Preprints
https://doi.org/10.5194/hess-2021-567
https://doi.org/10.5194/hess-2021-567

  15 Nov 2021

15 Nov 2021

Review status: this preprint is currently under review for the journal HESS.

Agricultural intensification vs climate change: What drives long-term changes of sediment load?

Shengping Wang1,2,3, Peter Strauss2, Carmen Krammer2, Elmar Schmaltz2, Borbala Szeles3,4, and Günter Blöschl3,4 Shengping Wang et al.
  • 1College of Hydraulic and Hydro-Power Engineering, North China Electric Power University, Beijing, 102206, P.R.China
  • 2Institute for Land and Water Management Research, Federal Agency for Water Management, A-3252 Petzenkirchen, Austria
  • 3Institute of Hydraulic Engineering andWater Resources Management, Vienna University of Technology, Vienna, Austria
  • 4Vienna Doctoral Programme on Water Resource Systems

Abstract. Climate change and agricultural intensification are expected to increase soil erosion and sediment production from arable land in many regions. However, so far, most studies have been based on short-term monitoring and/or modeling, making it difficult to assess their reliability in terms of long-term changes. We present the results from a unique data set consisting of measurements of sediment loads from a 60ha catchment (the HOAL Petzenkirchen in Austria) over a time window spanning 72 years. Specifically, we compare Period I (1946–1954) and Period II (2002–2017) by fitting sediment rating curves for the growth and dormant seasons for each of the periods. The results suggest a significant increase in sediment yield from Period I to Period II with an average of 11.6 ± 10.8 ton·yr−1 to 63.6 ± 84.0 ton·yr−1. The sediment flux changed mainly due to a shift of the sediment rating curves (SRC), given that the annual streamflow varied little between the periods (5.6 l·s−1 and 7.6 l·s−1, respectively, on average). The slopes of the log regression lines of the SRC for the growing season and the dormant season of Period I were 16.72 and 4.9, respectively, whilst they were 5.38 and 1.17 for Period II, respectively. Climate change, considered in terms of rainfall erosivity, was not responsible for this shift, given that erosivity decreased by 30.4 % from the dormant season of Period I to that of Period II, and no significant difference was found between the growing seasons of Periods I and II. However, the sediment flux changes can be explained by changes in crop type and parcel structure. During low and median streamflow conditions (i.e. Q < Q20 %), land consolidation in Period II (i.e. theparcel effect) did not exert an apparent influence on sediment production. Whilst with increasing stream flow (Q > Q20 %), parcel structure played an increasingly role in sediment yield contribution, and leading to a dominant role due to enhanced sediment connectivity in the landscape at extremely high flow conditions (i.e. Q > Q2 %). The increase in cropland in Period II at the expense of grassland had an unfavourable effect on sediment flux, independent of streamflow, with declining relevance as flow increased. We conclude that both land cover change and land consolidation should be accounted for simultaneously when assessing sediment flux changes. Especially during extremely high flow conditions, land consolidation substantially alters sediment fluxes, which is most relevant for long-term sediment loads and land degradation. Increased attention to improving parcel structure is therefore needed in climate adaptation and agricultural catchment management.

Shengping Wang et al.

Status: open (until 10 Jan 2022)

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Shengping Wang et al.

Shengping Wang et al.

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Short summary
We present the results from a unique data set over a time window spanning 72 years. We found that climate change was not responsible for the shift of sediment regime of the watershed, which, instead, was mainly explained by changes in crop type and parcel structure. At Q > Q2%, land consolidation substantially alters sediment fluxes. Increased attention to improving parcel structure is therefore needed in climate adaptation and agricultural catchment management.