Sediment Yield Research Articles

Prioritizing conservation practice locations for effective water quality improvement using the Agricultural Conservation Planning Framework (ACPF) and the Soil and Water Assessment Tool (SWAT)

Adopting the right agricultural conservation practices (CPs) at the right place is critical to maximizing water quality benefits. The Agricultural Conservation Planning Framework (ACPF) tool identifies all potential CPs and their locations within a target watershed based on the landscape characteristics. The ACPF tool suggests hundreds of CP locations in a watershed, making it challenging to prioritize the CP implementation. We develop and demonstrate an efficient approach using a multicriteria ranking technique for prioritizing the CPs suggested by ACPF, considering pollution hotspots and CP cost and effectiveness to support decision-makers. The pollution hotspots are estimated with simulations from an ecohydrological model, the Soil and Water Assessment Tool (SWAT). The CP cost and effectiveness were estimated from CP installation costs and pollutant reduction efficiencies from the literature. The methodology was demonstrated in the Conewago and Mahantango watersheds in Pennsylvania, US, for grassed waterways (GWWs) and water and sediment control basins (WASCOBs) for sediment load reduction. Multiple CP prioritization scenarios were evaluated with individual and combined criteria for reductions in total sediment load, yield (loading per area), and cost. In single criterion-based prioritization, the cost-based and load-based prioritization indicated cost efficiency and fewer CPs, respectively. The yield-based approach correctly prioritized CPs in sediment loss hotspots in the case study watersheds; however, it needed more CPs to meet the target reductions. The multicriteria approach efficiently prioritized CPs in sediment hotspots to meet target reductions. Although this approach was demonstrated in two case study watersheds and for sediment loss reduction, it is applicable for any location or pollutant for which similar input variables can be provided, thereby providing a means for prioritizing the results of ACPF for implementation in the Mid-Atlantic region of the US.

Assessing the hillslope-channel contributions to the catchment sediment balance under climate change

To get a full understanding of the impacts of global change on the catchment-scale sediment balance, models are needed that combine hillslope soil erosion processes with channel morphodynamics. Here we present a modification to the SPHY-MMF model that includes a novel channel morphodynamics module, which determines erosion and deposition in rills and channels. We applied the model to a Mediterranean study area in southeast Spain, in which we show that channel erosion contributes substantially (35%–40%) to the total sediment yield, highlighting the importance of accounting for channel erosion in catchment-scale sediment budget estimations. The climate change scenarios show that the different erosional processes (i.e. sheet, rill, channel) are projected to decrease or increase, depending on the projected change in annual and extreme precipitation. From this we conclude that interactions between different erosional and depositional processes should be considered when studying the impact of global change on the catchment-scale sediment balance.

Spatiotemporal changes of land use in response to runoff and sediment yield for environmental sustainability in the upper Blue Nile Basin, Oromiyaa, Ethiopia

Abstract Modeling and mapping hydrological responses of runoff and sediment yield to spatiotemporal land use changes are crucial concerning environmental sustainability. The research was aimed at quantifying the spatiotemporal effects of land use on runoff and sediment yields using three land use satellite images and the SWAT+ model. The increase in agriculture, settlement, and decreasing forest goes to the possibility of increasing sediment yield and runoff by 53.2 and 56.5%, respectively, affecting ecosystems. The areas vulnerable to high runoff were found at the lower and middle reaches with the annual average runoff of 10,825.1, 11,972.9, and 13,452 mm for each respective scenario. On the other hand, most of the soil erosion-prone areas designated as severe in the second and third scenarios were covered by agriculture and shrubland, with annual sediment yields of 301.5 and 267.5 tons, respectively. Deforestation for agricultural expansion has a significant role in environmental degradation, as forests play an irreplaceable role in ecological resilience. Generally, the dominant land uses that instigate soil erosion, runoff, and sediment yield are agriculture, shrubland, and deforestation. The simulation of runoff and sediment yield in response to land use change using the SWAT+ model is more scientifically reliable and acceptable.

