Sediment Loss Research Articles

Analysis and simulation of nitrogen loss during water erosion process on windward slope under wind-driven rain conditions

Wind-driven rain (WDR) is a common source of soil erosion in nature and usually occurs on windward slopes. This study investigated the effects of WDR events at different wind velocities of 0, 2, 3, 5, 7, 8 m s−1 and rainfall intensities of 30, 60, 90 mm h−1 on runoff, sediment yield, and total nitrogen (TN) loss processes on windward slopes. Additionally, the study constructed quantitative relationships between TN loss rate and simultaneous runoff and sediment using indoor simulated WDR experiments. The distributed soil erosion model KINEROS2 was then modified to embedded with these relationships, and used to simulate and verify the runoff, sediment yield, and TN loss processes during WDR events on windward slopes. The results showed an initial substantial increase followed by a gradual stabilization trend in runoff rates, sediment yield loss rates, and sediment-associated TN loss rates on windward slopes. As wind velocity increased from 0 to 8 m s−1 under a rainfall intensity of 90 mm h−1, the average runoff rate, sediment yield rate, and sediment-associated TN loss rate decreased linearly by 4.30%–16.13%, 9.82%–34.44%, and 14.54–46.42%, respectively. However, runoff-associated TN loss rate increased in a linear trend of 26.49%–137.59%. Similar trends were observed at rainfall intensities of 30 and 60 mm h−1. When simulated using the KINEROS2 and nitrogen migration model embedded with mathematical relationships between wind velocity and soil erosion and TN loss on windward slopes, the NSE and R2 of runoff, sediment, and TN loss processes were 0.49–0.83 and 0.59–0.89, 0.21–0.82 and 0.42–0.88, and 0.21–0.73 and 0.38–0.83, respectively. This study provides insights into the effects of WDR events on TN loss at plot scale and offers guidance for KINEROS2 application under WDR conditions at different slope directions and watershed scales.

Offshore Wind Energy and Marine Biodiversity in the North Sea: Life Cycle Impact Assessment for Benthic Communities.

Large-scale offshore wind energy developments represent a major player in the energy transition but are likely to have (negative or positive) impacts on marine biodiversity. Wind turbine foundations and sour protection often replace soft sediment with hard substrates, creating artificial reefs for sessile dwellers. Offshore wind farm (OWF) furthermore leads to a decrease in (and even a cessation of) bottom trawling, as this activity is prohibited in many OWFs. The long-term cumulative impacts of these changes on marine biodiversity remain largely unknown. This study integrates such impacts into characterization factors for life cycle assessment based on the North Sea and illustrates its application. Our results suggest that there are no net adverse impacts during OWF operation on benthic communities inhabiting the original sand bottom within OWFs. Artificial reefs could lead to a doubling of species richness and a two-order-of-magnitude increase of species abundance. Seabed occupation will also incur in minor biodiversity losses in the soft sediment. Our results were not conclusive concerning the trawling avoidance benefits. The developed characterization factors quantifying biodiversity-related impacts from OWF operation provide a stepping stone toward a better representation of biodiversity in life cycle assessment.

Runoff, Sediment Loss and the Attenuating Effectiveness of Vegetation Parameters in the Rainforest Zone of Southeastern Nigeria

The research was conducted to assess the pace of sediment loss in deserted 3-, 5- and 10-year-fallow traditional farmlands, as well as cultivated farmlands, in a remote forested zone in southern Nigeria. During the 2012 rainy and cropping season, field measurements of sediment and runoff caused by rainfall were carried out. Pearson’s correlation revealed that crown cover positively and significantly correlated with runoff on the cultivated farmland (r = 0.652, p < 0.01). The results showed that the vegetation characteristics assessed on the different fallows explained 73.1%, 89.9%, 53.7% and 86.7% of the runoff variations. In addition, Pearson’s correlation demonstrated that girth explained sediment loss on the 5-year fallow (r = 0.807, p < 0.01), while a strong positive and significant association existed between sediment loss and crown cover on the farmland plot (r = 0.835, p < 0.01). The vegetation components were mutually responsible for 48.4%, 84.3%, 95.1% and 85.9% of the changes in sediment enrichment on the 5-year-, 10-year-, 3-year-fallow and cultivated farmland, respectively. The study found that mature/older fallows had a more substantial attenuating impact on soil erosion control than younger fallows.

