Sediment fingerprinting and hydro-sedimentary monitoring as tools for catchment management in Mediterranean environments
[eng] Soil erosion is a natural process that encompasses weathering, transport and deposition of soil particles. These processes are essential in terrestrial geochemical cycles. However, the on- and off-site erosion effects are considered to be one of the most important causes of terrestrial and aqu...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2021 |
| País: | España |
| Institución: | CBUC, CESCA |
| Repositorio: | TDR. Tesis Doctorales en Red |
| OAI Identifier: | oai:www.tdx.cat:10803/672333 |
| Acceso en línea: | http://hdl.handle.net/10803/672333 |
| Access Level: | acceso abierto |
| Palabra clave: | Sediment fingerprinting Mediterranean catchments Hydro-sedimentary monitoring Catchment management Cuencas mediterráneas Monitoreo hidro-sedimentario Gestión de cuencas de drenaje Conques mediterrànies Monitorització hidro-sedimentària Gestió de conques de drenatge Hidrologia i Geomorfologia 55 57 |
| Sumario: | [eng] Soil erosion is a natural process that encompasses weathering, transport and deposition of soil particles. These processes are essential in terrestrial geochemical cycles. However, the on- and off-site erosion effects are considered to be one of the most important causes of terrestrial and aquatic ecosystems degradation. The characteristics of the Mediterranean region are marked by complex relationships between natural, human, biotic and abiotic variables. In addition, an irregular rainfall distribution, strong seasonality and the physiographic landscape characteristics promote divergent responses in erosion rates and sediment yields. In this context, the Mediterranean basin has the highest sediment yields in all of Europe. In addition, it is emerging as a hot spot point in Global Change dynamics, especially with reference to climate and land use change, which could generate an increase in erosive and sediment transport processes. At the catchment scale, sediment transfer occurs in hill slopes, between hill slopes and channels or within channels. Information on the nature and relative contribution of sediment sources is a key aspect with regard to designing and implementing erosion control strategies in catchments. The main objective of this thesis is to identify erosion and sediment transport processes in two Mediterranean catchments affected by different global change processes at different spatio-temporal scales, improving current techniques for sediment origin determination (i.e., reducing uncertainties, time and cost) so it can better implemented in catchment management plans. For this purpose, the hydro-sedimentary dynamics and the origin of the sediments has been investigated on the island of Mallorca (Spain), in two small catchments; the Sa Font de la Vila catchment -4.8 km2, affected by wildfires - and the Es Fangar catchment (3.4 km2), affected by land use changes. The combination of sediment fingerprinting and hydro-sedimentary monitoring made it possible to assess its hydro-sedimentary dynamics during the study period. In Sa Font de la Vila, results showed a gradual decrease in contribution from burned sources over time, while in Es Fangar the contributions from crops dominated throughout the study period, without substantial changes. Sediment yields were 6.3 t km2 yr-1 and 4.5 t km2 yr-1 for Sa Font de la Vila and Es Fangar respectively, low results in comparison with other Mediterranean catchments. This was mainly attributed to the calcareous lithology, land uses (in Es Fangar catchment), vegetation recovery (in Sa Font de la Vila catchment) and agricultural terraces. The use of soil colour parameters as tracers was successfully evaluated in the two catchments, confirming its suitability as a fast and inexpensive tracer, even in fire-affected catchments. Furthermore, the strong correlations between the measurements made with a spectro-radiometer and a scanner make colour even more accessible for its implementation in catchment management plans. The experiment on tracer conservatism confirmed that in-channel changes suffered by all the analysed tracers (coefficient of variation x̄ 8.1 ± 8.8%) were generally lower than their spatial variability within the catchment (coefficient of variation x̄ 16.3 ± 18.5%). Furthermore, the colour parameters were the least variable tracers (i.e. the most conservative). with a coefficient of variation of 2.6 ± 2.2%. Finally, it was not possible to identify the activation patterns of different sediment sources combining hydro-sedimentary monitoring and sediment fingerprinting. This was probably caused by Es Fangar's catchment stability in terms of the origin of the suspended sediment. Es Fangar catchment sediment source stability is attributed to lithological characteristics, land uses and the presence of agricultural terraces in the study area. However, events of higher magnitude could exceed the sedimentary (dis)connectivity thresholds of the rest of the sources, promoting a sediment cascade effect. The results presented in this thesis are relevant and represent an advance in the optimization of the sediment fingerprinting technique. Despite some limitations that need to be further investigated, hydro-sedimentary monitoring and sediment fingerprinting used in combination was shown to be very useful for integrated catchment management plans in Mediterranean environments. |
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