On the Relationship between Suspended Sediment Concentration, Rainfall Variability and Groundwater: An Empirical and Probabilistic Analysis for the Andean Beni River, Bolivia (2003–2016)

Abstract

Fluvial sediment dynamics plays a key role in the Amazonian environment, with most of the sediments originating in the Andes. The Madeira River, the second largest tributary of the Amazon River, contributes up to 50% of its sediment discharge to the Atlantic Ocean, most of it provided by the Andean part of the Madeira basin, in particular the Beni River. In this study, we assessed the rainfall (R)-surface suspended sediment concentration (SSSC) and discharge (Q)-SSSC relationship at the Rurrenabaque station (200 m a.s.l.) in the Beni Andean piedmont (Bolivia). We started by showing how the R and Q relationship varies throughout the hydrological year (September to August), describing a counter-clockwise hysteresis, and went on to evaluate the R–SSSC and Q–SSSC relationships. Although no marked hysteresis is observed in the first case, a clockwise hysteresis is described in the second. In spite of this, the rating curve normally used ( SSSC = aQ b ) shows a satisfactory R2 = 0.73 (p < 0.05). With regard to water discharge components, a linear function relates the direct surface flow Qs–SSSC, and a hysteresis is observed in the relationship between the base flow Qb and SSSC. A higher base flow index (Qb/Q) is related to lower SSSC and vice versa. This article highlights the role of base flow on sediment dynamics and provides a method to analyze it through a seasonal empirical model combining the influence of both Qb and Qs, which could be employed in other watersheds. A probabilistic method to examine the SSSC relationship with R and Q is also proposed.

The Role of the Rainfall Variability in the Decline of the Surface Suspended Sediment in the Upper Madeira Basin (2003–2017)

“…The reported changes in the inter-annual variability of rainfall during the DJF wet season suggest possible changes at shorter time scales (i.e., daily or hourly), probably affecting rainfall erosivity. Ayes et al (2019b) found a long-term coincidental peak of rainfall and SSSC at Rurrenabaque in January. As expected from the high correlation between monthly rainfall and SSSC, the same authors identified a linear function relating the direct surface flow and SSSC at Rurrenabaque for the 2003-2016 period.…”

“…The negative SSSC trend in February detected at Porto Velho deserves a more comprehensive explanation. Whereas, the sediment recorded at Porto Velho in February comes from the Andes, the sediment dynamics at this time of the year is already influenced by the dilution associated with the base flow at Rurrenabaque (Ayes et al, 2019b). At Porto Velho, the already significant sub-surface and base flow coming from different parts of the floodplain (Miguez-Macho and Fan, 2012;Frappart et al, 2019) also contributes to dilution.…”

“…positive rainfall trend in February does not have a concomitant SSSC trend (Figures 4F, 6C). This could be explained by the relevance of the base flow that dilutes SSSC from February onwards in the Rurrenabaque watershed (Ayes et al, 2019b). Thus, the positive rainfall trend in February does not necessarily convert to a rise in SSSC.…”

“…This information (D) at Guayaramerin (GY) on the Mamoré River. Sources: for the rainfall: CHIRPS.v2 (Funk et al, 2015), Q and SSSC adapted from Ayes et al (2019a) and Ayes et al (2019b) with data from SO-HYBAM, ANA, and SENAMHI. Please note that the two left y-axis differ in (C) because of the magnitude, and the x-axis is the hydrological year, from September (9) to August (8).…”

Regression Models for Soil Water Storage Estimation Using the ESA CCI Satellite Soil Moisture Product: A Case Study in Northeast Portugal

“…However, hysteresis has been known for a long time in soil physics and soil hydrology and associated with water flowing through porous media [68,92]. Furthermore, hysteresis is found in surface hydrology, where sediment transport studies in streams show that sediment yields may depict such behaviour, as well as ionic species dissolved or adsorbed to the soiled phase [64,93,94].…”