Patterns and drivers of water quality changes associated with dams in the Tropical Andes

Abstract. The Tropical Andes is a biodiversity hotspot facing pressure from planned and ongoing hydropower development. However, the effects of dams on the region's river ecosystems, as mediated by physicochemical changes in the water quality, are poorly known. Colombia is unique among its peers in South America with respect to managing central public environmental databases, including surface water quality data sets associated with the environmental monitoring of dams. To assess the relationship between hydropower and Colombian river conditions, we analyze monitoring data associated with 15 dams, focusing on oxygen availability, thermal regimes and sediment losses because these properties are influenced directly by river damming and impose fundamental constraints on the structure of downstream aquatic ecosystems. We find that most Colombian dams (7 of 10) seasonally reduce concentrations of total suspended solids by large percentages (50 %–99 %) through sediment trapping. Most dams (8 of 15) also, via the discharge of warm reservoir surface waters, seasonally increase river temperatures by 2 to 4 ∘C with respect to upstream conditions. A subset of four dams generate downstream hypoxia (< 4 mg L−1) and water that is 2 to 5 ∘C colder than inflows, with both processes driven by the turbination and discharge of cold and anoxic hypolimnetic waters during periods of reservoir stratification. Reliance on monitoring data likely leads us to under-detect impacts: many rivers are only sampled once or twice per year, which cannot capture temporal shifts across seasons and days (i.e., in response to hydropeaking). Despite these blind spots, the monitoring data point to some opportunities for planners and hydropower companies to mitigate downstream ecological impacts. These findings highlight the importance of implementing environmental monitoring schemes associated with hydrologic infrastructure in developing countries.

Effects of varying the spatial configuration and scale of terraces on water and sediment loss based on scenario simulation within the Chinese Loess Plateau

To optimize soil and water conservation measures, it is important to consider the spatial configuration and construction scale of terraces on the Loess Plateau in China. However, there are few existing efficient technology frameworks for assessing the impact of changing the spatial configuration and scale on reducing water and sediment loss at the basin scale. To address this gap, this study proposes a framework that employs a distributed runoff and sediment simulation tool coupled with multi-source data and scenario setting methods to identify the impacts of constructing terraces with different spatial configurations and scales on reducing water and sediment loss at the event scale on the Loess Plateau. Four scenarios (i.e. baseline, realistic, configuration changing and scale changing scenarios) were established to evaluate the associated impacts. The results show that, under the realistic scenario, the average water loss reductions within Yanhe Ansai and Gushanchuan Basins are 15.28 % and 8.68 %, respectively, and average sediment reduction rates are 15.97 % and 7.83 %, respectively. The effect of reducing water and sediment loss in the basin is highly related to the spatial configuration of terraces and that terraces should be built as low as possible on hillslopes. The results also show that, if terraces are disorderly constructed, the threshold of the terrace ratio that effectively contains the sediment yield in the hilly and gully regions of the Loess Plateau is approximately 35 %, whereas if the scale of terraces is increased, the sediment reduction effect is not significantly improved. Furthermore, if terraces are configured near the downslope, the threshold of the terrace ratio that can effectively contain sediment yield is further reduced to approximately 25 %. This study can be used as a scientific and methodological reference for optimizing terrace measures at a basin scale in the Loess Plateau and in other similar regions in the world.

Investigating the effect of seismicity on spatial sediment sources and loads using the fingerprinting approach