Sediment organic carbon and nitrogen trapping in a small reservoir within a typical agricultural granite catchment

Small reservoirs are more widely distributed globally than larger reservoirs, and they have characteristic sediment total organic carbon (TOC) and total nitrogen (TN) trapping patterns that differ from those of larger reservoirs. Few studies have quantified the TOC and TN trapping in a small reservoir within a catchment underlain by a single lithology, particularly in non-karst terrain, from the perspective of environmental change. Based on the chronologies established using 137Cs and 210Pbex, we assessed the temporal patterns of sediment TOC and TN trapping in a small reservoir within a typical agricultural granite catchment (Yimeng Mountains, China) by examining depth trends in TOC and TN concentrations in three sediment cores and temporal trends in TOC and TN deposition rates in the reservoir over the past ∼60 years. The TOC and TN concentrations and C/N ratios show an overall upward increase in the three cores. The TOC and TN deposition rates were relatively high during 1954–1962, decreased to the lowest rates during 1963–1972, and generally increased thereafter. Anthropogenic sources associated with agriculture were the dominant factor in the up-core increases in TOC and TN concentrations, although natural sources were the main contributor to TOC and TN deposition. The temporal changes in TOC and TN deposition rates were mainly due to the sediment yield rather than anthropogenic sources associated with agriculture. The changes in TOC and TN concentrations with depth, and temporal changes in the TOC and TN deposition rates determined from the three cores, reflect the temporal patterns of sediment TOC and TN trapping in the small reservoir over the past ∼60 years. Sediment yield exerted a greater effect on the TOC and TN deposition in the studied reservoir, as compared with a previously reported reservoir within a small agricultural limestone catchment, and the different results of the two studies originated from the contrasting lithologies in the two catchments. Moreover, a comparison with data obtained for a previously studied large reservoir suggests that differences in TOC and TN deposition (including concentrations, specific deposition rates, and temporal trends in deposition rates) are related to catchment size, and the comparison highlights the characteristic patterns of TOC and TN trapping in the small and large reservoirs. The present findings improve our understanding of the temporal patterns of sediment TOC and TN trapping in a small reservoir within a typical agricultural granite catchment in terms of environmental changes influenced by human activity. This study also enhances our knowledge of the barrier effects of a dam on the downstream transport of TOC and TN in a small catchment in a non-karst setting, and the redistribution of sediment TOC and TN in a large river, which can help guide strategies for water resource management on the river basin-scale.

Modelling storm event-based sediment yield and assessing its heavy metal loading: case of Lake Victoria's Inner Murchison Bay catchment in Uganda

Modelling storm event-based sediment yield and assessing its heavy metal loading: case of Lake Victoria's Inner Murchison Bay catchment in Uganda

Bedrock Fragment Induced by Intensive Tillage Effect on Hydrological Properties and Erosion Processes under Different Rainfall Patterns

To investigate the influence of bedrock fragmentation by intensive tillage on the hydrological characteristics and soil erosion processes on slopes, two experimental treatments (soil–bedrock mixtures, WB, and pure soil, CK) in steel tanks were subjected to simulated rainfall under five rainfall patterns (constant, increasing, decreasing, decreasing–increasing, and increasing–decreasing) with the same total rainfall of 90 mm. For each rainfall event, runoff and sediment concentration were sampled at regular intervals. The flow velocity (v), effective/critical shear stress (τ/τc), Darcy–Weisbach resistance coefficient (f), unit stream power (p), and soil erodibility factor (Kr) were calculated to analyze the differences in hydrodynamic characteristics between the WB and CK. Our experimental findings show that significant differences in runoff volume and sediment yield were observed among different rainfall patterns and stages. Bedrock fragmenting significantly promoted runoff and sediment production under different rainfall patterns, with runoff volume and sediment yield increasing by averages of 59.29% and 71.62%, respectively. An increasing trend in average contribution rate of bedrock to runoff volume and sediment yield was observed across three distinct intensities: 6.37% and 4.61% for 30 mm h−1, 12.53% and 7.53% for 90 mm h−1, as well as 14.79% and 36.98% for 150 mm h−1, respectively. The v and p values under various rainfall patterns exhibited an increasing trend from the upper to the bottom slope positions, whereas the f and τ values showed an opposite trend, regardless of the WB and CK. Compared with the CK, the v, f, and p values for the WB increased by 23.34% to 48.94%, 1.59% to 53.16%, and 3.86% to 27.86%, respectively, whereas the τ value decreased by 1.52% to 22.19% for varying-intensity rainfall patterns. Among the variable rainfall patterns, the WB significantly increased sediment yield and also had a promoting effect on runoff generation. However, the WB displayed better erosion resistance compared to the CK under constant rainfall patterns. Therefore, varied-intensity patterns had a profound impact on bedrock-induced runoff and sediment transport processes.

