Typical Catchment Research Articles

Legacy and emerging per- and polyfluoroalkyl substances (PFASs) in Australian biosolids

Biosolids samples were collected from 19 Australian WWTPs during 2018 that cover a range of catchment types (urban, rural, industrial waste discharges) and treatment technologies. Samples were analysed for 44 PFAS using isotope dilution and alkaline extraction coupled with quantification with LC-MS/MS. The Σ44PFAS mean concentration was 260 ng/g dry weight (dw) and ranged between 4.2 and 910 ng/g dw. The dominant compound class detected were the di-substituted phosphate esters (Σ3PAPs mean 140 ng/g dw; range ND - 730 ng/g dw) which contributed 45% of the total mean Σ44PFAS mass, followed by perfluoroalkyl carboxylic acids (Σ11PFCAs mean 39 ng/g dw; range 2.3–120 ng/g dw) contributing 17%, and the perfluoroalkyl sulfonates (Σ8PFSAs mean 28 ng/g dw; range 0.9–220 ng/g) which contributed 16%. Using the population data supplied by the participating WWTPs, the mean annual estimated biosolids-associated PFAS contribution is 6 mg per person per year and ranged between 0.6 mg and 15 mg. A similar population normalised concentration regardless of WWTP, region or capacity suggests that the domestic environment provides the baseline PFAS loading. Statistically significant higher Σ44PFAS and PFOS concentrations were observed at urban locations. A weak correlation was observed between annual mass of PFAS associated with each individual WWTP and their percentage industrial waste contribution. This may be important for elevated PFAS concentrations observed in WWTPs with higher industrial waste inputs and requires further research.

Comparison of measured and simulated snow cover occurrence using two versions of the TUW hydrological model

Recent rapid developments in the hydrological sciences are markedly related to the development of mathematical modeling and its application in engineering practice, e.g., for the purposes of hydrological forecasting, the extrapolation of hydrological data over time and in space, as well as the estimation of hydrological extremes. Simulation of the water balance is also important for the effective management of water resources. Snow accumulation and melting fundamentally affect the water balance and belong among the most important components of the hydrological cycle. Snowmelt is a significant source of runoff, especially in mountainous regions. The basic snow cover characteristics are the bulk density of the snow, the snow water equivalent, and the height of the snow. This paper is focused on a comparison of snow cover occurrences as simulated by the TUW lumped and semi-distributed conceptual models, with measured values of the snow depths for two selected Austrian river basins. For the comparison, two types of catchments with flat and hilly characters were selected. The results show that the semi-distributed version of the TUW model simulates the occurrence of snow cover more accurately on both flat and hilly catchments. The spatially differentiated model inputs allow for a more representative representation of snow accumulation and melting than using lumped model inputs.

Baseflow estimation in typical catchments in the Yellow River Basin, China

Abstract Baseflow is crucial to maintaining river flow during low-rainfall periods. The baseflow estimation is important to water supply and ecological environmental protection in the Yellow River Basin (YRB), China. This paper comprehensively assessed the applicability of four single-parameter digital filtering, recursive digital filtering, and HYSEP (streamflow hydrograph separation) methods across four typical catchments in the Yellow River Basin: the Zuli River Basin, the Kuye River Basin, the Tuwei River Basin, and the Jingle sub-basin. We also investigated annual and monthly variations in baseflow. We found the standard deviation and coefficient of variation of baseflow index through recursive digital filter were relatively small. And the baseflow process line was smoother and more reasonable in typical year and typical storm-flood events, which conformed to the damping and hysteresis effect of the underlying surface. Thus the recursive digital filter method had the best performance, which was recommended for baseflow separation in the YRB. The estimated baseflow index of typical basins were between 0.354 and 0.502. In addition, inter-annual baseflow showed a decreasing trend and intra-annual baseflow was characterized by uneven distribution, which was subject to the characteristics of each basin.