Elevated soil erosion and suspended sediment loss are some of the most severe environmental problems in the river catchments of Iran. Seismic activity is known to elevate sediment loss and this study investigated sediment sources and loads in the Talar Drainage Basin in Iran, in the context of earthquake frequency and magnitude. A catalogue of earthquakes in the study region was assembled to estimate the expected high-frequency ground motions (i.e., Peak Ground Acceleration (PGA)). The horizontal ground acceleration was estimated using five global and reginal attenuation relationships. To fingerprint sub-basin spatial sediment sources in the study area, two size fractions (<63 μm and 63–125 μm) and 49 geochemical elements were analysed on 30 sediment samples collected from three potential tributary sub-basin spatial sediment sources and 10 target sediment samples collected at the overall basin outlet. Source contributions were estimated using a Bayesian un-mixing model. The estimated relative contributions of the individual spatial sediment sources for both the <63 μm fraction (51.9% (48.6–55.3), 48 % (44.6–51.3), and 0. 1% (0–0.2)) and 63–125-μm fraction (68.2% (66.4–69.8), 31.7% (30.1–33.6), and 0.1 % (0–0.2)) correlated with recorded seismic events. The correlations between sub-basin specific sediment loads and PGA were r = 0.68 for the <63 μm fraction and r = 0.99 for the 63–125 μm fraction. The results demonstrate that seismic activity and ground acceleration can elevate erosivity and erodibility factors. This study supports environmental planners for targeting management to reduce elevated suspended sediment loads and preserve fluvial habitats.

Crop and livestock productivity, soil health improvement and insect dynamics: Impact of different fodder-based cropping systems in a rainfed region of India

CONTEXTFarmers in rainfed areas of South Asia depend on livestock to augment income, and provide manure for soil and crops. However, the full potential of the livestock is not realized due to the non-availability of quality fodder. The deficit may be attributed to limitation in expansion of cultivable land as well as non-availability of fodder from the protected forest areas. It is possible to enhance the productivity of the livestock by crop-livestock systems. OBJECTIVESThis study was conducted to determine the crop and fodder production potential, nutritive value of the fodder, and reductions in soil nutrients loss and pests of the seven fodder-based inter-cropping systems in a rainfed region in South India. METHODSA medium-term field experiment was conducted from 2015 to 2021 at the Gungal Research Farm of ICAR's Central Research Institute for Dryland Agriculture (17o05’ N, 78o39’E) with seven fodder-based cropping systems involving conventional crops either alone or in combinations with annual or perennial fodder species. The seven systems (treatments) were: sorghum + pigeon pea - hedge lucerne, sorghum + pigeonpea - guinea grass, castor - hedge lucerne, castor - guinea grass, sorghum - fodder - clusterbean - fodder-cowpea - fodder -horsegram, sole sorghum, and sole pigeonpea. Impacts of these systems on crop and livestock productivity, reductions in surface soil erosion and nutrient loss, and soil health and pest dynamics were studied. Livestock based studies were also conducted with the harvested fodders. RESULTS AND CONCLUSIONSWe found that sorghum + pigeonpea-hedge lucerne on average can produce 3865 kg ha−1 of sorghum grain equivalent yield and 37,820 kg ha−1 of sorghum fodder equivalent yield. The sorghum + pigeon pea-guinea grass would benefit the farmers with no animals, by selling the high biomass grass fodder and minimizing the risk of crop failure. These two systems are also better in providing green fodder for at least 8–9 months without any supplementary irrigation. We also observed increase in soil N, OC and soil microbes. There was reduction in runoff (by 51–52%) and sediment loss (by 52%), and reduced pest and disease incidence in these systems. SIGNIFICANCEOur study demonstrated that perennial fodder-based cropping systems are an excellent option to enhance the sustainability and livelihood security of rainfed farmers by reducing the risk of crop failure and supporting the livestock. These systems also open up the scope of integrating tree fodders especially in the bunds and farm borders.

Straw Mulch Effect on Soil and Water Loss in Different Growth Phases of Maize Sown on Stagnosols in Croatia

