80 mm/h) on soil erosion and nutrient loss on the sloping fields of Miyun Reservoir were explored using the indoor artificial rainfall simulation testing system. Based on the results of the study, the variation of runoff coefficient with slope gradient was not noticeable for rainfall intensities <40 mm/h; however, for rainfall intensities >40 mm/h, the increased range of runoff coefficient doubled, and the increase was the fastest under 0° among the four slope gradients. The slope surface runoff depth and runoff rate showed positive correlations with the rainfall intensity (r = 0.875, p < 0.01) and a negative correlation with the slope gradient. In addition, the cumulative sediment yield was positively related to the slope gradient and rainfall intensity (r > 0.464, p < 0.05). Moreover, the slope surface runoff-associated and sediment-associated loss rates of total nitrogen (TN) rose as the rainfall intensity or slope gradient increased, and significant linear positive correlations were found between the runoff-associated TN loss rate (NLr) and the runoff intensity and between the sediment-associated NLr and the erosion intensity. In addition, there were positive linear correlations between slope runoff-associated or sediment-associated TN loss volumes and rainfall intensity, surface runoff, and sediment loss volumes, which were highly remarkable. The slope gradient had a significant positive correlation with the slope surface runoff-associated TN loss at 0.05 (r = 0.452) and a significant positive correlation with the sediment-associated TN loss at the level of 0.01 (r = 0.591). The rainfall intensity exhibited extremely positive correlations with the slope surface runoff-associated and sediment-associated TN loss at 0.01 (r = 0.717 and 0.629) Slope gradients have less effect on nitrogen loss on sloped fields than rainfall intensity, mainly because rainfall intensity affects runoff depth. Based on the findings of this study, Miyun Reservoir may be able to improve nitrogen loss prevention and control.

Comparing two weather generator‐based downscaling tools for simulating storm intensification and its impacts on soil erosion under climate change

AbstractStorm intensification is projected to increase under climate change; however, it is quite challenging to statistically downscale storm intensification for climatic impact assessment. The objectives of this study are to compare two weather generator‐based tools in simulating daily precipitation extremes at a point scale, both with and without storm intensification options, and to further evaluate the responses of simulated surface runoff and soil loss to generated precipitation extremes under various cropping and tillage systems at a station in central Oklahoma, U.S.A. Results show that all data sources including raw GCM, raw RCM, and statistically downscaled GCM datasets are capable of providing information on future storm intensification, depending on particular ensemble members or models in each source. Thus, it is recommended that all data sources including as many members as possible should be used in model screening. Compared with the SYNthetic weather generaTOR (SYNTOR), the Generator for Point Climate Change (GPCC) tool tends to generate a stronger storm intensification, partially because GPCC takes into consideration the increased variance of monthly precipitation as projected by GCMs in adjusting daily precipitation variance for future climate generation. However, there are no discernable differences between storm intensification options with each tool because weaker signals of storm intensification are projected for the study site coupled with a projected decline in future annual precipitation. Simulated soil loss and surface runoff rates with GPCC were significantly greater than those with SYNTOR due to GPCC generating more frequent and heavier storms. Given the sizable differences in extreme precipitation generation, both tools could be used to generate a range of the potential impacts of storm intensification under climate change on soil erosion and surface hydrology.

Hydrological and water quality performance of Waste Tire Permeable Pavements: Field monitoring and numerical analysis