Assessment of Reservoir Sedimentation Using RS and GIS Techniques: A Case Study of Singda Dam, Manipur, India

Through the use of remote sensing (RS) and geographic information systems (GIS), the study sought to evaluate the reservoir sedimentation at the Singda Dam in Manipur, India. The sedimentation assessment was performed using the SWAT (Soil & Water Assessment Tool) model. In order to determine the LULC (Land Use Land Cover) of the Singda watershed between 2011 and 2020, this study also used RS and GIS methodologies. Datasets from Landsat-7 (ETM+) and Landsat-8 (OLI) were used for the chosen time period. According to the results, the proportions of the various LULC kinds in the study region between 2011 and 2020 were found to have significantly changed. The SWAT model was successfully executed, according to several outputs. Sediment yield and discharge were considered to be relevant factors for this project and are the subject of analysis. The Singda Watershed produces and discharges sediment at an average yearly rate of 2014095.53 tons and 635.92 cumecs, respectively. The coefficient of determination (R2) was found to be 0.82, or 82% for sediment loss. According to the study, this model provides satisfactory results and can be used in reservoir areas with comparable geology.

Variation of runoff-sediment relationship at flood event scale in three typical watersheds of the Loess Plateau

River runoff and sediment load are characterized by topography, climate patterns, and vegetation in the watershed. The relationship runoff and sediment load has been greatly altered in many rivers throughout the world, as well as rivers in the Chinese Loess Plateau (LP) due to large-scale ecological restoration and soil conservation measures implementation. This study attempts to identify the changes of runoff-sediment relationship in three watersheds: the Gushanchuan River watershed, Jialu River watershed and Xichuan River watershed by using the flood event data during the periods of 1974–1989 and 2007–2019 in the LP. The results indicated that both runoff depth and sediment yield of flood events during 2007–2019 reduced significantly compared with those during 1974–1989 in all the watersheds. The highest decrease was found in the Gushanchuan River watershed, exhibiting reduction of 56.48% and 95.03% in runoff and sediment yield, respectively. The ratios between sediment yield and runoff depth in all three watersheds showed significant decrease during 2007–2019 when comparing to those in 1974–1989. The correlations between runoff and sediment variables became worse in 2007–2019, compared with those during 1974–1989. The implementation of soil and water conservation (SWC) measures (vegetation restoration, terraces and check dams) accounted for the changes in runoff-sediment relationship in all three watersheds. The result of this study could provide valuable information for the influences of SWC implementation and guide soil erosion control in the LP.