Soil and water loss due to traditional intensive types of agricultural management is widespread and unsustainable in Croatian croplands. In order to mitigate the accelerated land degradation, we studied different cropland soil management strategies to obtain feasible and sustainable agro-technical practices. A rainfall simulation experiment was conducted at 58 mm h–1 over 30 min on 10 paired plots (0.785 m2), bare and straw covered (2 t ha−1). The experiment was carried out in maize cultivation (Blagorodovac, Croatia) established on Stagnosols on slopes. Measurements were conducted during April (bare soil, after seeding), May (five-leaves stage), and June (intensive vegetative growth) making 60 rainfall simulations in total. Straw reduced soil and water losses significantly. The highest water, sediment loss, and sediment concentrations were identified in tillage plots during May. Straw addition resulted in delayed ponding (for 7%, 63%, and 50% during April, May and June, respectively) and runoff generation (for 37%, 32%, and 18% during April, May and June, respectively). Compared with the straw-mulched plot, tillage and bare soil increased water loss by 349%. Maize development reduced the difference between bare and straw-mulched plots. During May and June, bare plots increase water loss by 92% and 95%, respectively. The straw mulch reduced raindrop kinetic energy and sediment detachment from 9, 6, and 5 magnitude orders in April, May, and June, respectively. Overall, the straw mulch was revealed to be a highly efficient nature-based solution for soil conservation and maize cultivation protection.

Quantification of Impact of Land Use Systems on Runoff and Soil Loss from Ravine Ecosystem of Western India

Ravine and gully formations are both spectacular and also the worst forms of water-induced soil erosion and have in situ and ex situ impact on geomorphology, hydrology, productivity and environmental security, and they are the root causes of degradation of marginal and adjacent land along with reduced production potential. A long-term (2011–2019) study was conducted on marginal land of the Chambal ravine to assess the impact of six land uses, i.e., Agriculture (T1—Rainfed Soybean), Agri-horticulture (T2—Soybean + Manilkara achras), Horti-Pastoral (T3—Emblica officinalis + Cenchurus ciliaris), Pasture (T4—C. ciliaris), Silviculture (T5—Acacia nilotica) and Silvi-pasture (T6—A. nilotica + C. Ciliaris) on soil properties, runoff interception, sediment trapping and soil loss reduction. The lowest average annual soil loss (4.83 ton ha−1 year−1) and runoff (109.52 mm) were recorded under T4, while the highest sediment loss (8.09 ton ha−1 year−1) and runoff (136.07 mm), respectively, were under T5. The runoff coefficient of land uses was in the order of T3 (20.30%) &lt; T4 (20.56%) &lt; T1 (21.95%) &lt; T2 (22.26%) &lt; T6 (22.83%) &lt; T5 (25.54%). The C. ciliaris improved bulk density and recorded lowest in horti-pasture (1.63 ± 0.04 g cm−3) followed by pasture (1.66 ± 0.03 g cm−3) land use system. The active SOC content in pasture, horti-pasture and silvi-pasture was 0.95, 0.87 and 0.64 times higher, respectively, than agriculture land use. Under pure C. ciliaris cover, resistance to penetration varied from 0.68 to 1.97 MPa, while in silviculture land use, it ranges from 1.19 to 2.90 Mpa. Grass cover had substantial impact on soil loss and runoff reduction, SOC content, soil aggregation and resistance to penetration. In degraded ecosystems, Cenchrus ciliaris can be used alone and in combination with plants for protection of natural resources from water-induced soil erosion, runoff conservation, soil quality improvement and maximization of precipitation water use.

Assessment of soil vulnerability to erosion in different land surface configurations and management practices under semi-arid monsoon climate

Soil erosion leads to reduction in land productivity. Concentrated rainfall under monsoon climate increases the erosion vulnerability of poor soils of semiarid regions. Soil vulnerability is the response to impact of slope and land management practices. Assessment of soil vulnerability to soil erosion is crucial for devising an effective soil conservation plan. Therefore, a 7-year long experiment has been initiated for assessing vulnerability to soil erosion for a sandy loam soil using Pearl millet (Pennisetum glaucum) as the test crop in a typical semiarid monsoon climate. In case of runoff, samples were collected and measured every 24 h. These samples were analyzed for sediment, clay, organic carbon (OC), and nitrogen content. A positive linear relation between rainfall and runoff at 2% slope (R2: 0.58–0.72), curvilinear relation at higher slope (R2: 0.81–0.86), and positive linear relationship between runoff and soil loss (R2: 0.47–0.64) were observed. An increase in slope length from 11 to 66 m increased runoff and soil loss by 1.62 times and 1.72 times, respectively. Similarly, an increase in slope steepness from 2% to 9% increased runoff and soil loss by 1.84 times and 3.84 times, respectively. In response to the 56.4% of the total rainfall received, the contribution of runoff and soil loss during the initial 30 days of the crop growing period to the total runoff and soil loss was 68–74% and 80–90% respectively. Sediments were enriched with organic carbon (1.62–3.12) and clay content (1.14–1.55), however, enrichment ratios reduced with the increase in slope. The total loss of nitrogen through erosion had a positive correlation with the sediment loss. Manure and mineral fertilizer application in pearl millet reduced the mean seasonal runoff by 14.4–24.8% and soil loss by 22.7–32.6%. Under bare soil conditions, application of manure and fertilizers reduced runoff by 6.4–8.7% and soil loss by 6.5–7.8%. The knowledge derived from this study can thus improve our understanding of hydrological responses and erosion process of both land configuration and land management practices. The data generated in the study is an important starting point to develop concepts for better management and effective mitigation of land degradation. The findings also suggest the need of initial soil cover, minimum soil disturbance at steeper slope (>3%) and need of conservation measures even on the milder slope (≤ 3%).

