137Cs Tracing Dynamics of Soil Erosion, Organic Carbon, and Total Nitrogen in Terraced Fields and Forestland in the Middle Mountains of Nepal

Su, Zhengan; Xiong, Donghong; Deng, Wei; Dong, Yifan; Ma, Jing; Padma, Poudel C.; Gurung, Sher B.

doi:10.1007/978-981-10-2890-8_11

Cited by 1 publication

(2 citation statements)

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“…Gardner and Gerrard (2002) suggested that ground cover is more important than canopy cover in reducing runoff and water erosion in the mid-hill forest. The average rate of soil loss and the contribution to total soil loss from steeper slopes are tremendously high compared with that from gentle slopes (Bahadur, 2012;Garcia-Ruiz et al, 2015;Su et al, 2016). Moreover, unfortified dirt roads located inside the broadleaf forest are highly vulnerable to erosion due to rutted surfaces.…”

Section: Controls On Sediment Sources: Land Management Activitiesmentioning

confidence: 99%

“…Most of the rural roads in the mid-hills are unpaved and poorly maintained without roadside drainage systems, leading to concentrated flow, resulting in soil erosion (Merz et al, 2006;Su et al, 2016). Additional tracers such as fallout radionuclides may provide further insight into the major erosion processes generating sediment from different land uses, which is lacking in this study.…”

Section: Controls On Sediment Sources: Land Management Activitiesmentioning

confidence: 99%

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Community managed forests dominate the catchment sediment cascade in the mid-hills of Nepal: A compound-specific stable isotope analysis

Upadhayay

Smith

Griepentrog

et al. 2018

Science of The Total Environment

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Soil erosion by water is critical for soil, lake and reservoir degradation in the mid-hills of Nepal. Identification of the nature and relative contribution of sediment sources in rivers is important to mitigate water erosion within catchments and siltation problems in lakes and reservoirs. We estimated the relative contribution of land uses (i.e. sources) to suspended and streambed sediments in the Chitlang catchment using stable carbon isotope signature (δC) of long-chain fatty acids as a tracer input for MixSIAR, a Bayesian mixing model used to apportion sediment sources. Our findings reveal that the relative contribution of land uses varied between suspended and streambed sediment, but did not change over the monsoon period. Significant over- or under-prediction of source contributions could occur due to overlapping source tracer values, if source groups are classified on a catchment-wide basis. Therefore, we applied a novel deconvolutional framework of MixSIAR (D-MixSIAR) to improve source apportionment of suspended sediment collected at tributary confluences (i.e. sub-catchment level) and at the outlet of the entire catchment. The results indicated that the mixed forest was the dominant (41 ± 13%) contributor of sediment followed by broadleaf forest (15 ± 8%) at the catchment outlet during the pre-wet season, suggesting that forest disturbance as well as high rainfall and steep slopes interact for high sediment generation within the study catchment. Unpaved rural road tracks located on flat and steep slopes (11 ± 8 and 9 ± 7% respectively) almost equally contributed to the sediment. Importantly, agricultural terraces (upland and lowland) had minimal contribution (each <7%) confirming that proper terrace management and traditional irrigation systems played an important role in mitigating sediment generation and delivery. Source contributions had a small temporal, but large spatial, variation in the sediment cascade of Chitlang stream. D-MixSIAR provided significant improvement regarding spatially explicit sediment source apportionment within the entire catchment system. This information is essential to prioritize implementation measures to control erosion in community managed forests to reduce sediment loadings to Kulekhani hydropower reservoir. In conclusion, using compound-specific stable isotope (CSSI) tracers for sediment fingerprinting in combination with a deconvolutional Bayesian mixing model offers a versatile approach to deal with the large tracer variability within catchment land uses and thus to successfully apportion multiple sediment sources.

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Section: Controls On Sediment Sources: Land Management Activitiesmentioning

confidence: 99%

Section: Controls On Sediment Sources: Land Management Activitiesmentioning

confidence: 99%