Transport Of Suspended Solids Research Articles

Satellite observations of suspended particulate matter concentration in Lake Gaoyou in the past four decades

Suspended Particulate Matter (SPM) concentration stands as a pivotal determinant of water quality within lake ecosystems. However, comprehension of the enduring dynamics of SPM within lakes is severely hindered due to a shortage of long-term records. Our research has developed a robust remote sensing algorithm to retrieve the SPM concentration in Lake Gaoyou, situated in the lower reaches of the Huai River basin in China. The algorithm demonstrates commendable performance, with an uncertainty of 28.68 %. Leveraging Landsat series sensors imagery, our investigation yields high spatial resolution SPM concentration maps, which first provide a four-decades record of the SPM distribution within Lake Gaoyou. Our findings unveil a significant annual reduction of 1.35 mg L−1 in SPM concentration over the past four decades. This notable decline is probably attributable to a series of ecological initiatives to enhancing the management of the eco-friendly within the basin. Furthermore, our research delineated the influence of environmental factors on the intra-annual SPM dynamics across distinct spatial domains, encompassing the natural inlet region, semi-obstructed inlet region and outlet areas within the lake The SPM concentration in the natural inlet region exhibits a conspicuous correlation with precipitation. Increased precipitation induces runoff within the basin, facilitating the transport of suspended solids and sediment into the lake, consequently augmenting SPM levels. Conversely, the semi-obstructed inlet and outlet areas are predominantly influenced by the wind field, with variations in SPM attributed to sediment resuspension caused by water mixing driven by wind forcing. Our research can be considered an important reference to the evaluation of the management of the lake over long periods.

Distributed dynamic modelling of suspended sediment mobilization and transport from small agricultural catchments

Erosion, soil loss and consequent nutrient fluxes impair water quality and can degrade arable soils. Erosion rates in Sweden are generally low but episodic losses of suspended solids (SS) can affect water quality. Identifying critical source areas (CSAs) and “hot moments” is essential to reduce erosive losses from arable land. Here we use a distributed, dynamic high-resolution erosion model that simulates the sum of all transported material, i.e., erosion within the soil profile, on the soil surface and transport through drainage systems. We simulate monthly SS transport in six small agricultural catchments with varying soil texture over 8 years. Kling-Gupta Efficiency (KGE) was used as model performance statistics, and calibration (KGE = 0.45–0.78) and validation (KGE = 0.64–0.83) showed acceptable model performance for all catchments, with mean annual SS losses between 2.1 and 31.5 t km-2yr-1. Equifinality could be minimised by using more precise initial parameter values. We suggest that the model can be applied to comparable unmonitored catchments to identify erosion-sensitive periods and CSAs.

Flows, Transport, and Effective Drag in Intertidal Salt Marsh Creeks

AbstractIntertidal creeks (channel width <5 m) weave through salt marshes, delivering water, nutrients, and sediments into the marsh interior and affecting spatial heterogeneity in plant and animal distributions. Despite their global prevalence, creek connectivity, and the mechanisms controlling cross‐marsh hydrodynamics, remain poorly resolved. In this study, we measured flow and total suspended solids transport in three intertidal creeks within a confined drainage basin in a Georgia, USA salt marsh. We discovered that the effective drag is 3–12 times greater than bed drag, reaching levels similar to those observed in coral reefs. Furthermore, the drag between tidal flood and ebb phases differs, indicating an asymmetric drag. Analyses of along‐channel momentum reveal that pressure gradient m/s2 and friction m/s2 dominate creek momentum balance. Divergence in tidal and suspended solids transport between adjacent creeks revealed contrasting tidal transport asymmetries (i.e., flood or ebb dominated) within this confined basin. We discuss how these differences may alter the eco‐geospatial evolution of salt marshes and their response to sea‐level rise.