Quantitative Study on Improved Budyko-Based Separation of Climate and Ecological Restoration of Runoff and Sediment Yield in Nandong Underground River System

Serious soil and water loss affects the economy and the living quality of the population in faulted basins. Since 2002, China has carried out large-scale ecological restoration projects in karst areas. However, the karst faulted basins have experienced complex climatic changes, which makes it difficult to assess the ecological restoration effects quantitatively. Using the improved Budyko model, basin factor (n) and sediment content factor (C) were divided into climate influence and ecological restoration influence by second-order approximation, and the change ratio of climate influence and ecological restoration on sediment yield and loss was quantitatively calculated in the representative basin of the Nandong Underground River System (NURS). This was carried out in order to effectively distinguish the effects of climate change and ecological restoration on runoff and sediment change in the NURS. Furthermore, this study sought to understand the mechanism of runoff and sediment change and to evaluate the ecological restoration in the faulted basin to provide a scientific basis for the next stage of soil and water conservation policy formulation. The results showed that: (1) Using Pettitt to test the abrupt change of water and sediment in the NURS from 1987 to 2018, we found that 2002 was the abrupt change year of water and sediment in the basin. Before and after the mutation, the runoff and sediment yield decreased significantly, with the change rates of −15.5% and −51.8%, respectively. The decrease in precipitation and the increase in E0 were not significant, which were −4.5% and 1.4% respectively. (2) By calculating the correlation coefficient and the double logarithm function, it was found that the maximum temperature is the main climatic factor affecting the underlying surface factor n, and precipitation is the main climatic factor affecting the sediment concentration c. (3) Climate change reduced runoff by 77.6%. Ecological restoration has reduced sediment by 51.3 percent. The sensitivity of runoff to maximum temperature was 3.61. The sensitivity of grain yield to precipitation and NDVI was 5.37 and 3.26, respectively. The results show that climate is the main factor of runoff reduction, and ecological restoration is the main factor of sediment reduction. Ecological restoration has greatly reduced sediment production, and ecological engineering has made remarkable progress. However, the reduction of runoff caused by climate change should be paid more attention. The results of these studies will help to better formulate land use management policies for soil and water conservation.

Effectiveness of side-inlet vegetated filter strips at trapping pesticides from agricultural runoff

Agriculture can be a contributor of pollutants, including pesticides and excess sediment, to aquatic environments. However, side-inlet vegetated filter strips (VFSs), which are planted around the upstream side of culverts draining agricultural fields, may provide reductions in pesticide and sediment losses from agricultural fields, and have the additional benefit of removing less land from production than traditional VFS. In this study, reductions of runoff, the soluble pesticide acetochlor, and total suspended solids were estimated using a paired watershed field study and coupled PRZM/VFSMOD modeling for two treatment watersheds with source to buffer area ratios (SBAR) of 80:1 (SI-A) and 481:1 (SI-B). Based on the paired watershed ANCOVA analysis, runoff and acetochlor load reductions were significant following the implementation of a VFS at SIA but not SI-B, indicating the potential for side-inlet VFS to reduce runoff and acetochlor load from a watershed with an area ratio of 80:1 but not a higher ratio of 481:1. VFSMOD simulations were consistent with the results of the paired watershed monitoring study, where simulated reductions of runoff, acetochlor loads, and TSS loads were substantially lower for SI-B than SI-A. VFSMOD simulations of SI-B with the SBAR ratio observed at SI-A (80:1) also show that VFSMOD can be used to capture variability in effectiveness of VFS based on multiple factors including SBAR. While this study focused on the effectiveness of side-inlet VFSs at the field scale, broader adoption of properly sized side-inlet VFSs could improve surface water quality at the watershed or larger scales. Additionally, modeling at the watershed scale could aid in locating, sizing, and assessing the impacts of side-inlet VFSs at this larger scale.

