Naziano Filizola

The use of Doppler technology for suspended sediment discharge determination in the River Amazon

Abstract Abstract An experiment on water discharge gauging and suspended sediment sampling performed in the Amazon River basin on 24 March 1995, during a rising-water period is described. The experiment involved different devices, including an Acoustic Doppler Current Profiler (ADCP) for water discharge measurements. From the different samplers used, one specially built for the HiBAm project was tested successfully. An attempted use of the relationship between the ADCP signal and the total suspended sediment (TSS) was performed for sediment yield calculations. Different calculation methods were used with the TSS data obtained by the samplers and the results are discussed. The mean water discharge (Q) and TSS sediment yield (Qs) results were 172 400 m3 s-1 and 3.15 × 106 t day-1, respectively. A relationship between the Qs value at depth and the surface Qs value is also proposed.

Sediment production and delivery in the Amazon River basin quantified by in situ-produced cosmogenic nuclides and recent river loads

We use cosmogenic nuclide-derived denudation rates from in situ–produced 10 Be in river sediment to determine sediment production rates for the central Amazon River and its major tributaries. Recent developments have shown that this method allows calculating denudation rates in large depositional basins despite intermediate sediment storage, with the result that fluxes of the sediment-producing hinterland can now be linked to those discharged at the basins’ outlet. In rivers of the central Amazonian plain, sediment of finer grain sizes (125–500 μm) yields a weighted cosmogenic nuclide-derived denudation rate of 0.24 ± 0.02 mm/yr that is comparable to the integrated rate of all main Andean-draining rivers (0.37 ± 0.06 mm/yr), which are the Beni, Napo, Mamore, Ucayali, and Maranon rivers. Coarser-grained sediment (>500 μm) of central Amazonian rivers is indicative of a source from the tectonically stable cratonic headwaters of the Guyana and Brazilian shields, for which the denudation rate is 0.01–0.02 mm/yr. Respective sediment loads can be calculated by converting these cosmogenic nuclide-derived rates using their sediment-producing areas. For the Amazon River at Obidos, a sediment production rate of ∼610 Mt/yr results; non-Andean source areas contribute only ∼45 Mt/yr. A comparison with published modern sediment fluxes shows similarities within a factor of ∼2 with an average gauging-derived sediment load of ∼1000 Mt/yr at Obidos, for example. We attribute this similar trend in cosmogenic versus modern sediment loads first to the absence of long-term deposition within the basin and second to the buffering capability of the large Amazon floodplain. The buffering capability dampens short-term, high-amplitude fluctuations (climatic variability in source areas and anthropogenic soil erosion) by the time the denudation rate signal of the hinterland is transmitted to the outlet of the basin.

Damming the rivers of the Amazon basin

More than a hundred hydropower dams have already been built in the Amazon basin and numerous proposals for further dam constructions are under consideration. The accumulated negative environmental effects of existing dams and proposed dams, if constructed, will trigger massive hydrophysical and biotic disturbances that will affect the Amazon basin’s floodplains, estuary and sediment plume. We introduce a Dam Environmental Vulnerability Index to quantify the current and potential impacts of dams in the basin. The scale of foreseeable environmental degradation indicates the need for collective action among nations and states to avoid cumulative, far-reaching impacts. We suggest institutional innovations to assess and avoid the likely impoverishment of Amazon rivers.

Application of retracked satellite altimetry for inland hydrologic studies

We explored the application of satellite radar altimetry for the monitoring of small inland bodies of water and hydrologic studies using a water-detection algorithm, optimally retracked TOPEX/POSEIDON data at 10-Hz sampling, and investigated the use of radar backscatter to improve land cover classification. The procedure was demonstrated over Manitoba and south-western (SW) Ontario, and the Amazon River Basin study regions. Compared with an L-band synthetic aperture radar data generated water-land cover mask, the water-detection algorithm detected more water points over the Amazon basin. High correlation of 0.98 between the retracked 10-Hz altimetry and the gauge measurements in Manitoba confirmed that the retracked TOPEX data are more accurate than the non-retracked data, and with higher along-track spatial resolution by virtue of its higher sampling at 10 Hz.

The Amazon Dense GNSS Meteorological Network: A New Approach for Examining Water Vapor and Deep Convection Interactions in the Tropics

AbstractThe complex interactions between water vapor fields and deep atmospheric convection remain one of the outstanding problems in tropical meteorology. The lack of high spatial–temporal resolution, all-weather observations in the tropics has hampered progress. Numerical models have difficulties, for example, in representing the shallow-to-deep convective transition and the diurnal cycle of precipitation. Global Navigation Satellite System (GNSS) meteorology, which provides all-weather, high-frequency (5 min), precipitable water vapor estimates, can help. The Amazon Dense GNSS Meteorological Network experiment, the first of its kind in the tropics, was created with the aim of examining water vapor and deep convection relationships at the mesoscale. This innovative, Brazilian-led international experiment consisted of two mesoscale (100 km × 100 km) networks: 1) a 1-yr (April 2011–April 2012) campaign (20 GNSS meteorological sites) in and around Manaus and 2) a 6-week (June 2011) intensive campaign (15 G...