Analysis of Event-based Hydrological Processes at the Hydrohill Catchment Using Hydrochemical and Isotopic Methods

Abstract. Hydrochemical and isotopic techniques have been widely applied in hydrological sciences because isotopic tracers can identify water sources and hydrochemical tracers can discern runoff flow paths. To better understand the hydrological process, we combined hydrochemical and isotopic techniques under controlled experimental conditions to investigate hydrological process from rainfall to runoff in the Hydrohill experiment catchment, a typical artificial catchment in Chuzhou, China. Hydrochemical and isotopic data, i.e., pH, electric conductivity (EC), total dissolved solids (TDS), anions (Cl−, NO3-, SO42- and HCO3-), cations (K+, Na+, Ca2+ and Mg2+) and dissolved Si, 18O and D in water samples were collected during a rainfall event in 2016, and used to determine the hydrochemical and isotopic characteristics of rainfall and runoff components. We applied EC, TDS, SO42-, Ca2+, Mg2+, 18O and D as tracers to investigate rainfall-runoff processes in the experimental catchment. Runoff flow paths could be well identified by the relationship between 18O and EC, TDS, SO42-, Ca2+ and Mg2+. The quantity of flow flux and mass fluxes of main hydrochemical and isotopic tracers gauged at the catchment outlet shows applicable tracers (Ca2+, Mg2+, SO42-, and 18O) are mainly from deep groundwater runoff (from soil layer of 60–100 cm beneath ground surface). Contributions of the event water and pre-event water to the total runoff during the rainfall-runoff process are different. The quantitative results were very encouraging as a basis to develop hydrological models for further study.

Ensemble flood simulation for the typical catchment in humid climatic zone by using multiple hydrological models

Abstract. A good performance of hydrological model for flood simulation is of critical importance for flood forecasting. Taking Yandu River catchment, as the study area, three hydrological models (i.e. Xin'anjiang model, TOPMODEL, artificial neural network model) and a multi-model ensemble simulation method (i.e. entropy-based method) were applied to simulate the hydrological processes of 30 flood events occurring in 1981–1987. The performance of the ensemble members and multi-model ensemble simulation method was evaluated by comparing indicators of Nash-Efficiency coefficient, errors in root mean square, peak occurrence time, and relative errors of flood peak discharge, event runoff depth. Results show that the three hydrological models perform well for hydrological simulation of all 30 storm floods with Nash and Sutcliffe Efficiency coefficient of above 0.75 and relative error of less than 10 %. However, different model exhibits a difference in simulation errors of peak discharge and peak occurrence time. For example, BP model has the smallest error of 3.78 % for peak discharge simulation while that of Xin'anjiang model and TOPMODEL are 20.9 % and 24.7 % respectively. The entropy-based ensemble simulation method improved flood simulation accuracy to some extent for all evaluation criteria comparing to the three hydrological models. It is feasible to apply entropy-based ensemble approach for improving accuracy of flood forecasting in humid regions of China.

Analysis of spatial and temporal variations in bacterial community dynamics within stream biofilms

ABSTRACT Stream biofilms play an important ecological role in the supply of energy and organic matter to aquatic food webs. Bacterial community composition in stream biofilms is shaped by biotic interactions as well as physicochemical conditions which vary across space and time. However, knowledge of the relative importance of spatial versus temporal factors for microbial community composition is lacking. Here, we applied 16S rRNA gene sequencing to characterise the biofilm bacterial community composition of 732 stream biofilms. These biofilm samples were collected within six streams located a maximum of 118 km apart and draining different catchment types (forest, urban and rural land uses). Samples were collected at monthly intervals for 30 months over 2013–2015. Bacterial community composition was explained better by monthly changes (PERMANOVA; p < 0.01) than by differences observed among streams and catchment types (PERMANOVA; p = 0.44). Bacterial community composition over months and years followed a discernible cyclical seasonal pattern, as quantified using periodic regression analysis. Temperature, TN, light, and soil moisture deficit were identified as factors most significantly correlated with seasonal variation in bacterial community composition. Overall, these findings suggest that temporal changes are more important than spatial changes across the scales investigated in this study.

What do models tell us about water and sediment connectivity?

Connectivity has been embraced by the geosciences community as a useful concept to understand and describe hydrological functioning and sediment movement through catchments. Mathematical modelling has been used for decades to quantify and predict erosion and transport of sediments, e.g. in scenarios of land use change or conservation measures. Being intrigued by both models and the connectivity concept, as a group of modellers we aimed at investigating what different models could tell us about connectivity. Therefore, we evaluated the response of contrasted spatially-distributed models to landscape connectivity features and explained the differences based on different model structures. A total of 53 scenarios were built with varying field sizes and orientations, as well as the implementation of soil conservation measures. These scenarios were simulated, for two rainfall intensities, with five event- and process-based water and soil erosion models – EROSION3D, FullSWOF_2D, LandSoil, OpenLISEM and Watersed. Results showed that rainfall amount plays the most important role in determining relative export and connected area of runoff and sediment in all models, indicating that functional aspects of connectivity were more important than structural connectivity. As for the role of structural landscape elements, there was no overall agreement between models regarding the effects of field sizes, crop allocation pattern, and conservation practices; agreement was also low on the spatial patterns of connectivity. This overall disagreement between models was unexpected. The results of this exercise suggest that the correct parameterization of runoff and sediment production and of routing patterns may be an important issue. Thus, incorporating connectivity functions based on routing would help modelling forward. Our results also suggest that structural connectivity indices may not suffice to represent connectivity in this type of catchment (relatively simple and monotonous land cover), and functional connectivity indices should be applied.