Effects of Land Use and Cropping on Soil Erosion in Agricultural Frontier Areas in the Cerrado-Amazon Ecotone, Brazil, Using a Rainfall Simulator Experiment

Agricultural soils provide ecosystem services, but the removal of natural vegetation reduces water infiltration capacity, increasing surface runoff. Thus, monitoring erosion is critical for sustainable agricultural management. Sediment losses and surface runoff were evaluated using a simulated rainfall of 75 mm/h in areas with crops and pastures in both the Caiabi River and Renato River sub-basins of the Teles Pires River watershed in Mato Grosso State, Brazil. In both the Caiabi and Renato sub-basins, data were collected from 156 observations in the upper, middle, and lower regions where (1) soybeans, (2) maize, and (3) pasture were grown alone, with another crop, or with soil that was scarified. Erosion occurred independent of soil texture and was closely related to the management and use of systems involving fewer crops and more soil scarification, regardless of sub-basin location. In uncovered, scarified soil, the soil losses from erosion were greater compared to covered soil, regardless of sub-basin and sub-basin region. In the Renato River sub-basin, soil losses in cultivated areas not planted with crops but with scarification were 66.01, 90.79, and 60.02 g/square meter in the upper, middle, and lower regions, respectively. Agricultural producers need to increase the planting of crops throughout the year and minimize soil disturbance, which will reduce soil erosion and improve sustainability.

Soil and Water Conservation Effects of Contour Reverse Slope Terraces on Red Clay Sloping Farmland against Short and Heavy Rainfall

To explore the effect and applicability of contour reverse slope terraces in water and soil conservation of karstic red clay soil area in northern Guangxi, rainfall simulation experiments were conducted on bare red clay soil slopes laid with contour reverse slope terraces to find the erosion pattern in response to different rainfall intensities (15, 30, and 50 mm/h) and bedrock porosities (1%, 3%, and 5%). The results showed that contour reverse slope terraces can change the spatial distribution of surface runoff, divert surface runoff to the underground, and increase underground sediment yielding. It is found that contour reverse slope terraces can effectively reduce surface soil erosion though it still remains dominant erosion for red clay terraced farmland, with surface runoff reduced by 71%, 52%, and 46% and surface sediment loss reduced by 70%, 65%, and 63%, respectively, when the rainfall intensity is set at 15 mm/h, 30 mm/h, and 50 mm/h. It is concluded that contour reverse slope terraces can help reduce water and soil erosion of red clay terraced farmland in northern Guangxi.

Using the colour of recent overbank sediment deposits in two large catchments to determine sediment sources for targeting mitigation of catchment-specific management issues

The effective management of sediment losses in large river systems is essential for maintaining the water resources and ecosystem services they provide. However, budgetary, and logistical constraints often mean that the understanding of catchment sediment dynamics necessary to deliver targeted management is unavailable. This study trials the collection of accessible recently deposited overbank sediment and the measurement of its colour using an office document scanner to identify the evolution of sediment sources rapidly and inexpensively in two large river catchments in the UK. The River Wye catchment has experienced significant clean-up costs associated with post-flood fine sediment deposits in both rural and urban areas. In the River South Tyne, fine sand is fouling potable water extraction and fine silts degrade salmonid spawning habitats. In both catchments, samples of recently deposited overbank sediment were collected, fractionated to either <25 μm or 63-250 μm, and treated with hydrogen peroxide to remove organic matter before colour measurement. In the River Wye catchment, an increased contribution from sources over the geological units present in a downstream direction was identified and was attributed to an increasing proportion of arable land. Numerous tributaries draining different geologies allowed for overbank sediment to characterise material on this basis. In the River South Tyne catchment, a downstream change in sediment source was initially found. The River East Allen was identified as a representative and practical tributary sub-catchment for further investigation. The collection of samples of channel bank material and topsoils therein allowed channel banks to be identified as the dominant sediment source with an increasing but small contribution from topsoils in a downstream direction. In both study catchments, the colour of overbank sediments could quickly and inexpensively inform the improved targeting of catchment management measures.