Rainfall characteristics of sediment connectivity activation from plot to watershed scales on the Loess Plateau

Sediment connectivity is a fundamental concept for understanding sediment dynamics within watersheds, serving as a crucial component in watershed management and soil and water conservation. However, quantifying sediment connectivity remains a challenging task due to its complexity and the difficulties associated with direct measurements of sediment flux at multiple temporal and spatial scales. Our research aims to address this challenge by monitoring functional sediment connectivity at various scales using two key indicators: sediment yield and sediment marks. Sediment yield is monitored at slope plots, slope-channel cascades, and watershed outlets, while sediment marks provide additional insight into functional sediment connectivity along the sediment transport path, particularly in slope-channel cascades and channels following rainfall events. To record sediment marks, we used wooden sticks wrapped with clean gauze as an alternative to assessing functional connectivity. Our results revealed that the activation of sediment connectivity was influenced by rainfall amount, intensity, and type, with the highest activation observed at the slope plot, followed by the outlet of the slope-channel cascade and the watershed outlet. Notably, strong sediment connectivity at slope plots, slope-channel cascades, and main channels exhibits a weak correlation with sediment connectivity at the watershed outlet. In upper contribution areas with lower vegetation coverage and higher human disturbance, rainfall amount and I60 values associated with sediment connectivity activation tend to be lower. Furthermore, our research indicates that medium-duration and moderate-intensity rainfall events have a more significant impact on sediment connectivity at slope plots, while rainfall types characterized by longer durations, lower intensity, and larger amounts have a more pronounced effect on sediment transport paths. This suggests that the identification of sediment connectivity switch nodes can be achieved by considering both rainfall characteristics and underlying surface features. Looking ahead, future research can leverage long-term observations and data-driven models to explore rainfall thresholds for sediment connectivity at various scales, ultimately improving sediment transport prediction within watersheds.

Water Quality Assessment and Nutrient Management by SWAT from Sanitation and Agricultural Sources in Warana River Basin, MH, India

The Warana river watershed in Western Maharashtra, India has been recognized for exporting some of the highest nitrate-nitrogen loadings in western Maharashtra and is also a major source of sediment and other nutrient loadings. An integrated modeling framework has been constructed with Soil and Water Assessment Tool (SWAT) model and the interactive SWAT CUP. The simulation framework includes a detailed land use and management data such as different crop rotations and an array of nutrient and tillage management schemes, derived from the various source including the state department of Agriculture. This paper presents the calibration and validation of SWAT for the streamflow, sediment losses, and nutrient loadings in the watershed. Streamflow, sediment yield, and nitrate loadings were calibrated for the 1979-1984 period and validated for the 1984-2014 period. Secondary field data on organic nitrogen, organic phosphorus, and mineral phosphorus is used in model to validate for the 2007-2014 period. Model predictions generally performed very well on both an annual and monthly basis during the calibration and validation periods, as indicated by coefficient of determination (R2) and Nash-Sutcliffe simulation efficiency (E) values that exceeded 0.7 in most cases. The first scenario set with application of fertilizer and no sanitation practices and set of land use change scenarios based on taking cropland out of production indicated a significant benefit in reducing sediment yield at the watershed outlet. A second scenario set found that relatively small reductions in nutrient applications resulted in significant reductions in nitrate loadings at the watershed outlet, without affecting crop yields significantly.

Responses of soil erosion and sediment yield to land use/land cover changes: In the case of Fincha'a watershed, upper Blue Nile Basin, Ethiopia

BackgroundLand use/land cover change (LULCC) exacerbates the global environmental changes through affecting ecosystem services. Soil erosion, which is the most significant global environmental problems caused mainly by LULCC, negatively affects agriculture and water resources development projects by increasing siltation of a reservoirs. As such, up-to-date and reliable information on the LULCC, trends, and its impacts on soil erosion and sedimentation is highly required. However, such an integrated study that uses high spatial earth observation data is limited in most basins of Ethiopia including the Fincha'a watershed. This study was, therefore, to quantify changes in LULC and its impacts on soil erosion by integrating RUSLE model and geospatial technologies. MethodsFor this study, spatial datasets such as Landsat TM, ETM+, and OLI/TIRS satellite images, satellite rainfall, soil, and digital elevation model (DEM) datasets were employed. As such, land use/land cover maps of the 1991, 2006, and 2021 were produced using the supervised image classification techniques of maximum likelihood algorithm. In addition, the impacts of changes in LULC on soil erosion were assessed by changing the C-and P-factors and keeping the other parameters constant. ResultsThe result showed increasing cultivated land, settlement land, and waterbody at the expenses of forest land, shrub land, and grassland. In response to the changes in LULC, the mean annual soil loss increased from 34.5 t ha−1year−1 during the 1991 to 46.4 t ha−1year−1 during the 2006 and to 58.7 t ha−1year−1 during the 2021 year. The result further shows that about 29,180.1 ha (7.6 %), 40,095.6 ha (10.5 %), and 40,969.0 ha (10.7 %) of the watershed were severely eroded during the 1991, 2006, and 2021 years, respectively. Likewise, increasing sediment yield from 1991 (6.7t ha−1year−1), 2006 (8.5t ha−1year−1), and to 2021 (10.3 t ha−1year−1) were observed. ConclusionThe increased soil erosion and sedimentation negatively affects water resource availability and agricultural production. Therefore, proper land management systems should be employed in the watershed to minimize the off-site and on-site effects of soil erosion.

