Use of Monitoring Approaches to Verify the Predictive Accuracy of the Modeling of Particle-Bound Solid Inputs to Surface Waters

Katharina Allion,Stefan Halbfass,Mario Uhlig,Michael Gebel,Stephan Bürger,Stephan Fuchs,Lisa Kiemle

doi:10.3390/w13243649

Abstract

For particle-bound substances such as phosphorus, erosion is an important input pathway to surface waters. Therefore, knowledge of soil erosion by water and sediment inputs to water bodies at high spatial resolution is essential to derive mitigation measures at the regional scale. Models are used to calculate soil erosion and associated sediment inputs to estimate the resulting loads. However, validation of these models is often not sufficiently possible. In this study, sediment input was modeled on a 10 × 10 m grid for a subcatchment of the Kraichbach river in Baden-Wuerttemberg (Germany). In parallel, large-volume samplers (LVS) were operated at the catchment outlet, which allowed a plausibility check of the modeled sediment inputs. The LVS produced long-term composite samples (2 to 4 weeks) over a period of 4 years. The comparison shows a very good agreement between the modeled and measured sediment loads. In addition, the monitoring concept of the LVS offers the possibility to identify the sources of the sediment inputs to the water body. In the case of the Kraichbach river, it was found that around 67% of the annual sediment load in the water body is contributed by rainfall events and up to 33% represents dry-weather load. This study shows that the modeling approaches for calculating the sediment input provide good results for the test area Kraichbach and the transfer for a German wide modeling will produce plausible values.

Highlights

Particle-bound substance inputs to surface waters still contribute significantly to missed legal quality standards [1,2] by many water bodies [3,4]
With SEA[t total a−1 ] as use-specific sediment input, and A [t ha of 43 composite samples were collected from March
Within the framework of the work presented here, it can be shown that the tools used to model the long-term mean sediment input provide plausible results in comparison with the suspended solid loads recorded via continuous large-volume samplers (LVS) sampling and under consideration of the dry-weather load

Summary

Introduction

Particle-bound substance inputs to surface waters still contribute significantly to missed legal quality standards [1,2] by many water bodies [3,4]. The need to quantify substance inputs to surface waters and derive adapted mitigation strategies stimulated the development of diverse model systems at the regional scale [7,8,9,10,11,12,13,14,15,16,17,18]. These models have in common that they used predominantly empirical or stochastic rather than process-related approaches. Long-term composite samples instead of grab samples are better suited here, as they capture the load in the water body more realistically [19,20,21]

Methods

Results

Discussion

Conclusion