Assessing the Effect of Spatial Variation in Soils on Sediment Loads in Yazoo River Watershed

Sediment deposition in river channels from various topographic conditions has been one of the major contributors to water quality impairment through non-point sources. Soil is one of the key components in sediment loadings, during runoff. Yazoo River Watershed (YRW) is the largest watershed in Mississippi. Topography in the watershed has been classified into two types based on land-use and slope conditions: Delta region with a slope ranging from 0% to 3% and Bluff hills with a slope exceeding 10%. YRW spans over 50,000 km2; the Soil and Water Assessment Tool (SWAT) was used to estimate soil-specific sediment loss in the watershed. Soil predominance was based on spatial coverage; a total of 14 soil types were identified, and the sediment contributed by those soils was quantified. The SWAT model was calibrated and validated for streamflow, sediment, Total Nitrogen (TN), Total Phosphorus (TP), and Crop yield for soybeans. Model performance was evaluated using the Coefficient of determination (R2), Nash and Sutcliffe Efficiency index (NSE), and Mean Absolute Percentage Error (MAPE). The performance was good for streamflow, ranging between 0.34 and 0.83, and 0.33 and 0.81, for both R2 and NSE, respectively. Model performance for sediment and nutrient was low-satisfactory as R2 and NSE ranged between 0.14 and 0.40, and 0.14 and 0.35, respectively. In the case of crop yield, model performance was satisfactory during calibration and good for validation with an R2 of 0.56 and 0.76 and with a MAPE of 11.21% and 10.79%, respectively. Throughout YRW, soil type Smithdale predicted the highest sediment loads with 115.45 tons/ha/year. Sediment loss in agricultural fields with a soybean crop was also analyzed, where soil type Alligator predicted the highest with 8.37 tons/ha/year. Results from this study demonstrate a novel addition to the scientific community in understanding sediment loads based on soil types, which can help stakeholders in decision-making toward soil conservation and improving the environment.

Edge-of-field monitoring to assess the effectiveness of conservation practices in the reduction of carbon losses from the foothills of the Himalayas

Agriculture intensification and land use changes in the foothills of the Himalayas have concerning inferences on the carbon pool and storage of the soils. The foothill Himalayas (Shivaliks) are prone to large-scale soil erosion by water. There have been rising concerns regarding accelerated soil carbon loss and an increase in carbon emissions to the atmosphere. There exist limited studies in the Himalayan region to quantify the loss of soil carbon under different conservation strategies, therefore, the present study was carried out to assess the impact of conservation practices. The treatments include conventional tillage (CT), minimum tillage (MT), and zero tillage (ZT) combined with mulching (m), residue retention (r) and intercropping (i) on carbon losses through soil erosion in the foothill Himalayas. The results from one year of observations revealed that the carbon concentration in runoff water is comparable to or even greater in conservation tillage practices than under conventional tillage practices. While comparing mulch and intercropping combinations, the minimum amount of C losses were in Zero tillage + intercrop. The application of residue or mulches or intercropping with pulses effectively reduced the C losses mainly because of the reduction of runoff generated during different rainfall events. The concentration of carbon losses in sediments ranged from 1.5 to 2%. C loss in sediments during the growing season ranged from 11.87 kg ha−1 to 53.40 kg ha−1. The maximum values for sediment-associated carbon loss occurred under CT (53.40 kg ha−1) while the least was in ZTm (11.87 kg ha−1). A very high carbon enrichment ratio of 3.3 to 4.4% was observed. We observed that no till reduced soil carbon losses in sediments while covering the soil helped in controlling runoff losses as well.