A test of the cosmogenic 10Be(meteoric)/9Be proxy for simultaneously determining basin‐wide erosion rates, denudation rates, and the degree of weathering in the Amazon basin

We present an extensive investigation of a new erosion and weathering proxy derived from the 10Be(meteoric)/9Be(stable) ratio in the Amazon River basin. This new proxy combines a radioactive atmospheric flux tracer, meteoric cosmogenic 10Be, with 9Be, a trace metal released by weathering. Results show that meteoric 10Be concentrations ([10Be]) and 10Be/9Be ratios increase by >30% from the Andes to the lowlands. We can calculate floodplain transfer times of 2–30 kyr from this increase. Intriguingly however, the riverine exported flux of meteoric 10Be shows a deficit with respect to the atmospheric depositional 10Be flux. Most likely, the actual area from which the 10Be flux is being delivered into the mainstream is smaller than the basin-wide one. Despite this imbalance, denudation rates calculated from 10Be/9Be ratios from bed load, suspended sediment, and water samples from Amazon Rivers agree within a factor of 2 with published in situ 10Be denudation rates. Erosion rates calculated from meteoric [10Be], measured from depth-integrated suspended sediment samples, agree with denudation rates, suggesting that grain size-induced variations in [10Be] are minimized when using such sampling material instead of bed load. In addition, the agreement between erosion and denudation rates implies minor chemical weathering intensity in most Amazon tributaries. Indeed, the Be-specific weathering intensity, calculated from mobilized 9Be comprising reactive and dissolved fractions that are released during weathering, is constant at approximately 40% of the total denudation from the Andes across the lowlands to the Amazon mouth. Therefore, weathering in the Amazon floodplain is not detected.

Epidemiological analysis of malaria and its relationships with hydrological variables in four municipalities of the State of Amazonas, Brazil

Abstract This work comprises a spatial, temporal and statistical analysis of the epidemiology of malaria occurrence in four municipalities of the State of Amazonas, Brazil: Coari, Codajás, Manacapuru and Manaus, for the period 2003–2009. The number of malaria cases, precipitation, water level and temperature data were analysed in this study. The strength of the relationship between these hydrological/meteorological variables and the occurrence of malaria was determined by employing the Spearman rank correlation coefficient. Seasonal peaks of malaria were registered, on average, about 1–2 months before the annual maximum temperature and after the river’s seasonal high-water level. The phenomenon called repiquete (notable variations in the water level) was observed during periods of between 9 and 56 days. The results showed a statistically significant correlation between malaria, temperature, precipitation and water level. Temperature influenced malaria occurrence the least, while rainfall was the most important factor, especially in the municipality of Coari. Water level had an important influence on the records of malarial occurrence in the municipality of Manacapuru. Editor Z.W. Kundzewicz Citation Wolfarth, B.R., Filizola, N., Tadei, W.P., and Durieux, L., 2013. Epidemiological analysis of malaria and its relationships with hydrological variables in four municipalities of the State of Amazonas, Brazil. Hydrological Sciences Journal, 58 (7), 1495–1504.

Monitoring water level in large trans-boundary ungauged basins with altimetry: the example of ENVISAT over the Amazon basin

Brasil and Bolivia have water plans projects on the Beni-Madeira river, a major tributary of the Amazon. There are four main tributaries to the Rio Madeira: the Guapore, the Mamore and the Beni rivers into the Bolivian territory, and the Madre de Dios River crossing the North of Bolivia, coming from Peru. Most parts of these rivers are very far from the Andean capital cities of Bolivia and Peru, unreachable for long periods of time. Very few gauging stations are in operation, either for the Bolivian or the Peruvian part, most of them being located at the Andes piedmont or near the confluence at the Brazilian border as they form the Madeira river. This situation is exemplary of large transboundary basins in the tropical part of the world. We have computed 39 water level time series using ENVISAT altimetry data over the four tributaries of the Madeira and the Madeira itself. We present a preliminary study mostly conducted onto the Guapore river, in order to assess the quality of these time series for a variety of situations, but mostly narrow and meandering riverbeds. Comparison between water levels variation in the mainstream and within the inundations plains and lakes are drawn. We conclude by the perspectives offered by the combined use of radar altimetry and SAR imagery for the global monitoring of water resources, in large tropical transboundary basins.

The significance of suspended sediment transport determination on the Amazonian hydrological scenario

Rivers play an important role in continental erosion as they are the primary agents of transferring erosion products to the ocean. Understanding rivers and their transport pathways will improve the perception of many processes of global significance, such as biogeochemical cycling of pollutants and nutrients, atmospheric CO2 drawdown, soil formation and their erosion, crust evolutionin short the interaction between the atmospheric and the lithospheric compartment of the Earth s system (Allen, 2008). This interaction is characterised by the relative proportions of mechanical degradation vs. chemical weathering, whose products are, in dissolved or solid form, transported by rivers. The sediment load of rivers is thereby controlled by catchment relief, the channel slope and its connectivity to the hill slope, but also by climatic factors such as precipitation. The latter, together with temperature, exert control over chemical weathering that is dependent on physical erosion to a degree that is yet unknown (Anderson et al., 2002; Gaillardet et al., 1999; Riebe et al., 2001). Both mechanical erosion and chemical weathering, are, however, governed by tectonic activity, which drives processes of landscape rejuvenation and preconditions the fluvial transport regime (von Blanckenburg et al., 2004). On the shorter time scale, humans may act as geomorphic agents by constructing dams and reservoirs, and changing land use by deforestation and mining (Hooke, 2000; Syvitski et al., 2005; Wilkinson and McElroy, 2007). In tropical regions around the globe, large river basins are especially concentrated, and their behaviour plays an important role in river sediment transport (Latrubesse et al., 2005). For example, the tropics represent 25% of the total continental lands and contain 57% of the

Inundation Risk in Large Tropical Basins and Potential Survey from Radar Altimetry: Example in the Amazon Basin

Altimetry turns out to be a highly valuable source of data in remote areas such as the unmonitored wetlands at the upstream part of contributors in continental-scale basins. We illustrate this for the Amazon basin, in the area of upper Rio Madeira, where the inundation risk increased recently on populations downstream because of changes in the local economy. With use of satellite altimetry, the hydrological relationship between the main stem and the related water bodies that cyclically retain and liberate large amounts of water can be explained with sufficient details to aid in risk mitigation.