An exploratory study of benthic diatom communities in stormwater ponds of different land uses and varying biocide contamination

Stormwater retention ponds receive a variety of urban and highway pollutants that may have adverse effects on water-dwelling organisms. In this exploratory study, the benthic diatom community composition at genus level of nine such ponds servicing highway, residential, industrial, and mixed industrial/residential catchments was examined. Thirteen biocides were measured in the pond water as one of the possible explanatory factors for diatom taxonomic variability. The uppermost 1 cm of sediment was sampled, and a total of 50 diatom genera were identified. Moderate to high similarities were found among the diatom communities of the ponds. Two genera, namely Navicula and Nitzschia, were the most abundant and accounted for 19–47% of the relative abundance in the ponds. Estimated relative abundances of diatom genera and measured biocide concentrations in the ponds were grouped according to land use. Highway ponds were found to be significantly different from ponds servicing residential and industrial catchments, while no significant differences were found between residential and industrial ponds. The presence of biocides alone could not explain diatom taxonomic variability, although some evidence was found that communities differed depending on the catchment type of the ponds. The results of this exploratory study are an important contribution to future works investigating stormwater diatom communities, where combined effects of biocides and other stormwater contaminants and community stressors, e.g., metals, PAHs, road salt, should be explicitly looked at.

Applicability of Hydrological Models for Flash Flood Simulation in Small Catchments of Hilly Area in China

Abstract Flash flood in small catchments of hilly area is an extremely complicated nonlinear process affected by catchment properties and rainfall spatio-temporal variation characteristics including many physical-geographical factors, and thus accurate simulation of flash flood is very difficult. Given the fact that hundreds of hydrological models are available in the literature, how to choose a suitable hydrological model remains an unsolved task. In this paper, we selected five widely used hydrological models including three lumped hydrologic models, a semi-distributed hydrological model and a distributed hydrological model for flash flood simulation, and studied their applicability in fourteen typical catchments in hilly areas across China. The results show that the HEC-HMS distributed hydrological model outperforms the other models and is suitable to simulate the flash floods caused by highly intense rainfall. The Dahuofang model (lumped) has higher precision in peak runoff time simulation. However, its performance is quite poor on the flood volume simulation in the small catchments characterized by intense vegetation coverage and highly developed stream network. The Antecedent precipitation index and Xinanjiang models (lumped) can obtain good simulation results in small humid catchments as long as long-term historical precipitation and runoff data are provided. The TOPMODEL also shows good performance in small humid catchments, but it is unable to simulate the flash floods characterized by the rapid rise and recession. Our results could be very beneficial in practice, since these provide a solid foundation in the selection of hydrological model for flash flood simulation in small catchments in hilly area.

Siltation and radiocesium pollution of small lakes in different catchment types far from the Fukushima Daiichi nuclear power plant accident site

The Fukushima Daiichi nuclear power plant accident caused radioactive pollution in northeastern Honshu Island, Japan. This study examined the influence of snowmelt and rainfall on soil erosion processes and siltation of small lakes in Miyagi Prefecture (150 km northwest of the power plant). Two sets of slopes and lakes, respectively in pasture and forest catchments, were examined. Snowpack thickness, soil infiltration, surface runoff volume, soil and sediment physicochemical properties, Cs concentration of precipitation, meltwater, and rainwater, and lake siltation rates were determined. The total radioactive Cs content in precipitation was 0.7–7.4 BqˑL−1 and was below the Japanese standard (10 BqˑL−1). Total radioactive Cs was at the allowable level in water flowing down the pasture catchment slope (0.1–9.2 BqˑL−1) during snowmelt and rainfall, as well as in pasture (0.9–8.8 BqˑL−1) and forest (0.7–5.2 BqˑL−1) catchment lake water. There was no soil erosion (surface runoff) in the forest catchment. Soil losses in the pasture catchment were 23 due to rainfall and 9 kg ha−1 yr−1 following spring snowmelt. After snowmelt, a 0.5 and 0.2 mm thick layer of silt was deposited in pasture and forest catchment lakes, respectively, and 1.4 and 0.6 mm were deposited during the rainfall period. Average siltation rates were 1.9 and 0.8 mmˑyr−1 for pasture and forest catchment lakes, respectively. The upper layer of lake bottom sediments is represented mainly by silt fractions (2–50 μm), with high organic matter (4.0–5.7%) and radiocesium (1100–1600 kgˑha−1) contents.