Climate Change Impacts on Surface Runoff and Nutrient and Sediment Losses in Buchanan County, Iowa

Nonpoint source pollution from cultivated croplands has often been associated with downstream water quality impairment in various watersheds. Given projected changes in global climate patterns, this study contributes to the existing literature by elucidating the impacts of climate projections on edge-of-field surface runoff and sediment and nutrient losses. We apply a well-tested ecohydrological model, Agricultural Policy Environmental eXtender (APEX), to continuous corn and corn–soybean fields in Buchanan County, Iowa, using climate scenarios developed from three well-known representative concentration pathway (RCP) climate projections: RCP 2.6, RCP 4.5, and RCP 8.5. Our results indicate that there will be a moderate to substantial increase in surface runoff, sediment, and nutrient losses depending upon the reference point of comparison (baseline scenario) and upon which climate scenario actually materializes. However, regardless of which climate scenario materializes and regardless of the baseline for comparison, soluble nitrogen losses are bound to increase, the magnitude depending upon the climate scenario. We find also that nutrient losses will be higher from continuous corn fields than from corn–soybean fields, given the tillage practices implemented on corn versus soybeans in the study area. Similarly, we find that nutrient losses may be higher from fields that receive manure than fields that receive only inorganic fertilizer, though this latter finding may be predicated upon the specific nutrient application rates utilized.

A Bayesian network model for bluff retreat on the southern Lake Erie coast, United States

Coastal bluffs on the 73 km Pennsylvania mainland coast of Lake Erie consist of unconsolidated glacial through paleo-lacustrine Quaternary strata overlying Devonian shale bedrock. Erosion is a significant environmental hazard on this coast where the long-term average annual retreat rate at the bluff crest is ∼ 0.15 m/yr. As the primary geomorphic feature used to track land loss on high-relief coasts, understanding the processes that drive bluff-crest retreat and concomitant sediment and infrastructure losses remains a challenge in coastal-hazard management. This paper shows that bluff retreat on the Lake Erie coast of Pennsylvania can be successfully modeled using multivariate statistics that may have application to bluff settings across the Great Lakes basin and globally. A Bayesian Network (BN) model is developed using long-term historical data (1938–2007 training datasets) and validated against subsequent crest retreat mapped from recent lidar data. Seven field sites were sampled for environmental data that collectively covered ∼ 30 % of the 33.5 km length of the western Erie County littoral cell (WECLC). A BN with eight inputs correctly predicted bluff retreat rates for 95.4 % of transects and had a mean posterior predictive probability of 84.1 %. Scenarios show that greater crest-retreat rates were more likely to be associated with greater wave impact hours, less-resistant stratigraphy, narrower beaches, lower and steeper bluffs, a more energetic run-up regime, and a lower or absent bedrock-toe ledge. These diagnostic attributes should be useful across the WECLC to help identify, with finer spatial resolution, sectors with higher probabilities of having or developing significant erosion problems.

Downstream changes in riverbank sediment sources and the effect of catchment size

Study region: In this study, we compiled and analyzed the results of previous sediment fingerprinting research that examined the riverbank as one of the sediment sources, representing 118 catchments across the globe, most of which were located in the UK (n = 84), the USA (n = 14), and Brazil (n = 10). Gathered studies included catchments ranging from 0.31 to 15,000 km2 and which were predominately agricultural. Study focus: It is essential to understand how riverbanks contribute to total sediment load at the catchment scale if we wish to develop better strategies for managing soil loss. Therefore, the main objective of this study was to assess different fingerprinting tracers quantitatively and analyze the influence of catchment size on riverbank erosion. New hydrological insights: We found that radionuclide tracers show the most consistent relative sources contributions. The share of riverbanks to total sediment loss was in the range of 1–25%. At the same time, the relative contributions of riverbanks and surface sources for many catchments exceeded 25% and 90%, respectively. This variability emphasizes the number of factors affecting riverbank erosion. However, despite this, there was a clear shift in contributions from surface sources to riverbanks with increasing catchment size. We suggest that, in nested catchments, there is a need for long-term longitudinal monitoring of sediment loads, including downstream changes of riverbank erosion.