Spatiotemporal Analysis of the Hydrological Responses to Land-Use Land-Cover Changes in the Manafwa Catchment, Eastern Uganda

This study evaluated the impact of land-use land-cover (LULC) change (LULCC) on the hydrologic processes of the Manafwa Basin in eastern Uganda using the Soil and Water Assessment Tool (SWAT) model. Model inputs included the 1995, 2008, and 2017 LULC maps; digital elevation model; and soil, climatological, and hydrologic data. The Calibration and Uncertainty Program Sequential Uncertainty Fitting algorithm was used to calibrate and validate the SWAT model. The model was validated for 2011 to 2013 using daily river discharge. Model statistical measures obtained during calibration and validation ranged from 0.79 to 0.94 for coefficient of determination, from 0.65 to 0.79 for Nash–Sutcliffe coefficient and between −12.0 and − 30.2 for percentage bias. Spatial coverage of commercial farmland and built-up areas increased by 405 percent and 337 percent, respectively, while wetland and tropical high forests decreased 82 percent and 41 percent, respectively, during the period from 1995 to 2017. There is increased annual surface runoff (67 percent), sediment yield (109 percent), and water yield (72 percent) and decreased potential evapotranspiration (32 percent) and actual evapotranspiration (31 percent). Therefore, implementation of integrated basin management strategies such as soil and water conservation and afforestation could reverse the negative impacts and ensure effective water resources management.

Response of runoff-sediment processes to vegetation restoration patterns under different rainfall regimes on the Loess Plateau

Vegetation restoration dominates the changes of land surface and then results in the reduction of runoff and sediment yield within a catchment. This study investigated the responses of runoff and sediment yield to vegetation restoration patterns under different rainfall regimes in the paired catchments: Yangjiagou (0.87 km2) with afforestation restoration (Y-AR) and Dongzhuanggou (1.15 km2) with natural restoration (D-NR) on the Loess Plateau. A total of 133 and 164 measured flood events, respectively, were selected to access this investigation in the two catchments during 1954–1965 and 2005–2017. Compared with natural restoration, the benefits of annual runoff and sediment reduction by afforestation reached 60.4 % and 75.1 %, and the high-flow events (peak discharge: 0.1–27.1 m3/s) reduced by 78 %. The 190 erosive rainfall events were categorized into three rainfall regimes, including long-duration and low-intensity (LDLI), short-duration and heavy-intensity (SDHI), short-duration and low-intensity (SDLI). Under each rainfall regime, the flood events in the D-NR had sharply risen with high discharge and sediment peaks, whereas the events had relatively flattened hydrographs and sedigraphs with low peaks in the Y-AR. Hysteresis analysis suggested that anticlockwise and eight-shaped (or more complex) anticlockwise loops were the dominant types in the Y-AR and D-NR, respectively. The power regression model indicated good relationships for rainfall-runoff and rainfall-sediment under regimes LDLI and SDHI in the Y-AR, whereas it was slightly worse in the D-NR. By contrast, afforestation significantly reduced discharge peak and maximum suspended sediment concentration of SDLI events by 59.6 % and 46 %, respectively. Afforestation played a critical role in the difference in runoff-sediment yield processes between the two restoration patterns through the direct vegetation cover and increased ET (evapotranspiration) and soil properties changes. The findings could provide valuable insights on hydrological responses to different vegetation restoration patterns and improve the understanding for watershed management on the Loess Plateau.