Sediment transfer in an extremely low-gradient, low-relief and highly buffered system: Darwin Harbour catchment, northern Australia

Sediment yields from and sediment transfer within catchments of very low relief and gradient, which make up about 50% of Earth’s surface, are poorly documented and their internal sediment dynamics are poorly known. Sediment sources, their proportionate contributions to valley floors and sediment yield, and storage are estimated using fallout radionuclides 210Pb(ex) and 137Cs in the catchments that drain into Darwin Harbour, northern Australia, an example of this understudied catchment type that appears to be globally at the extreme end of this category of catchments. Unchannelled grassy valley floors (dambos, or seasonal wetlands) trap ∼90% of the sediment delivered from hillslopes by sheet and rill erosion. Further down valley, small channels transport ∼10% of the sediment that escapes from the dambos, and the remaining sediment comes from erosion of the channels. In this case, the fractional sediment storage is very high as a result of the existence of dambos, a landform that depends for its existence on low gradients.

Impact of Land Use and Runoff on Stream Quality

Climate changes, intensive agricultural production, and expanding urban areas make the study of runoff and its possible impact on stream quality increasingly important. In this study, we examined large datasets concerning catchment type, stream quality, and invertebrate composition in a comprehensive geographic information system study. The aim was to examine correlations between land use type and quality of the receiving waters to detect possible differences in anthropogenic impacts. The studied area covered 937 km2, and the dataset included 1672 stretches of streams and data from 468 fauna sampling stations. Runoff from agricultural areas more negatively influenced the stream quality than runoff from urban areas. Considering urban catchments, the areas with separate sewer systems generally influenced the stream quality less than catchments with combined sewer systems. In conclusion, the catchment of any specific stream must contain an area with a minimum of 20–30% without agriculture or urban areas to obtain good ecological status; when focusing only on the riparian zone (10 m on each side of the stream), a minimum of 40–55% is needed to create a good ecological status. Therefore, management focus on the entire catchment is important and separate sewers should be preferred rather than combined sewers.

Modeling the Ecological Impact of Phosphorus in Catchments with Multiple Environmental Stressors.

The broken phosphorus (P) cycle has led to widespread eutrophication of freshwaters. Despite reductions in anthropogenic nutrient inputs that have led to improvement in the chemical status of running waters, corresponding improvements in their ecological status are often not observed. We tested a novel combination of complementary statistical modeling approaches, including random-effect regression trees and compositional and ordinary linear mixed models, to examine the potential reasons for this disparity, using low-frequency regulatory data available to catchment managers. A benthic Trophic Diatom Index (TDI) was linked to potential stressors, including nutrient concentrations, soluble reactive P (SRP) loads from different sources, land cover, and catchment hydrological characteristics. Modeling suggested that SRP, traditionally considered the bioavailable component, may not be the best indicator of ecological impacts of P, as shown by a stronger and spatially more variable negative relationship between total P (TP) concentrations and TDI. Nitrate-N ( < 0.001) and TP ( = 0.002) also showed negative relationship with TDI in models where land cover was not included. Land cover had the strongest influence on the ecological response. The positive effect of seminatural land cover ( < 0.001) and negative effect of urban land cover ( = 0.030) may be related to differentiated bioavailability of P fractions in catchments with different characteristics (e.g., P loads from point vs. diffuse sources) as well as resilience factors such as hydro-morphology and habitat condition, supporting the need for further research into factors affecting this stressor-response relationship in different catchment types. Advanced statistical modeling indicated that to achieve desired ecological status, future catchment-specific mitigation should target P impacts alongside multiple stressors.

Uncertainty quantification of flood damage estimation for urban drainage risk management.