Permeable pavements can reduce the amount of surface runoff and peak flow rate and delay the occurrence of peak flow by allowing water to infiltrate underground similar to natural undeveloped catchments. Such suite of benefits of permeable pavements have made them one of the preferred stormwater control measures in most of the integrated land and water programs. Waste tire permeable pavements (WTPPs), as a relatively new permeable pavement technology, are designed with a surface layer made of up to 50% recycled tire particles. This study aims to investigate the hydrological performance of WTPPs to divert surface runoff and their impact on water quality. A large-scale trial in Australia was constructed and a comprehensive field performance monitoring program including double-ring infiltrometer tests and water quality testing was conducted to evaluate the performance of WTPP in real field conditions. Quality assurance tests on samples of the WTPP surface layer were conducted for permeability in the laboratory, and numerical simulations were done to estimate the surface runoff and investigate the sensitivity of the results to important design parameters. The physically-based models used for numerical simulations were developed in MUSIC X by replicating the layers of the constructed permeable pavement system as well as the impervious part of the trial site. The results indicated that the constructed system is capable of mitigating the surface runoff from the studied site, although only 25% of the discharge area was covered with WTPP. The infiltration rate of the WTPP over nine months with and without maintenance was studied. The results revealed that the infiltration rates even in areas without maintenance after nine months were found to be above the recommended values from ASCE permeable pavements task committee, but lower than the areas that were regularly maintained highlighting the importance of a regular maintenance regime for permeability recovery over time. Water quality tests were done on samples taken over a 17 month-long period indicating that the WTPP system successfully reduced most of the studied pollutants and chemical indicators, including most of the heavy metals, total suspended solids (69%) and turbidity (88%) by physically filtering the water.

Exploring the factors influencing the hydrological response of soil after low and high-severity fires with post-fire mulching in Mediterranean forests

Despite ample literature, the influence of the individual soil properties and covers on the hydrological response of burned soils of forests has not clearly identified. A clear understanding of the surface runoff and erosion rates altered by wildfires and prescribed fires is beneficial to identify the most suitable post-fire treatment. This study has carried out a combined analysis of the hydrological response of soil and its driving factors in burned forests of Central-Eastern Spain. The pine stands of these forests were subjected to both prescribed fire and wildfire, and, in the latter case, to post-fire treatment with mulching. Moreover, simple multi-regression models are proposed to predict runoff and erosion in the experimental conditions. In the case of the prescribed burning, the fire had a limited impact on runoff and erosion compared to the unburned areas, due to the limited changes in soil parameters. In contrast, the wildfire increased many-fold the runoff and erosion rates, but the mulching reduced the hydrological response of the burned soils, particularly for the first two-three rainfalls after the fire. The increase in runoff and erosion after the wildfire was associated to the removal of the vegetation cover, soil water repellency, and ash left by fire; the changes in water infiltration played a minor role on runoff and erosion. The multi-regression models developed for the prescribed fire were accurate to predict the post-fire runoff coefficients. However, these models were less reliable for predictions of the mean erosion rates. The predictions of erosion after wildfire and mulching were excellent, while those of runoff were not satisfactory (except for the mean values). These results are useful to better understand the relations among the hydrological effects of fire on one side and the main soil properties and covers on the other side. Moreover, the proposed prediction models are useful to support the planning activities of forest managers and hydrologists towards a more effective conservation of forest soils.

Effects of the Gully Land Consolidation Project on Runoff and Peak Flow Rate on the Loess Plateau, China

The Gully Land Consolidation (GLC) project, aiming to create land for agriculture on the Loess Plateau, heavily interfered with the underlying surface and thus affected the hydrological process. The purpose of this study was to investigate the effects of the GLC on the surface runoff and peak flow rates of watershed on the Loess Plateau under different rainfall events and hydrological years. A GIS-based Soil Conservation Service Curve Number (SCS-CN) model was used. The results showed that GLC reduced the mean event surface runoff by 6.2–24.7%, and the reducing efficiency was the highest under light rain events. GLC also decreased annual surface runoff, and the reducing efficiency was 12.04% (normal year) &gt; 7.63% (wet year) &gt; 4.45% (dry year). In addition, GLC decreased the peak flow rate of the watershed by 8.1–30.2% and prolonged the time to peak flow rate. The efficiency of GLC in reducing the peak flow rate was higher under light rain events than that under extraordinary storm events. The reason for the decrease in runoff and peak flow rate after GLC was that the GLC decreased the slope gradient and hydrological connectivity of the watershed. The results will provide guidance for the application of GLC on the Loess Plateau and watershed management for similar regions.