Synergy between vegetation patterns and sedimentation has a temporal effect on water erosion in a slope‐gully system

AbstractMultiple soil and water conservation measures applied together perform better at reducing runoff and sedimentation than individual measures, which can be attributed to their synergistic effects on water erosion. However, whether these synergistic effects are always effective at reducing water erosion remains unclear. In this study, a series of physical models representing a slope‐gully system were tested to quantify the trend of synergistic effects of multi‐measure over time through simulated rainfall. The tested scenarios included four vegetation patterns on the slope—Pattern A: no grass, Pattern B: grass on the up‐slope, Pattern C: grass on the middle‐slope and Pattern D: grass on the down‐slope—and five levels of runoff path length decrease (RPLD) in the gully caused by sedimentation of a check dam (0, 1, 2, 3 and 4 m). Synergistic effects on runoff and sediment yields were influenced by vegetation patterns and RPLDs. Under the same vegetation patterns, synergistic effects increased with increase of RPLD. Under the same RPLD, the mean value of synergistic effects on runoff was in the following order: Pattern D (0.10%) > Pattern C (0.09%) > Pattern B (0.06%), and synergistic effects on sediment yields had a similar order: Pattern D (0.60%) > Pattern C (0.42%) > Pattern B (0.22%). Under Pattern B, based on the Mann–Kendall trend test, the synergistic effects on the runoff yields decreased over time. Contrastingly, under Patterns C and D, the synergistic effects on the runoff yields increased over time. The results show that the synergistic effect has time effect, and its change trend is related to vegetation patterns. Additionally, the results suggest that the middle‐ and lower‐slopes should be prioritized when restoring vegetation as the synergistic effects on runoff tend to increase when these have good vegetation cover.

A validation of WEPP water quality routines in uniform and nonuniform agricultural hillslopes

Current watershed-scale, nonpoint source pollution models do not represent the processes and impacts of agricultural best management practices on water quality with sufficient detail. A Water Erosion Prediction Project-Water Quality (WEPP-WQ) model was recently developed which is capable of simulating nonpoint source pollutant transport in nonuniform hillslope conditions such as those with BMPs. However, WEPP-WQ has not been validated for these conditions, and prior validation work only evaluated calibrated performance rather than uncalibrated performance, with the latter being most relevant to model applications. This study evaluated uncalibrated and calibrated model performance in two plot-scale, artificial rainfall studies. 179 observations were compared to corresponding WEPP-WQ simulations of runoff, sediment yield, and soluble and particulate nutrient forms for both nitrogen and phosphorus. Uncalibrated validation results were mixed for the different field conditions, model configurations, and prediction variables. Nash-Sutcliffe Efficiencies for uncalibrated simulations of uniform conditions were generally greater than 0.6 except for soluble nitrogen predictions which were poor. Simulations of nonuniform conditions were generally ‘unsatisfactory’ except for runoff predictions which were quite good (NSE = 0.78). Performance was improved substantially for almost all endpoints with calibration. Some exceptions to this occurred because the objective function for calibration was based on log-space differences so as to more equally-weight calibration of unsaturated conditions that tend to produce lesser runoff volumes and sediment yields. Calibrated results for both uniform and nonuniform conditions were generally ‘satisfactory’ or ‘good’ according to widely accepted model performance criteria.