Water Erosion, its Relationship to Total Suspended Solids and Water Quality in the Lower Basin of the Usumacinta River, Tabasco, Mexico

Total suspended solids are an indicator of material constituted by sedimentable solids, suspended solids, and colloidal, whose origin is erosion, wastewater discharges, and agricultural waste. The objective of this research was to determine territorial water erosion, its relation with total suspended solids, and the water quality in the lower basin of the Usumacinta River in Tabasco. Three sampling points were established, located in the municipalities of Tenosique, Emiliano Zapata, and Jonuta, in the state of Tabasco. Water samples were collected during 12 monthly sampling campaigns in an annual cycle, and the total suspended solids were determined according to the provisions of the NMX-AA-034-SCFI-2015 standard. Water erosion was calculated based on the Universal Soil Loss Equation (USLE) and with the use of geographic information systems (GIS). The results obtained were statistically analyzed, finding that the measured maximum TSS concentrations are 130.92 mg.L-1 in Boca del Cerro, 165.28 mg.L-1 in Chablé, and 113.91 mg.L-1 in Jonuta which are within the permissible concentrations for protection of freshwater aquatic life and agricultural irrigation according to ecological criteria of water quality (CE-CCA-001/89), in Mexico. The lower basin of the Usumacinta River has areas with extreme erosion (990 tons.ha-1yr-1), with conditions that accelerate the erosion process, such as annual rainfall between 1805 mm and 2250 mm, clay soils located on slopes greater than 16%, and agricultural soils. These events cause loss of the soil fertile layer where agriculture is developed, also giving rise to the accelerated transport of suspended solids; which negatively alter the quality of the water of the Usumacinta River.

Computational Fluid Dynamics Simulation of Suspended Solids Transport in a Secondary Facultative Lagoon Used for Wastewater Treatment

The facultative lagoon hydrodynamics has been evaluated using computational fluid dynamics tools, however, little progress has been made in describing the transport of suspended solids within these systems, and their effects on fluid hydrodynamics. Traditionally, CFD models have been built using pure water. In this sense, the novelty in this study was to evaluate the influence of suspended solids transport on the hydrodynamics of an facultative lagoon. Two three-dimensional CFD models were developed, a single-phase model (pure water) and a two-phase model (water and suspended solids), for a conventional FL in Ginebra, Valle del Cauca, Colombia. Model results were compared with experimental tracer studies, displaying different tracer dispersion characteristics. Differences in the fluid velocity field were identified when suspended solids were added to the simulation. The fluid velocities in the single-phase model were greater than the fluid velocities obtained in the two-phase model, (0.127 m·s−1 and 0.115 m·s−1, respectively). Additionally, the dispersion number of each model showed that the single-phase model (0.478) exhibited a better behavior of complete mixing reactor than the two-phase model (0.403). These results can be attributed to the effect of the drag and slip forces of the solids on the velocity of the fluid. In conclusion, the fluid of FL in these models is better represented as a two-phase fluid in which the particle–fluid interactions are represented by drag and slip forces.

F-Specific RNA Bacteriophage Transport in Stream Water: Hydro-Meteorological Controls and Association with Suspended Solids

F-specific RNA bacteriophages (FRNAPHs) are commonly used as indicators of faecal and viral contamination in waters. Once they enter surface waters, the exact role of suspended solids, sediments and hydro-meteorological factors in their fluvial fate and transport is poorly understood, and long-term studies (e.g., over years) are lacking. In this study, FRNAPH concentrations and genogroup distribution were measured in the Orne River (France) during two years at weekly intervals, and during four storm runoff events. Hydro-meteorological driving factors were investigated at both time scales. FRNAPH concentrations and genogroups at different depths of a riverbank sediment core were also examined to better discriminate the origin of the faecal pollution. During low flows, the FRNAPH and the suspended solid transport were decoupled and the FRNAPH concentrations were mainly correlated with the air and water temperature. During storm runoff events, the FRNAPH concentrations only showed a significant correlation with conductivity, turbidity and water discharge. Despite the uncertainty of the predictions, multi parameter regression models using hydro-meteorological variables were suitable to predict log transformed FRNAPHs’ concentrations at low flows with a standard error of 0.46. Model performance using the storm runoff events dataset was low. This study highlights different driving factors at low flows and during storm runoff events, and the need to measure at both time scales to better understand phage transport dynamics in surface water.

Mechanistic modeling of peracetic acid wastewater disinfection using computational fluid dynamics: Integrating solids settling with microbial inactivation kinetics