This paper presents a method of quantifying the uncertainty associated with inundation damage data for an urban catchment when undertaking stormwater drainage design and management. Usually flood damage is estimated by multiplying the inundated asset value by the damage rate corresponding to the inundation depth. The uncertainty of the asset value and the damage rate is described by probability distributions estimated from an analysis of actual flood damage data from a national government survey. With the inclusion of uncertainty in the damage rate and asset value, the damage potential curve defining the damage-frequency relationship is no longer a deterministic single-value curve. Through Monte Carlo simulations, which incorporate the uncertainty of the inundation damage from the damage rate and asset value, a probabilistic damage potential relation can be established, which can be expressed in terms of a series of curves with different percentile levels. The method is demonstrated through the establishment of probabilistic damage potential curves for a typical urban catchment, the Zenpukuji river basin in Tokyo Metropolis, under two scenarios, namely, with and without a planned flood control reservoir.

Computation of Watershed Parameters of Kansa Watershed in Satara Using Remote Sensing and GIS

In present study Kansa watershed in Satara district of Maharashtra was characterized for watershed parameters. Geographical Information Systems (GIS) and a high-resolution Digital Elevation Model (DEM) has been utilized for the estimation of morphological parameters. Several morphometric parameters have been computed and analyzed viz. linear aspects such as stream order, stream number, stream length, mean stream length, stream length ratio; areal aspects such as drainage density, stream frequency, drainage texture, elongation ratio, circularity ratio, form factor, constant of channel maintenance; relief aspects such as relief, relief ratio, relative relief, ruggedness number, length of overland flow. Impacts of morphometric parameters on flash flood characteristics have also been investigated. The presence of the maximum number of the first order segments shows that the basin is subjected to erosion and also that some areas of the basin are characterized by variations in lithology and topography. The form factor is 0.21, and the circulatory ratio is 0.42, which suggests an elongated type of catchment. Elongation ratio is 0.52, which indicates that watershed has high relief and steep slope. The estimated catchment characteristics may be useful to stimulate hydrological responses of the catchment.

Computation of Watershed Parameters of Kansa Watershed in Satara Using Remote Sensing and GIS

In present study Kansa watershed in Satara district of Maharashtra was characterized for watershed parameters. Geographical Information Systems (GIS) and a high-resolution Digital Elevation Model (DEM) has been utilized for the estimation of morphological parameters. Several morphometric parameters have been computed and analyzed viz. linear aspects such as stream order, stream number, stream length, mean stream length, stream length ratio; areal aspects such as drainage density, stream frequency, drainage texture, elongation ratio, circularity ratio, form factor, constant of channel maintenance; relief aspects such as relief, relief ratio, relative relief, ruggedness number, length of overland flow. Impacts of morphometric parameters on flash flood characteristics have also been investigated. The presence of the maximum number of the first order segments shows that the basin is subjected to erosion and also that some areas of the basin are characterized by variations in lithology and topography. The form factor is 0.21, and the circulatory ratio is 0.42, which suggests an elongated type of catchment. Elongation ratio is 0.52, which indicates that watershed has high relief and steep slope. The estimated catchment characteristics may be useful to stimulate hydrological responses of the catchment.

The Impacts of Native Forests and Forest Plantations on Water Supply in Chile

Over the past 40 years, south-central Chile has experienced important land-use-induced land cover changes, with massive conversion from native forests (NF) to Pinus radiata D.Don and Eucalyptus spp. exotic forest plantations (FP). Several case studies have related this conversion to a reduction in water supply within small catchments (&lt;100 ha). In this work, we explore the impacts of NF and FP on streamflow by using a large-sample catchment dataset recently developed for Chile. We select 25 large forested catchments (&gt;20,000 ha) in south-central Chile (35° S–41° S), analyze their land cover and precipitation spatial distributions, and fit a regression model to quantify the influence of NF, FP, grassland (GRA) and shrubland (SHR) partitions on annual runoff. To assess potential effects of land cover changes on water supply, we use the fitted model (R2 = 0.84) in synthetic experiments where NF, GRA and SHR covers within the catchments are replaced by patches of FP. We show that annual runoff consistently decreases with increments of FP, although the magnitude of the change (ranging from 2.2% to 7.2% mean annual runoff decrease for 10,000 ha increment in FP) depends on several factors, including the initial land cover partition within the basin, the replaced land cover class, the area of the catchment, and the type of catchment (drier or humid). Finally, in the context of the mitigation strategies pledged in the Chilean NDC (Nationally Determined Contributions defined after the Paris Agreement), which include the afforestation of 100,000 ha (mainly native forest) by 2030, we quantify the impacts on water supply due to the afforestation of 100,000 ha with different combinations of NF and FP. We show that annual runoff is highly sensitive to the relative area of FP to NF: ratios of FP to NF areas of 10%, 50% and 90% would lead to 3%, −18% and −40% changes in mean annual runoff, respectively. Our results can be used in the discussion of public policies and decision-making involving forests and land cover changes, as they provide scientifically-based tools to quantify expected impacts on water resources. In particular, this knowledge is relevant for decision making regarding mitigation strategies pledged in the Chilean NDC.