Reservoir capacity loss and sedimentation assessment of Dholbaha dam located in Punjab, India using remote sensing and bathymetric survey techniques

Abstract A study was undertaken to assess the live storage capacity of the Dholbaha reservoir located in Punjab, India using remote sensing and bathymetric survey techniques. The primary objectives included comparing the estimated capacity with findings from a bathymetric survey, refining the elevation-area-capacity curve, and determining the rate of capacity loss due to sediments deposition. This analysis utilized water elevation data spanning from 1987 to 2022 and satellite imageries from Landsat 7, 8 & 9. The satellite data was processed using software tools such as Erdas Imagine and ArcGIS. The water extent of the reservoir was calculated using Modified Normalized Difference Water Index (MNDWI). Over the course of 34 years, the reservoir experienced reductions in its dead, active, and total storage capacities by 81.5%, 19.7%, and 28.9%, respectively. These changes correspond to annual depletion rates of 2.40%, 0.58%, and 0.85%, respectively. The sediment yield from the surrounding catchment area was determined to be approximately 1203.56 m3/km2/year. The findings demonstrate substantial declines in Dholbaha reservoir storage capacities over a 34-year period (1987-2022) attributable to sedimentation. This underscores the critical need for sustainable water management and provides key insights for monitoring and strategic planning. The study advocates immediate, targeted interventions within the catchment area to mitigate sedimentation in the Dholbaha reservoir, highlighting the importance of ongoing sedimentation rate monitoring and collaboration with stakeholders for informed reservoir management and sustainable solutions to maintain water capacity for the region.

A new approach to simulate watershed sediment graphs

Soil loss management requires reliable data for assessing the conditions prevailing in a watershed. Suspended sediment concentration (SSC) is one of the indicators of soil loss, and its data and associated properties are essential for integrated watershed management. However, until now, practical methods for estimating the temporal variation of SSC at the watershed scale, i.e., a sediment graph (SG), using measured data have been given less attention. Therefore, the current study was planned to simulate the SG through conceptual modeling of the soil erosion process and sediment yield. The Galazchai Watershed in West Azerbaijan Province, Iran, was selected as a case study. In this regard, the isochrone histograms were initially prepared using two methods of the longitudinal channel profile and spatially distributed travel time. Soil erosion was calculated in each isochrone segment using the Revised Universal Soil Loss Equation (RUSLE), applying the lumped and cellular automata approach. The soil erosion between isochrones was subsequently routed using the Hadley, WaTEM/SEDEM, and newly modified U.S. Forest Service methods. The last method was developed based on seven standardized variables for the current research. Synthetic SGs were ultimately derived from 12 different combinations of the study methods. The modeling performance was assessed using 38 storm events collected over several years. The base time, time to peak, peak value, and total sediment load of the simulated and observed SGs were evaluated using relative error. Comparison based on the evaluation indicators indicated better performance of the combination of the spatially distributed travel time method, cellular automata, and modified U.S. Forest Service method with the coefficient of efficiency and the normalized coefficient of efficiency varying from −1.16 to 0.99 and from 0.32 to 0.99 for the calibration and validation stages, respectively. However, none of the models were simulating satisfactorily the entire sediment graphs.

Elevation‐Dependent Periglacial and Paraglacial Processes Modulate Tectonically‐Controlled Erosion of the Western Southern Alps, New Zealand

AbstractExamining the links and potential feedbacks between tectonics and climate requires understanding the processes and variables controlling erosion. At the orogen scale, tectonics and climate are thought to be linked through the influence of mountain elevation on orographic precipitation and glaciation; the only documented erosional processes capable of balancing rapid rock‐uplift rates are glacial erosion or coupled river incision and landsliding. Our 20 new 10Be derived catchment‐averaged denudation rates from the Western Southern Alps of New Zealand generally range between 0.6 and 9 mm/yr, within the same order of magnitude as fault‐throw rates, exhumation rates, and erosion rates estimated from suspended sediment yields and landslide inventories. Combining our data with previously published 10Be denudation rates, we find that the proportion of catchment area in the 1,500–2,000 m elevation window is the variable that best explains denudation rate variability and the disparity between rock‐uplift rates and denudation rates. This correlation indicates that enhanced erosion likely occurs at 1,500–2,000 m above sea level, where periglacial and paraglacial processes have been proposed to be most active. We find that these temperature‐controlled erosional processes, which are also elevation‐dependent, can play a greater role in modulating erosion during interglacials than precipitation or glaciation. Our data suggest that temperature‐controlled peri‐ and paraglacial erosion could be efficient enough to balance some of the fastest rock‐uplift rates on Earth. Hence, temperature‐controlled erosion could contribute to limiting orogen elevations and modulating the erosion rates dictated by rock‐uplift, playing an essential role in linking tectonics and climate.