While the impact of suspended solids on chemical disinfection kinetics has been widely recognized, a detailed modeling framework for assessing their contribution on disinfection efficiency in municipal contact tanks is yet unavailable. In this paper, we conducted experimental and modeling studies to mechanistically describe the interplay between suspended solids (not removed by gravity settling in secondary clarifiers) and disinfection performance of an emerging disinfectant, peracetic acid, operated in a municipal contact tank. Specifically, we developed an integrated computational fluid dynamics (CFD) model to simultaneously predict the fate and transport of suspended solids, Escherichia coli and peracetic acid in a hypothetical reactor using an exposure-based (i.e., CT-based) inactivation rate expression. The integrated CFD model, calibrated against laboratory data, was used to gain insights on the vertical distribution and local PAA decay effect associated with solids settling and their impact on disinfectant decay and microbial inactivation. Results indicated that: (a) solids settling in contact tanks is a significant phenomenon that cannot be neglected, which can substantially impact disinfection efficiency under low flow conditions; (b) vertical solids distribution and stratification in contact tanks can strongly affect Escherichia coli inactivation by peracetic acid, as highlighted by the CFD modeling studies; (c) Escherichia coli settling is experimentally measurable, and strongly correlated with solids settling. These phenomena can be successfully integrated into a CFD model to obtain a comprehensive description of the PAA disinfection process in presence of changes in secondary effluent quality and flow, a situation typically encountered in municipal contact tanks operated in full scale wastewater treatment plants.

Analysis of the Suspended solids transport in a stream located in the southwest of the Buenos Aires province, Argentina

The total suspended solids (TSS) concentration is a relevant parameter for stream management. A high content of TSS has a negative impact on the ecological habitats and the aquatic environment, and could also be a limitation for the exploitation of surface water. The determination of TSS concentration through water sampling and posterior laboratory analysis is a complex and economically expensive procedure. In this regard, turbidity arises as a useful surrogate measure that allows the indirect estimation of the TSS concentration in a simple and economically convenient way. In the context of a severely deteriorated water supply system, the Napostá Grande stream constitutes a valuable resource for human and industrial consumption in the City of Bahía Blanca. The general objective of the present investigation is to develop statistically based relations between the parameters involved in the suspended solids transport, in order to characterize this phenomenon through the measurement of variables of simple and straightforward field determination. The statistical relationship between the TSS concentration and turbidity and between discharge and solid flow rate was explored. In both regression analyses, the statistical correlation resulted highly significant, and therefore represent valid calibration tools for future solids transport modelling analysis and prediction as well as for sedimentological balances. A comparative analysis of the solids transport between the closure of the medium drainage basin and at the outer limit of the suburban area of Bahía Blanca City, suggests the existence of erosive processes affecting the stream bed and its margins at the section between both sites.

Landslide-Induced Mass Transport of Radionuclides along Transboundary Mailuu-Suu River Networks in Central Asia

Seismically triggered landslides are a major hazard and have caused severe secondary losses. This problem is especially important in the seismic prone Mailuu-Suu catchment in Kyrgyzstan, as it hosts disproportionately sensitive active or legacy uranium sites with deposited radioactive extractive wastes. These sites show a quasi-continuous release of radioactive contamination into surface waters, and especially after natural hazards, a sudden and massive input of pollutants into the surface waters is expected. However, landslides of contaminated sediments into surface waters represent a substantial exposure pathway that has not been properly addressed in the existing river basin management to date. To fill this gap, satellite imagery was massively employed to extract topography and geometric information, and the seismic Scoops3D and the one-dimensional numerical model, Hydrologic Engineering Centre, River Analysis System (HEC-RAS), were chosen to simulate the landslide-induced mass transport of total suspended solids (TSS) and natural radionuclides (Pb-210 as a proxy for modeling purposes) within the Mailuu-Suu river networks under two earthquake and two hydrological scenarios. The results show that the seismically vulnerable areas dominated in the upstream areas, and the mass of landslides increased dramatically with the increase of earthquake levels. After the landslides, the concentrations of radionuclides increased suddenly and dramatically. The peak values decreased along the longitudinal gradient of river networks, with the concentration curves becoming flat and wide in the downstream sections, and the transport speed of radionuclides decreased along the river networks. The conclusions of this study are that landslides commonly release a significant amount of pollutants with a relatively fast transport along river networks. Improved quantitative understanding of waterborne pollution dispersion across national borders will contribute to better co-ordination between governments and regulatory authorities of riparian states and, consequently, to future prevention of transnational political conflicts that have flared up in the last two decades over alleged pollution of transboundary water bodies.