Assessment of debris-flow potential dangers in the Jiuzhaigou Valley following the August 8, 2017, Jiuzhaigou earthquake, western China

On August 8, 2017, an Ms 7.0 earthquake occurred at the Jiuzhaigou World Natural and Cultural Heritage, Sichuan Province, southwestern China. Eighty-three earthquake-induced landslides that directly damaged the Jiuzhaigou heritage sites were identified via remote-sensing interpretation and field survey. The coseismic landslides were concentrated primarily within 3 km of the seismogenic fault. Large volumes of sediments were transported into catchments of the Jiuzhaigou Valley, creating a geo-environment conducive to debris flow hazards triggered by post-earthquake heavy rainfall. A methodology combining the calculation of sediment augmentation, particle model, and numerical algorithm is developed to assess the potential dangers of post-quake debris flows. Five typical catchments strongly affected by the earthquake are chosen as study cases. The simulation results at Xiajijiehai Gully show a good agreement with the actual inundation area of the debris-flow event on September 25, 2017. The comparison of pre- and post-earthquake scenarios shows that an increase in sediment supply can greatly increase the debris-flow potential dangers characterized by higher maximum flow depths and larger inundation areas.

Uncertainty assessment in baseflow nonpoint source pollution prediction: The impacts of hydrographic separation methods, data sources and baseflow period assumptions

Effective management of nonpoint source (NPS) pollutants requires an understanding of their potential surface runoff and baseflow pathways. In this study, an integrated method was developed for separating baseflow and surface NPS pollutants at the watershed scale. Then, the uncertainty of the prediction of baseflow NPS pollutants was explored by comparing four hydrographic separation methods (the United Kingdom Institute of Hydrology (UKIH), the Lyne–Hollick (LH) method, the Eckhardt (ECK) method and the Soil and Water Assessment Tool (SWAT)), three data sources (monitoring data, SWAT and the LOADEST model) and two baseflow period assumptions. A real case study was performed in a typical catchment, the Three Gorges Reservoir Area, China. The results showed that the baseflow annually contributed 30.1% and 23.0% of the total nitrogen (TN) and phosphorus (TP) load, respectively, indicating that baseflow was identified as the key means of transport of NPS pollutants, especially for NPS-N during the dry season. The water quality data source represents the largest uncertainty source in baseflow NPS pollutant estimation, and the simulated baseflow loads of TN and TP were the largest when LOADEST and SWAT were used as water quality data sources, respectively. The baseflow NPS estimations were more uncertain for TN during the non-dry season and TP during the dry season. The results of this study could provide implications for the prediction and management of NPS pollutants at the watershed scale, especially for groundwater-polluted catchments.

137Cs-Based Variation of Soil Erosion in Vertical Zones of a Small Catchment in Southwestern China.

The study of the variability of soil erosion in mountainous areas provides the basis for soil and water conservation work and forest ecological construction in a targeted way. In this study, Liangshan Town catchment, a typical catchment in the Hengduan Mountains region, southwest China, was selected to investigate the variation of soil erosion in different vertical zones using the 137Cs tracing technique. The mean 137Cs reference inventories varied between 573.51 and 705.54 Bq/m2, with the elevation increasing from 1600 to 2600 m. The rates of soil erosion exhibited a significant variation. Under the same land cover condition, the average annual soil erosion modulus of high-elevation forest (elevation > 2200 m) was 400.3 t/(km2·a). However, the average annual soil erosion modulus of a low-elevation sparse forest (elevation < 1600 m) was as high as 1756 t/(km2·a). The average annual soil erosion modulus of the sloping farmland, mainly distributed at elevations of 1600–2200 m, was estimated to be 2771 t/(km2·a). These results indicate that effective soil management measures need to be implemented on the cultivated sloping land in the future.