Modeling hydrological processes under Multi-Model projections of climate change in a cold region of Hokkaido, Japan

Local hydrological systems are highly sensitive to global warming, especially in cold-climate-dominated basins. The integrated climate-hydrological model is a powerful tool to analyze and predict such effects. However, modeling hydrological processes contains considerable uncertainty in cold areas due to the complex dynamics of freeze–thaw cycles and requirements of lot inputs data. Here, we developed a fast and simple approach to modify the soil temperature module in soil and water assessment tool (SWAT) model in a cold region of the Ishikari River basin (IRB), Hokkaido, Japan. Water balance components and sediment yield simulations were explored by the modified SWAT model, outperforming the original SWAT model by PBIAS less than 15 % and NSE higher than 0.60 in monthly streamflow and sediment yield during both calibration (2011–2015) and validation phases (2016–2019). The future prediction was integrated with future climate datasets under four Shared Socioeconomic Pathways (SSP) scenarios (SSP126, SSP245, SSP370, and SSP585) derived from two Global Circulation Models (GCMs), in two future stages (2045–2069 and 2075–2099) with relative to the baseline stage (1990–2014). The varying climate with warmer temperatures (+3.05℃) and less precipitation (-7%) in the future would lead to that evapotranspiration (ET, 67 %) increased. Water yield (WY, −9%), surface runoff (SURQ, −18 %), groundwater flow (GWQ, −10 %), lateral flow (LATQ, −7%), percolation (PERC, −10 %), streamflow (-7%) and sediment yield (-14 %) decreased across the whole basin. However, due to climatic spatial variation, at the subbasin scale, hydrological components (e.g., WY, GWQ, LATQ, and PERC) would increase in the northern region, at the same time, SURQ and ET rise significantly in the central and southern areas. Our findings could offer evidence for future water and soil protection policymaking across the IRB.

Soil Erosion in a Changing Environment over 40 Years in the Merguellil Catchment Area of Central Tunisia

Soil degradation and erosion in semi-arid regions can significantly impact agricultural development, environmental sustainability, and hydrological balance. Understanding the impacts of land use changes and soil and water conservation (SWC) technique implementation on soil erosion and sediment yield is critical to planning effective watershed management. This study aims to evaluate the impacts of environmental changes in the Merguellil watershed (Central Tunisia) over the last forty years. To achieve this, remote sensing techniques and a geographic information system (GIS) will be employed to classify Landsat images from 1980 to 2020. Additionally, the Revised Universal Soil Loss Equation model will be utilized to estimate soil erosion rates, while the sediment delivery distributed model will be employed for sediment yield modeling. Spatiotemporal changes in land use and land cover and in areas treated with SWC techniques were analyzed as the main factors influencing changes in erosion and sediment yield. The combined impact of land use change and SWC techniques resulted in a decrease in the annual soil erosion rate from 18 to 16 t/ha/year between 1980 and 2020 and in sediment yield from 9.65 to 8.95 t/ha/year for the same period. According to the model’s predictions, both soil erosion and sediment yield will experience a slight increase with further degradation of natural vegetation and a reduction in the efficiency of SWC works. This emphasizes the importance of continued efforts in adopting and sustaining SWC techniques, as well as preserving natural vegetation cover, to proactively combat soil degradation and its adverse effects on the environment and communities. Continuous dedication to these measures is crucial to preserving our ecosystem, promoting sustainable practices, and protecting the well-being of both the environment and society.