Impact of an urban area on the dynamics and features of suspended solids transport in a small catchment during floods

The paper concerns the impact of the diverse land use in the Silnica river catchment, within the city of Kielce, on the size and dynamics of concentration and load of transported suspended solids, and the variability of the mineral particles mean grain size, during various flood types. This small river flows through the centre of Kielce, the city of 200,000 population in Poland. In its course, the river flows through areas of various land use. In the upper reaches, the catchment is dominated by forests, in the middle the river flows through a reservoir and the lower – through an urban area. Hydrological measurements and transport of the suspended solids were carried out simultaneously in three hydrometric cross-sections of the Silnica, which close the sub-catchments of the land use as mentioned above. The investigations were carried out during floods of various origins: induced by snowmelt, torrential rainfall and frontal rainfall. The analysis indicates that the two rainfall-induced flood types, characteristic for the summer season, show high runoff dynamics. In contrast, snowmelt-induced floods show high concentration and load of the transported suspended solids. In the section of the watercourse flowing through the city, there is an abrupt increase in runoff and suspended solids concentration. Thus, there may be periodic threats to fish and invertebrates, leading to a reduction in the population of living organisms.

Supplies of suspended matter by surface water of the Mazafran drainage basin (western Algiers, Algeria)

The Mazafran wadi is characterized by a strong connection of the solids flow in kilograms per second to the liquid flow in cubic meters per second. However, high solids flow can also be associated to low liquid flow after severe summer storms. We also note that high water flows generate low solids transport; this is probably because of the groundwater draining after major floods. The relation between the daily solids flow and the average daily liquid flow varies from 50 to 600 m3 s−1. It is represented as follows: Qs = 2.03 Qmj2.626. The correlation of suspended matter and liquid flow concentrations follows the Serrat model which is presented as a second-degree logarithmic-based polynomial equation. Both equations show that the Total Suspended Solid (TSS) increases with the downstream and upstream flow. The suspended solids transport occurs mainly in the winter and to a less extent in the spring and autumn.

Transport analysis of particulate matter in media-saturated mesh tube filter for the desalination primary pretreatment process

Roughing filters (coarse media filtration) are a type of porous media filters used as pretreatment systems when the raw water contains a large amount of suspended particles and organic matter. Mesh tube filter media, roughing filter media composed of LDPE, are used in the process of removing suspended particles in wastewater treatment. In this study, we investigated the transport of suspended solids in saturated mesh tube filter media using kaolin particles (sizes range: 0.5–40 μm) and spherical SiO2 particles with particle sizes of 1.5, 10.4, and 19.5 μm. The results showed that the mesh tube filter media effectively removed suspended particles at sizes of 1–20 μm, and the removal rate of suspended particles under artificial seawater conditions was 5–50% higher than under freshwater conditions. It was also found that mechanism of removal of suspended particles varies with the velocity of the fluid by mass balance analysis. With high ion concentrations in the seawater conditions, the size of the suspended particles increased by 5–20%, which caused the suspended particles to be more strongly affected by gravity. The DLVO interaction energy analysis showed that the electrical attraction between suspended particles and filter media increased strongly in artificial seawater conditions.

CFD model to characterize the physical processes of energy transfer in a secondary facultative lagoon.

In this paper, the energy transfer phenomena of a secondary facultative lagoon and its relationship with environmental conditions such as wind and solar radiation were studied. To this end, a three-dimensional computational fluid dynamics model was constructed within a conventional facultative lagoon located in the municipality of Ginebra-Valle del Cauca, Colombia. The model included the transport of suspended solids from inlet to outlet, the penetration of incident solar radiation into the body of water, surface wind, the transfer of heat through lateral walls and the temperature profiles of the wastewater. The model was validated using tracer studies and experimental temperature data. This demonstrated that simulated data of temperature and solar radiation penetration have an acceptable degree of consistency compared with the experimental data. The model demonstrated that temperature profiles were significantly affected by the wind at 0.45 m and 1.40 m depth, while no effect on the surface was obtained.

Predicting iron transport in boreal agriculture-dominated catchments under a changing climate

Increases in iron (Fe) concentration have been reported in boreal regions in recent decades, raising concerns about the fate of ecosystems along water courses. In this study, the SWAT (Soil and Water Assessment Tool) model was applied to the river Mustijoki catchment in southern Finland to determine the current state of Fe transport and to evaluate possible effects of ongoing environmental change in this agriculture-dominated catchment. The model was calibrated using five-year discharge, suspended solids, and Fe data, and validated with a three-year dataset of the same parameters. Further, the model was run with spatially downscaled and bias-corrected climate change scenario data to the year 2100 obtained using five different global climate models. The results were divided into 20-year time steps (2020–2039, 2040–2059, 2060–2079, 2080–2099) and compared against a reference modeling period (1997–2016). With present catchment characteristics of the river Mustijoki, Fe transport was shown to be related to soil erosion and suspended solids transport, driven by hydrological conditions. Arable fields, especially with steeper slopes, were identified as the most likely source of Fe loading. Climate change-induced alterations in riverine Fe transport were simulated as concentrations and as annual mass fluxes. High Fe transport season is already shifting from spring snowmelt events to autumn and winter, and this change is likely to increase in coming decades. Based on modeling results, annual peak concentration in the River Mustijoki was projected to decrease by up to 32% (from 6.2 mg L−1 to 4.2 mg L−1 in scenarios RCP4.5 and RCP8.5) in the coming 20-year period, while lowest winter concentration was projected to increase by 126% (from 1.5 mg L−1 in the reference period (1997–2016) to 3.5 mg L−1 in 2080–2099 in scenario RCP8.5. To compensate for these changes in Fe transport dynamics, water protection and land use management planning must be improved.

Estimates of suspended solid transport in the Pará River Estuary

Abstract The aim of the present study was to quantify the suspended solid concentrations (CSSL) and suspended solid transport (TSSL) in the mixing zone of the Para River Estuary. This estuary is located at the southeastern extreme of the estuarine complex of the Amazon River, and receives input from Tocantins and Para rivers and other local tributaries, with a total discharge of approximately 104 m3 s-1. Two field campaigns were conducted to collect samples of Suspended Particulate Matter (SPM) and measure turbidity. Bottom and surface samples were collected hourly throughout a semidiurnal tidal cycle at two points in the estuary (Left Margin [LM]: -0.7287° -48.2408° and Right Margin [RM]: -0.6051° -48.4048°) in both the dry and rainy seasons. The TSSL was determined using a linear correlation between SPM and turbidity. The results indicate that both the RM and LM points were export routes of suspended solids to the adjacent ocean. However, both lateral and seasonal differences were observed in the PRE samples, with the RM point exporting more suspended solids to the adjacent ocean than the LM point. The TSSL was higher in near-bottom layers on the RM, and the lutocline was broader in comparison with the LM. The correlation between the CSSL at the bottom and in the water column was higher on the LM, and indicated that approximately 80% of the CSSL on this margin derives from resuspension. The sum of the evidence indicates that both points export suspended solids to the ocean.

Modeling Proppant Transport Through Perforations in a Horizontal Wellbore

Summary Proppant placement plays a crucial role in ensuring that the conductivity of fractures is maintained after a hydraulic-fracturing treatment. The process involves the transport of suspended solids in a liquid, usually a water-based fluid, from the wellbore through perforations and finally into fractures. Many studies have focused on proppant settling and transport in fractures, but relatively few studies have investigated the proppant transport process in a wellbore through perforations. This paper addresses the important issue of proppant transport through perforations using a novel numerical technique. The objective is to evaluate the efficiency of proppant transport in a perforated horizontal well under different suspension flow conditions. In this paper, proppant transport through a perforated horizontal casing is modeled using a coupling of computational fluid dynamics and the discrete element method (CFD-DEM). Reasonable agreements are found between the modeling results and published experimental data. Furthermore, the effectiveness of proppant transport through a perforation is evaluated by the particle transport efficiency (Ei), which is defined as the mass fraction of particles transported through a perforation relative to the total mass of particles in the wellbore upstream of the perforation. The effects of casing diameter, proppant size, proppant density, proppant concentration, fluid-flow rate, fluid rheology, perforation size, and perforation orientation on Ei are investigated. The simulation results show that proppant inertia strongly influences proppant transport into a perforation. The proportion of proppant that goes into a perforation is typically much different than the proportion of fluid that goes into the same perforation. This results in an increase in the proppant concentration in the slurry as the slurry flows from the heel to the toe side of a plug-and-perforate stage. Results and models presented in this paper provide directions to quantify and potentially control proppant distribution in perforation clusters in horizontal wells.

Modeling the Impact of Land Use Change on Basin‐scale Transfer of Fecal Indicator Bacteria: SWAT Model Performance

Land use change from annual crops to commercial tree plantations can modify flow and transport processes at the watershed scale, including the fate and transport of fecal indicator bacteria (FIB), such as . The Soil and Water Assessment Tool (SWAT) is a useful means for integrating watershed characteristics and simulating water and contaminants. The objective of this study was to provide a comprehensive assessment of the impact of land use change on microbial transfer from soils to streams using the SWAT model. This study was conducted for the Houay Pano watershed located in northern Lao People's Democratic Republic. Under the observed weather conditions, the SWAT model predicted a decrease from 2011 to 2012 and an increase from 2012 to 2013 in surface runoff, suspended solids, and transferred from the soil surface to streams. The amount of precipitation was important in simulating surface runoff, and it subsequently affected the fate and transport of suspended solids and bacteria. In simulations of identical weather conditions and different land uses, fate and transport was more sensitive to the initial number of than to its drivers (i.e., surface runoff and suspended solids), and leaf area index was a significant factor influencing the determination of the initial number of on the soil surface. On the basis of these findings, this study identifies several limitations of the SWAT fertilizer and bacteria modules and suggests measures to improve our understanding of the impacts of land use change on FIB in tropical watersheds.

Spatial variation in low-level 134Cs in the coastal sediments off central Honshu in the Sea of Japan: implications for delivery, migration, and redistribution patterns

In 2014 and 2015, we examined the spatial distribution of cesium-134 (half-life: 2.06 years) from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) in marine sediments within coastal–basin areas (water depths of 40–520 m) off central Honshu Island (the main island of Japan) in the Sea of Japan. The 134Cs concentrations in both the surface sediment (0–1 cm depth) and whole-core inventory exhibited wide variations, and were highest at the site closest to the Agano River Estuary area (6.7 Bq/kg-dry and 886 Bq/m2, respectively). This indicates that 134Cs in coastal areas was delivered by riverine suspended solids (SS). Given the spatial variation in 134Cs concentrations, we believe that 134Cs partially migrated northeastward within ~50 km along Honshu Island (at water depths shallower than ~140 m), and southwestward, including the Sado Basin area. This is predominantly attributable to the transport of SS by bottom currents and unsteady downward delivery onto the steep slopes of the basin. The total amount of 134Cs in the study area in 2014 was estimated at approximately 0.6 TBq (decay-corrected to March 11, 2011, date of FDNPP accident).

The impact of two large floods (1993–1994) on sediment deposition in the Rhône delta: Implications for sustainable management

In October 1993 and January 1994, two large floods with peak discharge of 9800 and 10,980m3/s and total suspended solid transport of 10.7×106 and 9.7×106 tons, respectively, occurred on the Rhône River. Both floods led to multiple levee breeches in the Northern part of the delta resulting in the introduction of 131×106 and 54.9×106m3 of river water, respectively. In both cases, the flood water drained to the southern lagoons and was partly pumped directly back to the Rhône or to the sea. Most of the 390,000 tons of sediment introduced remained in the Northern inundated area with accretion ranging from 70mm near the breaches to 4mm 6–8km away. This last value is close to the mean accretion value (3.7mm) inferred from the water budget and the estimation of the total quantity of sediment introduced in the flooded area. In a small area near the mouth of the Rhône river still receiving natural overflow from the river, total deposition during both floods was as high as 10cm. The Rhône delta is facing an uncertain future with projected sea-level rise. The results of this study show that large introductions of river water can help sustain the delta in the face of climate change. Controlled introductions of river water using riverside closable structures, as in being done in other deltas, could be done in a way that delivers water and sediments to the places where it is needed most and at the same time protect important infrastructure.

A new method for modeling dissolved phosphorus transport with the use of WaTEM/SEDEM

This paper presents a newly-derived method for directly determining the amount of transported dissolved phosphorus by water erosion. The results of the method are compared to prediction based on enrichment ratio (as proposed by Sharpley) and average share of dissolved phosphorus (DP) in total transported phosphorus (5%) that is widely used in the Czech Republic. Four study areas (catchments of dozens of sq. kilometer) were chosen for their different characteristics (land use, average slope, average elevation, phosphorus concentration in the soil) which influence their rainfall-runoff behavior. The modeled results are compared with data measured in situ. The two methods provide similar results in intensively agriculturally used regions. Agreement among the methods was observed for three study areas with significant erosion intensity (above 4t/ha/year). In the catchment with significantly lower erosion intensity (0.5t/ha/year), the indirect method (Sharpley) underestimates the amount of DP transported in the watercourses. The sum of transports of suspended solids into watercourses and the average available phosphorus content in the soil determined by the Mehlich 3 method (PM3) are the main factors influencing the results provided by the two methods. An analysis of the impact of these factors on the difference between the results of the methods was provided. Transport of suspended solids is related to the method difference (R range from 0.37 to 0.71). However, no significant relationship was found between the difference in the results and the average PM3 content in the soil (R range from 0.15 to 0.36).